30 psi of compression on cylinder 8
03-11-2012, 12:44 AM
#11
The best test I would think to perform would be a cylinder leakage test. If unfamiliar, its a tester that has two air pressure gauges on a metal block with a regulator. You hook it up to shop air. One gauge will tell you how much air is being pumped into the cylinder, the other gauge tells how much is leaking out and how fast. Usually give that number in a percentage.
You would bring #8 cylinder to TDC on compression stroke, thread leakage tester into the spark plug hole, connect tester to shop air, regulate to 50-60psi, and see how fast it is leaking out. Since you know air is leaking somewhere, you should be able to pinpoint where. If you hear a hissing coming from exhaust, it be the valve. If coming out your throttle body, intake valve. If pressurizing the crankcase, it's the compression rings, if coming out of the spark plug hole in adjacent cylinder, head gasket.
Now, I'm in no way a professional mechanic, but this is the test I would perform. Anyone else familiar with a leakage tester? I picked mine up at JCWhitney for about 80 bucks, if I remember correctly. If I am leaving something out, someone please correct me.
Its a good test that will help pinpoint exactly whats up and where your problem is. Every good diagnostic toolbox should have one in there.
Hope this helps. I could upload a picture if you would like to see one.
You would bring #8 cylinder to TDC on compression stroke, thread leakage tester into the spark plug hole, connect tester to shop air, regulate to 50-60psi, and see how fast it is leaking out. Since you know air is leaking somewhere, you should be able to pinpoint where. If you hear a hissing coming from exhaust, it be the valve. If coming out your throttle body, intake valve. If pressurizing the crankcase, it's the compression rings, if coming out of the spark plug hole in adjacent cylinder, head gasket.
Now, I'm in no way a professional mechanic, but this is the test I would perform. Anyone else familiar with a leakage tester? I picked mine up at JCWhitney for about 80 bucks, if I remember correctly. If I am leaving something out, someone please correct me.
Its a good test that will help pinpoint exactly whats up and where your problem is. Every good diagnostic toolbox should have one in there.
Hope this helps. I could upload a picture if you would like to see one.
03-11-2012, 09:56 AM
#12
2nd Gear Member
Join Date: Jul 2009
Location: canada
Posts: 408
thanks for all of the help guys. i believe my budy has one at his shop so i can get it done to help find the problem i did a dry and wet compression tests and it was different by about 2-3 psi on the #8 cylinder. so im prying its not the piston rings. but im going to go ahead and get this next test done. again thanks guys
If it was the rings, there would be a tremendous amount of air getting into your crankcase. Easy test. Start the car, take out your oil dip stick or oil fill cap off. If air is blowing out a lot harder than you think it should be, good chance its the rings. All engines have a little crankcase pressure, but you'd be pumping 150psi into it on every compression stroke. It would be enough that as soon as you take the oil cap off, you'd be like, WTF????
Its worth a try. But that cylinder leakage test will give you the best results.
03-11-2012, 07:48 PM
#13
okay yeah imk getting a leakdown test but im almost positive its an exhaust valve. Im going to have my buddy take it to the shop and give it one. If so im going to be putting a new head on. so i guess this would be a good time to ask about a PI head swap? i found a pair of them for 400 plus shipping
03-11-2012, 10:40 PM
#14
2nd Gear Member
Join Date: Jul 2009
Location: canada
Posts: 408
okay yeah imk getting a leakdown test but im almost positive its an exhaust valve. Im going to have my buddy take it to the shop and give it one. If so im going to be putting a new head on. so i guess this would be a good time to ask about a PI head swap? i found a pair of them for 400 plus shipping
As for the head swap, that is something someone else will have to help you out with. I'm pretty good with diagnosing problems and such, but when it comes to swapping parts around, I'm clueless...lol
Hope you figure it out though...
03-12-2012, 01:46 PM
#18
3rd Gear Member
Join Date: Jun 2011
Location: East middle of no where, WV
Posts: 585
That's exactly what I mean. I can't imagine their head being less than $1300 if fully assembled.........which to me sounds like a waste, especially if they are Doorman...........
Edit: read the thread again, there is no way it's a fully assembled head, with cams.....or even without, and lifters and followers and valves. I just don't see it. You should get a set of real Ford PI heads, and an FRPP intake manifold. Just my opinion, don't want to see anyone waste money on junk.
Edit PT2: Just looked that info up on Autozone's site and I can't believe it but it is fully assembled. It still sounds too good to be true. If this IS the way you want to go, I think you are going to be the first to try them and will be a crash test dummy of sorts. From the description on autozones site, it sounds like a refurbed ford casting. If you do go this route, please take tons of pics of the heads and post them here. And let us know how it turns out.
Edit: read the thread again, there is no way it's a fully assembled head, with cams.....or even without, and lifters and followers and valves. I just don't see it. You should get a set of real Ford PI heads, and an FRPP intake manifold. Just my opinion, don't want to see anyone waste money on junk.
Edit PT2: Just looked that info up on Autozone's site and I can't believe it but it is fully assembled. It still sounds too good to be true. If this IS the way you want to go, I think you are going to be the first to try them and will be a crash test dummy of sorts. From the description on autozones site, it sounds like a refurbed ford casting. If you do go this route, please take tons of pics of the heads and post them here. And let us know how it turns out.
Last edited by 1998Slow 'Stang; 03-12-2012 at 01:54 PM.
