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What are compression test numbers?


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Okay so I officially screwed up. I've been replacing my head gaskets and got the full gasket kit with new everything on the engine. The engine should be running great, new clutch also. Except I finally got the engine in to start it and it just backfired. My crankshaft was 90° off the timing mark as I lined it up with the wrong freaking arrow. Fixed the belt and the engine fired up just fine. But now I'm worried about vent valves. It's a 97 legacy gt, 2.5 DOHC. I'm doing a compression test today and it's gonna be on a cold engine as we don't have any accessories hooked up to the engine.

 

I was wondering what good compression test numbers were for a cold ej25 and what is a safe range. Also what a for sure sign of a bent valve will be.

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Cranking with the plugs in but fuel injectors disconnected electrically you can hear the bent valves in the tailpipe. Same thing in the intake but that's harder to listen to. I don't know what the numbers should be, but I would look for 160-170 on all 4. If it's higher that's great, but all four pretty close to each other is the main thing for this situation.
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Okay so update, all cylinders were at 170 but 1 was at 162 ish. So I got the engine peiced back together after a full gasket refresh, new mounts, clutch kit, and uel headers. The car idles nice and smoothly but I'm having an issue with overheating. I replaced the head gaskets for that reason. Overheating, no hot air through the heater vents. I'm thinking either a air pocket in there that is very large or the thermostat is stuck, any opinions?
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What thermostat are you using? A lot of people have had issues with non Subaru thermostats overheating their engines. Before I replaced my thermostat I did a lot of research into the forums and found two main things. Use oem thermostat and fill very slowly. Also there is a thread on here about coolant bleeding techniques.

 

Sent from my SAMSUNG-SGH-I747 using Tapatalk

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Sounds like a big ol air pocket blocking the system to me. My method is back fill the motor through the upper radiator hose, fill the radiator and reservoir and then run it up to near temp with the radiator cap off while progressively adding coolant as needed. I've never had an air pockets (except minor ones that worked out within the first 2 heat cycles on their own ) with this method.
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We did try filling up the coolant while the car was running but it would just act like it was full. Still no heat and the temp Guage would fluctuate based on what you were doing with the throttle. Im wondering if it's just a huge air pocket, thinking about trying to bleed the system how it was described in that other forum at the heater core
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It helps to have the front higher than the back like on ramps. The higher the better. Sounds like times I've had an air pocket.

 

Also, I can second the OE tstat. I compared my aftermarket to OE when I was having high temps and weird fluctuations with the aftermarket. It was about 3/4 the openning size of the OE which I expect would be about 1/2 the flow of OE.

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Okay so did a coolant overhaul yesterday because I figured everyrhing else was new so why not dump more money into the radiator, hoses, clamps, etc. Taking everything out tho I found the culprit. Just like you were saying Chaz the oem thermostat is about twice as long as anything you would get from O'Reilly. While we pulled it out and looked at it it seemed like it was just too short to really good any sort of good coolant flow as the water pump sits higher up. But yes always get the oem thermostat

 

Thanks for the help guys, getting a 2.5 inch exhaust welded up today with the uel headers and a borla performance muffler and this poor legacy will be back on the road with legitimate everything new!

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Yep, I went through not one, but 3 aftermarket thermostats from O'Reilly and Autozone before I went to the Subaru dealer and spent 40 freaking dollars on an OE, but it worked. No more issues with the thermostat.
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