Engine shake/shudder/vibration
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Engine shake/shudder/vibration
1970 Ford Bronco with an 87 reman'd 302. 7 year frame off resto. Engine only had ~15K when I started the build, so I did not do much to it. It sat for most of the 7 years. I got it started about 2 months ago and it ran fairly well.. After running for a bit I noticed I had a blown head gasket on the Pside, probably for sitting for so long. Fixed that and compression test was good. Since then I have been chasing a vibration. I feel like I am chasing my tail with this engine shake/shudder/vibration. The one thing I have not done is a smoke check for a vacuum leak, although I have sprayed some carb cleaner around the intake and did not notice any changes. I have checked and replaced all plugs, and wires. Plugs looked good, maybe a little lean. Also replaced the dist cap and coil. Does not seem to be missing at all. I just pulled the Dside exhaust manifold and replaced the gasket as I thought I might have an exhaust leak, no change. I checked my harmonic balancer (its new), it case it slipped. The flywheel is also new. (both are 50oz) Timing marks at 0 when #1 cylinder is at TDC. I have it at 8-10 advanced at idle. I'm running a FiTech 400hp, that based on the logfiles, seems to be running as it should. The shake seems to have got worse over time. It is most notable when passing thru 1000-1200 rpm on both accel and decel. Motor mounts are new and tight. It is a 3 on tree, and does this while in neutral. I do not notice much if any change when depressing the clutch. One possibility that someone mentioned was an vacuum leak underneath the intake manifold. Thoughts?
Thanks,
Will
Thanks,
Will
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
Did you reuse the 1970 flywheel and harmonic balancer on the 87 motor ? If you did, there's your problem. Ford revised the crankshaft's in the 302 in 1982, removing a lot of weight off the counterweights and replace that weight with a heavier counterweight on both the flywheel and balancers. Old engine's used a 28 oz/in, newer used a 50 oz/in
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
Yea, I missed that. Not likely that you'd have a vacuum leak under the intake (the geometry of the intake to the heads doesn't allow this unless the intake is machined wrong to start with) unless the gaskets are bad. What gaskets did you use ? And what intake manifold ? Only other idea is the pressure plate isn't zero balanced. Or the balance is off on that reman engine or it's not an 87 engine.
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