Yes, the manual shows dist vac hooked to hollow stud on rear carb base = manifold vacuum. Which dist are you referring to?
A few q's RE: 348 3X2 set up
- Thread starter reastman
- Start date
Never thought about that - may be a viable solution.
Even if the Pertronix did have an adjustable vac, he still said that it works opposite of factory. Correct me if I'm wrong, but my current understanding is that with ported, the higher rpm = more velocity in venturi = more vacuum to dist = more advance; similarly, low rpm = higher manifold vacuum = more advance at idle and less advance as rpm increases. So the internal linkage in the Pertronix dist must be different from factory. I haven't messed with this for nearly 30 years, and am trying get a good refresh course from the experts here.
BTY, the dist I presently have on the engine is a Mallory p/n2534501A. It is solely a mechanical advance type, is no longer made, and has dual points like my original '61S/S.
Then you could get an adjustable vacuum advance and tune the mechanical advance with weights and springs…
Ported vacuum will only have vacuum once the throttle plates have opened, but when the throttle is open there will only be a small amount of vacuum and will go to 0 when you increase load on the engine.
With manifold vacuum to the advance it will have advance until you put a load on the engine and vacuum drops, this keeps it from having to much advance under load.
Manifold vacuum to the advance will give better fuel mileage.
With manifold vacuum to the advance it will have advance until you put a load on the engine and vacuum drops, this keeps it from having to much advance under load.
Manifold vacuum to the advance will give better fuel mileage.
I ran a Pertronix distributor for a couple years. Tried both ported and manifild vacuum with no obvious difference. My engine has 15 inches of vacuum at idle. I switched to a stock distributor with a Pertronix III conversion only because I needed the shorter distributor. I also run an Accel coil. Never any issues.
Gofish
Well Known Member
That is true. in addition and as La Hot Rods stated, the only difference between ported and manifold vacuum is at idle. At idle ported is no vacuum signal, whereas manifold is at whatever vacuum is present at idle (my tri-power 348 is about 20 inches). in general, the default is to use manifold vacuum for the vacuum advance. In fact, my tri-power doesn’t even have a ported port (I confess my center carb is a non-tri power).
I have a stock distributor with a Pertronix III in it. The III includes a rev limiter, which is nice. I also use their coil and wires.
John
Thanks guys.
I talked to Chris again at Pertronix. He said the original vac cannisters were pull - type, and typically used 15" vacuum. They are all now push-type and see a max of 10". At 15", the vac cans diaphragms did not last as well [personally, I don't ever recall replacing a vac can on my '61 or any other car]. He also said that the Rochester 4-jet was a ported carb. I told him they should say so in their website, as the 2GC carb is not ported vac. I clled MSD, as well. All their dist are for ported vacuum. Show Cars sells distributors and he said they use and sell the hollow stud. He was not aware of vacuum hook-up differences. They no longer sell original dist's
Pertronix also said no one mfrs a pull-type cannister - the adjustable ones are all push type as well. I talked to Joe @ Carburetor Exchange. He said the Rochester 2 GC's did not have ported vacuum until late 60's, and it was in the base.
Dick
I talked to Chris again at Pertronix. He said the original vac cannisters were pull - type, and typically used 15" vacuum. They are all now push-type and see a max of 10". At 15", the vac cans diaphragms did not last as well [personally, I don't ever recall replacing a vac can on my '61 or any other car]. He also said that the Rochester 4-jet was a ported carb. I told him they should say so in their website, as the 2GC carb is not ported vac. I clled MSD, as well. All their dist are for ported vacuum. Show Cars sells distributors and he said they use and sell the hollow stud. He was not aware of vacuum hook-up differences. They no longer sell original dist's
Pertronix also said no one mfrs a pull-type cannister - the adjustable ones are all push type as well. I talked to Joe @ Carburetor Exchange. He said the Rochester 2 GC's did not have ported vacuum until late 60's, and it was in the base.
Dick
Lots of W owners are using a stock distributor with a Pertronics, including me, a 3 with rev limiter. It works great, I’ve had one in my 283 or 409 since 2003. The Pertronics guy must be too young or works on Fords a lot?
I’ve seen lots of posts here where somebody is having issues, they find out their problem is using ported vacuum on the distributor, switch to manifold, problem solved. The crowd here work on 348-409’s so nothing newer than a 65. Some are also great with newer sbc’s and bb’s but all use manifold vacuum since most are not the new stuff with emissions.
I’ve seen lots of posts here where somebody is having issues, they find out their problem is using ported vacuum on the distributor, switch to manifold, problem solved. The crowd here work on 348-409’s so nothing newer than a 65. Some are also great with newer sbc’s and bb’s but all use manifold vacuum since most are not the new stuff with emissions.
Push type canister, that just doesn't sound right.
Lot's of good comments here. I think my best approach would be to find an oem dist. and install the Pertronix sytem in that. BTW, Pertronix said to use their 1.5 ohm coil. I checked my Mallory today: 2.5 ohms
I also got my two end carb plungers, but did not install, thinking I needed more info for possible ctr carb base mod to make it ported. and provisions to block off if I did not use. The end carb plungers I received were the circular spring type. The new ctr carb plunger I got last week has no circular spring. I did read on a Pontiac tri-carb thread that someone had the same issues as I: the spring pressure was causing the cup seals to "roll up" and tear. I did not notice any roll-ups, just tears. I will make sure, upon installation, that they are lubricated, along with the pump well walls.
Does anyone have a descent oem distributor for sale?
Thanks again, guys
Dick
I also got my two end carb plungers, but did not install, thinking I needed more info for possible ctr carb base mod to make it ported. and provisions to block off if I did not use. The end carb plungers I received were the circular spring type. The new ctr carb plunger I got last week has no circular spring. I did read on a Pontiac tri-carb thread that someone had the same issues as I: the spring pressure was causing the cup seals to "roll up" and tear. I did not notice any roll-ups, just tears. I will make sure, upon installation, that they are lubricated, along with the pump well walls.
Does anyone have a descent oem distributor for sale?
Thanks again, guys
Dick
I would find a accelerator pump that has a leather cup, they work much better and not bothered by the crap gas they sell these days.
I tend to not use the vacuum advance when I install a performance cam. I work on the mechanical advance to dial in my timing curve.
Gav, I use the factory 62 duel point distributor in the race car.
Gav, I use the factory 62 duel point distributor in the race car.
It did have a dual point - I can't remember about a vacuum can. Not much in shop manual - under "specs", there is an asterisk by the 283 dist [p/n 1110914] about setting dwell on their dual point dist. I worked at a Chevy dlr and remember asking a mechanic how to set it up.
It appears the consensus here is a non-vac factory dual point, or factory vac-operated single point with possibly a Pertronix pointless ignition mod. I don't know if my Mallory could be converted to pointless. I do know that a spring kit is not available.
The Pertronix will be here Friday. I already have a return label from Summit.
The Pertronix will be here Friday. I already have a return label from Summit.
I agree. That's all I used, back in the day.
Does my Crane cam fit the description of a performance cam? The specs are a little higher than the "hot" factory cam.
Yes that would in my book.