Hi all, getting ready to put my engine back together. It's a 1911 (1.7 with 96mm P's andC's)

Just finished measuring the combustion chamber volume of my heads and I'm getting 52.5cc +/-0.5 each. Deck height is .055 inches with no spacers. Plugged all my values into one of the online calculators and I would be getting 8.6/1 compression with no spacers.

I do have a set of .020 spacers new in their packages, if I used those I'd be dropping the C/R down to 8.2/1. And I also have a set of .040 spacers which would give me 7.8/1.

I'm going to be running Weber IDF 40's, no headgaskets.

Any opinions or guidance?

I did all I could to raise my CR.
Try to get the deck height down to .035.

I had my heads shaved a bit to reduce Comb chamber volume and didnt get as low as you are saying you already have. Are you sure of your comb chamber volume?

52 seems low for an unmodified head.
I ran a DH of ~.035, no head gaskets, comb chamber vol of 54 cc (down from 59), flat top pistons

The heads were gone through and rebuilt by the previous owner, then they sat unused for an unknown period of time. Previous owner wasn't sure what exactly was done to them it had been so long. They look minty though. I say all that to imply that there is a strong possibility that the heads have had machine work done.

To measure the volume i cut a disc of .25 thick clear plastic. Just the size to fit in. The edge, where the cylinder would mate, recieved a thin layer of grease. The disc has two holes, one for injection and one for air release. I used a 10ml (10cc) syringe with markings every 1/10cc. Only strange thing is that the plug I used was one I had just laying around, it did protrude into the chamber the correct amount, but its a dual electrode style. I will measure again though.

I'm also running flat top pistons, but of course that has no bearing on the head volume

18:1, add a turbo and run diesel.

No guidance here on selecting your final CR, just some observations.

52.5cc's sounds like 1.8 chamber volumes.

Stock 1.7 chambers are generally 49.5-50.5cc's stock.

Cam selection, altitude, and performance goals should influence your target CR

So a stock 2.0L head has 60cc Comb chamber volume?

Euro 2.0L 914 engines were 8.6:1. Leave it there.

What are you running for cam, etc.?
If stock cam i'd agree with a stockish CR.

Most un-cut 2.0 914 heads are in the 58-58.5cc range.

But like all T4 models most heads have been cut at some point, having been through some shops hands during their lifetime.

The cam is an unknown. The previous owner said that the cam and distributor were swapped out when the carbs were added, but the actual work was done by the guy that had it before him, many years ago. So info from him is not reliable.

One thing I do know is that the cam has rivets, which makes me think it's stock.



Cap'n Krusty said in this thread http://www.914world.com/bbs2/index.php?sho...mshaft++stamped that if there are numbers stamped on the end, that it's most likely an aftermarket grind. Which gives me hope.

One last bump to see if anyone can identify the cam. But as it sits I'll be moving forward with 8.6/1 CR after I measure a second time to verify what I have.

Who knows on the cam, back in the day many machine shops had cam grinders, 99.8% just used them to regrind stock cams and copy known profiles.

That looks to me as a stock cam.

Here is my webcam with the numbers stamped on and the bolts.
https://goo.gl/photos/bUqpVWZkhUwnAFhX8