I doubt that there will be anything earth shattering or even beyond common knowledge, but if only to document this project, here goes:
This is a big, first time project for me, an attorney and mechanic wannabe. My factory six with a 2.5L engine was missing. Turns out there was only 75% compression in #1 and it was leaking through the inlet valve. Auto Assets in Powell OH diagnosed and my friend and mechanic, Jay Kjoller confirmed. Thankfully, Jay, an experienced air cooled engine builder and racer who lives nearby agreed to take on the project and to let me help. I got the engine out and delivered it to Jay last week.
We started the disassembly yesterday.
Learned some things about the engine. It has an early aluminum case with Mahle 90mm pistons and Nikasil cylinders. Pretty sure they are 2.7L. It has a later 3-ribbed oil pump, which Jay says is sufficient for what I do.
The pistons have been lightened, which Jay said was unusual.
We expected to see something that would explain the problem with #1. Other than some carbon accumulation on the head where the valve closes there was nothing. But, having gone this far, we decided to go from top end rebuild to a full rebuild and we split the case.
Considerations. I think the engine was built into a 2.5 in the early 70's given SCCA classes at the time, but it is just a guess. My prior owner was Jim Chambers in Oregon. He bought the car in 2001 from Werks 2 in in Burbank CA, which was started a long ago by Harry Bieker (Bieker Engineering) and continued by his son, Galen Bieker. I exchanged emails with Galen but he couldn't remember any details that would help us decide how far to go on the rebuild. But Jay said whoever built it did a good job and he can recognize the approximate build date from the materials used, e.g., paper gaskets and 3 thin copper seals at the bottom of the cylinders. What I would call the wear points, (bearings, cam lobes, valve tappets, etc.) looked to be in good shape. But I wanted to be sure.
Jays says he has had good experience with something other than the existing E cam, a Solex cam? that is a little more aggressive. So, we are going to either source that or investigate grinding the E cam.
Friday, I will wash all the oily parts. Heads, valves, piston rods go to the machine shop, which is nearby. What can go into a hot bath tank will go there. What can be powder coated will go there. The air shroud, which is green, needs something. Not sure what to do about that.
Early aluminum case - score!
Are you running MFI or carbs?
I ask because I'm rebuilding a 2.2T carb motor right now and was considering trying to source a set of E cams for mine. If you're going to be regrinding anyway, would you consider a cam swap with some cash on my end? My T cams are in perfect shape.
The engine has Weber carbs. Let me see what the plan for the carbs is. Either way at my end, perhaps we can work a deal.
Looks like an interesting project. Good luck with it.
Konrad (fellow attorney and mechanic wannabe)
There's a lot more cam options today, than there was in the early 70's.
You'll have a good time putting this together!
Some additional HP sounds like its in your future.
Lot's of folks used the 2.7 CIS pistons and cylinders with the 66mm crank to get 2.5 liters. Unless the pistons were changed, this combination had a very low compression ratio (7.5/1). Hopefully yours has some higher compression pistons, but might be worth checking while it's apart.
Another attorney and wanna-be mechanic also rebuilding, this time a 2.7l. My engine guru says to use a solex cam for what will be a street car, not an auto crosser.
Knew Jay way back in the late 80's. He built my engine. I bought it from a fella named Yalman Balta. I'll bet Jay would remember him.
I think today's number is 40 hours but that doesn't take into account the 100+ hours for disassembly, cleaning, powder coating, sourcing parts, sending parts to the machine shop, etc.
I'd consider dumping the pistons, get the cylinders plated and put in a new set of JE 9.5CR pistons. Then match the cam to engine.
This would really wake the engine up.
Highly recommend the mod Solex cam (DC30). Peak power around 6200 rpm, pulls hard to 7200 and makes very gratifying torque from 2500 up. Not sure if they can be ground on E cams or not. With those, S ported heads and 9.5 JE pistons you would probably be making 200 - 210 hp.
That is a favorite combo of Henry Schmidt at
Supertech Performance. Check his build threads on Pelican. Great motor in a six !!
Turns out I was wrong. It is a 70.4 mm crank with 2.7L pistons and cylinders. Not the short stroker I thought it was. Perhaps someone was making a 2.7RS - like engine with a milder E cam.
Hey neighbor! Cool build. I didn't know people used CIS pistons for anything but CIS as someone stated. I like Mark's recommendations.
Jay recommends staying with the German Mahle pistons and I’ll stay with the crank we started with. Will change to the Solex cams however.
Distributor needs rebuilt. It is too sloppy. The heads, piston rods, case halves and new valve guides delivered to the machine shop. Engine tin headed to body guy for blasting and black power coating. I’ll have him weld patches for holes in tin. Also going to have him make the shroud look as good as possible in red. Powder coating alternator strap and air filter covers black. Jay is ordering bearings, fasteners, etc. can’t wait to begin putting it all together.
update on the build
got the engine tin and the engine shroud done, black and red, respectively and a big improvement.
after the Eric Shea/Jay Leno show, I started giving a twin spark ignition more thought. I was going to have to spend money to refurbish my OEM distributor and I was going to go to an optical trigger. more reliable, I think, but still a pain to get there being so close to the fire wall.
long story short, we are going to do a crank fire and twin spark. Jay has the jig to drill the hole. (Anyone have a suggestion as to who, east of the Mississippi can drill it?) I figure it will be reliable and easier to tune and it's what Jay has on his race car.
as for the cam, apparently there is one a little more aggressive than the Solex, an "S special" or something?, that Jay is going to look into.
can't wait to start the rebuild after the turn of the year
On the twin plug carbs with a trigger ignition here's a couple more options.
Megajolt Jr uses common Ford EDIS components that you have to source from a scrapyard. missing tooth trigger
SDS has an ignition only system, more money but it's new and more complete, IIRC it uses subaru coils. hall effect trigger
A bit spendy but this company has a missing tooth trigger wheel that come with their pulley
There's a few more of these type of systems on the market.
I believe you can also use Microsquirt now for 6 cylinder wasted spark control. It's a bit more expensive than Megajolt, but wouldn't require the super old EDIS components, or the specialized trigger of the SDS system. You'd just be running a few coils and basically whatever crank trigger you wanted.
A number of people on the Bird Board have been using Denso 90080-19016 COPs. They are relatively inexpensive on eBay and I believe have their own internal ignitors so you wouldn't need any coil drivers (**have to check my notes so this might not be 100% and they may need drivers**). Not the same look as the firewall mounted coils with long wires or 12 plug dizzy, but pretty clean/slick setup IMHO.
Just some more things to think about.
My uncle has a 2.5L in his '70 911, I was lucky enough to drive it a few times as a teenager. Man that is an awesome motor, so much instant power on demand. Got me hooked on flat sixes with webers.
Assuming mean the hole for twin plugs, I bet Craig can do the twin plug heads. CGAR over on the pelican forums. He does excellent work, easy to work with and very reasonable. He is in Wisconsin or Michigan.
As I am sure you know, these things run fine single plug up to about 9.5 CR. But if you want it you want it.
Probably not your cup of tea, but I saw a novel twin plug set up built by some guys running a 914-6 in vintage events here in Pittsburg. They run one distributor in the normal hole and a second distributor run off the E cam. Kinda cool but you gotta time two dizzy's.
It s really not hard setting the stock timing once you do it a few times.
I have the SDS system here, and the extra coil packs ar pretty easy. Can also do the machining if need be. Just take it into work.
BTW, If I was building a 2.7L std / std, I would go with a set of https://lnengineering.com/products/aircooled-cylinders-pistons/porsche-911-1965-77.html?p=3 if money no object. And that would get you to the 2.9L mark with better cooling and higher compression. For the cam, I have no idea as I am still debating that one, myself.
Since the OP is running carbs the MS box is another controller, just like in any other ignition only system.
But a debate on this is getting into hijack territory, if you want to argue this please start a new thread.
Another in agreement with the two above....I'm going the replated cyls with new higher CR pistons running single plug on pump gas.
Twin plug is cool looking for you'd nee more than 9.5:1 CR to make it worthwhile.
BUT those coil-on-plugs shown above are very interesting.
For now, I'm just going with my good carbs and dizzy (will check the curve to see if it's close enough to 2.7RS spec or send out for recurving) and running like that for a while. If I get flush with $ (haha) I'll do EFI and crank-fire ignition. But I figure doing changes in stages works well to not change too much at a time and feel if an upgrade is worth the $$.
I agree with the above.
no need to go to twin plug (and spend anywhere from 1k - 5k on ignition) without changing to a high compression piston.
Like Larmo, I have just installed single plug Clewett ignition on my 2.7 911 engine with Weber carbs and street cams, along with stock pistons and crank. Excellent outcome
But I'll raise you by 3.0
beautiful! now we're talking. almost too beautiful to put back in a car. mine should look about like that.
Brant and I are running TP dizzy's, Brant (like most) is doing it because certain race classes demand that you use a dizzy, I'm running it because a customer gave me a deal I couldn't refuse.
Don't get hung up on how beautiful the TP dizzy looks, because in a 914 you can't even see it, just a mess of snakes peeking out the top.
Like I said with TP you are going down the expensive slippery slope, you can make a very potent /6 with a single plug system at between 9 and 9.5CR. TP on it's own doesn't make a speck of HP, but it allows you up CR by at least a whole CR point, thus the HP gain of doing that.
A /6 engine is like a good recipe, there's a hundred different ingredients, but it only takes one bad ingredient to spoil the sauce.
Unlike a 911, you see mostly see the back of the engine in a 914.
I won't be running twin plugs in any engine builds...but I will definately will be watching this thread!
Making progress. Took the heads up to Craig Barrett in Grand Rapids MI who will be drilling twin spark holes. Then, yesterday, Jay Kjoller started the rebuild with yours truly lending a hand and trying to soak up as much of his extended knowledge as I can. Turns out that the casting mark says the case was cast in June, 1966. Put new bearings on the newly machined pistons rods. Then new bearings for the crankshaft. Jay is very deliberate and meticulous. It looked like medical surgery, very clean. Loctite flange sealer then the case halves mated. All new fasteners torqued to spec in 3 phases.
When we get the heads back, we will calculate the compression ratio. May do the JE pistons as posters here have suggested, depending on what we find. Going with a modified Solex cam.
Is that a small oil pump ?? 3 rib or sandcast ? any other 4 rib would have been better..
3-ribbed later oil pump
1966 did I read that right That is an early AL cases, that is like striking a gold vein in your basement. That case is worth $$$$$ if the numbers matchup. Great case to build off of also
Love this thread. But can we please rotate the images?
You need some 1966 chain cases from the 69s Eng. from #41 when I bought it?
I don’t understand the question
Spent the second day on the rebuild yesterday. Received the heads drilled for the second spark plug from Craig Garrett. He did a great job. Now, what is the current combustion ratio and do we need to buy higher compression ratio pistons to give effect to the twin spark? We suspect we will.
Here is what the heads look like. They were cast 7/73 for a 2.4L. They don't have a bevel where the flat edge meets the dome. Also, the 12mm spark plug is shrouded and that will adversely effect its exposure to the fuel/air mixture. Also, we measured the piston to head distance by having the piston at TDC smash a piece of solder and measuring its thickness. At .041 it is too close. All of this means another trip to the machine shop.
We next had to determine the swept volume and the combustion chamber volume to determine the combustion ratio.
The swept (cylindrical) volume is calculated knowing the stroke is 70.4 mm (7.04 cc) with a bore (diameter) of 90 mm, so r = 4.5 cc. Therefore = pi r squared stroke. = 3.1416 x 4.5 squared x 7.04 = 447.87 per cylinder, 2.687 total displacement. A good check to prove that the compression ratio calculation, next, will yield a reasonably accurate number.
The volume of the combustion chamber is measured empirically using a burette with a mixture of motorcycle strut oil and mineral spirits, The spark plug hole has to be at the very top for the liquid volume to be accurate
We measured (doing the procedure twice) 60.0 cc of fluid to the top of the spark plug hole, less 2.2 mL for the spark plug hole = 57.8 cc.
The compression ration, then, is v1 + v2 divided by v1 = 57.8 plus 447.87 divided by 57.8 = 8.75 combustion ratio.
Too low. JE pistons, 10.5 to 10.9, are on order and the heads are at the machine shop.
Attaching pistons, compressing rings, installing valves and valve springs, all necessary for what we did are a joy.
A post script. Getting to know Jay Kjoller is a joy too. He built his race car, including the engine, and drove it in the Daytona 24 hour race. Finished 17th overall and 4th in class as a rookie in 1981. He builds 'em and races 'em. I am very lucky to be able to watch, assist and learn.
What exactly are you measuring using the solder method? It seems to be head to piston clearance (that is usually what the solder method is used for). On one hand, you said it was too close, on the other you said compression was too low. These are contradictory.
Not trying to nit pick. Not questioning the competency of you or Jay, your builder. Just trying to understand so that you don't do some unnecessary machining (I doubt Craig would let that happen).
Have you checked and set deck height? This is generally adjusted by barrel shims that also affect piston to cylinder clearance.
There is so much at play here that there is a lot of room for confusion so sorry for the butt in, just trying to be helpful.
Powered by Invision Power Board (http://www.invisionboard.com)
© Invision Power Services (http://www.invisionpower.com)