Oddball sized distributor shaft (long and ranty lol)

[travis]

Today was FINALLY going to be the day to fire up the new 400-ish Hp 351w in my ‘83 F150, after constantly being derailed by a million things lately. The ‘87 F150 is done, home projects and honey-do’s are either done or well under way, a friends ‘74 Chevelle is done and out of my driveway, etc etc. Buttoned up the last few minor things on the ‘83 to where all that was left was swapping the distributor gear, dropping it in, and lighting it off. Apparently it just wasn’t meant to be.

The distributor is a 15 year old Mallory 85 series HEI that I have run in multiple engines over the years. Once I replaced the factory module some 14 years ago with a used stock mid ‘70’s GM HEI module, it has been trouble free for probably some 100-120k miles. Since it was still tight and functional, I decided to reuse it on the new engine but needed to replace the gear with one compatible with a roller cam. After some QC issues with the recommended comp cams distributor gear, I just called MSD (who apparently purchased Mallory at some point) to find the correct gear to use. They gave me a PN that was the steel Mallory replacement gear that had the pin hole in the right spot...supposed to be a quick swap and done. So today, doing the final steps to get this thing running, I knocked the pin out, pulled the old gear off by hand (???!!!), and slid the new steel gear into place. It was like throwing a hotdog down a hallway. WTF??? A quick measurement showed the shaft was .491” (Chevy size???)...the new gear is .531” ID. So doing some quick research showed no distributor gears available for a SBF in this size for a steel cam...no steel, no poly, nothing that I could find. You can find factory ford sizes all day long (.467” and .531” gears). More research seems to show that the .491” gear is common on Chinese sbf HEI’s...and nothing else. !@&$?(!

So, like any problem, there is always a more expensive solution. I’ve got a new DUI distributor with the correct gear on the way. It’s always something!

[rebelyell]

Perhaps you might get one of those .467" gears and ream it to fit ?

[dannobee]

Perhaps you might get one of those .467" gears and ream it to fit ?

Yup, that's what I would have done. Chuck it up in the lathe and hit it with a boring bar.

[travis]

Unfortunately, that’s not an option that I can do myself. I don’t do this for a living, or even work in the industry, so I’d have to pay someone else to do it. The machine shop I use said he could probably do it, but he is a one man operation and said he was buried right now

[midnightbluS10]

How exactly did you come to the conclusion that only Chinese aftermarket replacements have a .491" shaft? Well that's incorrect. Afaik, ALL sbc and bbc stock distributors used a 0.491" shaft.


You can still buy distributor gears DIRECT FROM GM FOR THEIR STOCK, OEM PARTS that's a .491" ID gear.

So how'd you come up with this exactly? For example, the stock shaft on a TBI sbc is .490/.491"

So?

Here's just one thread for reference. If they were only on Chinese crap, why would guys be buying them for their stock, OEM distributors? Why would gm sell a 491 gear if it's only on Chinese crap? Because it's not. It's in most all of the stock stuff.

https://www.thirdgen.org/forums/tbi/431 ... butor.html

FYI there are 3 possible GM gear ID's:

0.427"
0.490"
0.500"

I wouldn't expect a Ford person to know this but you said you did research???

[travis]

How exactly did you come to the conclusion that only Chinese aftermarket replacements have a .491" shaft? Well that's incorrect. Afaik, ALL sbc and bbc stock distributors used a 0.491" shaft.


You can still buy distributor gears DIRECT FROM GM FOR THEIR STOCK, OEM PARTS that's a .491" ID gear.

So how'd you come up with this exactly? For example, the stock shaft on a TBI sbc is .490/.491"

So?

Here's just one thread for reference. If they were only on Chinese crap, why would guys be buying them for their stock, OEM distributors? Why would gm sell a 491 gear if it's only on Chinese crap? Because it's not. It's in most all of the stock stuff.

https://www.thirdgen.org/forums/tbi/431 ... butor.html

FYI there are 3 possible GM gear ID's:

0.427"
0.490"
0.500"

I wouldn't expect a Ford person to know this but you said you did research???

So your telling me that a regular size Chevy distributor gear will work on a Ford 351w??? Reread my post

[af2]

Don't know which roller you have but take a look.

https://www.summitracing.com/parts/sum- ... /make/ford

[travis]

Don't know which roller you have but take a look.

https://www.summitracing.com/parts/sum- ... /make/ford

I did see that one, but my cam is steel (of course lol)

[rebelyell]

I doubt he's suggesting a Chevy gear in your Ford ... maybe same ID but otherwise quite different.

If you KNOW where to get a Ford gear that'll play well with your cam's steel but has about .467" ID ... Get It !

Find another shop who can work with you and leave both gear & old distributor with them.

that ol' K.I.S.S. principle still works

[ProPower engines]

How exactly did you come to the conclusion that only Chinese aftermarket replacements have a .491" shaft? Well that's incorrect. Afaik, ALL sbc and bbc stock distributors used a 0.491" shaft.


You can still buy distributor gears DIRECT FROM GM FOR THEIR STOCK, OEM PARTS that's a .491" ID gear.

So how'd you come up with this exactly? For example, the stock shaft on a TBI sbc is .490/.491"

So?

Here's just one thread for reference. If they were only on Chinese crap, why would guys be buying them for their stock, OEM distributors? Why would gm sell a 491 gear if it's only on Chinese crap? Because it's not. It's in most all of the stock stuff.

https://www.thirdgen.org/forums/tbi/431 ... butor.html

FYI there are 3 possible GM gear ID's:

0.427"
0.490"
0.500"

I have also mallory with a .489 shaft and a .491 gear is loose. Just went through the same deal with some other GM replacement distributor.
There is a .489 bronze gear available but have always had a hard time getting a cast gear in the odd ball sizes.

I guess you will have to contact MSD or Holley which is who owns it now directly with the issue as Mallory which was owned by Prestolite originally they sole to Sierra Marine products before being gobbled up by the Holley group that owns MSD now.

[travis]

That’s the thing that kills me...I did contact MSD for the correct steel distributor gear! What they told me to use was just flat wrong even after I gave them the distributor PN and the guy spent 20 minutes going through their books.

But...it is what it is at this point. I’ll have bragging rights to the most expensive mild truck engine around

[ProPower engines]

That’s the thing that kills me...I did contact MSD for the correct steel distributor gear! What they told me to use was just flat wrong even after I gave them the distributor PN and the guy spent 20 minutes going through their books.

But...it is what it is at this point. I’ll have bragging rights to the most expensive mild truck engine around

One other source is Pertronix. They were also bought by Mallory then so on and so on till they are MSD/Holley.
They used a .491 shaft as well I think I have a couple warranty returns that never went back on the shelf still that had a start and 1/2 hour run before they crapped out. If ya can't get a gear the other option is just get a new distributor.
I bet they are about as much as a new replacement gear is.

KMJ performance has a MSD drop in copy they are identical but also use a .491 shaft. I know this because I just replaced a cast with a bronze gear on one for a steel roller.
\
PM me as I still have the cast gear unused if ya need it.

[travis]

I did end up ordering a DUI HEI with a proper .531” shaft...I’ll save the Mallory for some other flat tappet build down the road. The only reason I am going with an HEI style again is because I’ve already got everything moved and setup for the big cap HEI. I like the simplicity and easy parts availability of the HEI, but the big cap does cause its own fitment issues. This truck originally had a DS3 ignition system and VV carb (California emissions junk)...when it failed and I couldn’t find replacement parts I switched to the HEI.