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Old 09-19-2006, 08:13 PM   #1
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Default supra 93-98 compression????

Hi guys

Just wondering if anyone knows what compression should be on the mkiv? I'm taking a tt 6spd into the shop to get tested before I buy?
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Old 09-20-2006, 03:35 AM   #2
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Originally Posted by supraboyz
Hi guys

Just wondering if anyone knows what compression should be on the mkiv? I'm taking a tt 6spd into the shop to get tested before I buy?

Each individual compression number is not anywhere near as important as the difference between the highest and the lowest #, in determining the health of the engine. That said, a brand new engine can have as high as 180psi of compression in each cylinder, depending on the calibration of your gauge, the length of hose your gauge has, and exactly how you measure (cold/dry/hot/wet/#revs/open tb/etc.). As per the link, if you have any one cylinder less than 128psi, it likely needs new rings&honing at the very least. Personally I'd never pay market value for an Mkiv if the difference between max&min is >14psi, OR if any cylinder was less than 150psi, the way I test. For example, an engine could read 176psi in one cylinder and 160psi in another and need to be rebuilt...even though 160psi all on its own might generally considered to be a # indicating a fairly healthy engine. Whatever you do, be sure to get specific/exact, per-cylinder numbers, and don't accept a blanket statement like "yeah we tested it and it's 160s across the board".

Fwiw, I'd strongly recommend you follow up any anomalous compression readings with a leakdown test.

Fwiw, I'd deduct at least $3k-$5k from the market value if the engine needs to be rebuilt. The process of removing & reinstalling the shortblock is a painstaking, labor-inten$ive, and sometimes tedious (eg. cleaning aluminum oil pan grooves of hardened fipg) process. In addition, if you haven't had it done before, proper machine shop work on a 1000hp/10k rpm capapble 2jz-gte shortblock is likely to be significantly more expensive than you would expect. Oh, and don't forget that detonation can damage more than just the pistons...I've seen a 2jz-gte head where a chunk of the aluminum was blasted away between two adjacent cylinders. Too much boost on pump gas is usually the cause of low compression & piston/head damage (pardon my rambling off-topic)...
Phil '94 Supra Turbo, 6spd, 'APU'+
Displacement is no replacement for boost.
Life begins at 30psi.

NB: Please consider posting any help requests in a new thread instead of asking me for help privately. About 99.9+% of the time, private help requests end up covering great information that could be very valuable to other forum members. If you have a good reason for needing the help request to be private, I'll consider it. If not, then why not give everyone else the opportunity to pitch in too, and/or learn from the information? Remember, there's no such thing as a dumb question. We're all here to help within this family of Supra owners.

Last edited by pwpanas; 09-20-2006 at 01:26 PM.
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