Crazy idea, timing gears

[NE57]

Does anyone know how the cam to crank centerline distance of a 392(or 318 for that matter) compares to a sbc or bbc or sbf?

I'm wondering if with careful re-machining the chevy set of pete jackson timing gears could be made to work in the tall hemi. Yeah i know its crazy but something about the mechanical sound of their "noisy" set might be interesting. I don't see a listing for the jackson drive for the small block mopar(which i understand the timing chain sets are interchangeable) The milodon would certainly work but are they "noisy" too?

A slow afternoon, the mind gets to wandering.

[polyspheric]

Better idea.

Am I still wrong?

[DblAdigger]

Sounds like somebody is not familiar with "dog bone" timing gear sets. Personally, I wouldn't let one in my shop.

[NE57]

>" I wouldn't let one in my shop."<

Why is that?

[polyspheric]

Sounds like somebody is not familiar with "dog bone" timing gear sets

Who did you have in mind?

[dan miller]

I believe that SBC Mopar LA series engines (273,318,340,360) share the same timing chain as early hemi's.

Danny

[NE57]

Thanks Dan, I'll look more closely at the idea now. What's wrong with dog bone gears? Are they problematic in some way? Just too noisey?

[mart]

What's wrong with dog bone gears? Are they problematic
in some way? Just too noisey?

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The problem with "dog bone" gear drives is they're inaccurate and
they wont hold your cam timing. The"dog-bone" idler gears aren't
fixed to the block. Instead, the idler gears float and move back and
forth between the crank and cam gears. The amount of back and
forth movement is determined and set by the clearence between the
teeth of the crank, idler and cam gears. Whenever the idler moves back
and forth, even slightly, your timing fluctuates. Even when brand new,
this movment is enough to cause variation in your cam and ignition
timing. And worse, the crank, idler and cam gears in these cheapo
"dog-bone" set-ups usually tend to wear fairly rapidly too, furher
increasing the clearence between the teeth, increasing the back
and forth movement and allowing evem more fluctuation and variation
in your cam timiing. As the gears wear, your timing really goes for a
crap. For accuracy and reliabiilty, you're far better off with even a
standard chain and sprocket set-up. If you really want or*need* a
gear drive, spend the bucks and go with a quality *fixed idler* gear
drive ie - like Milodon or Donovan. Even better for accuracy and
reliability....but a *lot more* money and hassle, would be to use a
reverse ground cam and a two-gear (- ie - crank and cam gear
with no idler gear) drive set. I don't know who or even if, anyone
makes a two-gear cam and drive set-up for an early hemi, but
"back in day" - about 35 years ago(!) I had I had a reverse ground
Isky 550R roller cam and matching Isky two-gear drive set-up in
a small bliock Chevy. The cam and ignition timing was rock steady,
even at 9000 rpm! I don't know If Isky made a simillar two-gear cam
and drive set-up for the early hemis, but if they did, you might be
able to find one used somewhere or maybe even still order it from
Isky! But whatever you use, you don't want one of those junk
"dog-bone" set ups!

mart
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[DblAdigger]

Well said.

[NE57]

Hmmm, doesn't sound like a viable thing for me then, even if a setup could be made to fit. Thanks for the insights.
On the Milodon fixed idler set, would that allow me to retain a mechanical fuel pump? I think I read the Milodon fits under the stock cover. While I'm on about covers...does anyone make a quick change front cover, if not do you suppose its possible to make/modify one without tremendous work? If it turns out I want or need a different cam it'd be nice not to have to drop the pan.

Thanks again.

[TrWaters]

I don't know who or even if, anyone
makes a two-gear cam and drive set-up for an early hemi, but
"back in day" - about 35 years ago(!) I had I had a reverse ground
Isky 550R roller cam and matching Isky two-gear drive set-up in
a small bliock Chevy. The cam and ignition timing was rock steady,
even at 9000 rpm! I don't know If Isky made a simillar two-gear cam
and drive set-up for the early hemis, but if they did, you might be
able to find one used somewhere or maybe even still order it from
Isky! But whatever you use, you don't want one of those junk
"dog-bone" set ups!

I suppose if you really wanted to experiment, you could take a look at a Chrysler marine cam and gears. Or opt for a belt drive.

[budmspeeco]

I think I have seen the belt drives advertised on eBay that fit the small block Chrysler and 392 motors. I would think they would be the ultimate setup BUT about four Milodon gear sets could be bought for about ONE belt drive. Those things are in the stratosphere for cost, around $1,300.00. I forget exactly how the marine gear sets look but I think they were only on 331/354 engines since Chrysler did not make a 392 marine engine so you could not just swap cranks. I guess you could turn down the nose on a 392 crank where the bottom gear goes and use the marine stuff . Then you could add the huge cast iron cover to enclose it. The cam would have pitiful lift and duration numbers, especially for a 392 with a decent intake setup. I am not familiar with the amount of meat on the cam so I don't know if they would be good candidates for regrinding. It would also alter the firing order. I seem to recall both right and left rotation cams were not only different from a normal hemi, they were different from each other as well. You would just have to rewire the distributor to match the cam. Or not. Two excellent ideas, whichever one you decide to try !!!! I am just using all my pennies on this one. Buddy

[budmspeeco]

I stand corrected !!! There is an industrial timing set on eBay with the big ( spelled real HEAVY) two piece front cover and what looks like a reverse rotation gear set. At least you would get a cover you wanted that could be removed without removing the pan. Maybe you could get the gears under an aluminum front cover if you didn't want all the weight. Take a look at # 270399542478. I don't know what you will do about a cam, maybe an old gear drive Isky. Sorry, TrW Buddy

[mart]

I stand corrected !!! There is an industrial timing set on eBay with the big ( spelled real HEAVY) two piece front cover and what looks like a reverse rotation gear set. At least you would get a cover you wanted that could be removed without removing the pan. Maybe you could get the gears under an aluminum front cover if you didn't want all the weight. Take a look at # 270399542478. I don't know what you will do about a cam, maybe an old gear drive Isky. Sorry, TrW Buddy

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Just an idea - I had a look at that ebay piece and it *might* be
possible to use that gear drive and just the inner part of the
two-piece cover.*If* the inner piece by itself is deep enough to
enclose the gears, you could do away with that heavy and bulky
outer piece and replace it with a piece of 3/16 or 1/'4 inch
thick aluminum plate bandsawed to the shape of the the inner
cover piece. Using just the inner piece, with a flat, homemade
cover , you'd have easy access to the cam without any problem
with the oilpan. It might look pretty trick too! You'd still need
a reverese ground cam of some sort to work with the gears
- either a stock Chrysler marine unit, reground to
high-performance specs or an aftermarket cam made for use
with a 'two-gear' gear drive.

mart

P.S. It looks like it might go pretty cheap - three days left on the auction
and so far, still with a just a starting bid on it of $9.99. If you think it
might work for you and decide to take a chance on it, you could probably
save a bunch on shipping by telling the guy to just send the gears and
the inner piece of the houising rather than the whole thing.
====================================================

[DblAdigger]

I'm sure you've already figured out that, with a two gear setup, EITHER the cam OR the crank must turn backwards. The usual solution that I've seen in reverse rotation marine engines, is to use a special cam with the lobes repositioned. Most cam grinders can accomplish this BUT, depending on the availability of the correct blank, it could be costly. That way, the crank turns opposite but the cam retains standard rotation...so the distributor and oil pump continue to function in the normal way. To get the crank to turn normally, you would have to do some fancy stepping with the cam, oil pump, and distributor.

[dan miller]

Weber makes a VERY NICE early hemi belt drive, which is marketed by Hot Heads. It's a beautiful piece that's a spin off of a Craftsman Truck Series small block Mopar (NASCAR) deal.

We're utilizing one on our EMC early hemi, and it makes cam changes and cam timing adjustments a snap.

One caveat: there is an oil hole on the face of the front cam bearing journal that lubricates the stock early hemi thrust plate. It must be plugged, or it will leak oil past the keyway on the cam hub.

Danny