SR head gasket issue.

[Dolby109]

I have an SR20DET with an APEX head gasket. I didn't put the head gasket on, but I've been driving it for about 5k miles with no problems.

Now (just after a turbo upgrade, but not really driven hard) it has started smoking from coolant getting into Cyl #4, esp after engine braking or any heavy vacuum.

So I get the cams out and all of the head bolts are tight, some seem a little overly so, but the lowest loosened at about 60ft/lbs.

My question is, can an APEX metal head gasket blow?
Should I try loosening and properly re-torquing all of the (ARP) head bolts, or is that just wasting time?

[Kingtal0n]

any gasket can blow. Apex and and others are notorious for having issues because nobody knows how to install them properly.

Verify it is in fact the head gasket (compression / leakdown test (make sure the valve are shut))

then plan to change it. I would go OEM if your under 400 bhp.

[Dolby109]

Trust me, I'm sure it was blown between a coolant line and the 4th piston. There were bubbles coming in the coolant, and piston #4 smoked for a bit when I took the spark plug out, and the spark plug was colored different than the others.

The guy who put everything together didn't appear to know very well what he was doing, and I had hoped he had someone assemble the head and install it for him.
Still I don't understand how you can screw up a head gasket. Make sure the surface is clean and smooth, put the gasket in place and make sure everything is lined up...If I remember right, the block even has alignment pins.

So you don't think re-torquing will fix this at all?

[fliprayzin240sx]

^^^You can try, I mean what else do you have to lose at this point?

[rbs14kouki]

When you do a metal head gasket you need to make sure the block and head are strait ! If its not perfect a mhg will leak

If you have bubble in the rad i wouldnt even waist time ... Double check the deck and head to be strait and slap a new gasket

What head bolts do you have ?? Stock one can stretch under high boost

[Rusker]

I wouldn't bother trying to fix this. If the MHG is blown then you are just wasting your time. Why risk damaging your engine anymore? Hopefully the head and block are straight and you can swap in an new gasket and new ARP bolts.

Good luck.

[Rusker]

When you do a metal head gasket you need to make sure the block and head are strait ! If its not perfect a mhg will leak

If you have bubble in the rad i wouldnt even waist time ... Double check the deck and head to be strait and slap a new gasket

What head bolts do you have ?? Stock one can stretch under high boost

He said he had ARP

[Kingtal0n]

He said he had ARP

which can further lead to HG issues. You Do NOT do NOT use head studs on an engine that hasnt been bored with a deck plate!

[camwhore]

which can further lead to HG issues. You Do NOT do NOT use head studs on an engine that hasnt been bored with a deck plate!

Can you elaborate? All else equal (read: no bore), wouldn't the old style VW ARP head studs and the OEM head bolts produce similar assembled distortion in the block as they're both torqued in the 80-85ft/lbs range? Or does the OEM bolt-stretch play significant role in absorbing some of that load?

Obviously, changing the bore without a plate/bell housing to replicate it's assembled state then using any stud/bolt combo could lead to issues.

Also, in this thread and additionally in my research I've seen that you're a proponent of the OEM head gasket. Can you explain a little more on your reasoning there too please? Weakest link theory?

[Kingtal0n]

Can you elaborate? All else equal (read: no bore), wouldn't the old style VW ARP head studs and the OEM head bolts produce similar assembled distortion in the block as they're both torqued in the 80-85ft/lbs range? Or does the OEM bolt-stretch play significant role in absorbing some of that load?

Obviously, changing the bore without a plate/bell housing to replicate it's assembled state then using any stud/bolt combo could lead to issues.

Also, in this thread and additionally in my research I've seen that you're a proponent of the OEM head gasket. Can you explain a little more on your reasoning there too please? Weakest link theory?


They are not the same. In the case of mains, it would be an enormous mistake to simply swap the bolts for studs without an align bore on many engines. Every engine is different of course, so it comes down to application specifics. In this case, we are talking about a very detail oriented, small displacement series high performance engine where even .0001" can make a difference. Therefore, the right way to do things, is the right way: bore the engine with a deck plate with the hardware you intend to run the engine with for it's service life. Anything else will not be optimal. Has anybody actually bolted down a deck plate with bolts, then studs, and measured the difference? You tell me, because I have not. The issue here becomes: why take the chance unnecessarily. Head bolts will suite this, and many other 400BHP sr20det applications just fine. So why take the completely unnecessary leap of faith?

The same way we see head gaskets: use OEM FSM proceedures whenever possible. Why install an aftermarket gasket when the OEM version will work perfectly fine? You would rather pop an OEM head gasket learning to fine tune your engine timing than put a hole somewhere else. a factory gasket will serve the 400BHP mark- end of discussion. No need for anything extra.



we can see many "weakest links rule" (I see you said weakest link :D)

non critical location bolt torque: use the weakest torque necessary to get the job done. Put the spark plugs in just tight enough and then check them once in a while. Better that than destroy your plug threads. I'd rather find a slightly loose spark plug than find a seized up plug and a ruined head. This applies to engines like the sr20det where you will be wanting to check plug colour on occasion. If we are referring to a KA24DE that is all OEM- simply install following FSM proceedure of course.

misc. brackets and clamps around the engine, including belts and non critical gaskets can all follow this: Put your radiator in with clamps somewhat loose. warm the engine up and tighten as necessary. You notice how nissan uses those weird clamps on all the oem hoses? and not normal hose clamps? Notice how they are practically maxed out most of the time- very little room for adjustment. The only "real" clamps you ever seem to see are on the fuel rail of turbo engines.

Belts can go on somewhat loose then tighten as necessary. Better to leave a little dust for the first 20 miles than find the upper half of your #1 main bearing scarred up.

[rotation3x]

Make sure you know what arp head studs you have.

There are 2 different versions out for the sr and have different tq specs

I have stock bore on both of my sr's they both have the arp studs 102-4701 which call for torque in 3 equal steps to 90 ft lbs.