when i install the vacuum actuator onto my secondary carbs, how can i make sure that the secondarys will close before the center carb, say like as if i hit the throttle and let off fast?
vacuum secondary question
- Thread starter 64 200 ranchero
- Start date
A return spring could work 
Also run mechanical linkage to the secondary carbs with a slotted linkage, so when you backoff the center carb the mechanical linkage also closes the end carbs.
Look at any holley vacuum secondary 4bbl carb & there is a link to the secondary throttle shaft which will mechanically close the secondaries on sudden deacceration.
Another option is check out GM engines with vacuum controlled end carbs on there tripower setup.
57 olds & up to early sixties pontiacs & chevys. Bill
Look at any holley vacuum secondary 4bbl carb & there is a link to the secondary throttle shaft which will mechanically close the secondaries on sudden deacceration.
Another option is check out GM engines with vacuum controlled end carbs on there tripower setup.
57 olds & up to early sixties pontiacs & chevys. Bill
hopefuly on topic , multi-carb help...
Vacuum asssist could add more options to Offenhauser sliding rod linkage kit for 3X1 . It's Simple and effective yet totally mechanical, variable geometry over center gives wide options , . . Works satisfactory but pedal is a little heavy pulling secondaries WOT at center setting - fun of Tri-Power is getting 3 carbs to cooperate especially at idle and WOT 8).
[
spring fever
Vacuum asssist could add more options to Offenhauser sliding rod linkage kit for 3X1 . It's Simple and effective yet totally mechanical, variable geometry over center gives wide options , . . Works satisfactory but pedal is a little heavy pulling secondaries WOT at center setting - fun of Tri-Power is getting 3 carbs to cooperate especially at idle and WOT 8).
[
spring fever
Ford, used mechanical linkage on their tri-power engines.
Holley carbs were used on 401HP 390's & 405HP on the 406 engins in the 61-64 era.
The mechanical linkage would be a lot easier than fooling around with a vacuum setup.
I remembering riding in a 61 pontiac with the 389-348HP engine with tripower. GM used rochester carbs.
When those end carbs opened that tin indian hauled like a raped ape.
Had decent fuel miliage if you just ran on the center carb.
I have a 61 pontiac shop manual which gives the whole rundown on the tripower setup. Bill
Holley carbs were used on 401HP 390's & 405HP on the 406 engins in the 61-64 era.
The mechanical linkage would be a lot easier than fooling around with a vacuum setup.
I remembering riding in a 61 pontiac with the 389-348HP engine with tripower. GM used rochester carbs.
When those end carbs opened that tin indian hauled like a raped ape.
Had decent fuel miliage if you just ran on the center carb.
I have a 61 pontiac shop manual which gives the whole rundown on the tripower setup. Bill
Since you've asked for How to vac secondary carb your tri power, you've got the best info from us all. Go have some fun.
As for me, I'd not personally ever use a vac sec carb, as its a well defined "air on demand" carb, verses the far more resposive mec sec, or independent runner or harmonically balanced 3rd, 4th and 5 th order tunnel ram. The latter ones give better results.
See http://forums.corvetteforum.com/c3-tech ... aries.html regards just the debate between vac sec and mec sec
The ideal vac sec is the 630 cfm vac sec 4180 Holley 4-bbl, then the 3514V Australian GTHO/Chevy Big block 396 750/780 cfm 3310. If you emulate the heavily dampened secondary, you'll always do well economy wise, with a nice,crisp mid range. For vac secondary 6-bbls, the Six Pack Mopar were okay when the secondary circuit was used but a nightamre when not. The Olds J2 were better, as the carb never suffered the problems the Holleys did with drying out.
(Do note, that as I've said before, GM out engineered everyone with there mechanical secondary Qjet and Rochester Mechancial outers on the Pontiacs. The 389 GTO and 421 Catalina were the best Tri Powers ever, especially mid range. Vac operation doesn't ever yield better performance, only lighter accelerator pedal and it covers fuel economy and adjustment simplicities, and later, the ability to eliminate the outers during the emission cycle, especialy true of the Mopar six packs. Adding a spring to the vac dashpot allows the level of severity to be tuned.
Its no different to a mech sec 4-bbl verses vac sec 4-bbl, mid range is stouter with up to 10% more torque with a mec sec. Fuel economy almost always takes a dive when mechanical secondaries are employed...unless the set up is expertly blueprinted to match the cam and ignition. Today, 5 liter 19701 to 1987 Holdens with blueprinted 4MV Qjetscan make a streetable 470 hp, and 6.6 liter Ponchos with tripowers go above the 600 hp mark with ease.Each is an example of the best mec secondary carb systems ever)
As for me, I'd not personally ever use a vac sec carb, as its a well defined "air on demand" carb, verses the far more resposive mec sec, or independent runner or harmonically balanced 3rd, 4th and 5 th order tunnel ram. The latter ones give better results.
See http://forums.corvetteforum.com/c3-tech ... aries.html regards just the debate between vac sec and mec sec
The ideal vac sec is the 630 cfm vac sec 4180 Holley 4-bbl, then the 3514V Australian GTHO/Chevy Big block 396 750/780 cfm 3310. If you emulate the heavily dampened secondary, you'll always do well economy wise, with a nice,crisp mid range. For vac secondary 6-bbls, the Six Pack Mopar were okay when the secondary circuit was used but a nightamre when not. The Olds J2 were better, as the carb never suffered the problems the Holleys did with drying out.
(Do note, that as I've said before, GM out engineered everyone with there mechanical secondary Qjet and Rochester Mechancial outers on the Pontiacs. The 389 GTO and 421 Catalina were the best Tri Powers ever, especially mid range. Vac operation doesn't ever yield better performance, only lighter accelerator pedal and it covers fuel economy and adjustment simplicities, and later, the ability to eliminate the outers during the emission cycle, especialy true of the Mopar six packs. Adding a spring to the vac dashpot allows the level of severity to be tuned.
Its no different to a mech sec 4-bbl verses vac sec 4-bbl, mid range is stouter with up to 10% more torque with a mec sec. Fuel economy almost always takes a dive when mechanical secondaries are employed...unless the set up is expertly blueprinted to match the cam and ignition. Today, 5 liter 19701 to 1987 Holdens with blueprinted 4MV Qjetscan make a streetable 470 hp, and 6.6 liter Ponchos with tripowers go above the 600 hp mark with ease.Each is an example of the best mec secondary carb systems ever)
i like the vac secondary idea because it will be simple and easy, i drive the car every day so i dont have time to make adjustments on it all the time, and i have already started building it, ill post pics when i can, thanks guys for all the info 
i hooked up the actuator to the ported vac off the center carb, it looks like it will work great but, the secondary carbs will be linked together and they will have a return spring that will put alot of tension on the vac actuator. how much vac will be needed to pull the carbs all the way open, or better yet, how much vac is at the vac port of my 1101 carb?
You will have low vacuum when you jump on it, so am thinking that you will need to have the spring pressure to open the end carbs. At cruise with high vacuum it will pull the end carbs closed.
How you doing on your triple setup?
im just waiting on some parts to come in the mail, ill try to post some pics soon, i like the way jdn21758 did his fuel lines, looks clean, im going to try somthing like that
Similar threads
All Small Six
Chasing vacuum leaks..the saga continues...
