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installed HKS 264 cams, headgasket, now crappy compression

sleepyvr4

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Motor had good compression - 150 on all 4 prior to tear down. installed head gasket & almost new 264's and mudd. 4-3-2-1 is 80-130-80-130.

Lifters are original - 160k - are they taking a dump with these cams?

The car runs like crap. IT IS IN PERFECT TIME. With a general tune today through 3rd gear - no knock - was smooth however it just felt like it was holding back timing. I had 2g maf installed which we thought was the culprit - but after putting 1g maf back on it still sucks. Really rough idle. I had to turn out biss to get the thing to idle. Car has 780's, 255, 14b @ 15psi. #2 spark plug stays black with 2g maf - but the cylinder is dry - so we don't think it's blow-by. ??? Haven't checked the plug since 1g maf went back on.

There's a lot of variables here. I know it needs a proper tune - an afpr would be nice - etc etc etc...

Gonna try swapping lifters between cylinders to see if compression changes also. So you know we've run similar setups and been successful in the past. A little upsetting after seeing that compression...
 

turbowop

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First off, you need to rule out why you're getting such low compression in those two cylinders. Time for a leak-down test.
 

atc250r

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When I first put my 280's in I lost my compression to the point the car wouldn't start. I gave the lifters some time to bleed down and it was fine.

John
 

sleepyvr4

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I've heard of compression getting a little lower with larger cams installed - anyone confirm this?
 

boostedinaz

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Quoting sleepyvr4:
I've heard of compression getting a little lower with larger cams installed - anyone confirm this?



Larger cams will create more overlap which will bleed off compression. The difference between that and your situation is that cams will do it evenly across the board.

If you don't have a leak down tester try and get a hold of one. That is the only real way you will be able to determine were the compression loss is going.
 

prove_it

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When you installed the cams did you bled the lifters down?

If not they may have been extended to far which is fine with stock cams, but put in a larger cam and the same lifter height can cause the valves to hang open. Now if you had the lifters sitting around for a couple days without pressure against them, they will slowly extend out. If the lifters do this and extend long enough and you install bigger cams, the moment you start the engine, you can possibly bend a valve. It happens on the first crank over. The lifters will bleed down on their own, but by then it's too late.

You may have bent some valves. I say may, it doesn't happen all the time, but it can happen. I agree, do a leakdown test and check the valves sealing ability.

I got my fingers crossed for ya buddy.
 

atc250r

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If my 280's didn't bend any then I doubt the 264's did.

John
 

prove_it

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It doesn't ALWAYS happen, but it can. Just my .02
 

atc250r

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I didn't say it NEVER happens but in my experience it won't. Just my .03. /ubbthreads/images/graemlins/grin.gif
 

Quoting boostedinaz:
Quoting sleepyvr4:
I've heard of compression getting a little lower with larger cams installed - anyone confirm this?



Larger cams will create more overlap which will bleed off compression. The difference between that and your situation is that cams will do it evenly across the board.




Quoting prove_it:
Now if you had the lifters sitting around for a couple days without pressure against them, they will slowly extend out.



I agree with both of you. However, Sleepy probably didn't allow the lifters enough time to extend. /ubbthreads/images/graemlins/smile.gif So chances are it's not the valves. If you can't get your hands on leak-down tester, try swapping the lifters as you suggested. Maybe they took a dump. If that's the problem, sweet. Solved. If it's not, you might give this a shot (if so equipped):

If you have a quick coupling by the gauge on your compression tester (most do) screw that bad boy into the motor, and hook it up to an air compressor. Once it's connected it'll leak like crazy. Then just turn the crank manually until it stops leaking out of the valves. If it doesn't stop leaking, your problem is with the valves. Once you've ruled out the valves as a problem, make sure air isn't leaking into the cooling system. If you've got bubbles, it's head gasket. (99/100 times you'll see gasket problems before valves). The only things you can't really test using this method is air pushing past the rings, or into your oil passages, which should be done with proper testing equipment, so that the results aren't inconclusive. That being said, if your fittings on the hoses don't leak, you can close the valve on the compressor side, turn the compressor off, wait a couple minutes and then open the valve back up. (Make sure regulated pressure in the line is less than the pressure in the tank) If you hear/feel/see a large rush of air come back into the line, it could be rings, but like I said this test can be inconclusive. There will be a lot more places for air to leak along the lines than there is in the motor and a proper test kit. Kind of a backwards way of doing it, but it's all I could come up with to help in this situation. Besides, trying this might just lead you to an easy diagnosis. If all that doesn't work, swap your cams back out. Or maybe you should just do that first... /ubbthreads/images/graemlins/dunno.gif Kind of strange to have two different sets of even numbers on alternating cylinders isn't it?
 

sleepyvr4

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swapped lifters between low cylinder and high cylinder and no change in compression (eventually) - however comp was different in every cylinder today. The first time I checked comp after swapping the lifters there was no compression in #4. I added oil to both low cylinders (4 & 2) and there was a very minor change - which is a good sign. getting a new set of lifters (oem with 20k - versus stock with 160k that sat for 2 years) Gonna try that, and if no luck gonna put stock cams back in. Rechecked head torque and all is sweet. Too peculiar...

IF I BENT VALVES WHY THE F WOULD COMP BE LOW IN 4 AND 2 ??? IF THE HEAD WAS WARPED WHY LOW IN 4 AND 2 ???
 

sleepyvr4

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also - if you bend a valve, doesn't it look like this afterwards:





If you smack a valve off of anything there will be no compression to speak of - unlike Eric Stoltz's cranium in that movie...
 

turbowop

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You really need to do a leakdown test. Zero compression is not a good sign and leads me to believe you bent some valves. It's possible only a couple lifters were pumped up, maybe just on those two cylinders.
 

prove_it

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+1 billion
If you had no compression today, I would strongly suggest getting a leakdown tester. Don't start swapping parts around just blindly guessing to what the problem is. You'll end up spending more time and money and could cause additional problems. You need to test it.
 

BoostedAWD91

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i have never heard of having to bleed the lifters before swapping in bigger cams. so with the 3g or stock lifters, even if they have already been bleed when installed and ran for awhile, after removing the stock cams and before you put in the larger cams you should re-bleed them?
 

dmj

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orlando FL
I hate to be the bearer of bad news but I have to agree with some of the comments before this post.Chances are you bent some valves by not bleeding the lifters when you changed the cams.That being said I hope that I am wrong.
 
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