Distributor & camshaft gear wear

[wsa111]

Posted: Fri Dec 17, 2004 10:44 pm Post subject: Distributor gear wear on the camshaft?

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I normally don't venture into your website. Your hardware is way ahead of our products in the states. Let me take a shot at a common post from you folks.
I see a lot of complaints of camshaft gear wear on your camshafts??
Why i post this article we don't have many complaints of this in the states.
so be it, is it caused by excessive oil pressure via shimmed pressure relief springs or is it a hardness problem with your camshaft or distributor gears?
I am in the process of reassembling my engine a 200 with new pistons & a camshaft & cylinder upgrade.
With the bare block in front of me if you drilled a very small hole .030 in diameter from the oil filter to the distributor bore in the block, below the oil ring seal on the distributor but just above the lower annulas, then with a hacksaw knotch the lower ring on the distributor with a .025 vertical cut at the point just above the contact point of the camshaft gear & the distributor gear with a constant supply of oil rather just the oil spray.
I have used this for over 30 years even before crane camshafts published this in their cataloge. The engine is the small block chevy which with increased oil pressure demands causes excessive wear at the camshaft & distributor gears.
I have not tried this on the ford block or distributor but the prinicipal would apply.
Addo & xtaxi what do you think?? I will be happy to take a photo of the above description. What do you think. William

 

[xctasy]

Sounds great!

The often 'munted' state of the bush in the distrubtor is not a precurser to any problem, so I'd say that a bunch of failed cam gears and shafts should be stockpiled by some one in Aussie like Crow Cams, for further inspection. Irrespective of whos cam it is. There is an inability for people to trace if the failure of the cam is due to a low rockwell hardness gear or cam shaft. Untill then, Will, your idea looks like the best first step.


The stock distributor drive is under a lot of load form crank harmonics on the 250, with scant oil supply. Remeber, 'our' 250 doesn't have the heavy duty sprokets and crank balanacer, and the cam runs closer to the crank than the US 250 in a more modestly proportioned block.


In Chebby's and Holdens, cam drive wear is also an issue. Most people blame the iron grade, but I think addo or backlash said a while back that the pre 70's traditional oiling practice of a a table spoon of oil in the distributor drive is never done today. Nada for preventative maintenace. An x-flow distributor sits under an intake manifold which gets forgotten about. In any case, the oiling and eletronic reluctor on post 1980 x-flows means its silly and pointless (!) to try a top down oil of the shaft. Lithium based grease is all that is needed, but the 10 dollar 90 thou bush still cops a hammering.

 

[addo]

Any Bosch distributor with mech and vacuum advance needs oil applying to the felt "wick" under the rotor cap. This services the mech advance parts.

I am reasonably certain there's a small mismatch of pitch or tooth profile between the worm drive and the driven gear. You can reprofile a cam and it will run fine with the old gear, but put in a similar grind cam off a billet and that original dizzy gear will chew out rapidly.

Oiling would likely ameliorate the wear rate, but if it's gear mismatched, may only postpone the failure to "middle of nowhere"! If I was happy with the idea that excess oil was being delivered up top, redirecting some of it would be a good move. But I'd rather do that case-by-case than prescribe. Pics of your mods would be good food for thought.

Distributorless ignition is becoming a long-term idea for my motor plans.

Adam.

 

[Anonymous]

In the case of the crossflow, some have said it is due to a flaw in the block on most pre 82? motors not due to an oiling problem. My mate AlloyDave told me that the trick is to use the aftermarket dizzy gear from Crow whenever you replace the cam with an aftermarket one. I plan on doing that and from what I understand that should work fine.

 

[wsa111]

Adam, when i get a chance i will post photos of the modified distributor oiling modification. Remember this is just theory, i really need to drill a junk block from the oil filter flange cavity to the distributor bore area. i think there are no cavitys in the path of the drill from the oil filter area to the distributor bore. the size of the drill is a guess?? .025-.030 diameter.
After the oil under pressure gets to the area of the distributor in the space between the top o'ring seal & the lower ring or annulus a slot has to be made in the lower distributor ring to bleed preasured oil to the camshaft gear at the contact with the distributor gear. this modification has worked for many years on a small block chevrolet. the chevy already has oil pressure from the right bank lifter galley, so all you have to do is hacksaw a slot for oil to spray right on the contact surface of the 2 gears.
I will post photos in the near future. I don't know if this a bandaid approach to improper rockwell hardness of gears or type of material in the camshafts or distributor gears. I will persue this idea. Bill

 

[wsa111]

Enclosed are photos of the suggested area where a .025-.030 hole could be drilled into the distributor bore of the block. BEWARE i have never done this on a block, if any of you have a junk block to drill as shown to see if the area where you are drilling is solid casting. On the other hand the hacksaw slot about .025 deep in the lower annulus after your timing is set & the distributor is in the correct position where the cut can be made right over the contact mesh area of the camshaft to distributor gears has been done many times on any small block chevys. But remember on the chevy that area already has oil from the right lifter galley.
Just a thought, might save on some gear wear in your engine. William