jonboyb

My 1.5 is supposed to be a 3500 mile 2JZ bottom (new GTE stock crank, rods, and pistons) and a cleaned/resurfaced 1JZ head. However....I just did a compression test and got 197-195-194-196-194-195 Stock cams. There's a tab of HG visable and it looks to be a Cometic.

I've tested plenty of 2JZ's (in the 160 range) and just got done testing a member's (ATTZOR) straight up 1JZ (175-180) too. I know the 1.5 bumps compression....but these numbers seem unrealistically high. Even resurfacing the head to wihtin an inch of it's life shouldn't bump them that high should it. I was hoping for 175+ and ended up with more than I bargained for.

Don't get me wrong, I'm thrilled with the consistency....but just seems too high (especially to be running a PT76 turbo)

jonboyb

Although now I understand why the "stock" 1.5 is able to spool the PT76 faster than I expected

93MSB

iTrader: (8)

the turbo headgaskets are multilayer 1.3mm thick

they could have used a NA single layer headgasket.

how much was taken off the head to resurface it?

jonboyb

PO can't confirm how much was taken off during the resurface. I went through the receipts as soon as I saw the high numbers to confirm the piston part numbers and they are turbo pistons. There's also a HG number listed that matches the turbo headgasket....so I guess it's the multilayer I was seeing when looking at the little bit of HG that looked like a Cometic (it's white/silver like all the Cometics we used to use at the shop). Cometic gaskets look to be 2mm+ for the 2JZ so I'm pretty sure it's not one now.

The car has been running 17 psi (or more...who knows) since the engine was installed in Dec. 2008. At least 2500 miles of full boost operation after the 1000 miles the PO says he used as break-in miles before boosting. Probably be pulling the PT76 off now though as a safety precaution and go with something more reasonable. Don't want to run race gas all the time

How much of a compression bump does the 1JZ head produce on a 2JZ bottom (or is it even documented)

willhickey

iTrader: (1)

Dang man mad consistent though.... maybe carbon just built up crazy quick? haha i dont think so either not in 3500 miles but I wish you luck with it sweet ride and those 97+ parts you have or had were a steal!!!!!!!

93MSB

iTrader: (8)

im not sure on specific numberss but the 1j combustion chamber is smaller, which should result in higher compression.

maybe you need to look into a thicker headgasket to lower the compression

RyanV

iTrader: (9)

Its interesting that you point this out though. I've never seen anyone post up compression numbers in any of the 1.5 build threads.

I have read people saying to just use the 2jzgte headgasket though.

P2V is probably making this a interference motor for sure!

I wonder what the static compression is right now??

jonboyb

Borrowed a borescope and confirmed the pistons are turbo. What little is visable of the HG certainly looks thicker than a compressed .3mm gasket so I have to assume it's at least a turbo HG. I guess the resurfaced 1JZ head and decked 2JZ block have just raised my compression more than I would have suspected.

And I'm with you Ryan....I searched for compression numbers for a 1.5JZ and didn't find ANYTHING. If anybody has a compression test from a 1.5.....please post your results.

Another thing to note about my SC is that during the compression test I was shocked how fast this thing cranks over. I've never had an engine spin at this high of RPM. Didn't look at the tach....but boy was she turning.