Guys,

Might need a new short block. Taking the car to the engine shop monday for final diagnosis.

Can you give me some leads on some good short block deals.

Thanks

 

Ut oh, not you too!!! What happened?:(

 

Uh oh.......now what???????????

 

There is one in here... http://forums.corvetteforum.com/zerothread?id=369022

 

More details please ! What happened ?

Vic

 

Sorry guys to keep you hanging.

Here is what happened last night. I built a leak down tester and took it out to the dealership to try it out and see if maybe that is the reason I am running poorly.

Here is what I did, you tell me if I did anything wrong.

I tested the leakdown tester and it held pressure with out leaking down. This tells me that it is not the unit itself loosing pressure.

I took off the driver valve cover. Got the engine to TDC on the compression stroke. Both RR were up and I could wiggle them a bit back and forth, which tells me there is no pressure on the valves holding them open. I screwed my compression hose into the SP hole and attached it to the leakdown tester via a quick connect.

I then attached the supply line to the incoming side of the leakdown tester. Due to the fact that the guy at Autozone told me I could regulate the air pressure when in fact all it had was a shutdown valve I could not turn the air pressure down to 100 PSI to make comparing the two regulator during reading easier, I just had to use line pressure. ~140 PSI.
OK. The supply line side guage went up to 140 PSI as expected. I then opened the valve between the two guages to allow the pressure to enter the cylinders. While the valve was open, both guages read 140 PSI. I could hear a hissing sound that seemed to be coming from my lifter valley. I then closed the valves between the two guages and expected to see a slight, but not quick dropoff in pressure. Right?

Well my cylinders bled down in less than 5 seconds to zero...That is not right, correct? I tried it on different cylinders, different sides of the engine, everything did the same. I was really getting frustrated. No-one in this area knows anything about doing these tests. I called the engine shop that is going to degree my cam for me, and he said it sounds like I am doing everything right. What do you guys think?

I am taking the car to them on Monday and he said he would check everything out for me. He said he wants to make sure the lower half is OK, before I waste the money to do the cam. He is a really honest guy to deal with and they really know there crap.

Do you guys think my rings are shot? It doesn't smoke or anything. Even when at WOT. Doesn't burn oil either. When I had the engine apart, you could still see the cross hatch on the cylinder walls.

I think I was doing something wrong. I can also tell you if you did not have the piston at TDC it turned the engine over in a big hurry.

Let me know what you guys think.

Thanks.

 

Hmm....

I would think that if your rings were THAT shot you'd be burning a hell of a lot of oil and you would also have some pretty good fuel contamination in your oil. Nothing?

Your valves aren't open a tiny bit are they because of the cam? That to me would make me think the cam was definitely off.

 

That's not the way i've done leak down tests before.

typically the leak down tester has a way to limit soruce pressure...i usually use about 90-100 psi. Then the secondary guage reads the pressure in the cylinder for comparision. This is all done with source connected and some amount of air flowing thru the cyls....if none were flowing...the leakdown would be zero. However it's normal for some air to leak thru, particularly thru a well used stock bottom engine. You'd like to see no more than about 10%. So if the source would be 90psi, the cyl side should be 81psi or more. You should also back off the rockers to insure that there is no residual pressure on the valves. Although i've never tried it, i would assume the pressure in the cyls would drop very quickly if i removed the source.

btw, it's not unusual to hear the air hissing thru your oil system (lifter valley, opposite valve cover, etc.) You shouldn't hear it coming from your exhaust or your intake. That would indicate a leaky valve.



[Modified by ralph, 12:54 PM 8/23/2002]

 

Scorp as indicated, I could wiggle the valves back and forth. I did try it at while rotating the engine around to see if I could get a spot to seal everything off and when the valves were open, you ould hear a definate sound coming from the headers or the intake. As soon as they closed it was silent, yet the noise still came from the lifter valley.

Christ, if that thing is leaking that bad and still able to run low 13s/12s then I will be cranking with a new ring job or new short block.

Keep in mind though, I still have not solved the glowing headers problem, so there may be more to the story.

Ralph, I'm sure you have done these tests before. What does your experience tell you?

I was thinking about it last night in bed. I was thinking if there is any kind of leak which you will always have a little, then what would keep it from leaking down all the way? Maybe your suppose to read the pressure drop when the valve is opened between the two guages. But then mine would have been 0 loss, it never changed. I'm confused.

Someone clue me in. :confused:

 

You mean the rockers? The valves should be in darn tight.

 

Something doesn't sound quite right about your leakdown tester. The leakdown value is the difference between the two guages while pressure is being supplied to the cylinder, shown as a percentage of the 2.

If you shut off the air pressure to the cylinder it will bleed off. That part is normal.

 

read my post again (i have edited it some). I dont think you did the test correctly and/or your leak down tester is screwed up, and it's normal to hear air leaking into the oil system.

 

also......before my head gasket went bad, i had three cyls that had over 15% leak down (which is bad) and the car still ran strong....that is until the gasket blew....and even then i still ran a 13.2 on 6 1/2 cyls...lol. After i repaired the gasket, the leak down was back down to under 10% on all cyls with most having only about a 5% leak down

 

Yeah the RR. Sorry. Typing in a hurry.

 

The noise into the crankcase is air by the rings. Noise in the intake, intake valve, noise in the exhaust, exhaust valve.

When I'm doing a leakdown, and I hear exhaust or intake valve noise, I'll slap the valve with a ruber hammer and see what happens. Sometimes you can have carbon on the seat and the slap will seal it up. 5 to 10 percent leakdown is pretty healthy. You get above that, something isn't quite right.

I test at 100 psi. That leaves the other guage as your percentage of pressure held. So if the second guage reads 90 psi, there's 10% leakdown for that cylinder.

 

I think that I was doing it right. Except I was shutting off the valve between the two guages. I think the problem I am having is that my guages do not have regulators on them. Therefore everything goes to equilibrium and they read the same. Right?

Still I saw no real drop in the original reading when the valve between was closed. In other words. If the line pressure was 140 PSI with the valve between the guages closed, then I opened it, the second guage read 140 PSI but you could hear hissing. You follow what I am saying?

 

You're going to hear hissing. It's where the hissing is coming from thats important.

Your leakdown tester, itself, doesn't sound right.

 

I agree, the first regulator needs to have a regulator on it for it to work correctly.

The second one can just be a guage.

 

ralph and slowrvette are dead on, think about it. if you're not holding any immediate pressure on a leakdown (which is relatively low pressure), you'd get nothing at all on a compression stroke....nada. if that were the case in one or more cylinders, it would be very apparent. i gotta think it's your tester.... have you done a compression test? if you suspect a problem with the glowing headers combined with compression issues, i would think a burned exhaust valve or valve timing. do the headers glow on both sides? if so, you just might be a notch off on your chain....... :confused:

 

THey glow on both sides. I think its gonna be the cam. I doubled checked the dots on the two timing gears. THey lined up exactly through the centerline if the gears.

I called Lingenfelter and they made me feel less than comfortable with the fact that the cam was ground on the correct centerline. They said, "Yeah we get some of them back. Not all, but some!" wth is up with that! That is the reason I bought their stuff. So I did not have to be on John Forces pit crew to put this thing together.

I agree that the tester is not working as it should. And that my rings are probably OK. On the other hand, I will opt to have the shop check it out. I look at it like this. It puts to bed one other possibility. Then its onto the cam for degreeing it. After that I am lost, if it still runs like a turd.

I am bound and determined to unvail the root cause of this thing. I have made it my lifelong goal now :lol:

Pretty soon I am going to see my user % start dropping everytime I post something. You guys have to think I am a real dandy. But hey I am learning a lot.

Thanks for your help, its appreciated.