Kirby78

Hi All! I have a 78 Ford F250 with a 460. I recently had the motor out for fresh seals, paint & gaskets - it 'Looks' beautiful!! It only has about 25K miles on it since rebuild several years ago. My problem is, the engine has a TERRIBLE vibration at about 2500 RPM on up. We've messsed with the timing a bunch - it is set @ 5 right now, because the total advance is 70!!! Plus it really likes to overheat. Vacuum is at about 39, and centrifugal is at 31! My boyfriend thinks that the vibration is a miss - so, don't know if that could be related to the high amount of vacuum advance, or if I need a new ignition module, or distributor, or??? The truck runs well at idle, but doesn't have the get up and go it used to. Can anyone help? I don't know if we have one problem, or 10!! We're going to put a different distributor in it for starters, and it seems that with that amount of advance, we could do without one or the other type of advance. I appreciate any ideas or input!! I'm supposed to be heading out down the Alaska Highway in a couple of weeks - but not if I can't get my p/u running good 1st!!

Thanx a million for any replies!!

Paul Kane

First and foremost, make sure the plug wires are going to the correct spark plugs. It's easy to accidentally swap a couple of them and experience the vibration/overheating that you are describing. When it comes to tracing out the plug wires, remember that on a Ford 460:

• The firing order is 1-5-4-2-6-3-7-8
• the distributor turns counter-clockwise
• the cylinders are numbered = 1-4 passenger side front-to-rear, and 5-8 driver's side bank front-to-rear

4.........8
3.........7
2.........6
1.........5
--(fan)--

Paul

__________________

Kirby78

Hi Paul! Thanx for the input!! I'll definitely check the wires again - that would be something I could have easily messed up :) But it does idle fairly smooth. Also - I put the MSD plug wires on that you have to build yourself, so I could've messed one of those up. And we're gonna check the compression also. One thing my boyfriend's boss mentioned... if our timing light was acting normally when we had the rough idle at 2500, he feels that it wouldn't be a spark problem. I'm really concerned that the problem is caused by me not getting the rotating assembly balanced when I built it?? But ... my boyfriend doesn't feel that it's a balance problem. The only other thing is, I put a new Edelbrock cam in it - don't remember if I mentioned that & don't know if that could be causing the problem. The rough running doesn't feel like a normal 'lumpy' cam, and besides, it's only like an RV cam. Anyhow, I'll double check the plugs & wires & let you know & I SURE appreciate your help!! Thanx again & take care, Tru

Paul Kane

The ignition timing might be stable as viewed with the timing light but if you mixed up the wires and are sending the spark to the wrong plugs at the wrong time then the engine can be very rough.

Possible but not necessarily your problem, I'd need to know a few more details about the build and we'll revisit this subject when the time comes.

Let us know what you find after you double-check the spark plug wire routing.

Paul

__________________

Kirby78

Hi Paul! Okay - checked the routing on the wires & they wereon correctly (amazingly!!). I also pulled the plugs & checked them & they all look beautiful. I also did my Dad's trick of pulling the wires off the distributor one at a time with it running & had a drop in idle on every wire, which would seem to indicate that they're all firing correctly (until I pulled them off) - unless my thinking's mixed up, which is entirely possible. After doing all of these things, I took it out for a test drive & this is probably just my imagination, but it seems that it has a little more power, but still a terrible vibration under power at about 65-70 mph (I have no idea how many rpms since I don't have a tack, but I would guess about 2500-3000 rpm). When coasting, it goes away. Also, it kicks down & revs up at this speed when you put throttle in it, but doesn't go anywhere. I haven't gotten a chance to do a compression test yet, or to swap the distributor - hopefully we'll do that tomorrow or the next day.

As for the engine build. I knew nothing about building engines at the time (and not a whole lot more now) but I don't think it got balanced. It was bored & got new pistons, an RV cam, an Edelbrock carburetor, and headers. The crank, rods, block, heads (rebuilt), intake, et. al. were all original from the same engine. When I recently had it out, I put a new Performer series edelbrock intake and cam in it. Also - I can't say for sure that it hasn't always had this current problem since I originally built it. This is one of those learn as you go deals :) BUT - I am NOT giving up on it! Thank you again for your input! I appreciate ALL the help I can get! Have a wonderful day! Tru

Paul Kane

Tough one. In regards to not balancing the engine: The factory balance is pretty lenient and assuming you replaced the old pistons with new ones that are identical except for being the next overbore size, you should be within reasnable range to not cause a gross imbalance.

Have you checked for a vacuum leaks, maybe a missing vacuum cap on the carbuetor or a manifold vacuum leak? Are you certain that the carburetor mixture is adjusted correctly/not too lean? The engine could display the overheating symptom in an extremely lean condition.

I just re-read your first post in this thread and see the engine was rebuilt 25,000 miles ago; has the engine had this vibration for the entire 25,000 miles? Note this: The 1968-1978 429/460 engines are internally balanced while the 1978-1997 engines are externally balanced. If the machine shop mixed up components between the two different engine types...perhaps maybe gave you a replacement flex plate (starter ring gear) for an engine with the balance type opposite of your engine.

Paul

__________________

Kirby78

Hi Again!! Well - we checked the compression & all cylinders were in the 130's except one, which was 107. Squirted oil in it & it came up, so that means it's leaking past the rings, I guess. So, then we put a different distributor in it, which made the total timing better, & took it for a test drive. While test driving, it developed a bottom end knock!! So now, Kirby (my truck) is DEAD! I already pulled the engine back out. Haven't gotten to take it apart yet. Talk about a devastating blow!! But - at least now I can have it balanced so that will rule out that being the problem with the vibration!! I don't know if it's always had the problem - I think maybe it has, and I just didn't know any better! The motor is out of a '77 Grand Marquis, and I'm pretty sure all the same parts (except the new stock pistons) went back on it, including the flexplate & balancer. As for vacuum leaks, possible since I put a new manifold on it, but my boyfriend felt that if it was vacuum, it would be worse at idle and not as bad under power. And we did adjust the carburetor. It's as new as the rebuild, so should be okay. ANYHOW... I guess the vibration is the least of my problems, now!! :)

If I need to replace the crank, I'm thinking about stroking it. There are whole kits available for around $!500. Any tips or advice about that would be great! In the meantime, I'll let you know if I still have problems with the vibration when it's all back together!! Thanx a million for all your advice!

Paul Kane

Ouch, sorry about the engine failure.

Stroker kits are a subject unto itself and a lot to discuss. Many types, brands, displacements, combinations, etc. I suggest staying away from the cheapo kits. Also, when you increase displacement you will need cylidner head work i order to feed the engine...more air and fuel. This is particularly true with your D3VE cylinder heads that came on your 1977 460.

Paul

__________________