Thread: My Compression test results are all over the shop

Originally Posted by mike 90 RR

That why i was thinking that the compression should be brought back to a lower level so it can be managed better, say 9:1 cause he was going for 12:1??? ... I spun out when I say that number .. cause the slightest fart and it would play havoc ... was my thoughts

Ohhhh well .. I'm always learning
Still .. I am amazed at "what can be done" with gas ... cause I was brought up on the notion that it was a less powerful fuel that has no real High Performance values ... my EYES have been opened up here

It has less BTU's than petrol, hence why it can never match economy litre for litre, but will sustain knock much better allowing for more compression and/or timing

If he went back to 9:1, then all the machineing was a waste of coin and it'll be slower again

If he just controlled timing correctly and finished the job properly, it wouldn;t be an issue, you can;t half ass a high compression engine build

Thanks for the replies guys.

In the weeks leading upto pulling the heads off I had it running rich as I was playing around with mixtures. So that is quite possibly why there is so much carbon buildup inside. That and yes... the valve guides are letting some oil in. When I run the engine under a lot of compression braking (say down a steep hill when off road) the engine will blow a bit of smoke for a little while afterwards until it clears.

Since the bores a glazed it is possibly that it could be sucking oil up past the rings too further contributing to the carbon buildup.

Anyway, at the end of the day I built this engine with my dad when I was 18. I have learnt a lot from this stunt and when I get onto another project engine I'll probably give the 12:1 CR another go on an LPG injection engine.

The repairs I did were not perfect. But my intention was to get the car back on the road and last say another 12-24 months.

We did do a bit of cleaning before putting it all back together though













I will play around with the timing. It is true that there is a fair amount locked away there. I'll probably try locking out the mechanical advance and see how that goes.

She will go for another 200000 ks now Seriously it will last heaps longer with out detonation. Its a good one for your 1st I'll vote yes to stick with CR you have on gas on the next one. (Strocker may be)

Alright alright, since you guys kept insisting:
Series III Stage 1 with a bit of a difference