I seemed to have mis-placed my old Chevy power book
Anyone have a pic of the recommended timing curve mentioned in there?

 

Here you go. Not a big deal really. The curve is below the power band so this is less than essential.

Starts at 20 degrees at 1400 RPM and goes to 38 degrees at 3000 RPM.

 

Thanks. Just double checking my memory. Ain't what it used to be, and I haven't seen that book in a loong time!

 

Leigh,
those 2 different distributor autocams....If your cylinder pressure allows the faster action autocam, run it. If it pings below the top of the curve, the slower one is probably a better choice. Many times, the engine is "off the pipe" below 3000 RPM so cylinder pressure will allow the additional advance at earlier RPM. Emissions be damned.

 

Yep that's the plan. I just wanted to test everything so I know what kind of adjustments I can make.
The two mainshaft cams can make a 5 degree difference at 2000, when the curve is half-way in.

BTW the 1963 327 / 365 with T.I. had the fastest curve I could find...all-in by 2500!!! with a lot of initial, like 10 degrees. It was the only Chevy factory curve I could find that was that quick. and almost like the curve in the Chevy Power Book.

 

Did you need to reschedule dyno day?

 

Yeah - poly lok / valve cover interference issues, intake oil shield/roller lifter interference issues and OEM wires are back ordered.
Still making progress!!

 

Hi Leigh,
What "brand" / who is supplier on the two mainshafts ?
Thank you,
Jerry

 

Paragon.
The mid america shafts are indexed incorrectly.

 

Help me out here. Just engineering curiosity, or mechanical ineptitude on my part, but I'm unclear about the issue of the indexing (which I assume is the roll pin hole). The points cam assembly dictates when the points open, and where the rotor points to, and the distributor housing is always rotated to get the advance setting we want. None of that procedure needs to be in any special alignment with the roll pin hole. The only thing I can think of, if the index hole is in a different place than the stock shaft, the housing might need to be rotated a half tooth different to get the timing set. Other than on a Corvette, where the tach cable gets fussy in its routing angle, the half tooth rotation difference shouldn't be a big deal.
This subject brings up another question I've been curious about. Does/did Chevrolet mill/index the camshaft rear gear in the same place on all their camshafts? I'm trying to understand if there's some significant reason to make sure that the rear gear is machined in a specific indexed position on the camshaft. If it's not in a constant (rotationwise) location for all camshafts, then the location of the distributor shaft indexing hole seems irrelevant to me.

I'm asking strictly for clarification, correction, or enlightenment. None of my comments or questions above should be interpreted as an argument for or against a particular placement of the indexing hole. I'm just trying to get this straight in my head.

Thanks.

 

Far right is NOS TI.
Far left is Mid America.
Center two are Paragon, both types available.
Notice the tang, roll pin hole, oil grooves, and gear are different on the MA unit.
My imediate thought was indexing the gear dimple to the rotor, and what else is wrong?
The oil grooves are different place.
The tang is longer, and the pin hole is not in the meat.
The gear is longer. Good or bad, dunno.
Repops are 50-50, so I went with the accurate repop.
I tossed in the tach drive bushing.
The NOS unit is bronze, the repop is brass.
The slot is offset on GM, the slot is centered on the shaft hole.
Big deal? Not really, but I can tell across the room if its been messed with.
I had a tool made for the bushings. I used a repop as a pattern. It wont fit a GM bushing. Argh, I hate this crap.

 

Is it just an illusion - the MA shaft dia looks huge compared to the others - I can't see that it could possibly be that way but looks weird.

The gear pin hole also looks enormous ??

Thank you for the photo's and observations

 

The roll pin hole is just chamfered, but I bet a high volume pump would eventually snap the tang off. The hole is so close to the tang.
The shaft is .490. They had to get something correct.
My money goes to the accurate shaft, not the "brand X."
Is Mike correct? I leave that to his mind, but mine says no sale.

 

Mike is just asking questions and trying to learn from someone who has more experience with distributor hardware. Absolutely no disrespect intended.

 

I see where you are going with this Mike.
Does it matter how the oil pump shaft lines up to the distributor advance? No.
Does the engine even care of the relationship between the advance can and the manifold? No
Would that affect the look on top of the engine? Yes
Does the relationship of the roll pin to the distributor tab matter to the engine? No but it is a useful line-up everything guide.
But that roll pin hole is very concerning for strength purposes.

I bought a new distributor tach drive gear and bushing. The distributor would not even turn a full revolution, maybe a half. The drive gear teeth were not the same on both sides of it's shaft, or not centered properly, and it was binding badly. I am not sure if it was the teeth were too high or the groove between them not deep enough. A second set worked beautifully.

 

None taken. Never crossed my mind.
I have learned far more from you than I could ever teach you.

 

I sincerely appreciate that. When typing things, it's sometimes difficult for this guy who slept through English class to phrase things that will guarantee that the message will be interpreted as intended.

I got a one week vacation from CF a few years back when my question in PR&C was interpreted in a slightly stronger manner than what I had intended.

 

Hey Mike. Georges hand, agreeing that the tang will easily shear under load.

 

I agree. Looks like it was machined further up than an OEM part.

 

I don't know if it will shear under the load of driving an oil pump - but the point being missed is what about the placement of the drive gear.
That is / will be off a mile ( well at least 1/4" anyway)