Thanks for the linky - I hope it helps me overcome my disdain for the things.

This is exactly the way to do it. Stretched them about 3/4 to 1" then twist/rotate it in to place till it is tight and a long pic or thin screwdriver to slowly work it in. I wouldn't call it easy, but it wasn't bad.

So I imagine that your earlier measurements/assumptions were off? In an earlier post you said "Plugging bore (96mm), stroke (71mm), deck height (.039) and chamber volume (55.2) into the CB Perf. engine calculator it yields a CR of 9.3 - 1. Is that too much?"

If those number were correct, removing material from the jug will INCREASE your CR not reduce it. If you wanted to go from 9.3 to 9.1 you should have added to the cyl height with a spacer under the jug thus increasing cyl height not reducing. In other words when you reduce height you reduce the chamber size with same bore and stroke, this increases CR. Unless your initial measurements were off or you are doing new math. Either way its your engine man, do what you want.

Nope, my earlier measurements/assumptions were spot on. There is a 1mm step in the head which essentially adds to the deck height, and I was not including that in my original measurement (my posts actually describe this in great detail - maybe you could read more carefully).

I have now removed .72mm from the top of each jug and have re-measured deck height. Deck height in the jug is .33mm. Add that to the 1mm in the head for a total deck height of 1.33mm. Plug the numbers into the calculator and it returns CR of 9.00:1

Exactly what I was looking for. Not new math and yes - it is my engine and I shall proceed as I see fit. Thanks for your help...

Just seems odd that the entire 914 world has to add shims to get their CR set and you are having to build a special jig to remove material from the tops of the cylinders. Did you ask Len about the step in the head? I looked at the photos and can't tell if the step is a recess or if it is proud of the combustion chamber. If it's proud of the head then I guess I can see why you are doing what you are doing. Why do the heads have a step are they some kind of ultra low compression bus heads or something?

I still find this conclusion suspicious.
I had my heads machined significantly and barely made it to 55 cc without the 1mm step.
If the step is designed to add to deck height, then it is not obvious if the 1mm contributes to combustion chamber volume OR deck height.

I fear that you might be double booking that value in your calculations.
The only way to be sure is to measure them yourself or call Len and ask.

If you measured the comb chamber volume with the clear acrylic disk sitting on top of the 1mm lip vs sitting down flush with the comb chamber, you would get a difference of 2.3 CC

There has to be a simple answer to: "WHY is there a 1mm step in the heads?"
I have never seen or heard of that as that is an automatic deck height of .039 assuming that the pistons are flush with the top of the cylinders.
Maybe that step is for pistons with a non standard wrist pin height?

I agree it seems odd that I am seemingly the only guy on the planet (in the "world") to go down this road.

Len is the individual that informed me of the 1mm "step" in the heads. It is proud of the roof of the combustion chamber proper. I don't know if the heads are anything other than "standard" RS spec heads from HAM.

Len has weighed in on my build a few times by PM, which leads me to believe he is reading this thread occasionally. The fact that he has not weighed in negatively with respect to the removal of material from the jugs leads me to believe I am OK.

I test fit everything yesterday (a few times) and I measured .33mm (1/3 of a turn) of deck height in the jug with my calibrated screw/plate measuring device. The measurement is very repeatable, and is very (very) nearly identical across all cylinders.

The heads bolt up, with a small gap between bottom of head and top fin of the jug (no gasket at base of jug, or in the head). I did not measure this gap (yet) but since there is space there with everything torqued to spec, I believe I am OK.

The heads are brand new from HAM and the spec sheet that came with them (hand written - probably by Len) indicates that specific combustion chamber volume. I have not CC'd them myself as I (still) trust Len's number much more than I would mine. Len has communicated this 1mm step to my via PM, and he indicated I needed to add it to my overall deck height. I believe his words to me were "you'll have plenty of room". I choose to believe the guy.

I guess we'd need Len to weigh in on the reason for the 1MM step. It is there, I can see it and I even measured it (it is 1mm). I'll try to snap a picture of it today.

Thanks for the thoughts Stugray.

The mysterious 1mm "step" really does exist folks, pic below...

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Combustion chamber volume as measured by HAM...

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You would think that if Len saw this thread he would chime in. There must be some kind of explanation. Hopefully you aren't subtracting for a step that has already been subtracted.

I would probably mock up a pair of lifters, push rods and rockers and do the clay test to verify that you aren't going to have valves getting too close to pistons.

I have reached out to Len, and yes - I do intend to clay the heads. I will manufacture an adjustable pushrod this week such that I can use the exact ball ends that came with my pushrods.

The initial reasons we started putting a step in the new heads over 15 years ago was for head strength, and to simulate the thickness of the factory head gasket, which is ~.75mm.

Of course back in the '70's VW issued a bulletin calling for the removal of the head gasket, and restoring the lost deck ht by putting a spacer under the jugs. The 1mm step eliminates the spacer compensation requirement.

Over time we grew the step from .75mm to 1mm for a couple of reasons: it's a safe deck ht spec, and since most (every one I've ever seen, and I've decked over a hundred of them) cases need the spigots decked to correct sagging and warpage the increased step ht allows the cases to be decked to either allow zero deck in the jugs, or to at least compensate for the lost deck ht from a minimal spigot decking, which is generally in the ball park of .005", though bus cases can be quite bad and I've had to deck some of them as much .5mm to correct the sag/warpage.

I have no idea why Steve had so much deck in his jugs, but having decked as many cases as I have I know that these things do vary quite a bit, and I have seen some that were way off from typical factory specs. It happens.

The question is whether he should have used the 62.2 cc figure that you provided or whether he should have subtracted for the step and used 55.2 as his combustion chamber size. I vaguely remember that when you did my heads 9 years ago they came back with a step but I used the cc number that you calculated. It seems like if he subtracts for the step the compression ratio is going to be calculated wrong.

Assume the 62.2 chamber volume is inclusive of the 1.01 mm step (not an unreasonable assumption). Assume also flat top pistons.

Swept volume is 514.12 cc

Chamber vol is 62.2 cc minus 0.72x48x48x pi equals minus 5.2 cc yield chamber vol 57.0 cc

Add stated 0.039" (1 mm) deck height equals 7.2 cc

Total volume at bdc equals 514.12+ 57.0 + 7.2 = 578.32 cc

vol at tdc equals 57.0 + 7.2 = 64.2

Static cr = 578.32 / 64.2 = 9.008.

That's my maths anyway.

Looks spot on. Subject to the initial two assumptions

Dave

If you read the yellow spec sheet, which we prepare with every pair of our new heads, you'll see the following:
Chamber volume = 55.2cc's
1mm Step volume = 7.0cc's.
Total head related volume = 62.2cc's
Add 62.2cc's to the volume in the jugs @ TDC and you have total unswept volume.

Seems pretty straight forward to me, but if you guys have a suggestion of how to make this any clearer, I'm all ears.

Dave090s4's calcs are correct.

They match mine:
96mm X 71mm swept volume:
48X48X3.14159 X 71 = 513,914 / 1000 = 513.914cc

Head comb chamber (including 1mm step) = 62.2cc
Volume of step = 48X48X3.14159 X1 = 7.2cc
Comb chamber (minus step) = 62.2 – 7.2 = 55cc
Measured deck height before trim = 1mm
Cyl. Deck height after trimming of .72mm = 1.0 - .72 = .28mm
Deck height = 1mm (in head) + .28mm (in cyl) = 1.28 mm
Deck height volume = 48X48X3.14159 X 1.28 = 9.26 cc

Total volume = Swept volume + deck height volume + comb chamber volume
TV = 513.914 + 9.26 + 55 = 578.174
Compressed volume = deck height volume + comb chamber volume
CV = 64.26
CR = Total Volume / Compressed volume
CR = 578.174 / 64.26 = 8.997


So I think the answer is: this works just fine.
However if the OP had ordered the heads without the 1mm step, he could have shimmed the cyls UP to reach target CR instead of machining the cyls DOWN.

That is exactly how mine is setup, but I had heads with 56cc comb vol (no step), cyls shimmed for a total deck of .89mm for a final CR of 9.2.
My spigots HAD been decked so my cyl only deck was less than 1mm to start with.
If I had wanted to adjust down to CR = 9.0, I would only have had to add more shims.

Y'all are killing me. I think we are in violent agreement that my CR is very nearly 9.0:1?

Seems that way!!

Maybe revised spec wording along the lines "Total combustion chamber volume per chamber is 62.2 cc. This volume is measured from the cylinder head compression mating surface so includes the volume created by the 1.00 mm lip."

Just a suggestion.

DaveO

I even agreed a while back that it seemed right
At least all of my confusion/interest has been due to the trimming of the cylinders and the existence of that lip.

Sdoolin's method will work out fine, its just somewhat non-standard (unorthodox? :-).

Almost, but not quite, entirely Un-like tea?
It's all the same until he needs a replacement cylinder .... or head.

Waiting for some more parts to come in and waiting for my buddie's lathe to become available to manufacture an adjustable pushrod. Can't bring myself to bolt the heads on until I have the adj. pushrod in hand - they are just to pretty...

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So many parts still to go...

Dual Dells need to be completely gone through (and I purchased a second set) - I am comfortable rebuilding them - done it plenty with my old bus. Still need to find a dizzy and all engine tin and fan housing still being prepped for paint and/or powder coat.

I munged up (slightly) one exhaust manifold stud whilst installing into head. Really (really) pisses me off.

LOL, I feel your pain......... I am little better than an assembly monkey, and all the fancy pants math makes me head hurt....

You can check your attitude.... My only weighing in was my concern over the issue of how reducing deck height would increase your CR, but I'm just an Army grunt.... Looking at my HAM remanufactured heads (as in the original heads being remanufactured) I dont see the step.

In my 2056 build I used the HAM Remanufactured Stock Heads, Stock Crank, Stock Con Rods, 96mm Keith Black Pistons and EMW Jugs with a .060 spacer to get an 8.6 +/- CR. Why did I use a .060 spacer? Jorge at EMW recommended it No science involved. My goal was to stay as stock as possible and when I set up the pushrods, came out with measurements within .001 to stock pushrods, so I am guessing my deck height at least as it relates to valve train was pretty close to stock.

I'd hate to see you with a super high CR or to have unauthorized valve/position contact.....

This has been a great learning experience.

I have:
~9.2 CR
heads that were cut to give me a 56cc comb chamber
.035 Deck Height
~.500 Valve lift with stock valve sizes

And I have sufficient room to avoid valves hitting pistons.

he should be fine, but the clay test is in his plans to be sure.

Completed machine work on 1.7 rockers last night. Set the lathe up with a single rocker shaft and its mounts so that I could more or leass assembly line this procedure. Take material off, remove rocker, leave shaft in the "erector set jig", slide another rocker on shaft, repeat.

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Now - strangely I seem to have misplaced a single rocker shaft mount. This stuff has been bouncing around my garage and barn for like 20 years. So now on a search for a single item in order to bolt up the rockers...

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with all of the jigs and measuring capability you have, is there any way for you to measure the rocker ratio?

Good question, I'm not sure how to approach that? Amount of movement on the pushrod side of the rocker vs amount of movement on the valve side?

Not to highjack my own thread - but shouldn't rocker arm ratio for these rockers be known (I haven't googled it yet)? They are like 40 years old (probably older) and I'd think the spec would be published somewhere.

While I had not intended to measure this - in fact it never crossed my mind (ever), now I continue to mull it over...

Adjustable pushrod finally complete. It isn't pretty, but I believe it will work. Used a scrap piece of chromoly tubing with same OD as pushrods from T IV Store (Manton), squared up the ends on the lathe, welded in a nut on one side and a bolt on the other and off we go. Happily the ball ends are the _exact_ same ones that will go in the finished engine and my reading indicates that to be important.

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So in the picture we have all of the stuff I had to fabricate for this build (so far). The adjustable pushrod, the deck height measuring apparatus, and the much maligned fixture to deck the jugs. I put a high polish on the jug fixture since I am the only guy in the world to ever have to go down this road and I figure it'll never get used again. But - it will live proudly on a shelf in my shop.

Don't tell my lovely wife about the white faced gauges please...

What gauges? I'm eying that Whiskey Sour........ Or in my case Irish Mist/Drambuie & Lemon

Great looking shop and machining capability you have. Looking forward to seeing your project come together.

As the younger crowd says these days - "epic fail".

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Maybe I need less valve spring for this operation?

I really (really) wish Type IV Store would sell me their re-engineered adjustable pushrod (from Manton) that uses the exact same ball ends that they supply with their pushrods (again from Manton). This item is "with Jake's engine builder" for evaluation currently. Hopefully he will bless it (soon) and I can move on...

I cant help with your calculations but I can say Im quite amused with your attention to detail. Shold be a fun runner when you finish

I'm thinking I remember Len Hoffman saying that you should use the lighter valve springs to do the valve geometry measurements.....if your heads have the double springs. Since my RS+ heads just had the single spring, I didn't worry about it.
Perhaps Len will chime in here, or someone else with more knowledge than I!

Been following this one and what the OP is doing is a full blueprint motor,reason that Jake and others charge what they do,all about going past basic specs and doing it right,differance between average and top spec.

For my first iteration of checking my valve geometry I used some "surrogate" springs that I found at Ace that fit, but had far less strength than even my single spring setup.

If you cant solve your problem with the adjustable pushrod, I might consider loaning you mine.

I use full valve spring pressure. But I tapped the pushrod tube directly, so I'm using a thicker stud in between the rod halves.

Since the adjustable pushrod a manufactured was a failure, I thought I'd order one from Manton. Seemed easy enough, but you can see that what they sent me is not useful for a type IV build. This is becoming infuriating. I'll try aircooled.net next...

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OK so I couldn't take it any longer and I thought I'd give this Manton adj. pushrod a shot. Can't really use the locking nut on it due to its location, but I think I got it to work. Pics of my setup, (and as is the norm now my pics are rotated by 914world to ensure confusion of reader)...

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I used a piece of angle and drilled it to fit the rocker shaft studs. It is mounted very securely and the dial indicator is affixed to that. I ensured that the dial indicator returns to zero (the same zero) after turning the engine and even just from jiggling the engine stand. It is quite solid.

Some math (I'm not a math teacher but I did go to engineering school - but please feel free to double check my numbers if you are hugely bored):

Advertised cam lift = .435"
5% of advertised lift (.435 *.05) = .0218" (rounded to .022 below)
Max measured lift can be .435+.022 = .457"
Min measured lift can be .435-.022 = .413"

I managed to get a measured lift of 11.55mm = .454" after just a few adjustments to the pushrod. That number is very repeatable and is just under max measured lift value from above. So it seems I got this right?

This is all on the intake valve on #1.

With that measured lift, and with one spacer under the rocker shaft mounts (not measured yet), I get the following geometry at half measured lift (again pic rotated by 914world for some inane reason):

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That geometry looks pretty good to me. I think I could get the adjuster only slightly better lined up with the valve, but I would lose some lift. A very - very small amount of lift.

Wondering if I should do this measurement and setup for all valves individually? Would love someone that has actually been down this road to chime in if possible.

I checked each one so I could measure for each rod and cut them to exact length individually.

I think I am going to do the same.

I measured them all and found the average and cut them all to that length.
I didnt want to have to keep rods with certain valves.

And regarding the rocker ratio: If you know the cam lobe lift and now measure the valve lift, you can calculate the ratio.
If you felt like measuring it now, measure how much vertical motion you have on the pushrod with a second dial indicator while measuring the valve lift:



I used a tiny clamp on the pushrod

When I did this the first time I was given the lift at the cam and had to determine that the valve lift was within the 5% of predicted, but then you need to know the rocker ratio to at least two decimal places....

So while I am waiting on my 12" Vernier Calipers to arrive (so's I can accurately measure for pushrod length) I decided to go all creative on the oil fill tube block off plate with some custom engraving...

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This engine is officially "one of one".

I've gone over the top again. I didn't like the way the swivel foot adjusters were lining up on the valve stems. First pic shows how the #1 intake swivel foot is not even covering the entire valve stem...

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Pretty much all of the valves were like this, with the intakes being farther "off" than the exhausts. Back to the lathe to make each of the rocker shaft clamps slightly oval allowing them to move the rocker(s) over on the shaft...

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Each clamp was cut in the neighborhood of .5mm, one set was cut .75mm. This got the swivel foot adjusters nicely aligned with the valve stems (picture in next post). Note they are still slightly off center which may allow for the swivel foot to spin the valve, but I'm not sure that spinning the valve even happens with the swivel foot adjusters?

After the clamps were "ovaled"...

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Isn't that mis alignment there so that the valve is actually rotated over time as it is being opened?

Yes I believe that is the reason for the "mis-alignment", and why I left them somewhat mis-aligned. Though I don't see how the swivel foot adjuster is going to be successful rotating the valve. Maybe it does, I just don't know...

Yes the off set of the rocker is by design not a manufacturing error.

The rocker pushing off center causes the valve to rotate slightly each time it is opened, this helps keep the valve and valve seat clean.

Jim

Life has gotten in the way of this project for a few weeks, traveling for work and all. I believe I have finally arrived at a happy place with respect to pushrod length.

Cyl IN Lift EX Lift
1 0.449 0.427
2 0.451 0.426
3 0.452 0.416
4 0.450 0.423

Note 1: All with thickest rocker shaft spacer
Note 2: All with 10.754" pushrod

All of those lift numbers are within the +- 5% range suggested by Raby. Also all adjusters nicely aligned with the valve stem at half of measured lift. I still plan to measure valve - piston clearance before final assembly.

It does seem like the swivel foot adjusters may contact the valve covers, I still need to measure that.

Clayed the heads this weekend to ensure no piston/cylinder contact. Looks like I will be fine. Measures right around 2mm...

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How about with the valves opening? Or am I jumping ahead too far?

--DD