Overheating/coolant loss on long trips

[dannydavi]

Originally Posted by cre

You are aware that 200+psi is WAYYY too high.... right? The N/A is supposed to be mid 150's.

I thought it was supposed to be 185ish... what does it mean if the compression is higher than it's supposed to be?

[dannydavi]

Originally Posted by cre

Stock dish is 3mm below the crown. I don't know what's up if you've actually got different pistons; Usually the high readings are the result of oil draining into the cylinders from the plug galley.

Danny, what's your timing set to? Retarded timing (both mechanical and ignition) will cause higher engine temps.

Well I have the JDM engine so I have no clue what pistons are in it. I haven't checked timing since I put it in, I'll have to check again. I might just take it to a shop instead of dealing with this headache, I'll deal with a wallet ache instead...

[cre]

156psi optimum, 124psi min. If your engine was PERFECT and just had a lot of carbon buildup you still wouldn't see much past the lower 160's.

JDM uses the same pistons.

That's GE by the way; GTE is supposed to be about 15psi lower.

[87hilux7mge]

piston dish that on the pistons i bought was exactly as you said cre, 3mm, just under 1/8th inch (if my math is correct...??). i do remember gauging the other pistons and they are just under 1/16th inch, prolly around 1.5mm. so ill have to figure out what the serial number is today. ill get one and post back soon.. im very curious about these two sets of pistons i have...might have to use them in another build if i can find a good block. high compression 7mge

[dannydavi]

so just an update, block tested it today and it is blown I hate life

[cre]

Meh, still better than a hole in the side of the block with a mangled rod protruding.

[87hilux7mge]

Originally Posted by cre

Meh, still better than a hole in the side of the block with a mangled rod protruding.

my buddy john did that when he sunk his gte powered buggy bout a month ago. hydrolocked #6 cylinder and shot the bent rod through the block. quite impressive actually!

[87hilux7mge]

so i got one of the pistons yesterday, and the serial number is 42090. theres some in my album, linked below.

http://www.toyota-supra.info/forums/...albums198.html

hope someone has some light to shed on these pistons. i have two sets. but one set is pretty well screwed (person overheated the engine and welded the piston rings to the cylinder wall, as well as scraped the bejeezus outta the pistons).

btw danny, sorry to hear about ur block thats a bummer man :/

[cre]

It's an oversized piston for a Toyota Crown 7M. 0.50 over.

Which also means that block and head have probably been shaved at least once before they got to you.

The part number for the Supra 7M-GE in that size is 42070.

[87hilux7mge]

hmm. well they spec out at stock bore (83mm...) so idk how they could be .50mm/.020 over. both sets are stock bore for a 7mge, so now im really confused.

as far as i could find, the crown only used the 7mge for 4 years, 87-91, then they switched over to the jz series or various other 4 cyl and diesel motors. doesnt say whether they were high compression, but since it would be a jdm motor, its very possible. either way, its too bad we cant order pistons like that for our 7ms. id buy a set. might strip these down and use them on another block.