compression test results

[packinkimber45]

Hello guys, I did another compression test on the motor yesterday. Unfortunately the number doesn't look so good. 140/135/120/145. Between high and low, I probably need to rebuild? During the test, there was no indication that cylinders were losing compression on the gauge. I have not done a wet test yet. What other reasons could be for the cylinder being 120 besides rings? Could motor get colder and show different results? I only let the car warm up by letting it idle for a while. Per temp gauge on dash car was warmed up or should I have taken the car for a drive? Reason I didn't is due to car running rough. When I bought the car, the owner told me motor was swapped out on my 90 talon awd. I was told it is a 91-94 turbo 6 bolt motor. It is suppose to be a jdm motor, but owner took off cyclone manifold and jdm valve cover. Is there a way to verify if this motor is in fact a jdm motor? Also is it possible car was swapped with a 6 bolt n/t motor and added a turbo to car? How do I verify that the motor is in fact a "6 bolt turbo motor"? I know how to check for 6 or 7 bolt. I know it is a 6 bolt. Your help would be very much appreciated. Thanks.

Ps.
Hopefully I sell my gsx soon so I can have some funds to work on the car. I wonder if $1300-$1700 is enough to rebuild for a daily driver with goals of 300hp-400whp in the low 13's to high 12's? I already have my stage 1 mods by the way.

 

[packinkimber45]

anyone...

 

[fwdturbobov1996]

Hello guys, I did another compression test on the motor yesterday. Unfortunately the number doesn’t look so good. 140/135/120/145. Between high and low, I probably need to rebuild? During the test, there was no indication that cylinders were losing compression on the gauge. I have not done a wet test yet. What other reasons could be for the cylinder being 120 besides rings? Could motor get colder and show different results? I only let the car warm up by letting it idle for a while. Per temp gauge on dash car was warmed up or should I have taken the car for a drive? Reason I didn’t is due to car running rough. When I bought the car, the owner told me motor was swapped out on my 90 talon awd. I was told it is a 91-94 turbo 6 bolt motor. It is suppose to be a jdm motor, but owner took off cyclone manifold and jdm valve cover. Is there a way to verify if this motor is in fact a jdm motor? Also is it possible car was swapped with a 6 bolt n/t motor and added a turbo to car? How do I verify that the motor is in fact a "6 bolt turbo motor"? I know how to check for 6 or 7 bolt. I know it is a 6 bolt. Your help would be very much appreciated. Thanks.

Ps.
Hopefully I sell my gsx soon so I can have some funds to work on the car. I wonder if $1300-$1700 is enough to rebuild for a daily driver with goals of 300hp-400whp in the low 13's to high 12's? I already have my stage 1 mods by the way.

I thought 6 bolt motors were 90-92??? Maybe jdm is diff.

Did you let the car come to operating temp before doing the test? That can be a huge part.
How many times are you cranking it over before you let off?

 

[Stainbox12]

alright, those compression numbers are very low, and there's more than 14 psi difference beetween 2 of them, definetly you need a rebuild, but this could be several things, probably is just normal rings wear, in which, you take out the engine, buy new rings, use the same pistons, and just take the block to the machine shop and make it check it. rings are around 120 the set (original ). if the block is bad, then you would probably need oversized pistons and make the machine shop hone the block, or just rebuild the cylinder walls, and use stock pistons. N/T cars are kinda different though, but i don't think you have a N/A, because otherwise, the compression would be higher, and not that low like yours, the max compression is around 160 for a 1g turbo engine. the only thing that may change, is the block, if it was swapped with an N/A one, the only difference is that it doesn't carry oil sprayers. with 1300-1700$ i would be in the low 12's easly if you have done the stage 1 mods, just use your money wisely dude, and you will get there, also get a chilton's manual, and begin doing the stuff on your own. get a headgasket, rings, and if the block is fine, call it a day. good luck.

 

[matt j]

well from what i know that there is no difference between the actual motors from USDM to JDM, The only difference is the intake manifold having the second set of flappers, but you need the jdm ecu to run the second set. Other than that it is the same bore and everything as the USDM.

Anyway, i would honestly do a rebuild on it. For just a standard rebuild with second gen pistons would run around 1500 bucks or so. And the 6 bolt motors were from 90-92, 92.5 and up were the 7 bolt motor.

Also is the car smoking at all? like after boosting for a while does it blow out smoke after you restart it? i would verify that your HG isnt blown.

 

[packinkimber45]

I thought 6 bolt motors were 90-92??? Maybe jdm is diff.

Did you let the car come to operating temp before doing the test? That can be a huge part.
How many times are you cranking it over before you let off?

Maybe he meant 91-92. He did say that he had to use the 90 coil pack due to the plug differences. As far being 6 bolt, per vfaq I looked at the oil pan right below the crank pulley and it has the hump towards the driver side so it should be 6 bolt. I am not really that concerned if the motor is jdm, actually I just want to know if there is a way to tell if the motor is not a factory turbo motor. I was asked before if I have verified if the motor is a 6 bolt non turbo that was thrown stock turbo on it. Is there a way to tell this? If it has a 6 bolt n/t block? If it has non turbo head as well? Compression should indicate this right? When I did the compression test it was at operating temp per temp gauge. I was cranking until the needle stops. Is this wrong? Thanks.

Now I am debating if I should just keep my 91 gsx that smokes but has good compression or sell it still and dump the money into the talon motor or motor swap.

 

[packinkimber45]

The car does not smoke at all. I need to flush the coolant in the car since coolant looks orange to brown like it is corroded. Reservoir tank is empty. I haven't done this procedure yet; I have been dealing with other issues outside of car project. I checked for oil in the coolant and I found none. Once I flush and refill this week I will check again for coolant in the oil. How about the head, is there a way to tell if the head on the car is off of N/A motor? What are oil sprayers and how do you verify if a motor has them? I am assuming that once motor is overhauled that is when I will be able to verify this? I am kind of nervous to do my own work on my motor; I have a very limited mechanical experience. I am willing to learn though. I do have a Chilton's manual and I am looking for one of those factory manuals that are in more detail. Would you guys not recommend doing these things on my own if I have never done these things before? Mechanical work that is, especially overhauling an engine. Thanks.

 

[brknDSM]

When you perform the compression check, disable the fuel system and pull out all the spark plugs. Hook up your tester, and this is the important part: make sure your engine is at operating temperature and hold the throttle all the way open. Your readings will be low if you don't hold open the throttle. Usually compression checks are done with 5 pumps of the needle, not until it stops.

If you still have low compression, do a wet test. Spray some oil, WD40, or petroleum product into the chamber down the spark plug hole and repeat. If your readings go up, your compression rings are worn, if not and still low, it could be your valve guides, valve seats, or head gasket.

To help tell if the head is from an N/A engine, check out the letter stamps on the cams. Usually that's a giveaway, but doesn't work 100% of the time.

Hope that helps ya out

 

[brknDSM]

WOOHOO! I found this on one of my backup DVD's labeled "stuff I'll probably never use again"

2.0 DOHC turbo 5 speed up to 1994:

Intake valve, Cam ID Mark "D"
Opens: 21 deg BTDC
Closes: 51 deg ABDC
Overall duration: 252 deg
Lift: 1.4 inch cam height

Exhaust valve, Cam ID Mark "C"
Opens: 57 deg BBDC
Closes: 15 deg ATDC
Overall duration: 252 deg
Lift: 1.39 inch cam height

2.0 DOHC turbo 5 speed AND automatic 1995+:

Intake valve, Cam ID Mark "J"
Opens: 21 deg BTDC
Closes: 51 deg ABDC
Overall duration: 252 deg
Lift: 1.37 inch cam height

Exhaust valve, Cam ID mark "J"
Opens: 57 deg BBDC
Closes: 15 deg ATDC
Overall duration: 252 deg
Lift: 1.37 inch cam height