SR20DET Overheat damage

[Nikzilla]

Long story short, I fucked up bad, and let my SR overheat extremely for too long without noticing.

I've got the motor out of the car and I'm going over fixing everything.

Car shot white smoke out of the exhaust. Found evidence of oil between the gasket and the block, leaking into cylinder #2 and #3. Block is distorted out of spec (above 0.1mm near the coolant passages). Gasket is intact however. Head and block will be resurfaced with a new head gasket.

Question:
What is the stock head gasket thickness? What will be the benefits of lowering/raising compression with the gasket?

Radiator developed a massive crack in the top plastic bit.

Question:
The FSM states that the top plastic bit can be removed and replaced separately from the radiator. Can a shop do this for me?

When I tried to refill coolant at the scene of the accident, it oozed out from what seemed like the front cover. Upon later inspection, when I poured water in through the coolant passages in the block, it was dripping alone the edge of the front cover nearest the water pump. Upon removal of the water pump, I noticed a clear coolant streak coming from a little hole under the pump.

Question:
Is that a sure sign that I need a new water pump? Can heat destroy a water pump?

Extra Question #1:
Should I do a full inspection of the turbo?

Extra Question #2:
Do I need to disassemble the block before I can take it to a machinist, or can I just give it to them with the whole bottom end and front cover intact? (timing chain and guides are sticking out the block)


Anything else I should check?

[Kingtal0n]

Question:
What is the stock head gasket thickness? What will be the benefits of lowering/raising compression with the gasket?

Use a stock headgasket, brand new. I would not go thicker. If anything you could go thinner, but an OEM gasket is your best bet.Question:
The FSM states that the top plastic bit can be removed and replaced separately from the radiator. Can a shop do this for me?

With the price of aftermarket radiators I would not bother. Get yourself a brand new radiator or even an aluminum version for around $100 and call it a day. Question:
Is that a sure sign that I need a new water pump? Can heat destroy a water pump?

Yep you need a new water pump.Extra Question #1:
Should I do a full inspection of the turbo?

I wouldn’t worry about the turbo they get much hotter than you could ever get the coolant. Not to mention if it was hurt you couldn’t tell by just looking at it unless you pulled it apart and measured everything. not worth it.


Extra Question #2:
Do I need to disassemble the block before I can take it to a machinist, or can I just give it to them with the whole bottom end and front cover intact? (timing chain and guides are sticking out the block)

When they go to cut metal off the top of the block (deck) little metal pieces fly all over the place. So generally you want your rotating assembly and all wear related parts as far away from the flying metal as possible. Big risk here is, even with the block fully disassembled there is a still a chance some of that metal will stick around and ruin your fresh rebuild. This "problem" of yours is going to cost $600+ to fix, so my recommendation is to simply find a new longblock, around the same price. Your chances of using an all original OEM bottom end successfully is better than using one that’s been machined on, and re-assembled.

Anything else I should check?

I would buy a new oil pump and have it decked along with the block if you are going that route (rebuild). If you have the tools check everything the FSM has specs for, including the roundness of the cylinders. You will need the head decked if it also warped.

[Nikzilla]

Thank you for your reply!

But, if I'm shaving off like 1mm total, stock head gasket thickness will shoot my compression way up.

SR20DET aluminum radiators for $100? WHERE?!?!?!?!? Cheapest I could find was like $225

Sourcing a long block would be very expensive for me. And I do not have the tools ATM to disassemble and measure the bottom end. Those would be very expensive for me.

Is it really that dangerous to get it decked? I thought with all the proper precautions taken it was regular bizz.

P.S. In case you missed it, both my block and head are warped.

[Kingtal0n]

ebay all day
http://www.ebay.com/itm/95-98-NISSAN-240SX-S14-SR-SR20DET-MANUAL-TWO-ROW-CORE-ALUMINUM-CHROME-RADIATOR-/151236718207?pt=Motors_Car_Truck_Parts_Accessories&hash=item2336692e7f&vxp=mtr

Decking the block will not raise compression enough to cause any problems. In fact when rebuilding the sr20det most people opt for 9:1 compression while using 93 octane fuel.

it's "regular" but the sr20 like many small displacement engines has many places for teeny bits of material to hide. That material circulates around in the oil for a bit then lodges itself into a critical passage, such as a camshaft oil passage. Then you wipe out a lobe and send even more material into the engine. Its a viscious cycle.

[Nikzilla]

Would hot tanking the block after decking it solve the issue?

Also, I don't know if I really trust ebay for parts like that.

Is the stock 8.5:1 ratio set up for 87 octane use? Because I would love to raise it to 9:1 if it was safe on 91 with the stock tune. Regardless though, I'm going to shave off probably quite a bit, and since I'm going with an APEXI head gasket anyway, I can cherry pick a gasket for whatever compression I want.

On another note, there is a hole at the bottom of the upper oil pan that goes into the bell housing. It's supposed to have a plate cover it with 2 screws. Mine doesn't. What is the purpose of this hole, and should I order a plate to cover it up?

One more thing. Since I already have the bottom end disassembled, would it be a good idea to get new piston rings?

[Nikzilla]

One more question.

Do I have to get a new rear main oil seal if I took it off, or can I reuse it?

[Kingtal0n]

Would hot tanking the block after decking it solve the issue?

Also, I don't know if I really trust ebay for parts like that.

Is the stock 8.5:1 ratio set up for 87 octane use? Because I would love to raise it to 9:1 if it was safe on 91 with the stock tune. Regardless though, I'm going to shave off probably quite a bit, and since I'm going with an APEXI head gasket anyway, I can cherry pick a gasket for whatever compression I want.

On another note, there is a hole at the bottom of the upper oil pan that goes into the bell housing. It's supposed to have a plate cover it with 2 screws. Mine doesn't. What is the purpose of this hole, and should I order a plate to cover it up?

One more thing. Since I already have the bottom end disassembled, would it be a good idea to get new piston rings?

There is no guarantee you remove all material. A hot tank requires a complete dismantling of the engine, you would need all new everything to do it right, now you are spending over $1000.... a whole fresh motorset is $1600 And you could sell off the electronics for $300+ and have a whole new transmission etc....


8.5:1 is fine if you do not boost at all. But you are on boost. You will need 93 octane regardless of what compression you run for safety. Or 91 I guess if that is the best you can get. I doubt you can hit 9:1 with just a head gasket change so I wouldnt worry about it.

That hole is probably for the inspection of the flywheel, the missing plate is an inspection plate. Its a good idea to keep dirt out of the flywheel/clutch assembly yes block it off with something.

New anything is fine is as long as you do it right. You cant just throw new rings in an engine, it needs machine work, a fresh hone and a break in proceedure. Which is rarely done right, which is why I am still recommending a used longblock. You are throwing so many variable at this engine now "IF" you get the right bearing clearances set "IF" you remove all the free metal shavings "IF" the cylinder walls are set round and properly honed "IF" the piston rings break in right "IF" the oil pump height matches the actual deck height.

Furthermore, IF the person assembling the engine has not assembled at least 10+ SR20DET or similar engines in the past 5~ years the bearings will not get set right, the cylinder walls will not be set right, it will not go together properly. The engine will not go 15,000 miles and you will be out $1000+

rear main seals are cheap. always replace front and rear mains when you have the opportunity.