SR20DET lifting head??

[nizola]

So I just had it rebuilt for the 3rd time, for numerous reasons. This last time was because I blew both top and bottom tanks off of the radiator when it came on full boost(22psi) in 5th gear.

The result was a split in #2 cylinder which has now been sleeved for the 2nd time, this time using better sleeves. It turns out that the split was only part of the problem.

Long story short its all been highly modified and this latest rebuild should have fixed all of the problems.

Upon retuning it on the dyno, it got to 310hp atw @12.5psi. Anything above that and it started blowing boost into the coolant again. All compression and pressure tests are totally fine under normal testing procedures, which is what makes me think the head is lifting??

Obviously the headgasket, at this stage is still in one piece or it would show signs when tested. No? It has ARP head studs although im unsure to what settings they have been wound too, but have since heard it needs to be 90-100ft/lb.

It also has a metal headgasket.

If not tight enough already, should I wind up the head studs and hope for the best? Or is there something else going on that I havent picked up on?

Marc

[anthonyr sil8ty]

i would def re-check my studs. i did 60 ft lbs first with proper tightening sequence, then went to 90 ft lbs with proper tightening sequence. im @ 23lbs of boost an havent had any issues with lifting my head.

[jr_ss]

Were the head and block decked? ARP torque specs are 80-85ft-lbs. You could possibly be lifting the head, but I find that hardly likely considering your only at 12.5lbs of boost. What size turbo is it?

[PoorMans180SX]

Sounds like your engine builder doesn't know what he's doing.

[nizola]

It's a garret TO4S .70 I believe. Im not sure about being decked, im just getting my info from my dad whos in New Zealand and i'm out here in Cali. My memory isn't the best. But yea i agree its low boost, a stock engine should handle that no problem, but i have no idea on what else it could be?

[nizola]

@poorman, tell me about it! He has caught me with my pants around my ankles everytime

[Kingtal0n]

Hello, maybe I can give some insight to this issue.

When using head studs, generally because of the clamping forces involved, the engine needs to be bored using a deck plate torqued to the specifications of the head stud manufacturer, generally using the head studs you intend to use for the final build.

As to the head gasket, if you are going through all of the trouble of utilizing head studs and a deck plate and expensive machine work, you should be using a new head gasket during assembly, and generally it is acceptable to use some copper gasket spray on these (sr20) engines during assembly to help prevent the issue you are describing with metal head gaskets.
Some of them are very sensitive to mild inconsistencies in the flatness of the surfaces, so if your head was not decked to ensure a flat surface, and no gasket spray was used, and head studs were being used without proper deckplate/bore procedure, then yes it is likely that boost may escape into your coolant, no matter how tight you get those studs.

And finally, extreme spikes in cylinder pressure can also create an issue. If your engine is tuned with too much ignition timing (very common for sr20 engines) and you are using pump gas (93 octane) it is likely you are getting a pressure spike that will contribute to this issue. An EGT gauge may help here, try dialing back the ignition timing several degrees and if the EGT does not rise significantly and power does not drop then it was too much timing. A metal head gasket will accept more abuse than the OEM gasket will, so this situation may go unnoticed until something bad happens (such as a worn/flaked out cylinder) that may fatigue the internals until one of them fails.
Just for reference, not as an exact science, ignition timing during 18psi of 65% efficient boost that falls in an acceptable range of inlet air temperatures for this engine- you should have no more than about 9* of ignition timing BTDC. Most "tuners" blindly set it to about 15* which is far too much.

[fliprayzin240sx]

When the block was decked, was it decked with the oil pump cover on? Oil pump cover is almost always taller than the block. If the difference is large enough, metal HG won't completely seal the #1 cylinder.

[nizola]

Head studs have only been wound to 80, so will tighten them up and go from there. Fingers crossed. Otherwise perhaps the head has gone soft?

Incase anyones curious, I did a small blog on my car a few years back when it was completed NIZOLA (http://nizola.blogspot.com/)

It's in a 77 corolla in New Zealand.

[jr_ss]

ARPs are only spec'd to be torqued to 80-85...

[Kingtal0n]

ARPs are only spec'd to be torqued to 80-85...

Depends on the lubrication used. If using motor oil, torque specs are significantly higher than when using "MOLY" for instance.

[airman]

If you're using a metal head gasket and didn't have both the block and the head resurfaced, then that's probably your problem.

[codyace]

Did yo have the block itself checked for cracks?

[steve shadows]

I had the same issue before several times on my own car years ago...

Issue was the head gasket I was using at the time was shitty and the head bolts had been reused. Stock ones. It would lift under boost and pressurize the whole cooling system. Pulled the cometic gasket off, put on an apexi metal gasket with the fire ring design on each cylinder - resurfaced the head at a machine shop and cleaned the deck myself very clean and used ARP studs never had a leak again...

[S14 James]

I've had a lot of issues with mine @ 90mm bore, ended up having a cnc step deck with mazworx 1/2-inch studs. Granted this was with a T3 exhaust turbine with 30 psi of boost which personally I think was pushing the back pressure in front of the turbine.

(as stated above) With a 86-87mm motor, decked and smoothed head and block with a good finish and an apex'i type gasket should get it done with 85 ft lbs on the studs. I'm assuming no one has the old tapered junk ARP head studs . I made 550rwhp on a stock sleeve motor with the above.
I would go ahead and do a full sleeve Darton setup or just get a new block rather then just re-sleeve one cylinder....
-James

[TheWolf]

you have compression going into cooling but not water into the oil/crankcase?

and it's only when at flat out/high boost.. not at normal idle/driving around town...