Before building a whole new engine, why not take the heads off of this one and make the necessary measurements to determine the actual compression first-hand, and not based on what others have told you, and then proceeding from there? Seems like less work.

- Eric

 

did you try a 1 or 2 step colder plug like a r43s and retard the timin a few degrees

 

Just to clarify my statement above:

Three pages into the thread, we have almost no definite objective information on this problem yet.
We have not heard or felt your actual problem (not that I doubt you, but you are describing a fairly extreme and unusual problem, and it should be verified).
We have only your builder's word, from six years ago, as to what the compression was supposed to be.
We have only your builder's word, from six years ago, as to what the combustion chamber volumes were supposed to be.
We really don't know much else about this engine.

If you genuinely believe that you are having a detonation problem, and your engine builder completed the job six years ago, our usual advice of "bring it back to the builder" cannot apply. Therefore, your first step needs to be to gather objective facts, and the first facts you need to gather are combustion chamber volumes, piston-to-deck height, piston dish volume, and head gasket thickness.
Once you have these data, you can begin to be sure of whether your compression ratio has any role in your problem at all.

If this does appear to be a confirmed compression ratio problem, your next step will be to pull the engine and examine the main and rod bearings, because the amount of detonation that you describe, over a thousand miles of driving, may well have destroyed them.

I don't see any other way to go, myself.

- Eric

 

#8 heads would fix your issues if the low cylinder is valve related or the rings probably not just seated yet. Silly to blow up a motor you know what problem is, your money.

 

By the way, does the pinging go away if you retard the timing?
How about if you retard it massively (like 5°ATDC at idle)?

- Eric

 

Rings pretty much seat in the first half hour. This thing is 6 years old and has 1000 miles on it. IMO, if they have not seated, they aren't going to.

 

I wonder if the rings stuck from sitting so long? There has to be an explaination for that wide a variance in compression. I would do a wet test to compare. The really high compression cyl is a bit more puzzling.

 

If the rings were stuck, it'd smoke.

- Eric

 

It's only one cylinder that is low. Could be a compression ring and not the oil rings. No? I would agree it is far more likely to be in the valve train but he could confirm that with the wet test.

 

Jim there have been a few builds where rings didn't seat as they should, I realize modern rings, if you want to call those thick rings modern, are supposed to seat quickly. I would drain the oil and replace it will atf and run it a few times. Even slowly pouring a bit down the carb might help too. I know Shanghai used engine restore and it evened out/raised the compression on his 403 build done by J+S Machine.

 

I'm late to the party, and know very little about high power builds.
But if the engine has never run properly from day one, instead of running it to destruction with a face like a wet weekend while you drive it, take time out, pull the heads and do some measuring. The paperwork with the engine says it has given components, and some who know much more than me state that you need super octane fuel to run it as it is.
It could be something isn't as claimed, or you need thicker head gaskets or lower compression pistons.
But you won't find out until you do some dismantling.

Roger.