Thread: 302 Stroker??

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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 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 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.

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-)

Originally Posted by 34_40

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

OK Mike, first I have apologize for the grunge & grime in these pictures, but the car's headed into the shop for some fiberglass work so I didn't take time to detail the engine As you can see, my installation is extremely constrained with the throttle body extension immediately above, and the water neck boss all but surrounding the distributor body. This Mallory Billet distributor was made special for Edelbrock to be as short as possible for vertical clearance, but also small diameter.

Tucked in between the driver's side fuel rail and the water neck:
DSCN6093.JPG

Water neck clearance is all but nothing:
DSCN6091.JPG

Block boss beneath the hold down clamp to bottom of base is ~1.5" (very hard to measure with any accuracy):
DSCN6090.JPG

Tucked under the Throttle Body Extension - Intake has to come off to pull the distributor, but with the cap & rotor pulled there is room to lift it enough to shift the drive gear on the cam gear:
DSCN6095.JPG

The body is very nearly an exact 3.00 inches, not counting the mounting ears for the cap:
DSCN6097.JPG

Hope these help. As I mentioned to you before, I really think you'd be better served by calling Mallory and talking to them about putting something together that may not be "standard". They might have a small diameter body like this one, but with a more "standard" shaft length to get it up above your restrictions. That would be my approach before I started buying and returning units with Summit.

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.

ROFL... Just call me stubborn! But, I'll persevere!

Originally Posted by 34_40

ROFL... Just call me stubborn! But, I'll persevere!

OK, but remember I'll be glad to help you out of your dilemma!!!!!

Originally Posted by Dave Severson

OK, but remember I'll be glad to help you out of your dilemma!!!!!

I promise I won't forget!

Thank You for the pics / measures Roger! I' m thinking that the 1.5" from mount to bottom of body would be a killer! I believe my old mallory is 3" off the mount and it hits.

I was browsing MSD last night and I like the looks of one and am waiting for an e-mail reply as we speak. We'll see what happens.

Originally Posted by 34_40

Thank You for the pics / measures Roger! I' m thinking that the 1.5" from mount to bottom of body would be a killer! I believe my old mallory is 3" off the mount and it hits. I was browsing MSD last night and I like the looks of one and am waiting for an e-mail reply as we speak. We'll see what happens.

Mike,
I've said several times that the Mallory unit I'm running is a special build, commissioned by Edelbrock to get the lowest overall height they could get with a fully electronic distributor. I did not have any hope that this distributor would work for you, given the constraints. I knew it would be too short. Good luck on the hunt.