Well, I have this hydraulic cam in my engine. And last fall I committed to making it work, and so now I have an update.

I'm hoping I won't get called a moron again! But here I go! This will probably be done in 3 parts- lifters, pushrods, and rockers.

So I got convinced that the real issue with hydros is lack of adequate lube to the rocker boxes. I found a website that was discussing major problems with Lycoming (4 cylinder, air-cooled aircraft engines) when they transitioned to hydraulics in the late 70's. That was about the same time VW and Continental (aircraft) transitioned. VW had very similar problems, but Continental was virtually trouble-free. Many (all?) of the Lycoming problems can be explained by their implementation of hydros as opposed to the well known fact in 914 circles that hydos are, in fact, evil. In the article, it is observed that the hydraulic lifter has two roles- 1.) to adjust to changes in engine tolerances due to wear and temperature and keep the valves at zero lash, and 2.) to convey oil up the pushrods so as to lube the rockers. Inadequate oiling means inadequate cooling, stuck valves (due to oil coking on the stems), broken valves, bent pushrods, galled lifters and cams, etc, etc, etc... sound familiar? sound evil? How about valves failing (shattering) in flight?

In the article, the authors go on to "point out a major shortcoming of the Lycoming design that we believe substantially accounts for valve train problems including stuck exhaust valves, prematurely worn valves and guides, and camshaft distress and failure."

The early implementation in Lycoming (and VW?) focused on the first role and missed the second. I'm open to correction, but I think this was the VERY first use of hydraulic valve actuators by VW.

Anyway, here's the article: http://www.prime-mover.org/Engines/Marvel/tbo3.html
Every time I read it I get something more out of it.... It also touches on sodium filled valves...

On my own engine, I noticed that when I adjusted the hydros to +.006" (clearance) and then idled it, there was significant oil flowing out and all over my driveway. (This in spite of the fact that I installed a half valve cover to catch oil.) When I then adjusted to -.006", the flow virtually stopped- the pushrod seated in the rocker like a valve in its seat.

I re-read the article, and then started at the lifter. I bought three brands of T4 lifter- Meyle, Febi, and Isky. I disassembled them and looked at the various schemes of metering oil to the head.

Click to view attachment
Click to view attachment Meyle
Click to view attachment Febi (may be the same as Sealed Power)
Click to view attachment Isky (may be made by Delphi?)

Both the Febi and the Isky have a metering disk beneath the pushrod seat that meters oil from the plunger to the pushrod. The Meyle relies on oil leakage around the pushrod seat and then into the side hole and then through the pushrod seat to the pushrod. This does not seem to me to be a reliable way to forward oil up the pushrod.

Also, there is a reference to two designs of VW hydraulic lifter at this article- http://www.ratwell.com/technical/HydraulicLifters.html . In the article, Richard Atwell speculates that VW improved the design because it changed from having a paper clip style retainer to having a circlip retainer to hold it all together. Well, Meyle (questionable oiling) has a paper clip style retainer, and Febi (improved oiling) has the circlip. My theory is that VW migrated from Meyle to Febi, because the Meyle was causing failures due to inadequate lube. It's all anecdotal and speculative, but for the life of me I can't imagine how the Meyle can reliably and predictably convey oil to the head..... (beating the same dead horse)

Click to view attachment Meyle, Isky, Febi oil metering to pushrod.

In addition to the article on Lycoming and Continental, I looked closely at Corvair (freakin' Chevy to some). 1.7 million Corvairs were built over a 10 year period, and all had hydraulic lifters. And they were never considered a reliability issue. The Corvair is basically a six cylinder Type 4 (though Corvair predates T4 by almost 10 years). So I also purchased 2 Corvair lifters- one used original Chevy and one new Sealed Power. Upon disassembly, I found oiling similar to the Isky and the Febi- both have a method of metering the oil, as opposed to relying on leakage. When GM discontinued the original Corvair part number, there was quite a bit of activity on the internet about substitutes and how effective they are in transferring oil to the rockers, so clearly it's a more openly understood requirement with the Corvair-meisters than with us T4 guys whose starting point is solid lifters...... (one of these days I'll get around to taking photos of the Corvair lifters)

So anyway, after I was satisfied with which lifter I would use (I stuck with my Iskys, thought I wouldn't hesitate to use Febi either), I moved on to the pushrods.... and I'll get into that in my next post, probably in a few days....

Interesting... IIRC, lack of rocker (and associated parts) oiling is not the only flaw that the hydros are supposed to have, but it sounds like you are certainly addressing things as you can!

Very cool; I look forward to seeing more results on this!

Have you given any thought to external oiling for the rockers? A separate spray bar with an oil line run to it from one of the galleries? I know people have at least thought about that for the non-self-oiling "ratio rockers" that are out there.

--DD

Thanks! Looking forward to the rest of the 'series'.

Very interesting article. I just pulled apart a 1.7 that had an Isky hydro cam and lifters in it. The car had set for years but the cam and lifters are like new. I had the machine shop polish it and they said it was good to go. The lifters were also Isky. The sad part was the motor was running stock push rods. No wonder it did not run right! When you go to the Isky web site they show chrome-moly pushrods are required for this cam. It is an Isky 228 Hydraulic cam.

Does any one have any experiece with this cam?

Very interesting post. Thanks for doing all the research and sharing your information.

Mine is an Isky 229-hyd. According to their catalog, the 228 is a solid lifter cam. You might want to call them to be sure. It's possible they made a 228-hyd sometime in the past, and it's just not in the catalog.

As far as pushrods go- the Isky hydraulic pushrods were way too short in my engine. I'll have photos in my next installment, and get into what I did about it.

I have no issues with my Isky hydraulic cam. These guys have been grinding hydraulic-profile cams for over 50 years. The idle vacuum is a bit low, but I'm testing a work-around to that as well. I'm running pretty much stock Djet, except with Mercedes spec injectors.

Jim

A large portuion of the problem with Hydro equipped TIV engines lies in the fact that the cam never loses contact with the lifters, this makes for much more extreme wear, even on the heel of the cam lobe.

The issues with the Lycomings is a bit different than the issues we have had/seen in the past with hydros in the TIV, yes they can be the cause of failure with some valve related incidents, but most of the main reasons why I discourage them so much is wear that is related to the camshaft.

With a "windowed" valve cover one can see that at most any RPM over 3,500 the entire rocker box is filled with ouil on a TIV engine with an adequate oil pump, the only thing that really ever causes a valve failure with a hydro TIV is lack of maintenance and neglect that the hydros promote. Installing hydro lifters to most people means instant neglect as the general consensus is that they do not need to ever be adjusted and thats just not true.

The worst thing VW ever did to the TIV was give it Hydros from the factory and it wasn't the Engineers that did it, try the accounting and sales departments...

Jim, D jet really doesn't like Hydros, they delay the opening events a lot and can lead to those low MPs you are experiencing, Ray Greenwood went over this in detail in some of his posts at the STF, search for them.

!
I am no mechanical engineer but find this fascinating. Mr. Raby has stated the main reason for the hydros- laziness. Adjusting valves in a teener tedious @ best. Jake has said many times that he's neglected his engines' valves for 90k+ miles now, so he's managed to get the end result of the hydros w/ out going hydro . Someone here on a previous hydro post stated that they only work well/properly when you use them regularly, not let them sit & keep the oil immaculate. Somehow a mythos has developed over the years that hydro = no adjustments & they were never designed for that. Finally, I've never heard of using Mercedes injectors on stock D-jet; what's that about? This stuff is great !





Edit: reducing service intervals & proceedures is my definition of lazy.

Yes, I have purposely neglected my engines for the sake of record keeping and development. The engine in my 912E still hasn't had a valve adjusted since February of 2003, BUT I HAVE checked those valves religously and noted guide wear as well as valve clearances and have a log of these. That same engine went 23K miles on one oil change but that was never something I'd tell anyone else to do, I don't care if my personal engine blows to bits, I actually enjoy it.

Today the engine in my 912 has 127K on it, it racked that many miles up in less than 5 years and it is ready to come out for an autopsy- when I get the time.

The ONLY benefit to hydros is the fact that they run quieter, if one is willing to absorb all the other negative aspects they create to gain just that one benefit that is their perrogative, but they have been thoroughly warned!

Listen to my 4th Dimension radio show on the topic, two hours of real info from myself and my Canadian counterpart Mark Henry..

jk76.914, your timing is perfect.
I have hydros in my car, I wish I didn't, but that's the way it was when I got it. I'll be removing the valve covers for the first time soon to see exactly what kind of hydros I have in there and why they've been so noisy lately. Hopefully I won't find that the PO went with the Meyles.

Thanks for exploring this topic!

Loud hydros are usually due to oil pressure issues.. depending upon oil pressure to dictate valve actuation has those problems..

Thanks for all the replies. I wanted to get into the pushrods next. The rockers will take longer anyway.

So for the pushrods, I needed to address two issues- my kit pushrods were obviously too short, but I also needed to continue my quest for lubrication to the head. So I looked again to the Corvair. The Corvair pushrod has two holes on one end- one on the tip and an additional .020" hold on the side. Since the pushrod rotates with the lifter, and goes up and down, that side hole sprays oil around like a lawn sprinkler. In this case, there are 6 of those sprinkler heads in each rocker box, and believe me, it moves a lot of oil to the rocker box.

Hell, I have always thought with the head half full of oil that was enough to lube the rockers!
More??? its tough enough to get it to drain back fast enough.

When all your oil ends up in the valve covers and the oil pickup starves all those mods will send you back to the drawing board.. Each valve cover can hold 1.3 quarts of oil, so that means that you have less than 1.5 quarts in the oil sump to be picked up and distributed to the engine, not counting the volume of the oil filter..

It doesn;'t take much G force at all to push that tiny amount of oil to the side of the case away from the pick up, turning on the oil light, dropping pressure and introducing nothing but air to the oil pump and effectively the main bearings. Do that a few times and see how loud your rod bearings yell at you. (especially #4, it always hurts first)

Thanks for all the replies. I wanted to get into the pushrods next. Sorry I launched earlier by mistake- here's the whole story-

So for the pushrods, I needed to address two issues- my kit pushrods were obviously too short, but I also needed to continue my quest for lubrication to the head. So I looked again to the Corvair. The Corvair pushrod has two holes on one end- one on the tip and an additional .020" hole on the side. Since the pushrod rotates with the lifter, and goes up and down, that side hole sprays oil around like a lawn sprinkler. In the Corvair case, there are 6 of those sprinkler heads in each rocker box, and believe me, it moves a lot of oil to the rocker box.
Click to view attachmentKit pushrod and used Corvair pushrod.

Unfortunately, the Corvair pushrod seemed too long, and besides, the hole was too near the end- it was shrouded by the cup in the rocker that the pushrod seated into. So I looked for alternatives, including laser drilling a side hole in the hardened tip of a new pushrod, but I struck out.

Then I started thinking about length. With hydraulic lifters, when you adjust the screw, you are effectively changing the pushrod length. Think about it. If you screw the adjuster in, the valve doesn't open. No, the lifter plunger goes further into the lifter body and self-adjusts to that new position. In a solid lifter engine you get the same effect by shortening the pushrod. So how do I determine the "correct" pushrod length?

While I thought about that, I looked at the wear pattern on the tip of the adjuster screw. The tip has a spherically ground surface. With my short pushrods, this "skid mark" was skewed towards the edge nearest the rocker shaft, and the mark was very long. So the screw was sliding across the valve tip as it opened the valve, and then retreating as it closed the valve. Thinking about the geometry, I realized that the slide of the adjuster screw across the valve tip is minimized when the axis of the screw is perpendicular to a radius from the center of the rocker shaft, which is the pivot point.... A picture is worth a thousand words-
Click to view attachment
If you move the screw either in or out from this position, you move the tip further from the pivot centerline, and so its motion resulting from a fixed angular swing of the rocker increases.

To determine pushrod length, I started by setting the adjuster screw to this nominal position. I also made a tool- I took two Meyle lifters and assembled them with carefully cut lengths of pushrod tubing in the bottom, also filling the cavity with Gorilla glue. The tubing was cut to provide a pushrod seat height that is -.030" below the free length of a standard lifter. This gave me a "solid lifter" that emulated a 1 turn lash from zero- .030" x 1.3 (rocker ratio) = .040", which is extremely close to 1mm at the valve, which is 1 turn (10mm x 1 thread pitch).
Click to view attachment
Now I could put the modified lifters into the lifter bore, assemble with a test pushrod, turn the engine over 2 turns, and observe the valve geometry. Keep trying different length pushrods until it looked right at half lift, and I'm done.

The only trouble was, I was doing this with the engine in the car, and even though I managed to rig my dial indicator to find half lift, visualizing the screw axis being perpendicular to the valve stem was tough. I tried photographing it and then enlarging the photos, which actually worked, but it wasn't easy or precise- too visual.

So I tried taking advantage of the skid mark on the adjuster screw. I know that when my pushrods were too short, the mark was skewed off the edge, and that on my original screws on my original solid cam, they were nicely centered and short. So I tried coating the adjuster tip with blue dykem, carefully assembling the shaft, installing the assembled shaft onto the engine, and then turning the engine over my 2 turns. The movement of the screw across the valve stem tip left a very nice mark on the screw that I could "read" standing up in the comfort of my workshop.

Click to view attachment
This pushrod is too short. I could have improved this by turning the screw out, but I wanted to try and get close to perfect at 1 turn. That gives me +/- 1/2 turn to tweak to perfection.

So I tried a longer pushrod-
Click to view attachment
(I know this isn't the same one, but it illustrates the process. Also, this one is at the "nominal" screw position- see how short it is?)

I THINK THIS WOULD BE A GREAT WAY TO CHECK VALVE GEOMETRY ON A SOLID LIFTER ENGINE! (assuming you're using 10mm stock adjusters anyway) Just lash to spec, snug up the lock nuts, remove the rockers and shaft intact, clean, blue dykem, reinstall, turn over 2 turns, remove, and look at what you have.

Interestingly, to hold the adjuster screw to my "nominal" position, I had to shorten 6 of my rocker pedistals by .020". (Later I actually did the math, and learned that the amount of slide is very INSENSITIVE to the screw being off nominal. Oh well.)

MORE AMAZING- when I got through it all, turns out that the CORVAIR STANDARD LENGTH PUSHROD WAS PRECISELY THE CORRECT LENGTH ON MY 914!!!! It wasn't too long after all! I have nicely centered and short skid marks on my adjuster screws. Way different from the kit rods, which were about .200" too short-
Click to view attachmentIsky kit vs. Otto Parts Corvair.
The Otto Parts pushrod is now sold by Clark's Corvair Parts. This one is standard Corvair 10 7/32", but they are available in about .025" increments in about 10 lengths. Actual length required is greatly a function of your cam- base circle diameter as well as lift. With my Isky 229-hyd it happens to be the stock Corvair length.

The last piece of the puzzle was the oil hole. I decided to use the Corvair parts, and I solved the shrouding issue by grinding a relief in the rocker, being sure not to go near the polished part the pushrod seats into. The other big advantage of this approach- if I had found a way to redrill lower on the pushrod to clear the rocker cap, I would have buried it into the pushrod tube- even worse.
Click to view attachment
The pushrod isn't seated in the rocker in the photo, but you can see how I ground back the rocker to unshroud the oil hole. I got better as I went along! But notice that I only ground the half of the cap nearest the rocker shaft? I didn't want the oil to spray directly onto the valve cover gasket as the pushrod turns. Also, there isn't a straight shot with the VW valve scheme anyway, so I'm relying on filling the rocker boxes with an oil mist as much as spraying directly on any particular point.

So that's where I ended up with pushrods. There's a eplilog to the pushrod discussion though, but it'll wait for the rocker installment.

The .020" hole is actually less than you have with solid lifters and an annulus caused by .006" lash. I was trying to RECOVER this oil flow, which I lost by going to zero lash. It's not incremental.

Plus, in the next installment, you'll find out why I only ended up putting the Corvair pushrods on the two intake valves on each side. Also, keep in mind, this is a street car (hydraulic lifters, remember?), so you won't be revving it like the engines you guys build and drive.

One thing to consider is the fact that adding those oilers to the pushrods is going to drop the operating oil pressure within the lifter and oil pressure is what makes the hydro lifter function, so proceed with caution.

The .020" hole is actually less than you have with solid lifters and an annulus caused by .006" lash. I was trying to RECOVER this oil flow, which I lost by going to zero lash. It's not incremental.

Plus, in the next installment, you'll find out why I only ended up putting the Corvair pushrods on the two intake valves on each side. Also, keep in mind, this is a street car (hydraulic lifters, remember?), so you won't be revving it like the engines you guys build and drive.

That's a good point. But I don't think it'll drop below where is is for solid lifters, because that .020" hole (times 4 intake valves) is less "leakage" than 8 pushrods at .006" lash. Of course that's on paper, I know.

Also, my case is a '76 GC case without out the oil pressure regulator, though that only does anything above maybe 4500 RPM, I understand.

The lifters rely on oil pressure to fill them. When they rise up the ramp on the cam, the check valve closes and then the only way out is leakage around the plunger, which doesn't depend on engine oil pressure. I have noticed that I have to drive about 8 miles at 3000 RPM to get the lifters to fill from empty. Seems like too long, but I don't have other recent data points. I'd be smarter if I had a oil pressure gauge on the car so I can see what's going on.

Solid lifters do not rely on oil pressure to function, hydros do- huge difference.

What weight of oil and type (synthetic or non) is optimal for hydros?

Well, I'm still figuring this out as I go, but at this moment, I'm thinking that a 20W-50 is a good starting point.

If its too thin, it would leak down faster, which could affect timing at low RPM. For SBC, some companies actually make fast bleed lifters, which increase duration as RPM goes up. It's a questionable approach, because viscosity depends on both the oil and temperature so you aren't controlling the effect with precision.

If the oil's too thick, it would take a while to pump lifters back up after a cold start. When you shut down, whatever valves happen to be open will tend to collapse their lifters due to bleed down. I don't notice it after an overnight shutdown, but I do after a two-week shutdown. When you start up, there may be a tapping until they pump back up- usually a few seconds. If you were using straight 50W oil, that may take a minute or longer.

Also, because one of the original issues was potential for valves sticking due to inadequate lube, which then coked in the guide (aggravated by sodium cooled stems transferring heat to the guide), I'm running synthetic. Its a belt and suspenders approach- even though I'm trying to fix the lack of lube by careful attention at the lifter, pushrod, and rocker arms, I'm still taking advantage of synthetic's higher temperature capability.

So, I'm running Mobil 1 V-Twin 20W-50, which also has the higher zinc and phosphorus content. The zinc and phosphorus are important with hydros, as the lifter is always in contact with the cam lobe. In fact, the migration away from zinc and phophorus was coincident with the advent of roller cams, and some say was responsible for cam failures in the late 90s with flat tappet hydros- in all engines, not just T4. If you don't use an oil with high enough Zn and Ph content, add GM EOS or STP- there are articles that talk about how much to add, and it's been discussed on this forum as well.

The key with hydros though is to keep the oil CLEAN. I change oil and filter every fall, which is about 2000 miles. Use a quality filter- Purolator or Mobil 1. Grit in the check valve is what causes noisy lifters.

And I check it more frequently and keep it topped off. Even though I said I'm just getting back my oil flow to the head with the squirter holes in the pushrods, I have no way of knowing for sure, and I may be increasing the oil flow vs. solids. So I want to be sure I don't starve the pickup for oil. In no way am I overloading the pushrod tubes compared to the stock solid setup, though. That I'm sure of.

Jim

You need to change that oil every 3 months, even if it doesn't have 2K miles on it and thats because of the contaminants that it sees from sitting around, especially condensation....

20/50 is a good place to start for the oil, but not all 20/50 oils are created equally as we have been discussing recently.

Getting caught up in responses.... There was a lot of hydro "upgrading" going on the in the late 70's, which I think is related to tightening emissions. Namely, that self-adjustability helped keep the emissions down. This was about the same time as the mass migration to breakerless ignition. Auto manufacturers had to guarantee emissions for 50000 miles or something like that, which they couldn't do because they couldn't guarantee regular tuneups occured on schedule. Even the lowly Vega went hydraulic on its overhead cam.... and it was doomed to extinction by then.

My opinion is that having hydraulic adjustment improves emissions as well as performance over the operating envelope- engine temperature and air temperature- whether the valves have been adjusted recently or not. That, combined with more quiet running is why I have them in my engine. And I don't think I'm a lazy owner.

I will check my valve adjustment frequently, probably every 2 years (about 4000 miles for me). I'll check them by removing the rockers as an assembly, keeping the adjustment, and inspecting the bright wear marks on the tips. If they're centered and short, I'll reassemble without adjustment.

During my research, I also noted that although there were a LOT of competition cams available for the Corvair, all except one were hydraulic. The late Racer Brown had a whole line of Corvair cams, and he was quoted as saying that he believed the air cooled engine operated better with hydraulics because of the temperature variation. The one example of a solid lifter cam was Edelbrock. Interestingly enough, the Edelbrock kit included aluminum pushrods to help compensate for the temperature variations. (This is just an interesting data point, not meant to stir up controversy.)

Jim

I use 20W50 Castrol changed every few months with a Mobil-1 Filter. I've put almost 90,000 miles on this engine since putting it togetner around 1990 with a web-cam hydraulic camshaft and lifters, chevy pushrods, a high volume oil pump, and swivel feet rockers. It runs great, and the only times that the valve adjusters have required attention were when I did PR tube seals. But they are really difficult to adjust on the money. I think when I did address that it required three times over doing the complete process brfore I felt confident in the results. I'm waiting to learn more, Jim....

I have started to experiment with motors,and to have a better understanding of the type 4.interesting and good info.

james

Forget to reply to the Mercedes injectors- they're specced for a 1974 450SE. In theory, they flow the same as our 2.0 injectors, but they have the straight hose. I found a lot better availability and pricing options- take a look here-
http://www.partsamerica.com/ProductList.as...r=Fuel+Injector

I picked up the Niehof for $50 each brand new. Plus, the Niehof has updated design on the nozzles- similar to 1990's vintage GM.... it's a ball seat instead of a needle.
Click to view attachmentClick to view attachment
I have no idea if they're any good, but so far they're working fine on my 2.0L. I queried this forum and no one had any experience with them, so I'm trying them.
Jim

Thanks. I was wondering about that. Let us know how the Niehofs do over the long term.

I did some similar research regarding hydraulic lifter for Chevy v8 engines.

I found out that there are basically 2 or 3 companies that currently make all the lifters.

Here's a somewhat outdated chart. Some of those companies are gone, or been absorbed by other companies and renamed. For example, Johnson is now part of Topline/Hy-Lift.



My car had Johnsons. The picture of yours that you posted, with the metering disk with 4 holes in it, looks exactly like a Johnson made lifter, compare the internals. Here's a picture of the one that came out of my SBC. You can see where the problem in mine occured, the metering disk broke apart:




Compare with your picture:



This one, which you say may be made by Isky, probably is made by Johnson/topline/hy-lift. I doubt that Isky actually makes lifters. Companies like Isky, Comp Cams, etc. that sell lifters and cams, etc. don't usually actually make lifters, they buy from one of the big mfrs and relabel and sell as their own. They all obviously are not eager to talk about who makes what for who, but if you keep trying and are nice, you can eventually get them to admit it!

My opinion is that having hydraulic adjustment improves emissions as well as performance over the operating envelope- engine temperature and air temperature- whether the valves have been adjusted recently or not

I absolutely disagree with this statement in regard to our aircooled engines.

There's absolutely NO question about it. The Isky is a Johnson. Thanks for clearing that up. I was guessing Delphi (GM?) or Sealed Power (who may not make lifters either).

Why do you suppose that metering disk broke apart? It's basically flat steel under compression. It looks like it was pounded by too loose a valve adjustment.

Jim

I'll try and finish up my brain dump tonight. Left to go- rockers. Also, there is one big hole in all this, which I'll get into a bit as well, along with how I'm planning on checking valve adjustment and how often. Sorry this has dragged out so long.
Jim

OK, last installment. I know the lifter selection is very important to rocker oiling, and I've added a squirt hole (a la Corvair) at the top of the pushrods to make up for oil that isn't getting there through the valve clearance. I see no downside to either.

Now, how to get the oil to where it's needed- the valve stem tips and the guides? In SAE Paper 140C (Chevrolet Corvair engine) it is stated that the oiler holes were put in the pushrods because the pushrods enter the rocker box below the rockers and valves, and this was their means of getting the oil to go up north where it's needed. Some of this engineering team had transitioned from the original small block Chevy project, and were pretty familiar with its oiling, where the pushrods that enter from above give the oil a gravity assist.
Click to view attachment

Since Corvair rocker arms are Chevy ball and stud affairs, just like on the venerable SBC, there was lots of space between the rockers for the oil to spray, unlike the T4 which has that big old rocker shaft.

So this was my problem. These engines are engineered as systems, and you can't always swap one part from one system (pushrods, in this case) with the same part in another and expect it to do the same job it did in the original system (or engine). The Corvair pushrods definitely pump more oil to the heads than standard T4 pushrods (particularly at zero lash), but is it enough oil, and does enough get to where it's needed? I frankly don't know.


So that's what I was thinking when I looked at the T4 rockers. These rockers have oil passages going from the pushrod up to the shaft bore. The shaft has a relief that acts as a channel for the oil to flow around it and get picked up by another passage that goes out to the adjuster screw. There is a centrifugal pumping action up to the adjuster bore as the rocker rocks. Up at the adjuster screw, oil can seep between the threads and down to the tip of the adjuster to lube it. There is no additional relief between the threads, so oil is metered out by the normal clearance in the threads.

I'm getting my additional oil to the rocker box, but the side hole in the pushrod will lower the pressure at the tip, where the oil has to be pumped into the rocker to begin its journey to the valve stem. Thinking about this, I changed my tack and decided to install the Corvair pushrods ONLY for the intakes, NOT for the exhaust. My reasons-

1. intake guides are better lubed because of the higher and more steady vacuum on the port side.
2. intakes run cooler and can therefore probably run with less lubrication than exhausts without coking the oil and sticking the valve.
3. intakes are inboard in the head, so the spray from the side hole should cover much of the rocker box anyway
4. this keeps the oil pressure topped off on the exhaust rockers, leading to the adjuster screws, and the exhaust guides need the lube more than the intakes.

So this was my compromise and the hole I was talking about. I don't know if there is enough oil in the right place to do the job I set out to do, at lease not quantitatively. Back at Chevrolet in 1959, they had virtually unlimited engineering resources and test engines to figure this all out.

None of us have that, so we have to apply logic and try things that make sense. When I come up from the trees, I think I'm OK, mainly because I think the lubrication problem is marginal not major. Just being sure of the right lifter design may be all that's needed. Adding the side oil squirter on the intakes has no downside- it's still pumping less oil than the solids at .006" clearance. These squirters will fill the rocker area with an oil mist, I'm sure, that can only add more margin to the solution.

And finally, to add just a bit more, I opened up the clearance between the threads on the adjuster screws on the exhaust rockers only. I looked at lots of adusters-
Click to view attachment
I liked the idea of the internal oiling hole on the ball foot adjuster, but when I cut one open, I see that the ball will seat in the spherical chamber, and choke off much of the oil flow down the screw. Two on the right are where I experimented with adding relief for additional oiling. I filed an annular groove to distribute the oil around the screw body, and then flattened the threads with a file to increase the clearance between them and their female mates.

This is the idea, but in the final version, I didn't break the peaks of the threads nearly this much---
Click to view attachment
I ended up using 10mm brand new VW adjuster screws. At $12 each from VW, they cost almost as much as my lifters! At one time, I was thinking of using 911 elephant feet. I even bought a set of 8mm rockers. But I was afraid that with zero lash the valve tip wouldn't be exposed for adequate lube. So I went with the stock.

Anyway, as for adjustments- I got these very very close to perfect geometry at +1 turn from zero lash. This was done using the blue dye method I described earlier. Now I am driving it for a while. At probably 2000 miles, I will pull the rocker shafts, cylinder by cylinder, and look at the wear pattern on the adjuster screws. Even without the dye, it shows up as a bright line. If it's centered, I'll just put them back in as a set and go on to the next.

If it's skewed away from the shaft, I'll tighten it in 1/4 turn, set the lock nut, reinstall, and move on. If it's skewed outboard from the shaft, I'll loosen it 1/4 turn and so on.

The lesson learned here- WHEN YOU ADJUST THE VALVES ON A SOLID LIFTER ENGINE, YOU'RE SETTING THE CLEARANCE. ON A HYDRO YOU'RE SETTING THE VALVE GEOMETRY.

I can comfortably go another 1/4 turn (1/2 total in either direction from my 1 turn starting point). I'll keep a log, so I'll know if I went your first 1/4 turn already or not, and also so I can see if it's stabilizing or if something is changing- like a valve is sinking into the head.

I'm thinking it should stabilize after the first setting. Any further drift is more likely that I didn't get it right the first time. Once it's stabilized, I intend to go much longer time between checks- maybe 20000 miles? I don't know, I'll have to see what I see the first few times.

If your doing this on your engine, and you have no idea if your geometry is right, just pull the rocker shaft without disturbing the adjuster setting and examine the skid mark on the adjuster. If it's centered, your geometry is good. Reassemble and then check where it's set. Carefully unscrew exactly two full turns, then turn in until you get zero lash. Ideally it will be in about 1 turn. Then reset it to where it was and you're done. Log the setting. If it's not centered, then just set them at zero plus 1 turn, and drive it 1000-2000 miles and check again. If you can't get it centered and within 1/2 - 1.5 turns lash, your pushrods are too short or too long.... you take it from there...

So that's it. And how's it running? GREAT! It really sings! Starts instantly, idles smooth, pulls strong- especially from 4000-5000 RPM. When I stop at a light, I can actually hear the air being sucked in the air cleaner (stock). The Bursch exhaust is very much cleaner sounding than before. All in all, worth the effort. If anyone else already owns a hydro 914, or is thinking of maybe trying it, I hope this writeup gets you thinking about everything that is going on in there- it alway helps to know how something works before you get in and start changing it.

Hey

Man....serious good work here ! What do you do, 9-5?.

I had a brief encounter with a hydro 2.0l a long time ago, I remember wanting one then, and still wanting one now. The reliability issues of this swap seems to be addressed here. Only a long road test will conferm long term issues, but honestly, I can't punch any holes in your setup, and I've been changing cams for 25 years.


My vote to call this the "HYDROJIMSKY" setup.

Sorry if I missed it, but whats goin on in the spring area? Have you looked at roller rockers? I heard they are noisey...

Thanx for sharing
Later

thanks. I'm an ops manager at a national lab. We make things that get shot into space and bolted onto fast airplanes. Generally, we start with massive billets and machine everything from scratch. Lots of aluminum, magnesium, stainless steel and so on. Lots of inspiration around me.

I didn't do anything in the spring area. My objective was to maximize reliability with acceptable performance. Most people are looking to maximize performance with acceptable reliability. So springs and roller rockers I left alone.

Jim

Very cool and concise write up, thanks!

I have a 2 liter with hydraulic lifters & twin Webbers. It runs strong and the valves are quiet. I've been driving it for 3 years now as often as I can, with essentially no problems. I might not have done that myself, but that's the car I bought.

I recently stopped and talked with a mechanic in North Portland that specializes in air cooled VW engines and he said the same thing I've always read and always done; change the oil every three months or 3000 miles and it'll run a long time. I know that's not a particularly technical analysis, but I am very pleased with this engine configuration. For what that's worth.

Hah

I knew you were a hightec type of guy

I have never realy looked deep into the swap at this level but...pretty sure the hydrolifters run a completely different spring rate... and if your running unregulated oil preasure (modified oil releif), maybe just some food for thought...

Worst comes to worst...just shoot it into space...

Later

The engine oil pressure only ensures that the lifter fills with oil. It does not actually lift the valves. The pressurized oil is forced into the chamber below the plunger. When the lifter begins to ride up the cam lobe, it tries to collapse. This closes a check valve- either a ball or a disk- on the bottom of the plunger, which traps the oil in that chamber. The oil is not particularly compressible, so the lifter looks and acts like a solid lifter now as it rides up the cam lobe.

So, why would you need stronger springs? Stronger springs help keep the lifter in contact with the cam as the valve closes. especially at increasing RPM. There's a lot of inertia to move- valve, rocker, pushrod, plus lifter- and not much time to move it all. If all this mass can't keep up with the cam, the whole valve train becomes unloaded, and there's a risk that the lifter will self-adjust to a longer length. Then, when it finally crashes into the cam, it may have adjusted enough to hold the valve open. So there's about a 5500 RPM performance limitation on hydros. (Ron Iskenderian told me that I should be good for 6000, but I never exceed 5500.) Some SBC suppliers make claims of 7000 RPM but I'm skeptical.

As far as loading the heel of the cam during "normal" RPMs- The engine oil pressure acts on the plunger to keep a slight load on the valve train at all times. The diameter of the plunger in my Isky lifters (Johnson) is .670". That's an area of .3526 square inches. Thus, at 40 psi, the force on the heel of the cam is .3526 x 40 = 14.1 pounds. That's at 40 psi, at lower RPM it's proportionately lower. I assume the cam lobe is evenly hardened, and so the heel is as hard as the top, so I can't imagine wear of the heel ever being measureable compared to the wear at the top, where the forces are probably 10x that (I don't know, but it's the valve spring constant x the lift).

So in my view, you may be better off having an operational oil pressure relief (opens at 45-50 PSI I think) to unload the oil pump at high RPM and reduce the load on the engine. At any rate, having it there or not doesn't seem to make much difference conceptually to me in terms of whether your hydros are going to work or not.