too much compression

[partytownsri]

i have put my sri ported and polished head on my gsi with a cam and it sounds like the pistons are slapping,if i put a 2mm spacer and a headgasket on would that help or is that not a good idea. any help would be appreciated
thanks mike

[Stuart]

measure the compression ratio first.. this will need the head off.

what exactly is the noise, when does it happen (under what conditions, warm, full throttle, low revs etc etc).

what else did you change on the engine?

[partytownsri]

well i put it together last night and started it up, let it get warm and sounded ok apart from it tapping which later went away but when i give it abit of revs it sounds like the little end knocking or piston slap, it has a 270 deg piper cam, a 4 branch and a power boost valve

[Adam]

Does it tap when revving in neutral, or just under load?

Was the GSI engine running fine before you fitted the head?

[partytownsri]

yes the engine was fine before i put the head on, theres no tapping from the cam or followers and ive not drove it while ive had the head on. mike

[craig0120]

what head is it?

[Adam]

Check the cambelt is timed up properly, it might be the valves clipping the pistons if the belts a tooth or two out.

[partytownsri]

its a c14se head and i made sure the timing marks were lined up.

[craig0120]

has the head been skimmed as there higher compression when fitted to the 16 anyway

[stuartp]

this sound like it could get expensive

[SRI crazy]

it might be that the cam is hitting the valves hard enough that the tapping noise is them closing on the seats

[SRI crazy]

shouldnt realli do that much harm

[Chris Astley]

With a 270 degree camshaft even if the head is excessivley skimmed it shouldnt touch the pistons if the cam is timed up correctly! Sounds like you will have to recheck the timing and if its ok the head may have to come of again!

Do you have a compression tester?

Chris

[SRlew]

what should it read on the compression tester?

[Chris Astley]

i used to get 220psi on my old 1.6 8v, standard they measure between 150-180

Chris

[partytownsri]

rallyman - did you do anything to your bottom end eg new rings at the moment i have got an astra bottom end with 52 000 miles on it, and did you have any problems with your bottom end eg knocking or piston slap cheers mike

[Chris Astley]

i used my engine fine without any problems/noises e.t.c. for 7 months, then i built another engine with no problems either!

The engine did have new rings, bearings e.t.c. but not new pistons.

Chris

[SRlew]

i used to get 220psi on my old 1.6 8v, standard they measure between 150-180

Chris

does it affect your engine running to much psi?

[Stuart]

a compression gauge will not tell you your compression ratio! it will merely tell you if youve got good bore seal, good valve seal, cold/hot air etc lol

[Chris Astley]

Did i say it would tell you your compression ratio???, your compression ratio is only theoretical anyway, your actual compression is tested with a compression tester, your actual compression is what counts at the end of the day! If you have low cylinder pressures hen the compression isnt to high!

Chris

[Stuart]

never said you could..... it was merely a statement for the masses so they didnt think that you get your compression test figures and divide that by the ambient pressure for the day to get an answer. jeeezuz chill out! you "motorsport" folks dont half get wound up at the slightest thing lol

[Chris Astley]

Sorry mate, wasnt having a go! i Sometimes forget people dont always understand everything that is said!:thumb:

Chris