Last year, I melted a piston in one of my motors. I'm now building a "mule" motor, and removed the oil pump from the bad motor, to use in the mule. The bad motor only had 5 runs down the 1/4 mile and no street miles. It had the Mopar 528 cam. The wear pattern, on the pump gear was very short, compared to the pattern on some oem pump and cams, and seemed excessive for the short amount of running time. I'm wondering if the gear on the cam is at the correct angle. The oil pump is a Melling standard replacement pump, not a high voulume. Any thoughts on this?

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

The gear angle on the cam is hard to check, I tend to "mock-up" install the cam and pump and take a "contact pattern" of the gear mesh using lapping compound.

A small shift in the gear tooth angle would cause excess loading to a smaller surface, the trouble is that there is no easy way to correct something like this. (get a different cam)
DD

That is what seems to be the problem. the tooth contact pattern, is less than half, of the pattern on a oem stock pump and cam. I have two of these cams. I think I will just save them to use with an external belt drive pump.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

In 14 years as a journeyman machinist, I never had to cut gears. I wish I knew more about that particular field. I can do a pretty good job with hypoid gear setups, but know very little about worm gears, which I suppose is the type to which we are referring, and scratching our collective noggin about! Man, there has to be some old gear-hobber out there, somewhere, to steer us right.

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'66 Cuda 225/4spd
'66 Dart GT convertible 225/auto
'64 Dart GT 340/4spd

just thinking outside the box, here. We used to check threads with "thread wires." You take these so-called (3)wires, (which for the size of 'thread' we are talking about, would be more like drill rod), lay two of them in the adjacent valleys on the sides of one tooth, and position the other wire on the opposite side of the gear in another valley, and mike across them. Now I don't know what kind of number we would be shooting for, but I think it might tell us if the "pitch diameter" were different, if you compared it to a known good stock cam. Does that make any sense to you?

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'66 Cuda 225/4spd
'66 Dart GT convertible 225/auto
'64 Dart GT 340/4spd

In the past, I take the gear(s) in question to a gear hobbing shop and have them check them. In my area there are a bunch of them around.

The gear we are working with is a 30 degree, right angle helical gear, 13 tooth. There are a number of dimension to check and like all production parts, the tolerances range is pretty wide.
It is rare to find a combo that is "on the money" spec. wise so that is why I lap them in, doing that increases the contact area.

One other option for Charlie is to use a soft bronze gear to keep any wear on the oil pump gear and not the cam's drive gear.
DD

Hi Doug,

Any idea of the longevity of the bronze gear on a street car with a new cam?? Just wondering ? 10,000? 20,000? 30,000 miles? We may be interested in one of the bronze gears, to give it a try.

Rick

I agree, compatibility is important. Remember when Chevrolet had compatibility problems with their OEM small block cam and lifter sets? As I recall, you can't just have two equally hard surfaces rubbing against each other. One of the two needs to be 'softer'.

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'66 Cuda 225/4spd
'66 Dart GT convertible 225/auto
'64 Dart GT 340/4spd

Sorry to say that I do not have any data on this, I have never run one or gotten any feedback for anyone who has.

I should stick a bronze gear on the "test stand" engine I have and fire it up and run it for a while to see what happens. There is no load on an engine running on a test stand but it could give us some data points.
DD

second year of the bronze gaer on the race car...........no problems
I look at it after every race and it is still there

Will

Thanks Will,

Is that on a steel billet cam? Or just a standard cam like I would be running.

Rick

billet.

Has anyone ever considered the motor oil factor?

The heavier the oil (lets say 20w-50 in my old truck) the harder that gear works, particularly when the engine is cold. Has anyone ever examined the effects of using heavy weight motor oil on gear wear. It just seems like a question to ask after future failures. (or before)

5w-30 might be good for the gear, but too thin for everything else, and synthetics are supposed to be even easier to pump. I've always put heavy oil in old smoking/leaking engines, but now i'm wondering if it could do more harm than good.

I run 10-30 in all my engines, street and race. Back in the 70's, we did back to back test, of Quaker State 10-30 and Quaker State straight 30. 3 runs with 10-30, drain, change filter, refill with 30, 3 runs, change back to 10-30, 3 more runs. Ran an average of 1 1/2 tenths quicker with 10-30. This was with my Z/SA 65 Valiant with a 170 engine.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

We have run synthetic in my sons dart ever since it was broke in (about 1000miles). Since our gear showed premature wear with synthetic, I was actually thinking we should try some 10/30?? I don't really think it would change anything though? Just grabbing for straws.


Rick