Compression issues

Hi

I have had quite some problems getting my Octane to run, and in the end it has turned out to be compression issues. New piston and sleeve seemed to make a change, for a short while. I cant really see any issues with the piston, piston ring, and sleeve, that should cause these problems however.
And then today it struck me, it can of course be many other things causing compression issues. Made me wonder if surfacing the head could be a possibility/option.

Any thoughts on that?

I have put mine away. After 4 gallons the chassis needs some work and I was never able to get it to consistently run well enough to spend more money on it.
As for surfacing the head if you have the capability I would try it. At least enough to true the mating surfaces. It it is leaking compression there you should see signs of blowby on the gasket, head ,case. It could be the plug threads too.
Do you have anyway to tell if the sleeve it true in the case and the clamping surfaces are parallel?

I haven't seen any blowby on the head, and my thought was rather to surface it to increase compression, rather than securing the seal. I have however at some points seen blowby at the sparkplug. So good point there! Will keep an eye out for that. But then again, when I measured the compression, it was tight and the compression was low.

I read somewhere someone mentioned crank-case compression, which is needed to transfer the fuel-air mix from the crank case into the combustion chamber, and that this may fail due to poor crank case sealings, so that could be something to check out as well.

Then there's a valve between the carb and the crank-case, to prevent the fuel-air mix to blow back into the carb. And I am quite certain that I at some point noticed blow-back, so that is the thing I willl check first for sure. Shouldn't be any blow back throgh the carb, I guess.

I found an interesting article on piston ring gaps.

Haven't measured mine, but from a simple visual inspection, the gap is huge. I have noticed som scratch marks on the inside of the sleeve, and thought these might be causing loss of compression resulting in the engine not running. But having noticed the size of the piston ring gap, the scratches really cannot have any impact what so ever.

So the question then is, what is a correct gap size for this engine.

Looking at rules of thumb for piston ring gaps, the gap on this engine ought to be 0,10 - 0,15 mm. I'd say mine is atleast twice that.

http://www.badasscars.com/index.cfm/page/ptype=product/product_id=393/prd393.htm

seems to me

Nitroblock to gasserblock.....BIG FAIL
just like
Oldsmobile 350 to 6.2L diesel....EPIC FAIL

lol

F-Type said:

I found an interesting article on piston ring gaps.

Haven't measured mine, but from a simple visual inspection, the gap is huge. I have noticed som scratch marks on the inside of the sleeve, and thought these might be causing loss of compression resulting in the engine not running. But having noticed the size of the piston ring gap, the scratches really cannot have any impact what so ever.

So the question then is, what is a correct gap size for this engine.

Looking at rules of thumb for piston ring gaps, the gap on this engine ought to be 0,10 - 0,15 mm. I'd say mine is atleast twice that.

http://www.badasscars.com/index.cfm/page/ptype=product/product_id=393/prd393.htm

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too young to remeber those days in the eighties when general motors come up with the stupid idea to convert an oldmobile gas engine to deisel and rebrand it a 6.2L? it was a fail by epic standards. most of them were junk.
seems this converting a nitro engine to gas is a fail by all that i read also

Here's a small and simple test I made. There's clearly some blowback, question is if that's normal or how it may affect how the engine runs.