I'm putting three deuces (rochesters) on a chevy 350, what size gas lines run into the individual carbs? I want to make them out of metal, possibly brake lines, but don't know what size they should be. And, when I get around to putting everything back together, and start to set the carbs, at what rpm do I set it up, so the front and rear carbs start to be activated? Thanks much for the help!!!!! kbyounger

 

My guess is that 5/16" fuel line [to each carb] would be adequate; 3/8" would be the largest you would want. I'd recommend that you set up the outside carbs on a mechanical linkage [rather than vacuum]. That guarantees that you only run on the middle carb unless you push the accelerator far enough to activate the other two. Usually, you only want the outer two operable when you 'floor it', anyway. Set it up so that the outers start to come in at 50-60% throttle and are all the way in at full throttle. With that set-up you will get better economy in the city and at normal highway speeds (only running on 2-bbl), but it will get it on pretty fast when you kick it.

 

Very intriguing...

Assuming these are 2G's, the only reference I've got on setting up Rochester trips indicates that the tang on the accelerator pump lever should open the vacuum switch when the primary throttles have opened to ~60* (degrees, not percent). That would seem to be even more conservative, no? Thus, you're probably safe to play around with that point a bit to suit your liking.

Can't find an exact spec on fuel line size(s), but if you'd like to see an old pic of the fuel pipe arrangement on a 348 I've got from a 35 year old book, email me and I'll send it to you.

BTW, what's it going into?



edit - Just guessing here - 3/8 tank to pump, and maybe to and in the "log" between carbs, with possibly 5/16" to each bowl...

 

Thanks, it going in a 77 vette. Also trading out the t350 for a 700r4 tranny.

 

Thanks - that's what I'm hoping for... "cheap" to drive around the city, and even on the open country roads in overdrive, yet sitting at the light, its got what it needs to beat that mustang sitting next to me...

 

I've got a '69 Coupe and I have the same thing going on a 383 Stroker (3 Rochester 2G's / Edelbrock Intake). I bought a custom fuel log and custom bent chrome lines from Vintage Speed that fit perfectly. The lines they supplied are 3/8" and they look VERY cool!!! If you are going for the shiny chrome look, you should check them out.

 

Thanks, I've seen those, but did not realilze their diameter. Let me ask you about the linkage. The set up I have now, seems to be a one to one ratio between all three carbs - so if I set the first and third to be activated when the center carb is about 50% activated, I only get about 50% of the other two carbs - which amounts to the remaining 50% of the center carb. My thoughts were that when the center carb is wide open, so too are the first and third carbs. The way it is now, when the center carb is wide open, the others are only 50% open. The adjustment must be in where the linkage is connected to the other two carbs' "arms" - how does yours work? Does this make sense? thanks

 

Sorry, I had thought you were working with a vacuum "secondary" setup. Such a 1-to-1 linkage as you apparently have, which opens the throttles simultaneously, is either going to require giving up some % of total capacity or drivability issues, including poor economy, if you set them all together for full opening at WOT. You need to get a progressive mechanical linkage, per the factory's original design, which is meant to begin opening the secondaries at ~65% primary opening.

It looks like Vintage Speed can set you up with the progressive linkage you need.

 

I intend to put the barry grant sixshooter on my 69....how much hood clearance will i need? will a stock big block hood clear it or will i need an aftermarket hood to get the height?

 

Don't know the exact height of that 6-shooter setup, but the intake looks closer to the height of the taller C2 tri-power manifold, so I'd suspect a taller hood could well be in order.

 

I have built 2 of these setups. Check my corvette pictures. The one on the motor is a small base tripower. They are 600 CFM total. Each carb is 278 CFM but they are rated different than 4 bbls I liked it so much I had to have tripower on my new 383 but the small base ones are too small so I built a large base set W/ a plate nitrous system. These are 378 CFM carbs. Total equivilent 4 BBl CFM is 816. Lots of issues and modification. Here is a picture of the second set. Notice the linkage can be adjusted at the lever on the side to kick in the secondaries when you want. I used 1966 pontiac repro base plates and tops for the end carbs and a Mercruiser boat carb for the middle carb with electric choke and side inlet. The end carb bodies are 1970 chevy 400 2 bbl carbs. You have to eliminate the power valves and idle circuits on the end carbs. If you have any questions I would be glad to help

 

Nice tri-power set-up. Very similar to the 3x2 carb set-up on my '65 Pontiac 421. It had tons of torque and instant kick [when WOT]...but better highway/city mileage than most full sized cars with 4-bbl carbs.

 

I had to go with a L-88 hood to clear the tri power
i have check the gas milage once and I was getting
17 mpg when i keep my foot out of the other carbs
which is almost impossible to do
my fuel lines is set up with brake lines that i polished and cleared

 

Hey Rev'sVette: Sorry so late getting abck on this. The guys on this forum are THE Vette experts bar none. Like they said, you'll need a progressive linkage. When I started with these things, I had the same thought......my two outer carbs will never reach WOT...only 50% open at center carb WOT...that is until I started looking closely at existing units. What a progressive linkage does is not just allow the end carbs to start dumping fuels when you want and cause all 3 to reach WOT at the same time. The point that is missed sometimes in explanation is how the end carbs close the gap and catch up with the center carb in its opening up Essentially they have to open faster than the center carb in order to reach WOT at the same time as the center carb. If you notice, there is always an arm of some type that sticks up where you attach your linkage to. Essentially by moving the linkage connection down that arm, closer to the pivot point, you are shortening the distance that the end carbs have to cover to catch up with the center carb. You are pulling them open faster by moving closer to the pivot shaft. Depending on what kind of setup you have, you'll also have some sort of sliding adjustment that you set to grab the end carb and start pulling it open at a particular time. Just keep adjusting that until it grabs soon enough to have all three open at WOT. I'm sure there are more precise and scientific ways to do this and describe it...but this worked for me. I bought my carbs from a place down in Texas and got linkage with them, but they were pretty flimsy, so I've been making my own custom set. Hope this helps.

 

That's the ticket! You just change the 'throw' on the outer two so that they start to open at 50-60% throttle and you find the holes on the [front & back] throttle arms that allow full throttle at the same time as the center carb.