archangelus2

Well after finally getting my cylinder head to the machine shop the verdict is warped intake valve. I have never used this machine shop before and am hoping they know what they are doing.

I had been having a sticky idle (1500rpm) that would eventually even out and the engine was missing for a brief time after start up. Eventually ended up doing a compression test and found 7/8 cylinders were around 200psi while cylinder #4 was only getting 90psi. I tried to do a leak down test but my results were a little off so I figured they were inconclusive (I don't know what I'm doing). Everything was pointing to a bad exhaust valve, so the intake valve was a little bit of a suprise. I wasn't experiencing any smoke out the exhaust on start up which was a little weird if it was an exhaust valve.

I bought these heads as a replacement for some that were mollested (manifold bolt holes were torn up) by the previous owner. I got them off of ebay and had them checked for straightness before I put them on and everything checked out ok.

So my question is what can lead to a warped intake valve??
Or do you think that it was bad from the get go?

Another weird thing was that my scantron fuel trims were reading in the 110-120 range.


Any advice or help is greatly appreciated. This is my daily driver in college and I would like to get it back together while avoiding all possible mishaps to avoid doing this again in the future.

Thanks,

-Gabriel

archangelus2

Should I try this in the Advanced Tech forum?

MaxLean

Perhaps the previous owner floated the valves and that one was the first to hit the piston thus bending it?
Scott

SStrokerAce

Yeah it was probably bent, meaning the cylinder didn't seal and cause this issue. That sucks.

Bret

archangelus2

Are there any measures I can take to avoid this happening again? What exactly does floating a valve mean and how do you keep from doing it?

shoebox

Be nice to your engine and know it's limitations. Don't know your mods, so that makes it hard to predict what you might have to worry about.

archangelus2

Shoebox,

My car pretty much just has bolt on's. MAC mids, borla cat-back, tb bypass. I am usually pretty easy on my engine so that's why this situation doesn't make a lot of sense. To float a valve I thought you had to have been revving your engine at redline alot. I usually am trying for the best gas mileage I can get, with maybe a fast romp onto the freeway now and then. I think I either did something wrong the last time I replaced my head gasket (Felpro 1074) or something was wrong with the head (off of a 75000 mile 95' vette) when I got it. I am really surprised it was the intake valve as well. I figured if it was a valve it would have had to have been the exhaust as my car would eventually idle ok and stop missing. I Just hope when I get it put all back together that it will work ok until I graduate next May.

Also doesn't make alot of sense that my spark plugs were carbon fouled, if I had a cylinder at low compression wouldn't the PCM try to lean things out because of all of the unburnt fuel??

speed_demon24

I'de just throw a set of LT4 springs on it while the heads are off, it would be cheap insurance.

Z-RATED94

Wouldn't hurt, and maybe a set of good condition used 1.6 roller rockers. Throw in a good mail order tune and you could probably pick up about 25HP and still have a dependable car.