Odd timing problem 360

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Remow2112

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I have an odd problem with the timing on my 360. Rebuilt 360 .30, Stock heads with valve job, comp cams 942 springs with lunati 402 cam and lunati lifters, new harmonic balancer.

My timing mark jumps around starting at about 3k and up. New timing chain, I have tried 3 different distributors (2 stock and a billet) 2 different MSD 6als. Changed out the oil pump from a high volume to stock. I am running out of things to check.

Now sometimes right after it first warms up I can rev to 6500 and the timing mark looks ok or 4000 rpm but if the engine runs there for more then a couple seconds the timing mark starts bouncing.

I thought it might be lifter pump up but I am using brad penn 10w-30 and a stock oil pump now.

Someone throw me a clue please?!?

Thanks,
Dan...

ps. using a craftsman dial back timing light a Taylow 8mm plug wires (also tried with a set of the MSD 8.5 wires.) The same timing light on my brother's engine shows a rock solid timing mark all the way to 6500. He is using a smaller Crane cam.
 
Msd can interfere with the light. Should really have a light that doesn't use the car for power.

Balancer rubber is ok right?
 
Pull the dist cap off and move the rotor back and forth and see how much play you have. I had a problem on my magnum 408 stroker where the slot in the intermediate shaft was too large and sloppy, allowing the dist end to move around. A new intermediate shaft cured the problem.
 
On mine was easy since I am using EFI and the shaft is fixed. With a normal dist I imagine you could pull the plate out of it and wedge the mechanical advance and then see if the shaft moved.
 
Try a different timing light. If the mark is moving, disconnect the vacuum advance. If you dont have one or it doesnt change, look for play in the oil pump drive shaft. If there is any lateral play (like DGC said... Check this by using a large flat blade screwdriver and try to wiggle it side to side, not twisting..) then replace the drive and the bushing at the same time. They wear together so if the bushing's bad, so's the drive.
 
Another thing I forgot to mention is the timing chain/gears. Even if they are new there could be enough slop to cause erratic timing.

Turn the crank by hand until the rotor moves and then turn the crank the other way until the rotor moves. If you have more than 5 or 6 degrees of free play the chain/gears have to much slop.

Try this in several places plostions of the crank because you can have tight and loose spots on the chain.
 
I would try another light. i just broke in my stroker last weekend and had a brand new Equus dial back light hooked up and it was all over the place. we pulled the 30 year old craftsman out and it worked fine. i am running msd ignition and wires. The timing light directions make reference to some kinds of wires causing problems. i made a call to the Equus tech dept and pointed out my problem with the new light, and typical to most tech lines, it was a waisted phone call.
 
Mopar makes a timing chain tensioner that is supposed to help with stuff like this. It goes on in place of the cam plate.

Sometimes the intermediate shaft has too deep a slot in it or is worn and it will move up and down slightly on the cam gear. Hughes sells a collar that attaches to the dizzy to take up the slop.

Steve
 
MSD and it's multi-spark can really mess with lights too. My Snap On digital light is fine but some plug wires will confuse it. My buddy's Matco big $$ LED wonder light has issues like that too. Usually the cheap plain oldschool lights are not quick enough to be affected by it.
 
Yep! My Snap-On light doesn't work right with my MSD but the 30 year old $20 Sears unit works just fine.
 
Thanks for the responses.

For the record I have and Edlebrock roller timing chain and the 3.9 chain tensioner in place. I pulled the distributor/oil pump gear out and replaced it with one I had out of a 67k 360 motor. Did not have time last night to warm it up and test. But at first glance it seemed better.

Just more FYI. We use the same timing light on my brother's Duster which is the same as my engine except for the cam and pistons. My Sears light works just fine on his.

Someone mentioned changing the busing the oil pump gear shaft rides in. Can I do that without pulling the intake?

I am going to try testing the timing chain tonight and see about the rotor moving too much.

Thanks again,
Dan...
 
The oil pump drive and the bushing wear like a brake pad and rotor. If they are both good, it will last thousands of miles. If one is marginal and one is good, it won't last 1/2 as long. If you have a slide hammer you can make a bushing removal tool easy enough. Get a 3/8 x 14" carriage bolt from the hardware store, grind a notch about 1/8" up from the bottom of the threads, try to make it barb shaped and about .140" deep. Slide the slide from the hammer on the bolt, slide the bottom of the bolt through the bushing, applying light pressure directly opposite of the notch. You will feel it when the notch passes the bottom of the bushing. Keep steady heavier pressure in the same direction, and using the slide hammer pop it up. To install the new bushing, cut the gear teeth off the old drive and use it to drive in the bushing. You may have to work the drive a bit to get it back out because the bushing reduces it's ID when being driven in. I use a loop of mechanic's wire to go under the drive gear and pull up while workign the drive back and forth with a large flat blade screwdriver. Once it's out just drop in the new drive and go.
 
Ed Hamburger and possibly someone else use to make a little aluminum bushing that slid over the bottom of the distributor shaft. A distributor may have a little bit of up/down play and the cam/oil pump drive can also move up & down a bit if the distributor shaft isn't actually bottomed out on the cam gear. By snugging the bushing with a set screw low on the dist. shaft, one can press it down into the cam/pump drive. Then remove it and tighten the set screw where it was pushed up to. That can help reduce any up/down movement that may be there.
 
It was the oil pump/distributor gear and shaft. Switched to one out of a 67K motor and the timing mark is solid as a rock.


Thanks for all the help!

Dan...
 
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