Bend pushrod on #4 intake

[zeroaxe]

Originally Posted by Moog

I would say those readings are OK as far as making sure the pistons are not going to tap the heads while revving, BUT...

Variation from piston 1 to 2 is quite a bit - why is this? Is it piston variation, or are the cylinders sitting at different heights. Both cylinders on each side must be perfectly matched in order that the head sits square - if not then it sits askew and you blow out of one side of each chamber - as at least one of the heads seems to be blowing on one side of each cylinder only, maybe this is part of the problem?

Moog, I get what you are saying. I am going to torque down the cylinders and re-measure, at least once to see if I get the same reading/s. I suspect that the head is not sitting straight. There is too much evidence to ignore the facts.

Originally Posted by Moog

With these deck height readings what does the compression ratio work out at - have you cc'd the combustion chambers to work it out?

Ok, so I just CC'ed the heads today. And what a surprise. I must eat *some* of my words. This guy actually had a good eye for machining those heads. Here are the readings:

48,48,48,49cc !! The 49cc reading is on the head where the valve hit the piston(#3). But this doesnt make sense to me. If it was machined 49cc, that means he took 'too little' off. And the piston doesnt come up that high compared to #4. So I dont get that, that should be the problem. Or am I missing something obvious?

According to this site's calculator I calculated the compression ratios per cylinder as follows:
#1 - 1.26mmDH 48cc = 8.9CR
#2 - 1.5mmDH 48cc = 8.69CR
#3 - 1.26mmDH 49cc = 8.76CR
#4 - 1.22mmDH 48cc = 8.93CR
They are all over the place!

Originally Posted by Moog

Of course, there is still the possible issue of coil bind, and at least one valve tapping a piston - put some thin layer of plasticene / blu-tack on each piston crown, do a dry build, turn the engine over by hand, then take it apart to see the marks the valves leave in it - slice it carefully and you can measure how close the valve is getting to the piston crown.

Hope this helps...

Moog

After rechecking deck height, I am going to clean the piston crowns and do the blu-tack thing. following that with the coil bind check.

I also want to ask... Under the rocker shaft, do I need some kind of washer/spacer? I have been told just to assemble it with the little rubber ring/washer underneath to prefer an oil leak