[besserspat]

Hi everyone,
I noticed BOP sells a .491 Polymer (composite) distributor gear , that fits Stock HEI, but is this .491 gear fitting a Mallory 4758001 Distributor ( Unilite with Vac Adavance).

Mallory distributors seems to share the same gear shaft dia (.491) but are dimensions and design same as the stock HEI? (Pin location and height)

I have a Mallory 4758001 on my 350 and its working fine, I wanted to re-use the mallory distributor on my 461 but the new motor will get an Old Faithful Cam (Roller).

Now I have the choice of a bronze gear on the Mallory dist. (Mallory makes one for 65$) or Get a BOP composite .491 gear for 130$ , but i need to see if it fits the Mallory Dist.

Last option would be finding a cam manufacturer that will press an iron gear on a faithful cam grind.

The last option would enable me to run whatever distributor on the 461, down the road.


What do you think ?

[Skip Fix]

I'd check with Mallory and see if their distributor takes a stock gear. Maybe Sun Tuned here can answer it also.

[jonmachota78]

I would follow skips advise but I think only the MSD distributors use the .500 gears.
There's been alot of discussion here about dist gears on billet core cams.
basically if you dress the cam gear, you can go straight to the composite gear.
Otherwize you should run a bronze gear for a few miles to debur, then switch to composite.

[Formulajones]

On the rollers I've done, I prefer the iron gear pressed on the cam, then I don't have to worry about distributors. Comp does this.

Since Dave uses Comp cores and/or lobes (I believe the magnum stuff) I would assume Comp is probably grinding the cams with Daves specified LSA, I don't see why Comp couldn't do the iron gear as well upon request and be done with it.

I've also dressed the cam gear and then used the composite or melonized gear which works fine. The iron gear on the cam just saves an extra step or two, and allows any dristributor swap down the road without robbing the gear off the distributor shaft (again not a big deal either)

So it's just personal preference.

[TransAm525]

While I haven't personally swapped the gears between the Mallory and HEI distributors myself, I imagine the Mallory gear is a copy of the stock Pontiac gear and should interchange. As mentioned, MSD distributors use a larger shaft, necessitating their own gear. Between running a bronze or composite gear, I would chose the composite for its superior wear resistance and ultra low reciprocating weight. FWIW, I've been running a BOP composite gear in my 400 since 2007. After about 7,000 miles the gear still looked new when I had the distributor pulled for the camshaft swap.

[Formula8]

I spoke to Dave re: the cast cam gear option and he said he doesn't trust them. I asked if he knew of any failures and I believe he said no but that he just doesn't like the potential for the gear to slip on the cam.

[Sun Tuned]

Well the bop gear is already drilled for 3/16 roll pin.
Is your Mallory distributor built with a 3/16 the pin in the gear? It should be...

At that point it becomes plug and play. Might at most have to add a shim .007 but I haven't made this swap on a Mallory dist yet.

I do know all of Mallory replacement iron years are drilled only on one side for a 1/8 pin. Why? Well they figure you can install it either on an early shaft with a 1/8 pin by simply putting on a 1/8 shaft lining up the one drilled hole and then completing the other hole using the original shaft as the pilot.

When you use this gear on a 3/16 shaft u gotta be really careful and drill hole 3/16 on one side first and then do the same as above for the 3/16 shaft. You must be careful to drill straight and you'll be fine. Not after your 5th or 6th beer.

I think you are ready to go with just plug and play though. To definitively answer this...
What size is your Mallory shaft pin hole currently???

[besserspat]

Thanks, i would have to pull the Distributor off the engine , the 350 is in the car and running fine , maybe I should get in touche with Mallory and ask them.

Im just trying to cover all bases since I hate having to stop a swap or project for a silly distributor gear.

Thanks for all the replies so far its been helpful.

I even thought of going HEI for my set up , but I believe in re-using the parts I have instead of constantly buying new ones.

The plan is to run my Mallory Unilite vacuum distributor (its a 80% street ride), and use a Mallory 685 box for its timing retard and adjustability for the 250 shot im adding on top.

Im not a fanboy of Mallory products , I had MSD and Crane before, this car just happen to have a new Mallory Unilite on it...


cheers

[68blackbird]

Let me get this straight... virgin roller cam should not be run with a composite distributor gear until broken in with a bronze gear?

How many miles before the change to a composite gear?

Rich

[Sun Tuned]

I'm 99% confident it has a 3/16 pin in it already so you should be fine.

I don't remember but I think bop sells a gear with 1/8 pin hole but I've slept a few times since then. Couple phone calls should get Ya straight on that.

Bottom line it can be made to work just fine for hardly any stress, money, or aspirin consumption.

[Formula8]

Correct. Dave says run your cast gear for start up then swap to the BOP gear after you shut it down after a few minutes.

[Sun Tuned]

I guess...

I say if the cam is not in the engine yet, great! deburr the cam gear, then go immediately to whatever you want to run.

Now that's an opinion, it's mine, and one might think it wrong or right, but I don't like junk floating or circulating in my oil. Especially if I did something to cause it to be there in the first place. I feel so strongly about that that even if I had the cam installed I would In Fact pull it the hell back out and buy new gaskets to put it back in there when I got done.

I've built 11 engines in the past 2 years and all got the cam gears deburred.... None flew apart yet, so we will call that peace of mind.

Formulas is correct on what Dave feels is the current thinking...
I just choose not to go that way.

No I'll will meant towards anyone on this deal at all.

I mean really it makes no more sense to spend all the money and time making sure all that stuff fits and is clean as hell only to pitch a brass grenade in the deal just cause we are in a hurry.
Deburr the junk and be done with it!!!!

[Formula8]

I'm nowhere near ready to go roller cam but I was kind of surprised to hear the procedure. I think I would rather debur as well then check the gear for abnormal wear after a couple of cycles. Worse thing that could happen is the I would have to replace the gear.

[Formulajones]

I agree and would do it just as Suntuned described if you don't want to go the iron press on gear route.

I'd debur it before the cam goes in, and then go straight to the composite or melonized gear. I don't care to run an engine with a bronze gear in an effort to only "clean up" the cam gear knowing it's coming back off anyway for a melonized gear, and then having the brass in the engine to boot. Not a fan of that. Dressing it first also saves the trouble of pulling the distributor again to swap the gear.

[jonmachota78]

Originally Posted by Formula8

I think I would rather debur as well then check the gear for abnormal wear after a couple of cycles. Worse thing that could happen is the I would have to replace the gear.

Worse than replacing a composite gear would be the carbon fiber shards floating around in ur engine.

I did the gear dressing bit and went straight to the composite gear. It does have a little wear on it but in my estimation looks 'ok' to keep in service. Ive probably got about 8000 mi on it now. I gotta say, dressing those billet cam gears is not straight forward as the metal is very hard. The metal seemed just as hard as the files i was dragging over it. I dont have a blaster so next time maybe ill just hit the gear real good with a wire brush on a drill.

[Schurkey]

1. Mallory isn't very good about assuring that their distributor shafts are drilled on-center. DO NOT drill a Mallory gear without select-fitting it to the distributor shaft first. The real reason Mallory sells replacement gears that aren't drilled all the way through is because of their poor machining tolerances on the original distributor shaft pin-holes. I don't know if this is a problem with some distributor models, or just with Chevy stuff...the complaints I have heard of are from Chevy owners.

2. I've got a steel roller cam/pressed-on and pinned iron gear camshaft in my boat. I've got NO interest in playing games with a steel cam gear. Having the iron gear saves too many potential problems; and once pinned in place I don't see how it's going to turn/spin on the shaft.

[Formulajones]

Originally Posted by Schurkey

2. I've got a steel roller cam/pressed-on and pinned iron gear camshaft in my boat. I've got NO interest in playing games with a steel cam gear. Having the iron gear saves too many potential problems; and once pinned in place I don't see how it's going to turn/spin on the shaft.

It won't. Peoples fear of it moving is just that, a fear, with no real reason for it. There are no instances of problems at all, anywhere, that I've heard. If it were an issue then the gears on the distributors themselves would have been an issue 100 years ago, and those aren't press fit,,,,just pinned.