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Old 05-03-2004, 12:14 AM
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Exclamation distributor gear / oil pump rod issue??

Hello, I am new to this forum. I am looking for some suggestions on my issue.
I have already pulled my engine once, and am getting ready to do so again ?? maybe
I have looked for information, but to no avail. I have looked in the archives, and have found nothing.
Any help would be greatly appreciated

okay so for the background,
this is for a circle track dirt car, we have 15 lb@ 1000 inch vacuum rule, no aluminum anything, and no headers.

now for the parts
i have a fresh, (now with about 45 minutes of run time)
clearanced, decked, and line bored 400 .030 over (406)
6 in crower rods, 4340 internally balanced crank, kb hypers,
fully balanced rotating assembly
GMPP cast iron intake P# 14097499 (steel rules)
comp cams xtreme energy 268h grind 224/230 (vacuum rules)
stock distributor
modified vortec heads
hv oil pump, steel sleeved oil pump pushrod.

the engine developed what sounded like a rod slap, after only 45 minutes to an hour. so very little running time; only cam break in, and a trailered trip to the glass pack (more rules ) and alignment shops.
so i tore it all down, all tolerances were perfect, piston walls looked great. But there were the dreaded metal shavings. the distributor gear was wearing very badly (not touching the top and grinding more and more to the bottom) and the very end of the oil pushrod shows some twisting type wear, so we talked it over with some fellow racers and thought that the cam was more than likely walking. so i installed a cam button, replaced the gear with a bronze one. i replaced all of the bearings, and replasti-guaged everything. I considered myself lucky we caught it.

upon firing it up to time it, it seemed to make the similar noise again. the distributor was a little looser than it should have been to time it; but it popped up. NOT spinning a little, but popped up.
Just as if it were hitting the bottom or just getting enough to nip the metal. the wierd thing is that oil pressure is steady 60 lbs at idle, 80 - 90 at mid rpms, say 3500.

i have ideas going through my head like maybe it is the line bore, i had to get a special timing chain for that...
or maybe the decking of the block changed the distributor insert depth...
or could the intake be special in some way
or could the oil pushrod length be wrong?, are there even different size oil rods?
what is the sound, i am obviously having issues if i have filings in my oil??

help please i am drowning



Brian

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Old 05-03-2004, 12:55 PM
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It sounds like you need a distributor shim, to raise the dist. up just a tad.
If it is setting too far down it won't mesh with the cam gear very well and end up chewing teeth off of the cam gear or dist. gear.
The guys at the machine shop that did all of the machine work should've mentioned that when you got the block decked.
Call them up and tell them that you need a shim to compensate for the amount of the decking.
Hope that helps....
Later,
WEIMER
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Old 05-04-2004, 01:24 PM
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If you drop the distributor in without a gasket it should sit down on the intake. If not Moroso sells nylon shims that will raise the distributor. If the distributor is sitting up due to block decking and head milling and it gets tightened down then the whole assembly (oil pump driveshaft, oil pump, distributor) binds. I've seen this condition wear our a distributor gear in an amazingly short amount of time.
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Old 05-13-2004, 01:49 PM
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Also the cup guys pay attention to the lash between the cam gear and distributor gear. Oversized distributor gears are use to take up the lash and provide better "mesh" between the gears. This trick was invented by the late John Reed of Reed Cams.

Chris
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Old 05-17-2004, 11:23 AM
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The metal shavings could be from the drive gear in the oil pump being forced down against the pump body cover, this would happen when tightening down the distributor. running the engine
with everything stacked tight would cause metal to metal contact in the pump.
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Old 05-29-2004, 10:55 AM
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Quote:
Originally posted by engineczar
If you drop the distributor in without a gasket it should sit down on the intake. If not Moroso sells nylon shims that will raise the distributor. If the distributor is sitting up due to block decking and head milling and it gets tightened down then the whole assembly (oil pump driveshaft, oil pump, distributor) binds. I've seen this condition wear our a distributor gear in an amazingly short amount of time.

I am going through this exact same problem with stock GM roller cam engines. Havent come up with a solution either.
When I pulled the pan with distributor installed there is plenty of up and down clearance on the oil pump shaft, I can feel endplay in distributor shaft with cap removed. But it still wears out the gear.
I think it would be impossible to mill the deck down so far to cause distributor shaft to have no end play with these engines. It almost seems like its too far the other way that theres too much clearance.
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Old 05-30-2004, 02:23 AM
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I've seen a problem similar to this in my Dad's Cleveland engine...not sure about yours, but for what it's worth, there was a roller pin that kept getting broken in there, which as I recall from the faint memory meant that the top of the distributor was free from the gear. If yours has a similar setup, perhaps you have a weak pin. Also, the stock dizzy was too soft for the cam, and it ended up getting chewed up by the cam which had a much harder gear material. We swtched to an MSD, problem solved.
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Old 06-10-2004, 03:41 PM
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It seems to me you may have a couple of problems at work here. High volume oil pumps are famous for excessive distributor/cam gear wear... sometimes in a very short period of run time. If you are seeing 80 to 90 psi of oil pressure at 3500 RPM, you are probably asking the pump to bypass an incredible amount ... more than even the bypass can handle. The result is more hp required to turn the oil pump than the gear design can handle. The advice to check the distributor installed height is also sound.

I don't mean to offend anybody but, could your noise possibly be a rod hitting the block? 400 chevys are notorious for requiring additional machine work and grinding for rod cap and bolt clearance, depending on the rod/crankshaft combination you have. Align boring would also have some affect on this clearance..... just a thought.

Good Luck.
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Old 06-11-2004, 08:02 PM
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a roller engine gets a brass gear

The distributor will need shimmed. I would completely disassemble the engine and clean out all the rubbish left from jamming the distributor gear into the cam shaft. Take a good look at the cam gear while you are at it.


Tazz


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