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Short block compression test??

Old 06-04-19, 06:56 PM
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Short block compression test??

I got a 1994 Mazda RX7 . Iím about to start rebuilding the engine Iíve never done this before, so my main question is there a way to do a compression test on the short block before I install it. I assume I need to install the transmission the starter the oil pan get some new oil in there. Get myself a compression tester and go from there. Wouldnít want to find out blah compression is present after I install everything and I have to pull everything out again.
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Old 06-04-19, 07:39 PM
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BTW. Even tho Iíve never rebuilt an engine, I am very mechanically incline. Iíve familiarized my self with the compression test threads in the forum, but I wasnít able to fine short block testing. Iím from California. I live in the SF Bay Area, and I just canít find anyone who rebuilt this engines anymore. The few people Iíve talked all want to just buy a new engine. My current engine is the second engine in the car since I got the car. First engine went out in a year from getting the car. Second engine I bought rebuild and installed it myself. But now itís compression is in the low 90ís.
So, I want to learn how to rebuild this engines, since I am planning to keep the car as long as I can. Got the car very cheap so I have room to build it considering I can spent the money I save in the purchase.
Anyways. Anything you would like to know to help me would be much appreciated. Thanks in advance. This site rocks!!!
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Old 06-05-19, 09:47 AM
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Mazda will sell you a brand new engine for the same price as a pair of rotor housings and all the seals, its just not cost effective to rebuild an engine right now.
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Old 06-05-19, 04:21 PM
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If you just need to replace the seals, it's cheaper to rebuild. But if you need to replace any of the metal bits, new is the way to go.

As for bench testing, you could probably hook a bell housing with a starter and a 12v source. it needs to crank ~200 rpm to get a good reading
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Old 06-05-19, 04:59 PM
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I called Mazda 6 months ago and they said they no longer sell the 13 b engines anymore.
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Old 06-05-19, 05:04 PM
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Iím gonna disassemble the engine and look how bad it is. Once I do that Iíll determine if itís rebuildable. Irperformance sell new engine for $4699 + 300 shipping. I just didnít think there were new engines anymore in the states. I thought they were all rebuild and sold as new. Thanks for the feed back guys.
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Old 06-05-19, 05:10 PM
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As the others have stated, it's possible to compression test a short block prior to installation. Obviously you'll need to have the oil pan, oil filter pedestal & filter installed and have oil in the engine. You'll need to either temporarily plug the 2x oil cooler ports on the block, or just plumb them together with a temporary hose & fittings. Since you'll only be cranking the engine for 10's of seconds, you don't need the oil cooler, or need to worry about engine coolant & a radiator. To crank the engine you'll need to have the flywheel installed, plus a tranny bell housing installed to mount the starter to, and have it wired to a fully charged car battery. And of course some means of holding the engine steady & safe while testing it.

But I'm not too certain any of this would be worth all the effort - compression testing procedure per the FSM is done on a engine that is brought up to operating temperature and then shut down shortly before hooking up the compression tester. The compression numbers you get on a cold engine are typically higher than you would get on a warmed up engine, so it's possible that the values you read could give you a false positive indication of the engine's health.
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Old 06-05-19, 05:21 PM
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Alright. New engine it is.
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Old 06-05-19, 05:23 PM
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Originally Posted by chapi199 View Post
Alright. New engine it is.
Capitol Mazda in San Jose usually stocks a couple
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Old 06-05-19, 05:27 PM
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Iíll still disassemble the two engines. Maybe someone in the forum can use some parts. Anything I can sell would be great to fund the new engine. And Iíll experience the tear down.
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