460 performance problems
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460 performance problems
I recently bought a 1987 F-250 Heavy Duty. The previous owner thought he knew how to disable all the environmental garbage. What a mess!
The truck is an XLT Lariat, C-6 trans, had a 4.10 rear end, but is now 3.08, Holley 4160 carb, everything disconnected but vacuum advance and pcv valve.
I have been getting 6-9 mpg, popping in the carb when cold, bad dieseling when I turn it off, loss of power as rpms increase. Can't get the timing anywhere near 12btdc and still drive it.
Somebody please tell me where to start!
The truck is an XLT Lariat, C-6 trans, had a 4.10 rear end, but is now 3.08, Holley 4160 carb, everything disconnected but vacuum advance and pcv valve.
I have been getting 6-9 mpg, popping in the carb when cold, bad dieseling when I turn it off, loss of power as rpms increase. Can't get the timing anywhere near 12btdc and still drive it.
Somebody please tell me where to start!
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Joined: Aug 2001
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From: Nevada
460 performance problems
Did you disconnect and plug the vacuum advance when setting the timing?
The 4160 has a couple of vacuum advance timing ports. One at the top front of the carb, I believe this is the timed vacuum port, and another at the front below the front fuel bowl with full vacuum. I've always had better luck using the one on the bottom for full vacuum.
Check to make sure your distributor rotor is pointing at the #1 plug when the crank timing pointer is at TDC and#1 is on the compression stroke. To make sure I'm on the compression stroke of #1, I screw a fuel fitting into the spark plug hole and put a piece of tubing on it that extends up to where I can hear the air being pushed out of thecylinder. Or you can have someone hold their finger over the spark plug hole.
The 4160 has a couple of vacuum advance timing ports. One at the top front of the carb, I believe this is the timed vacuum port, and another at the front below the front fuel bowl with full vacuum. I've always had better luck using the one on the bottom for full vacuum.
Check to make sure your distributor rotor is pointing at the #1 plug when the crank timing pointer is at TDC and#1 is on the compression stroke. To make sure I'm on the compression stroke of #1, I screw a fuel fitting into the spark plug hole and put a piece of tubing on it that extends up to where I can hear the air being pushed out of thecylinder. Or you can have someone hold their finger over the spark plug hole.
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460 performance problems
I took the <a href="http://www.motorhaven.com/">Holley</a> 4160 off and put an Edelbrock 1<a href="http://www.motorhaven.com/">406 </a>I had on and it runs much better. Starts and idles now and no more dieseling or popping.
I tried the things you suggested, results are not good. When the #1 cylinder is compressed the rotor points approx. 135 degrees away from #1. Can't even see the timing marks anywhere when running.
Still has a rough idle, kind of a lope or shake.
Is this a slipped timing chain?
Fuel usage is up to a steady 9 mpg but the odometer reads about 12 percent low based on checks vs. mile markers. Probably due to oversize tires.
Thanks for your interest and expert advice.
Bob
I tried the things you suggested, results are not good. When the #1 cylinder is compressed the rotor points approx. 135 degrees away from #1. Can't even see the timing marks anywhere when running.
Still has a rough idle, kind of a lope or shake.
Is this a slipped timing chain?
Fuel usage is up to a steady 9 mpg but the odometer reads about 12 percent low based on checks vs. mile markers. Probably due to oversize tires.
Thanks for your interest and expert advice.
Bob
Postmaster
Joined: Aug 2001
Posts: 2,882
Likes: 0
From: Nevada
460 performance problems
If you (or the prior owner) haven't moved the distributor by pulling it out and replacing it and it is off that much, it could be a slipped chain. I'd be more inclined to suspect the distributor.
