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Old 03-17-2013, 02:36 PM
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Lifters from Heck!

Rebuilt a 87 roller 302 from a Mercury Grand Marquis. Installed new lifters. No compression in half the cylinders. When I back off the rockers, compression is good. I can't remember putting all the valve springs and retainer clips back on the valves they were originally on. There's so much talk about valve spring height. If the exhaust and intake valve springs were switched, could this cause the problem? I tried ordering a replacement set of lifter with the same results. I've tried moving one set of lifters from a cylinder with compression to one without and now both cylinders are dead. I've talked to many engine rebuilders who are just as confused as I am about the lifters. So, I'm questioning the springs before having to remove the heads.
Please help.

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Old 03-17-2013, 02:47 PM
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Depending on the head. Yes, the intake springs are taller than the exhaust. Exhaust springs are shortet to allow for the extra thick exhaust rotator used on many engines. Tall spring with rotator means excessive seat pressure and possible spring bind at lift. Short spring with intake retainer will result in very little spring pressure and loss of seat seal/compression.
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66Ponycar (03-17-2013)
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Old 03-17-2013, 02:55 PM
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I think you answered you own question when you said that when you back off the rockers the compression is good. I'm not up to speed on the fordsas to if they still have ajustable rocker studs. If so, are you adjusting the rockers too tight? I've seen time where tightening the nut until you can't spin the pushrod will end up with the lash to tight. Make sure the lifter is on the base circle of the cam and tighten the nut until you can get no verticle movement in the push rod. This puts you at 0 lash, now go a 1/2 to 3/4 turn tighter. If your engine doesn't have adjustable rockers I think you have some part compatability issues going on.
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Old 03-17-2013, 06:56 PM
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These head have bolt-on rockers, no studs. I yanked the heads to look at the springs. They're all the same height, yet the caps on top of the springs are different. One is of a bearing design while the other just has a center piece to work with the retaining clips. I noticed that one cap, the bearing type, has a thinner "lip" where it sits on the spring. I wonder if this is how the spring tension is matched to the intake or exhaust valve. Has anyone seen this type of valve spring set up?
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Old 03-17-2013, 07:46 PM
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Common procedure for a stock head. Bearing design is a rotator usually on exhaust valve. If springs are all same length. The exhaust springs must be deeper in the head. From your description, the lip is from a shim, used to correct spring tension.
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Old 03-17-2013, 08:11 PM
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Ok it has the pedestal style rocher arms then? Assuming that you have the correct pushrods and other valve train parts the valve stem height must be too tall for the lifter to make up. When you do a valve job the grinding of the seats and valves causes the valve stem to set higher in the assembled head. A quality machine shop will check this and grind some off of the stems to make up for this. If this is whats going on don't worry there is more than one way to skin this cat. Jegs has a pedestal shim kit for under 10 bucks that can fix this. Pull the intake and leave it off until you can see the lifters. If the lifter plunger is bottomed out when the lifter is on the base circle you basically now have a solid lifter. With this shim kit you can shim the pedestal until the plunger is in the middle of it's travel. For extra pump up protection you can shim towards the upper end of it's travel, say .020" off of the plunger retainer. I'm still guessing here because it's not in front of me so check this out carefully. Even if the shop did touch up the stems milling the heads and block affect this too.

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Old 03-17-2013, 08:23 PM
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Take a strait edge and lay it across the valve tips from end to end of the head. All the valve tips should be the same height. plus or minus .010"
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Old 03-17-2013, 08:34 PM
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Just looked at some old pics of the heads before the valve job breaking this motor down. Valve set up is the same as before the rebuild. Should have thought of this before yanking the heads. I'm just friggin' lost with this thing. Notches on the valve stems are at different positions. Intake notch is lower, but has the bearing type cap.
I think it's time to just scrap this thing, find another one and write this whole project off as a costly learning experience...
Stay away from Fords!!!
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Old 03-17-2013, 08:44 PM
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I haven't dealt with Fords in about 15 years but a piece of iron doesn't know what badge is hanging on the fenders. These things must be correct n matter what brand it is. Take this week to calm down and attack it next weekend you get it.
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Old 03-18-2013, 06:07 AM
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are the lifters full of oil? if so you should allow them to bleed down before you check compression
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