?'s about aftermarket distributors

[Ryan 79]

I need a new distributor. Mine doesn't advance properly, and even if it did, it only has about 16 degrees of total advance. I checked another distributor in a Chevy today, and its the exact same way.

So I'm looking at this one

http://store.summitracing.com/partd...889122+4294925143+4294881256+115&autoview=sku

but have never had an aftermarket distributor, so I have some questions.

First off, if the module or pick up coil goes bad in this, will stock Chevy parts replace the MSD parts?

Second, the ad says no tach drive. What does this mean? Every HEI ignition I've seen has a hook up on it for the tach straight off the coil.

Third, I do NOT want to run a spark box of any kind. Will this distributor perform correctly without the box?

I basically want a stock replacement distributor that will advance correctly. I'm not having too much luck with either stock Chevy HEI's or supposedly stock replacement HEI's, as they're both doing the same thing.

Any info on this or other similar distributors is appreciated.

 

[jakeshoe]

Ryan,
Keep in mind that most engines actually need more initial advance than the factory called for (on emissions applications anyway).
So a distributor with 16 degrees of advance will usually work very well.
If you are after 36 total (and you probably are if not 38 or more on your BBC), then having 20* of initial timing should help it to idle better.

20-25* of initial usually works very well on a mild performance engine.

Most of the HEI's I've messed with have TOO MUCH advance.

 

[79rallysport]

Jake, when you say 20* initial, you are including the vacuum in that figure too right?

 

[jakeshoe]

Jake, when you say 20* initial, you are including the vacuum in that figure too right?

No I am not including vacuum.

Vacuum advance is not included in "initial timing". Initial timing is what you have with no vacuum or mechanical advance. It is also called "base timing".

You can cheat and use vacuum advance to pull in more initial timing but if you have a distributor properly setup, you won't need to do this.

On a performance engine with decent compression and moderate to large camshaft you will find that they need plenty of initial timing to idle properly.

~20* for a milder setup, 25* for a moderate deal, and full timing (locked out distributor) for more radical setups.

Even a completely bone stock smog era 350 SBC will work best with about 20* of initial timing. The reason they spec'd such slow timing figures at that time and used ported vacuum for the vacuum advance was purely emissions reason, mainly HC's at idle.

 

[Ryan 79]

Ryan,
Keep in mind that most engines actually need more initial advance than the factory called for (on emissions applications anyway).
So a distributor with 16 degrees of advance will usually work very well.
If you are after 36 total (and you probably are if not 38 or more on your BBC), then having 20* of initial timing should help it to idle better.

20-25* of initial usually works very well on a mild performance engine.

Most of the HEI's I've messed with have TOO MUCH advance.

I just had the ignition and carb set up by an excellent carb guy.

He set the initial at 20, got the total to 36, and it ran excellent. It had a little knock if you let the OD kick in. The weights were sticking when I took it in there, and he re curved it and put new weights in it, and the problem went away for a while.

When I took it to him, it didn't have much gas in it. I filled it up right after I left his shop, and it started knocking. I jacked the timing back down to 8, but not too long after the weights started sticking again.

I really don't want to screw around with this thing anymore, and would rather just put a better distributor in it. The mechanic who worked on my car recommended a new distributor even before he tried to fix mine to get the proper adavnce I needed, so I don't think he's trying to rip me off.

I can get the total correct, or I can get the intial correct, but I can't get both without knocking, so I think its time to try something else.

 

[Rick WI]

Tach drive means it won't work in a Corvette. They need a mechanical tach. You will have a trigger terminal in the cap connection for your Camaro Tach. You may need a special connector though to get it to work correctly, I don't know if MSD supplies these in the Street Fire line though. I also don't know if they supply bushngs and springs to set the mechanical and centrifugal advance either. You will want those parts.

Give MSD a call 915-857-5200, they are great to work with and can help you figure out what you need. Then call Summit and order the parts.

I do think you would really like the performance of an MSD 6 box with a small cap distributor and Blaster coil, but I can understand wanting to keep things simple.

 

[jakeshoe]

If it's knocking, it probably has to do with the vacuum advance. Unhook it and see if the knocking goes away.
36* of total and 20* of initial should be about perfect. You MIGHT need to knock it back down to 18 & 34* because you are closer to 9.5-10-1 now right?

The clattering is probably coming in under the right conditions where you have too much vacuum advance. This is an easy $25 fix using a Crane adjustable vacuum advance kit. Just limit the vacuum advance back down about 12* or so. That will give you a max timing of 48* with total at 36.

If you have sticking weights, be SURE your guy used the STOCK weights with the spring kit. Also you may have to go back a bit to slow down how fast the timing comes in. It could be too fast on the mech advance. Most guys just throw the "fast" springs in, and the best setup on a BBC like yours is to use one light spring and one medium, using the stock weights.

Clean the weights really good, install the new nylon bushings that came in the spring kit, and it shouldn't be sticking.

 

[Rick WI]

I posted prior to seeing these last few posts. That's what happens when you over advance. Ping ping. True, engines like quite a lot of advance at idle, 20% efficiency tends to slow combustion. But that excessive advance can play havoc on detonation when efficiencies begin to move higher and combustion speed increases.

 

[jakeshoe]

Rick knows....

 

[Ryan 79]

Jake,

I tried unhooking the advance, it made no difference. It already has a Crane adjustable vacuum advance on it, and its set on the slow side.

I would put a different set of weights and springs in it if I thought that would make any difference in the overall picture. Even if I can slow down the advance rate, I'm still looking at an 18 to 20 initial, and I'm afraid I'm still going to be seeing problems at this much base timing. It has the new nylons in it, but I will say that when the advance weights stick, the can stick at very low RPMs that jack up the timing very quickly. When its set at 8 degrees and the weights stick, it jacks the idle speed up to around 1100 RPMs. With the new idle speed of 1100, the timing is already advanced to around 22 degrees.

One thing I did forget to mention. After I put the new pistons in it(it's around 9.6 to 1), I had an almost full tank of 87 octance in it when I pulled the engine out, so I went to Napa and got some octane booster, and put this in the tank. The last of that gas ran out as soon as I got it out of the shop and re filled the tank with 93 octane, so this is really the first tank that its run on regular pump gas.

Jake, you've forgotten more about this stuff than I know, so in your opinion, if I get the weights straightened out, would it be ok to run this at 16 to 20 initial and 32 to 36 total without knocking? And if I do get it to where you say it should be and it still knocks, what do I do then?