Hi All, anyone seen a good write up on how to set up 69 3x2 carbs?
thanks, Rog.

 

Actually, it's been a while since I've seen a comprehensive article on setting up the Tri-power, but basically you should consider them as one big vacuum secondary Holley, split into three pieces. Tips, 1) don't try to re-engineer the OEM vacuum secondary linkages (more on those in a minute), 2) I suggest removing the bowl inlet filters in favor of a larger one, upstream, 3) get two vacuum secondary diaphragm spring kits (Holley # 20-13) and install the weakest ones possible which don't result in a bog at WOT while driving (never mix & match sets, btw).

Now comes the trick: For primary adjustments (for which I'll assume you know your way around a Holley 4-bbl already), disconnect the secondary linkages from the center carb, making sure the end ones are and remain completely shut. After getting the center carb dialed in, then reconnect the linkages, making absolutely certain that they are adjusted so both secondaries are fully closed when the center carb returns to the idle position, but without the linkage being pre-loaded. Tedious as this may seem, it is very worthwhile to fiddle with this until you are satisfied that both ends are at the best possible lengths to achieve this adjustment.

IMHO, trips aren't as complicated as they appear at first sight, if you take this divide and conquer approach. Hope that helps.


TSW

 

Thanks TSW, Just got the car and am trying to get it all set up. i think the carbs are actually ok but need to check everything. I have great torque and HP, solid smooth idle, easy starts, good temp control, the problem is at 4000 RPMish, power drops off dramatically and feels like its missing with vibes ond pops. I have no BB experience but am told it should pull hard at least to 5500. From headlight action I know ther are vaccum leaks but I can feel the secondaries open but have no idea if they perhaps are not full at hi rpm. Have changed the fuel filters and tank intake sock.
Any suggestions on where to go from here?
As I am not overly concerned about correctness and have changed the fuel filters and destroyed the fuel lines, you can bet next time around they are gone to be replaced with an inline filter as per your suggestion.
Any other advice greatly appreciated.
Thanks, Rog.

 

Has anyone ever set up a tri-power setup in a 454 ?

 

Nice car CW62, I believe the set up is exactly the same as a 427. TSW's comments above should apply. Unless you have stumbled upon a tri-power intake and carbs, I would stick with the 4bbl set up. I don't think you will see a performance increase on the monster you already drive.
Later, Rog.

 

A certain carb guru who's no longer with CF once said that 90% of all carb problems are ignition problems. So, I'd make sure that's up to snuff before messing with the carbs.

IMHO, 3x2's should work equally well on most any BB, but just keep in mind that the low rise C3 intake doesn't flow all that great, compared to performance manifolds, if you're after huge top end. FWIW, there are better setups available, but I've never had anything else quite deliver the combination of power and economy as with a well tuned 3x2. The cool factor speaks for itself.

 

I had 3x2 on 468 (060 464) now going to 498 stroked and 070.

 

Are the carbs vacuum or mechanical?

 

Chevy BB Holley Tri-powers use ONLY vac 2nd's. Tho Bubba has tried to convert a good number of them, they're simply not meant to operate mechanically. That said, the SB 3x2 Rochester's were available either way, but that's a whole different animal.

 

Hi

Modifying them to mechanicals is not possible due to no squirter pumps on the 2ndaries like DP have.

Should be possible to reinstall the vacuum pods if missing.

Rgds. Günther

 

Thankfully I have a pre Bubba version, 3 2bbl holleys and the secondaries are still Vaccum controlled. Thinking about going with MSD ignition, what say you All?
Thanks, Rog.

 

They do, they do...doesn't matter if 396 or 540...

I suppose you are correct on this....but to tell you the truth, I would not take off my tri power for any 4 bbl combination, even if it were free.
I have unbelievable throttle response, no bogs, my springs are between the lightest and the factory, the secondaries come in in an instant without hesitation...

What did I do to tune them? Nothing, absolutely nothing...other than to use a 6.5" power valve, use lighter springs, and adjust the throttle linkage so that the blades are at 90 degrees when fully opened...

There is nothing on these carbs to tune...adjust the idle screws with a vacuum gauge to the highest reading and mess with the jets...secondaries...nothing except playing with the springs

I love the performance of this setup..oh...the economy...533 cubes, solid roller cam 3.55 gears 10.5 cr..cruising at 70, tach reads 2800 rpm, mileage is 14.2 mpg...






For the curious, yes, I am using stock valve covers with full roller rockers and poly locks....

 

Where can I get a setup like this for my 71 BB. I have a LS6 454 currently setup with a Damon 750.

 

Hi

E-bay always has setups, also overhauled once.

Pricey , but worse it.

I tried Holley DP 650, 750 & 850 CFM carbs and the tripower I run now is by far the nicest to drive. You can cruise it with a fantastic low consumption and you can burn the tires all the time with a fantastic high consumption.

http://forums.corvetteforum.com/c3-t...airfilter.html

Good luck. Günther

 

Will the tri-power setup fit under the stock BB hood ?

 

Yes, that's the reason the hood was made like that.

Hans

 

'67 3x2 manifold is taller. You want one for a 68 or 69.