Bent valves? I dont know

davec73

SCCoA Member
Well guys as you all know my car had a problem at the shootout building compression and appeared to leak air through the intake when we did a leak down test on cyl#1. I pulled the heads yesterday and you can not see any damage or knicking to the heads or pistons?
cil1
cyl1.jpg

cyl2
cyl2.jpg

cyl3
cyl3.jpg

cylh1
cil1h.jpg

cylh2
cyl2h.jpg

cylh3
cyl3h.jpg

I am taking them to Stegemier thurs to get them checked out but I pulled the other side and got the same result and I also filled the heads with fluid and didnt see any leaks from the valves? Any ideas other than dry cylinders?
 
Did you use gasoline as the liquid to fill the chambers? Do you have too much preload? Thoes valves and pistons look great and I cannot see any evidence of clearance issues.
 
Did you use gasoline as the liquid to fill the chambers? Do you have too much preload? Thoes valves and pistons look great and I cannot see any evidence of clearance issues.
Rich, chris and and I removed the preload on the #1 cyl and put air to it and you could hear it in the intake with the valves closed I had the heads tqed to 80 ft lb with mls gaskets and copperspray on both sides but the rings were washed out on all cylinders
 
Last edited:
Did you do any bottom end work to this engine? Did you do cylinder leak down testing at the shootout or compression testing? What were your numbers? Other than having the heads checked for cracks and that they did a correct valve job it all looks ok to me. I doubt your gaskets were leaking. I still feel you have a valvetrain problem or a piston compression problem. Btw, I would change the oil, you may have some in your crankcase that doesn't lubricate the bearings very well.
Chris
 
Last edited:
Did you do any bottom end work to this engine? Did you do cylinder leak down testing at the shootout or compression testing? What were your numbers? Other than having the heads checked for cracks and that they did a correct valve job it all looks ok to me. I doubt your gaskets were leaking. I still feel you have a valvetrain problem or a piston compression problem. Btw, I would change the oil, you may have some in your crankcase that doesn't lubricate the bearings very well.
Chris
It has fresh 5 w 20 amsoil in it. We just put air to both of the cylinder # valves and heard air on top of the motom. When we added oil to the 1st cyl and checked it the comp went from 30 to 50 with both the valves closed
 
the cylinders were all dry the cross hash looks good but I a fuel problem before and with continuous cranking and no firing it looks to have dried the cylinders out

That won't stop it from running. If you are really worried about that, just spray a bunch of WD40 in there.

BTW, I'd never run 20wt oil in an SC engine.
 
That won't stop it from running. If you are really worried about that, just spray a bunch of WD40 in there.

BTW, I'd never run 20wt oil in an SC engine.
Ive already oiled it with rotella and I am going to change the oil after I get the heads back, do you have any oil recommendations?
 
I have seen a leaky fuel injector cause a cylinder to lose compression from washing the oil away from the cylinder but what you are describing sounds altogether different. Was this engine bored out? If not maybe your cylinders are wider at the bottom than the top due to many miles of mis-detonation? It would also help to know what your leak down numbers were across all 6 cylinders so that we have something to compare. 50% leakage on a cylinder isn't terrible but not great. I would run the test on the remaining cylinders.
 
I have seen a leaky fuel injector cause a cylinder to lose compression from washing the oil away from the cylinder but what you are describing sounds altogether different. Was this engine bored out? If not maybe your cylinders are wider at the bottom than the top due to many miles of mis-detonation? It would also help to know what your leak down numbers were across all 6 cylinders so that we have something to compare. 50% leakage on a cylinder isn't terrible but not great. I would run the test on the remaining cylinders.
The bottom end in question only has around 3000 miles on it and ran great before I tore it down. Unless I did something really stupid in a very very short period of time trying to crank the motor while I had fuel and timing issues the bottom end is fine. I dont have a clue how to do a cylinder leak down test, I have never had to do one and I have never set up a valve train like this one or degreed a cam. I am just in a place where I dont know what is causing the compression loss but I will know for certain if it is the heads or valves after thursday but all signs lead to no. I also had these heads set up for one cam and ended up having to order another in the middle of my build because the cam I bought would have had to be degreed and I might not have been able to get the $300 timing gear set in time to get it together so I just ordered a new cam. We had the valve train pretty well set up in the parking lot at the shootout where none of the valves where staying open when they wernt supposed too. So when I get the heads back I am going to make sure and oil the cylinders while it is still at that point and check the compression on each cylinder before assembling it the rest of the way and make sure I dont need to go ahead and pull the bottom end and have it rebuilt which if I dont have good comp once I get the heads back and get them bolted down would be very easy to do at this point an I will put it on an engine stand and assemble it right.
 
I have seen a leaky fuel injector cause a cylinder to lose compression from washing the oil away from the cylinder but what you are describing sounds altogether different. Was this engine bored out? If not maybe your cylinders are wider at the bottom than the top due to many miles of mis-detonation? It would also help to know what your leak down numbers were across all 6 cylinders so that we have something to compare. 50% leakage on a cylinder isn't terrible but not great. I would run the test on the remaining cylinders.

Also my timing and crank sensor was wrong and it was fludding the cylinders I had the injectors dynoed and they are all fine.
 
If you hear air thru the motor with no preload your valves are bent, they don't necessarily leave a mark on the pistons.
 
Through the throttle plate or the intake tube? If the noise could be heard through the intake tube then it could be rings as the air would come out of the left side valve cover vent tube, assuming the oil cap were still in place, which crosses over to the intake tube. The air would have to go that route as it would be the path of least resistance at that point. However you are correct if the noise was heard further up at the throttle plate with the intake tube removed it would be a bent valve.
 
Last edited:
They were listening for the air out the exhaust if I'm not mistaken.

We were listening for air out of the exhaust and intake. It could be heard listening to the lower intake opening the return adapter bolts to. As stated before a bent valve can hold liquid in the chamber upside down. Remember you did make 50 psi during cranking and air will leak faster than most liquids.

Another thing is and Dalke can chime in here if he has an opinion too. MLS gaskets are supposed to be insalled dry without any contamination. Copper spray won't necessarily cause them to leak but they are designed to seal by themselves on an RA surface finish under 50ish. Just a thought.
 
Slightly leaking valves will not prevent start-up. In fact many "remanufactured" cylinder heads won't pass a liquid leak test yet they still run. If you got 50psi then you have enough compression to run. Chances are you have some other issue. I don't think it's mechanical. Make sure the cam is timed correctly. Also check your tune. Make sure the QH is connected properly, the datalogging works, and your injector sizes are right, etc. Wouldn't be the first time someone was trying to start their car with the stock tune file.
 
We were listening for air out of the exhaust and intake. It could be heard listening to the lower intake opening the return adapter bolts to. As stated before a bent valve can hold liquid in the chamber upside down. Remember you did make 50 psi during cranking and air will leak faster than most liquids.

Another thing is and Dalke can chime in here if he has an opinion too. MLS gaskets are supposed to be insalled dry without any contamination. Copper spray won't necessarily cause them to leak but they are designed to seal by themselves on an RA surface finish under 50ish. Just a thought.

I have never had a bent valve hold gasoline but there is always a first. That's what I use for testing but I absolutely agree with everything you stated. Ar50 or better and a dry and clean gasket surface should be fine. This is why I always get an older engine block decked if I am going to run an mls.
 
Back
Top