maybe found the compression loss?Dee, Float, R34?

[ca18det240hatch]

I was having problems with compression after my build as you know. Ive been told that because i machined the head, but not the deck surface of the block, and using a metal headgasket, it may be leaking. does this sound likely? Theres no coolant in my oil or vice versa, and i dont have any blowby, which is wierd for compression that low.

ideas?

[boost_boy]

I was having problems with compression after my build as you know. Ive been told that because i machined the head, but not the deck surface of the block, and using a metal headgasket, it may be leaking. does this sound likely? Theres no coolant in my oil or vice versa, and i dont have any blowby, which is wierd for compression that low.

ideas?

I can understand coolant and even oil, but the only way your combustion is losing compression via the headgasket is if you did a crappy job at cleaning the deck of the block or you didn't fasten the head to the block properly.

Dee

[ca18det240hatch]

well, i have the correct torque specs on the head bolts, and did it in the right order....and i spent a bunch of time on the deck with emery cloth, making sure it was clean...so i guess i can chalk it up to rings not seating or bad end gap clearance. One thing tho, total seal recommends 3000miles before the engine is broken in, wonder if maybe i was too early to check compression? I hear the rings break in, in the first 20 minutes, but total seal says the above....

[bentvalves]

they offer a few different ring types, I believe the moly type is the one that takes the longest to bed.

How many miles do you have on it after the build?

[Masterdebater]

did u use new head studs?stock ones arent reusable correct?

[boost_boy]

Stock headbolts are reuseable, but should be changed after the 3rd off/on sequence.

Dee

[ca18det240hatch]

i was told by my machinist that the pistons could also be a lower compression variety. theres a guy that got the exact same pistons from madscientist, id like to know what his compression numbers are looking like....

i have about 2500km on the build.

[boost_boy]

Unless those pistons were dished, I won't worry too much about what the machinist says. Now, if your headgasket is "saaaay" 1.6mm-2.0mm, then your compression will be in a lower than stock range. Be wary of the head or headgasket. I've had similar ghost problems like yours with perfectly low compression and I straightened it out with a different head and stock headgasket. I used that same head on someone else's car with a new metal H/G and compression was normal. You got one of them problems and you're probably just going to have to wait until your rings seat to figure this out. I honestly don't think it's your rings. But I seriously do believe it's in between the head and headgasket.

Dee

[ca18det240hatch]

its a 1.2mm head gasket, and i took a caliper to the brand new stock one i have and its also 1.2mm.

i had my head machined, but they only took 4 thou off, and that would raise compression anyways if anything. Does make sense that it could be at the head tho, ill look more into that when im confident that the rings have seated completely

[r34 gtr]

go beat on it for another few thousand km, do a compression test and let us know. if its running well i just probably wouldnt worry about it.