carb to quadrajet

[jdheff1982]

Vacuum secondaries run off existing vacuum to open them up. Mechanical is just linkage and more reliable.

Just do what you want to do. I bought the 750 because of the price. I mean, if you are just running a stock engine, then the 750 probably is too big, but that doesn't mean it can't be tuned for your motor.

[jojoman]

so i got a question.I have a dist with no vacuum advanced this is what i got http://www.jegs.com/i/MSD+Ignition/121/85551/10002/-1
im trying to put this on my 383 will it work http://www.summitracing.com/parts/HLY-0-83670/
right now i have a dp 650 mechanical holley what you guys think let me know before i hit the order button thanks oh and i just want to make sure this carb will work on my chevy 350 automatic trans since it says it has the ford kick down thanks

[RUSHNBOBO]

Carb good ....distributor no.....get the one with vac advance, even if for some reason you don't use it there about the same price.
If you are running an OD trans and or low numerical gears, vac advance will save gas, give better throttle response, keep plugs cleaner.

Here's the exception a high numerical rear gear and no OD .....this is what I run and my cruise rpm is over 3000 rpm at a fairly low vac reading so the vac adv would almost never activate, so I run a optimized mechanical curve and a fairly high 15-17 degree initial. I have the vac adv model MSD but disconnected the vac portion....even with an adjustable canister it rarely would do anything, because my engine and gearing combo rarely shows high enough vac.

Also, do you have a MSD box? 6a 6al 7 series ? If you don't have a box you need this one, ready to run MSD Ignition 8360 - MSD Pro-Billet Ready-To-Run Distributors vac adv.

If your running a Msd box ....this one MSD Ignition 8361 - MSD Pro-Billet Street Distributors vac adv.
This distributor as well as the one you noted above are dedicated to run only with external spark boxes ( they only trigger a signal.....and don't produce a current to energize the coil)

[jojoman]

but this is the dist i got already in there you think it will still work or would i hsve bad problems with it

[RUSHNBOBO]

Originally Posted by jojoman

but this is the dist i got already in there you think it will still work or would i hsve bad problems with it

Sure it will work ....I thought you hadn't purchased one yet. As far as acceleration you won't notice any difference at all (at WOT a properly set up motor will show zero vacuum anyway), but cruising at a higher vacuum reading you will be giving up some fuel economy...it does depend on your gearing and trans setup though...refresh my memory ?

Also I assume you have a spark box ?

[jojoman]

I do have a spark box with a coil I really dont know my gear is a 84 all original besides motor and the trans is a 350 and when you say I won't notice any difference on acceleration what do you mean by that. the spark box is a 6a
Posted via Mobile Device

[RUSHNBOBO]

Originally Posted by jojoman

I do have a spark box with a coil I really dont know my gear is a 84 all original besides motor and the trans is a 350 and when you say I won't notice any difference on acceleration what do you mean by that. the spark box is a 6a
Posted via Mobile Device

In a mech/vac advance distributor vs. a mechanical adv only distributor, the vacuum chamber on the first will do nothing at very low vacuum readings such as....whenever your under acceleration or a load such as climbing a hill, and towing. In this scenario the throttle plates are open to far and as a result the manifold vacuum drops off ...which in effect disables the vacuum advance canister (insufficient vacuum).
The mechanical portion works the same all the time, it is purely based on engine rpm and nothing else. Both types of MSD distributors, this portion is almost identical and is easily adjusted with sets of springs and a chart which should have came with the distributor .....if you don't have it I'll post the link

The 6a is the original MSD box been around since the seventies,,very reliable, I'm running the same one on the dually.

Have you already installed the distributor ? ....if not I'd seriously try and get the vacuum advance model. That way you'll have the best of both worlds good cruising fuel mileage, potentially cooler running engine and all the rest of same features of the high performance model (non vacuum advance)

[jojoman]

well the dist was on the truck when i bought it do you think all this will work better if i just get a mechanical sec. ditributor or no is better all way around to change the dist.and go with the carb that i want which is the holley 670 vacuum sec. oh but wait if i get the carb with mechanical it will just end up being worst cus it will be a double pumper ant thats not what i want for my truck right. what you think is best set up. oh and how can i tell if my trans is over drive or has od

[RUSHNBOBO]

sent pm