upper timing chain broke UPDATE!

[sunnys14]

i finally had the time to swap a new exhaust cam and upper timing chain, since mine previously broke as i started the motor. this motor has NO miles on it and has a fresh rebuild of wiseco 9:1 pistons, toga main and rod bearings, cometic HG and arp head studs.

long story short, i was hoping i didnt bend any valves when my upper timing chain and exhaust cam broke from the sprocket. i just compression tested it with the new chain and cam as this is what i got

cyl #1 150psicyl #2 90psi (wtf?)cyl #3 150psicyl #4 150psi

i dont get how just #2 cyl would be low, and not some of the others. maybe compression is so low in that cylinder because of the rings not settling yet? any feedback would help!

[sunnys14]

also, i did a cold compression test and i also have lower comp pistons, thats why compression numbers are a bit low.

[Charlie240sxt]

pour alittle oil into the cyl see if the nuber comes up

[fiznat]

^^ Yup do that, and why didnt you pull the head off to check? With damage like yours I'd say that pulling the head was almost a necessity!

Did you find out what went wrong? ...Wouldnt want it to happen again...

[Iamjohnhayes]

leakage test might also be a good idea

[KATwo40]

Yeah, leakdown test is more telling than just compression test.

[Chezedik]

Yeah, but if you are getting low compression on only one cyl, and oil doesn't fix it, I would say you bent one.

[sunnys14]

i just compression tested it again... im gettin weird numbers. #1 dropped to 130ish and #2 went up to 110ish. whats goin on? weird stuff here... i decided to just pull the head anyways, i got a spare head but no time to get the head machined. anyone think i can just use some light sand paper to take off all the pieces of the old head gasket and bolt it back on?

[180sx]

HAHAH is ur psi gage ok? also is ur throtle open?

[Chezedik]

Depends on what kind of head gasket you will be using. I would just use a spray on gasket remover, use a known straight edge to check for trueness and slap it on, if you don't see any light.

[sunnys14]

im using a cometic MLS head gasket and ARP head studs. my compression tester gauge seems ok... hasnt failed me yet. i guess ill just use some gasket remover then.

[Chezedik]

NO! MLS are notorious for requiring ultra fine finishes, down to 9 na or less. Most surfacing machines can't do that well (learned that one from the AERA publication, Engine Builder). You will certainly not do it with a bit of paper. Just check a stock head for trueness and use it if it is true enough, I believe .004" is the limit, but check the FSM to be sure.

[emperor_lunchbox]

I believe its .003

[240sxinlv]

Sorry to thread jack...

sunnys14, do you still have the rear valances for sale?

Thanks!!!