Yes, have a professional do it for you....Well, had a moment to play with it. Backed out all the lifter preload, still can't get the intake valve to seal at the proper time.
I ended up hooking up the leak down tester and running only like 20 psi of air in to the cylinder. Enough to hear it but not enough to do the actual test. I then slowly spun the engine around by hand, several revolutions, both listening to the hissing and, since I don't have the intake manifold on, watching the lifters raise and fall. Also, I decided to try it on the the worst cylinder. The one that had the previous leak down test of 72psi being put in and only reading 20 psi staying in.
As I turned the crank, very slowly, there is one very small moment where the intake valve seals and no air comes out of the runner, but, instantly, the exhaust opens and the air starts coming out of exhaust. Even looking at the 4 stroke animations, it seems there should be a good amount of time that both intake and exhaust valves are sealed as the piston compresses the mixture. I don't have that.
Here are some things I'm thinking-- before I pull the head off.
1. The heads came from marketplace with the TFS stronger springs already installed. I took them off during cleaning, re-measured the height and re-shimmed as required. If I recall, most places required 1 more 0.015 shim then they previously had. Could I have messed something up here that would cause my issue?
2. In the TFS spring instructions, it said the keepers for the springs come in 2 bags-- 1 for exhaust, one for intake. The keepers were already on the valves when I got the heads. Could the previous owner have mixed them up? Would that cause my issue?
3. Can the cam be so much defective that it doesn't open/close the valves at the right time? Does that even happen?
Any other ideas? Thank you!
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If I bought a set of used heads, unless I got them from a machine shop, that'd be what I'd do, now a trick a guy taught me was to take brake cleaner or some alcohol and spray on the back side of the valve, we did this with the head off, and looked on the combustion side for wetness.
Just spit-ball'n
Just spit-ball'n
I wasn’t talking about the preload. I mean completely back the rockers off so all of the valves are closed. This is where the springs are exerting all of the closed pressure they have on the valve. Pressure up each cylinder and listen for leaks at the intake and exhaust ports of the heads. If any of them leak then you have a problem. The used heads I bought had six valves that leaked at the seat and another three or four that leaked up through the guides. Several hundred dollars later they were good to go.
Moral of the story is take used heads to a shop and get them checked before you install them.
Moral of the story is take used heads to a shop and get them checked before you install them.
Just a quick update. I did end up pulling all the rockers off and re-doing the leak down test. The air was still leaking out on the intakes on all cylinders.
Unfortunately, I don't have the money to take the heads to a shop. My wife would kill me as is if she knew how much this is costing me. Anyway, I took the head with the worst reading off, and after doing more research online about valve lapping, I re-lapped the valves. This time I used a drill (online opinions differ on the goods and bads of this approach). I also decided to spend $50 and get new intake valves. Alex's store online is great. They had the lowest price, fastest shipping and all the info I needed to choose the right valves. http://alexsparts.com
Anyway, I used an old valve from each cylinder and lapped it about 20 times in one direction, 20 times in the other. Then, I'd put the New valve in with spring and spacers, flip the head, spray wd40 over the valve face and cover the intake port with a towel and blow 100psi air in. At first, I saw big bubbles. I'd repeat the lapping. After a 2-3 rounds, the bubbles were small. I figure I shouldn't push my luck and I'd stop there. 1 cylinder even fully sealed.
To be sure I'm on the right path, I took the old head that I took of the mustang in disassembly, still covered in oil and carbon, and ran the same air test on 4 cylinders. 3 out of 4 had bubbles coming out. Again, this is from a running mustang. So, I figure the new heads should do ok. Maybe later I'll have some money for the AFR heads, or decide to get the gt40p ones to a shop, but for now, they should run.
For comparison, the new leak down test numbers are in black:
Here's and example of the old valve and seat after lapping:
Unfortunately, I don't have the money to take the heads to a shop. My wife would kill me as is if she knew how much this is costing me. Anyway, I took the head with the worst reading off, and after doing more research online about valve lapping, I re-lapped the valves. This time I used a drill (online opinions differ on the goods and bads of this approach). I also decided to spend $50 and get new intake valves. Alex's store online is great. They had the lowest price, fastest shipping and all the info I needed to choose the right valves. http://alexsparts.com
Anyway, I used an old valve from each cylinder and lapped it about 20 times in one direction, 20 times in the other. Then, I'd put the New valve in with spring and spacers, flip the head, spray wd40 over the valve face and cover the intake port with a towel and blow 100psi air in. At first, I saw big bubbles. I'd repeat the lapping. After a 2-3 rounds, the bubbles were small. I figure I shouldn't push my luck and I'd stop there. 1 cylinder even fully sealed.
To be sure I'm on the right path, I took the old head that I took of the mustang in disassembly, still covered in oil and carbon, and ran the same air test on 4 cylinders. 3 out of 4 had bubbles coming out. Again, this is from a running mustang. So, I figure the new heads should do ok. Maybe later I'll have some money for the AFR heads, or decide to get the gt40p ones to a shop, but for now, they should run.
For comparison, the new leak down test numbers are in black:
Here's and example of the old valve and seat after lapping:
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