Need advice...
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Joined: Feb 2005
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From: Tomah Wisconsin
Need advice...
Looking to finalize my 3x2 set-up on a rebuilt 350, with Edlebrock intake, and could use a retail source that will help me to determine sizing for the main jets in the outboard carbs, unless of course some one of you may be able to help. Using Rochester 2GC's with 0.50 mains in all 3 carbs, outboards have been converted to eliminate idle passages. Thanks, Marv B.
Racer
Joined: Apr 2006
Posts: 477
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From: Millbrae California
most of the rochester 3x2s that we have jetted have used jets in the 57 range but we have had to do major work on the idle system of the center carb plus update the accelerator pump on all three carbs to a custom made accelerator pump to avoid the pump cup swelling problems that are common with the rochester 2g carbs.
if you are using the 3x2 set up for the look that is fine but you will lose over 50 horsepower when compaired to a modern intake with a single 4 bbl performance carb or the barry grant six shooter 3x2 package. the power loss is due to the small ports and runners of the rochester based 3x2 manifold plus the low air flow rochester carbs
henry @ oles carb
if you are using the 3x2 set up for the look that is fine but you will lose over 50 horsepower when compaired to a modern intake with a single 4 bbl performance carb or the barry grant six shooter 3x2 package. the power loss is due to the small ports and runners of the rochester based 3x2 manifold plus the low air flow rochester carbs
henry @ oles carb
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Joined: Feb 2005
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From: Tomah Wisconsin
Thanks for the advice Henry. I realize you promote Barry Grant products and now that I am this far into my project, wish that I had looked harder at that set-up versus trying to save a few $ by doing it myself. I am too far into my choice to start over on this set-up and realize some of the disadvantages to doing what I am regarding the loss of HP and possible performance. I'm at the point of ordering jets, but was hoping not to have to shotgun order a bunch of different sizes at $5 a pop so that I could do the switch & play until I found the right combination.
I appreciate the heads up on possible accelerator pump problems. In fact I may already have that problem with the center carb, however I'm going to try to make this set-up work as it is on a street application where I want to run somewhat economically on the highway, but have some kick under acceleration when the outboards come in.
I may find that this set-up isn't going to work the way I hoped, but thanks again Henry for your advice. Marv B
I appreciate the heads up on possible accelerator pump problems. In fact I may already have that problem with the center carb, however I'm going to try to make this set-up work as it is on a street application where I want to run somewhat economically on the highway, but have some kick under acceleration when the outboards come in.
I may find that this set-up isn't going to work the way I hoped, but thanks again Henry for your advice. Marv B
Racer
Joined: Apr 2006
Posts: 477
Likes: 43
From: Millbrae California
we have done quite a few rochester 3x2 set ups and most of the owners expct more power than they make. on a engine dyno we took off the 3x2s and put a performer intake with a holley double pumper and gained 50 horsepower with no other changes. most of the power gains were in the intake manifold design, now if you could come up with a more modern intake for a small block with rochester 3x2s i could live with it.
we are making pumps that work on the rochester 2 bbl but the idle and off idle system of the center carb will need a fair amount of modifying unless the engine is a small displacement (283) and has a stock cam because the a stock 283 rochester 2bbl was never designed to work with the air leaks of the 2 outer carbs or a high performance cam. we have made it work and if you have the patience to tune it it will work it is just the manifold used is a real air flow restriction when compaired to modern 4 bbl manifolds or the barry grant 3x2 package. (i think someone else besides BG also makes a good manifold for a small block with holley/demon carbs)
good luck henry @ oles carb
we are making pumps that work on the rochester 2 bbl but the idle and off idle system of the center carb will need a fair amount of modifying unless the engine is a small displacement (283) and has a stock cam because the a stock 283 rochester 2bbl was never designed to work with the air leaks of the 2 outer carbs or a high performance cam. we have made it work and if you have the patience to tune it it will work it is just the manifold used is a real air flow restriction when compaired to modern 4 bbl manifolds or the barry grant 3x2 package. (i think someone else besides BG also makes a good manifold for a small block with holley/demon carbs)
good luck henry @ oles carb
