Thread: 302 Stroker??

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Originally Posted by rspears

Mike, I really think you'll have a lot better luck calling Mallory or MSD direct and talking to their tech guys instead of Summit. There's gotta be a distributor out there that fits. They used the manifold back in the 60's, right? Maybe a magneto.....

I think you're right...

Originally Posted by jerry clayton

--the centrifugal only advance distributors have smaller bottom housings and will clear that manifold------

The distributor that is shown in the pics is a centrifugal only advance, it's close but, just not quite there..

Originally Posted by 34_40

HMmm.. I'm wondering what you're really saying? LOL... I was just in New York this week. Town of Hillburn. Right next to Mahwah, NJ.
I might get back out there in 4 to 6 weeks. I'll PM if / when it happens. TIA

That's the wrong direction from Schenectady/Saratoga area - but detours have been know to happen .........

So this talk got me thinking (may be dangerous ) that in my old days I never messed with a distributor that didn't have vacuum advance, and now everything I mess with is total electronic/computer controlled. As I'm thinking about it, the mechanical advance can be adjusted, via springs & weights, to yield the slope you want and the rpm where curve starts climbing but you've got one curve of advance vs rpm which means the advance at say 2500rpm is what it is, whether WOT or 1/4 Throttle. Adding the vacuum advance lets you overlay a second advance curve for part throttle operation, which lets you pull in a few degrees at cruise for improved economy, right? The ECU controlled spark goes a step further, allowing the spark to be mapped over rpm and vacuum independently to create a "topo map" of timing. So if you run a distributor with mechanical advance only you set your advance curve for WOT operation, and then tune the carbs to get the best economy you can? Are there any "tricks" for weights and springs to change the shape of the curve to get closer to optimum? Guess this is why the old shops had the Sun machines with O-scopes, right? Just curious, and not trying to get too far off the path here....

Roger - exactly why I now run a distributor with a vacuum advance.

Now - as Jerry pointed out that vacuum advance has to be screwed to a boss on the distributor which in its normal location may interfere with the intake in a factory designated location. True, but that distributor really doesn't care where that boss is installed - only where the rotor and contacts to each cylinder are located - the vac advance can, its mounting boss can face forward - as long as the wiring is correct in relationship to the rotor which ..... well most of us know about crankshafts, camshafts and how they all work in conjunction with each other.

No rocket science here - the body of the distributor either fits - or it doesn't. My guess is that my small diameter MSD billet dist. will fit, but a $299 plus shipping trial gets expensive.

With the new, big cap


With the small dia. cap:

Originally Posted by IC2

That's the wrong direction from Schenectady/Saratoga area - but detours have been know to happen .........

I think that's how I ended up in York, PA once!!!

Originally Posted by rspears

So this talk got me thinking (may be dangerous ) that in my old days I never messed with a distributor that didn't have vacuum advance, and now everything I mess with is total electronic/computer controlled. Adding the vacuum advance lets you overlay a second advance curve for part throttle operation, which lets you pull in a few degrees at cruise for improved economy, right? So if you run a distributor with mechanical advance only you set your advance curve for WOT operation, and then tune the carbs to get the best economy you can? Are there any "tricks" for weights and springs to change the shape of the curve to get closer to optimum? Guess this is why the old shops had the Sun machines with O-scopes, right? Just curious, and not trying to get too far off the path here....

You got all the basics Roger. 2 points tho'.,
first at wide open throttle (or under heavy acceleration) there is little to no vacuum! That vacuum chamber does nothing but retards timing in that situation so it prevents ping.
And 2, when tuning centrifugal only or dual advance systems, you MUST KNOW the rpm range you want to work in and what the available vacuum will be in that range. Being at wot is really immaterial as the full timing should be "all in" before say 3K rpm.

Tricks like adding weight or where you can add weight to the flyweights can be fun. Also drilling the weights can accomplish things!
Also changing the springs for lighter/heavier springs, sometimes 1, sometimes both, I won't have access to the sun distributor machine like I used to so this one will take a bit longer.

OH, one last point, If we're talking cars / motors and it's "MY" thread! You can't stray

I'm sorry boys, but the distributer in the pic that Roger referanced has a vacume advance unit on it!!!!!!!!!!!!

Originally Posted by 34_40

...first at wide open throttle (or under heavy acceleration) there is little to no vacuum! That vacuum chamber does nothing but retards timing in that situation so it prevents ping. And 2, when tuning centrifugal only or dual advance systems, you MUST KNOW the rpm range you want to work in and what the available vacuum will be in that range. Being at wot is really immaterial as the full timing should be "all in" before say 3K rpm.

Yeah Mike, we're saying the same thing but from different directions. You're considering running at cruise and going to WOT, where the vacuum drops out and it "retards" back to the mechanical curve; while I was looking at accelerating at full throttle, and backing off to cruise, where the vacuum recovers and pulls in more timing. I peeked at my spark map, and indeed it goes "all in" to 35.5 degrees (pistons say not to exceed 36) at 3000 rpm and above. But it also throws in more timing above 3000rpm but with MAP at zero, 10" and 12", going all the way up to 40" advance. I had a hard time getting my head around that until I realized that the only way to get to that condition was to be coasting down the mountain above 3000 rpm, off the throttle. One of the guys at Edelbrock helped me understand that area of the map.

Originally Posted by jerry clayton

I'm sorry boys, but the distributer in the pic that Roger referanced has a vacume advance unit on it!!!!!!!!!!!!

Indeed it does, Jerry, indeed it does. So you're saying that the old mechanical advance only distributors actually have a different body, where they use the same shaft but everything sits higher since they don't have the vacuum canister boss & linkage?

Originally Posted by jerry clayton

I'm sorry boys, but the distributer in the pic that Roger referanced has a vacume advance unit on it!!!!!!!!!!!!

So it does.. I had forgotten that the accel one was in the pic. , The mallory does clear better because it doesn't have the vacuum chamber but it still needs a smaller diameter for clearance as the mounting flange is still not touching the block.

Sorry for my confusion.

Originally Posted by rspears

Yeah Mike, we're saying the same thing but from different directions. You're considering running at cruise and going to WOT, where the vacuum drops out and it "retards" back to the mechanical curve; while I was looking at accelerating at full throttle, and backing off to cruise, where the vacuum recovers and pulls in more timing. I peeked at my spark map, and indeed it goes "all in" to 35.5 degrees (pistons say not to exceed 36) at 3000 rpm and above. But it also throws in more timing above 3000rpm but with MAP at zero, 10" and 12", going all the way up to 40" advance. I had a hard time getting my head around that until I realized that the only way to get to that condition was to be coasting down the mountain above 3000 rpm, off the throttle.

Yes, my "typical" approach, using a different direction!
I usually find most folks "forget" that vacuum goes away at WOT and they think it's doing all this work for them when it can't! It's at zero! And it's actually retarding the timing.

Off the top of my head I cannot remember working with 40 degrees "all in".. that's pretty cool. But if handled wrong that could raise some havoc and quick I think!

Originally Posted by rspears

Mike, The Mallory Billet Comp on mine looks to be just a hair under 3" OD below the cap. The ledge on the cap makes it 3.25" but that should be well above your manifold. ..

Roger, could I trouble you for a pic or two? Measurements?

Originally Posted by 34_40

Roger, could I trouble you for a pic or two? Measurements?

Sure, but it will be Tuesday/Wednesday before I'm back where I can get it for you.

Originally Posted by rspears

Sure, but it will be Tuesday/Wednesday before I'm back where I can get it for you.

I'm nothing if not the picture of patience!

I used the "Live Chat" on Summits website and here's what they said to a question I asked.

Chad: Hi, my name is Chad. How may I help you?

Mike Frade: I've got an old Shelby Ram Box intake and I'm trying to find a dizzy that'll fit. If I order one and it doesn't fit, can I return it and try a different one?

Chad: Hi Mike, As long as the item is new and unused, we will accept the return 90 days from the date of purchase.

Mike Frade: So inserting it into the block to test fitment is acceptable?

Chad: Yes, that is fine, as long as it doesn't get scratched up.

Mike Frade: Great! I guess it's time to go shopping! :-)

Chad: Ok, have a good day!

So after Roger gets me some measurements.. we'll order one in.. or maybe two... 8-)

I think it's just waaaaaaaay too much hassle for a busy man to contend with!!!! You'd do better to just send me the intake and carbs, then just forget the whole mess!!!!!!!!!

PS--I'd even pay the freight just to help you do away with all this unneeded stress!

Originally Posted by Dave Severson

I think it's just waaaaaaaay too much hassle for a busy man to contend with!!!! You'd do better to just send me the intake and carbs, then just forget the whole mess!!!!!!!!!
PS--I'd even pay the freight just to help you do away with all this unneeded stress!

Mike,
Dave may be right! Seriously, one thing you didn't mention to the Summit guy is that you get to pay the shipping both ways on every one you order, and that runs into some bucks these days! Back at home, and will get you a picture or two and some measurements tomorrow. I'll tell you now that my installation is VERY tight, so I'm not sure pictures are going to show you much.