Problem with valve installed height possibly? (single cyl miss)

[93'colttsi]

Car is a evo 1 GSR. Stock engine internals as far as I know, but it could have had a head job at some point, Im not sure though. Car ran fine and like stock before the following mods.

Installed brian crower stage 1 single springs and retainers, installed new supertech valve stem seals at the same time along with 3G lifters and 264 crower stage 1 camshafts.

Immediately after starting her up I noticed a really rough idle and it ran off 3 cyl's in the lower RPM range, smooths out at higher rpm (over 3000 rpm) Did a compression test and got 5 psi on cyl #1 and 160 on all others. used camera and checked out the valves through the plug holes. intake and exhaust valves are both opening and closing together, no impact marks or anything to be seen on pistons or valves. Was hard to see if they seated perfectly against the seats though. Did a leakdown on cylinder 1 and got 100% leak at first (TDC #1 compression). After about 30 seconds it just went to 5% leakdown magically by ifself (WTF) without the engine turning over. I turned the engine forward, then back again several times, duplicating the loss of compression and then the valve seating itself after 15-30 seconds. Found if I put slight pressure on the intake valve closest to the belt, I could keep it leaking, as soon as I let off pressure on the spring retainer the valve would shut and leakdown would go to 5% again.

I tried two different lifters (bled them and installed). Instantly I got consistent leakdown on number one, and performed a compression test and got 160 psi again. Put VC back on and started it up. ran great off all 4 cylinders again, but obviously the bled out lifters were ticky for 10-20 minutes. as soon as the lifters bled the air out and quieted down, I got the misfire again at lower RPM. Loss of compression in #1 once again. But now, with a very slightly different lifter in there (just a different brand) the misfire goes away at 1800-2000 RPM now instead of 3000ish rpm as before.


My instincts tell me this is a valve installed height problem... i have no lifter tick once the lifters bleed themselves out.... but the engine just runs like crap!!

Or could this be a problem with the camshaft? or something to do with the spring/retainers??

HELP! D

is it possible to machine a small portion of the lifters off the bottom to reduce its overall height as cheap remedy?

 

[1990TSIAWDTALON]

This sounds awful but when I made the mistake of not bleeding lifters, I rolled my cams over with pistons at mid-bore and the lifters that hadn't bled off hung the exhaust valves open ever so slightly and allowed my intake valves to JUST BARELY touch them (and made this "ting" once but never again), but it was enough that they wouldn't seat completely unless I pried up on the spring just a bit then they would hold until the next rotation. Maybe the open and close of the valve at a higher RPM is allowing it to close properly but not at idle. Its pure speculation but it did happen to me and only when my machinist put those valves in his grinder could he see the heads wobble. They bent right at the point where they are exposed in the guide, thus allowing them to hang open. I hope this is not your problem but thought I would put this out there as possibly one valve bent ever so slightly. Just a guess and I sure hope I am wrong. You never did anything to the valves that would change its installed height so it should be a constant, you only changed springs and seals. See if you can gently pry up on the spring and make it hold....that would mean that it has somehow bent just barely. Good luck, I don't want that to be your problem!

 

[93'colttsi]

With the lifters out, the valves seat instantly without any issues. The same valves also seat fine when the lifters still have some air in them (normal after bleeding them). Its not until the lifters stock ticking, and the air is all out, then the valve has issues seating. For all I know it could just be a bummed crower intake cam... this will take some investigating!

 

[1990TSIAWDTALON]

That's a good sign! Glad to hear that they seat properly except in your pumped up issue. Do you think the springs have enough seat pressure and are at the correct installed height? Could that be the problem? Maybe they needed shimmed.

 

[93'colttsi]

Well im pretty sure installed height has to do with just the height of the valve stem. to adjust you need to grind the margin of the valve. The BC springs SHOULD have enough spring pressure.... the base circle on the crower cams should be the same as stock.

 

[1990TSIAWDTALON]

Well sometimes you have to shim the springs to get correct installed spring height which will determine how much pressure that spring has....too tall and it doesn't have enough pressure and too short and you get into coil bind. Maybe something hard to tell if it is correct on the car. My springs have a card that gives the specifics of free length and compressed length. I have never had to grind the tip of a valve stem and since you didn't change the valves I would assume that nothing there changed, I mean there isn't any way that valve grew and changed length is what I'm getting at but trying to be as helpful as possible.

 

[93'colttsi]

Okay, talked to the owner of the evo and he did confirm the engine had been rebuilt at one point. This would make the option of incorrect installed height more plausible.

the installed height can change sometimes if a valve gets to hot and "tulips" (pulls stem up higher) or also if the seat or valve face wear a bunch (which I have never seen on a dsm motor),

 

[90gsxProjectCruiser]

Did you pull the valves out? Could you have not put the valves back in the the same order? I've Hurd many times that its best to put valves back in the same location if you are reusing them.

 

[90gsxProjectCruiser]

Did you take the valves out? Is there a chance you didn't install them back to their original location? I've Hurd many times that you want to put the valves back in the same location if you are reusing them.

 

[bastarddsm]

sticky valves letting the lifter pump up? It's almost impossible for it to happen any other way. Even if you had full oil pressure at the lifters theres not enough area.

 

[donniekak]

Try putting your old lifters back in after you bleed them with a needle. Some of the new lifters have issues.

 

[93'colttsi]

Okay, I'll try and swap the old lifters into the problem cylinder and see what happens (small oil hole 1g style lifters)

Also I did the work with the head installed using the on-car special tool and compressed air.

 

[93'colttsi]

Okay. Swapped lifters back in (original ones). Ran off all 4 cyl's untill the lifters bled out the air, then lost compression on #1 again. Time to look very close at the cam lobe. Used a dial indicator and checked the base circle. Found that both intake cam lobes have a dip on the base circle right before the ramp up. Measured a drop of .003-.004" on the cylinder 1 lobes. Checked the other base circles on the other intake lobes, and they stay within .001" on the base circle the whole way, with no drop like cylinder 1. Removed the intake cam... swapped in the stock evo 1 intake cam (left the crower 264 exh. Cam in there for now). Car runs like a champ again. Lifters bled out, (also threw he new ones all back in again) and there's no more missfire. Problem solved! (defecttive/improperly machined crower 264 intake cam). I took some vids of me checking the base circles with a dial indicator... I'll post up the vids when I have a chance to upload them.

 

[93'colttsi]

http://vid274.photobucket.com/albums/jj242/93tsicolt/badlobe.mp4
a short video of the suspected defective cam lobe base circle.

 

[93'colttsi]

car is back on the road and running great! (with the stock intake cam back in (\
going to send the crower 264 intake cam back to crower and see if they will possible check it out and maybe replace it as incorrectly machined.