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348 Posts
Discussion Starter #1
Hello Staff at Real Street Performance

I throughly enjoy watching your supra videos and dyno uploads on instagram, and this has inspired me to reach out for help and advice to you guys!

1 year ago my ultimate dream car a USDM LHD Hardtop Supra.

It is a 5-speed NA-T.

Long story Short me and my mechanic, rebuilt the low compression N/a Motor, and we used GTE oem Pistons and Rods with brand new GTE rings and polished crank with brand new OEM bearings, has ARP hardware for the headbolts however rod bolts and mains are oem bolts since the stretchness was still good on them.

Long story short we put it back together with a OEM N/A headgasket and ran it for a bit until it started smoking blue like crazy and we did a compression check and Cyl #4 has 120psi. This brings me to here today where it is time to rebuilt my motor again so i can enjoy the car this summer.

I have purchased brand new Wiseco GTE pistons that are 86.5mm .05 Over, and 8.5:1 Compression ratio on these pistons. I will be taking my N/a Block to get bored and honed to the machine shop and they will be using a deck plate to make sure it gets done properly.

The bottom end setup will be Wiseco GTE pistons, stock GTE rods, Brand new oem toyota bearings, polished oem Crank.

The Top end setup will be a Stock N/a GE cylinder head with stock everything, just brand new GSC valve stem seals in it.

Which brings me to my question…..What headgasket do i use on this motor??? On previous build i used OEM GE headgasket but im afraid that oem GE headgasket will pop at higher power.

I asked local shops but they were douches and did not want to advice a younger fellow like me or steer me in the right direction they told me 'its up to you and your engine builder to figure it out'.

Anyways thats the car's setup, below i will list the car's mods so you can kinda gauge what the car is.

-Boost logic Single Turbo Na-T kit with precision 6162 Turbo

-Oem Timing gears

-Oem Cams

-JDM 440 CC injectors (will be upgrading soon)

-ARC front mount intercooler

-Stock GE intake manifold

-Ecu it has a Megasquirt MS3 PRO ecu.

-Ignition will be LQ9 Corvette coilpacks running off distributor harness

-Distributor Block off plate.

Anyways thats the cars entire mods list. Let me know if you guys want me to call you guys to discuss over the phone, but yeah overall my question is what headgasket do i use for this next motor build given the mods of the car.

My Power goals in the end once i do fuel system and cams will be 550-575RWHP.

Also whats your guys advice on breaking in a brand new motor thats freshly rebuilt such as my next build, we used the motoman break in last time.

If this Thread is Not allowed here, please remove. The only reason i posted in this section and NOT main supra section is because i would like technical help and advice from people who build these engines all the time and not newbies who scroll on the forum boards acting like they know everything. Sorry End/Rant

4,400 Posts
Thread is absolutely allowed here, no problem. I personally would use the GTE OEM Headgasket. Keep in mind that your GE cylinder head will have a different chamber volume than a GTE, so I would suggest having your machine shop CC the combustion chamber and that way you can figure out the actual compression ratio your engine will have. Since you have done two rebuilds there is likely some decking of the block and/or milling of the head so I wouldn't want to hazard a guess - investigate that so that you don't go through this again.

Did you figure out why the first engine broke? Were you running too much boost for the octane vs compression or making too much power for your injectors? Can the car make a low enough base pressure that the injectors and fuel pump can keep up?

If any metal was running through the engine make sure that everything is thoroughly cleaned including the cylinder head and crankshaft. If you are using an oil cooler, I honestly would recommend replacing it, it's too difficult to get the particles out of it.

Motoman break in is fine.

Let us know if you need to order the head gasket or any other items for your build - main studs, gaskets, oil pump, head studs, etc. [email protected] or +1.407.695.7223.

P.S. - good job on purchasing your pistons before having your block bored, that is a mistake that countless people make. Now you can bring the pistons to your machinist and they can make sure all six have similar piston to wall clearance.

boost life
2,502 Posts

is their a specific reason you say gte hg over ge .. both being made of same material , one being multi layered and one single layer .. i ask for i plan to use a cp gte 9:1 piston with a na head and na hg and my machine shop did the math and stated will yield me approx 9:7 ish cr which to me anything just under 10 is fine but over 9:5

my hp goals will never exceed 700 ish rwhp on e85 maybe touch 750ish afterwll my car isnt a race car in my eyes

4,400 Posts
Typically you want to have a minimum of .035" crown to cylinder head clearance, given that the crank, rod, and piston you can generally always trust to be as long as the block was originally intended, once you start milling the head, decking the block, etc...especially putting billet main really start to tighten that up. Since the GE gasket is so much thinner we just use the factory GTE gasket because it gives us more room to work. Technically you could be a little proud on the piston and still safe. With the GE gasket, even a zero deck engine is really on the edge since it's so thin. At least that's MY answer since I've had to order a couple hundred sets of custom pistons for people over the years for different engine combos, others may have a different answer.

If your car isn't a race car, my response would be that you don't need the slight compression bump you're going to get from the thinner gasket but it's always a good idea to be on the same page as your machine shop. Ask them how they feel about where the piston-to-head clearance will end up with your set up, if they're comfortable and you're comfortable then go for it. I've just been told keep it at .035"+.
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