Purpose of 3x2 setup

[Kevin Whiteley]

What is the purpose (i.e., engineering rationale, etc.) behind the 3x2 carburetor setup? Don't get me wrong, I love the look of it, but if the L88 could be fed by the 850CFM 4bbl, why couldn't the lower horsepower engineS use a similar carb?

[Joe L.]

Re: Purpose of 3x2 setup

Kevin----

The purpose was exactly what impresses you about it----the looks of it and the "cache" it. In my opinion, it was strictly a marketing thing. Your other observation is also correct; on the real racing engine GM used a single large Holley 4 barrel. They knew that for racing, where performance and reliability are of paramount importance, the single 4 barrel arrangement was the "only way to go". After all, you might fool "street racers" of the day with a "3 deuce" set-up, but you weren't going to fool (or satisfy the requirement of) REAL racers with such a contraption.

The single Holley 4 barrel provides all of the fuel that a 427 requires even at high RPM. So, what functional reason could there possibly be for going with "3 deuces"?

[Craig Skaaden]

Re: Purpose of 3x2 setup

Kevin-

I think Joe is correct.
Only reason for the 3x2 had to be marketing and looks.
I raced with the 3x2 back in 68-69 with disappointing results.
Once I changed to a progressive 3-barrel my whole world changed.
Racing times improved which much less hassle.

Craig

[Dick W.]

Re: Purpose of 3x2 setup

Back in the dark ages when the C-2's were new, a good 66 427/425 could have a 67 427/435 for lunch anytime, anywhere. I think that the only multiple carb setups that were performance boosting were the 2X4's. And what a wonderful sound they made at about 6,000 rpms in high gear. Granted that the new FI cars run smoother, cleaner, etc, but something audible is missing. Or maybe my hearing is a goin'

[John H.]

Re: Purpose of 3x2 setup

"Marketing, Son, Marketing.....that's where the real money is..." Same guys who invented sidepipes that were more restrictive than under-car exhaust, but looked great and sounded neat

[Mike Cobine]

Re: Purpose of 3x2 setup

Without a doubt, marketing since the Mopar 6 pack was out and several cars had three dueces or dual quads. Heck, we all know those old four Hilborn injections are only good for the quarter, but haven't you seen them on street rods and in car shows?

This is probably 99% marketing, but I can say that a friend's '69 with the 435 hp was almost like running fuel injection. The center two bbl didn't give that bog like when mashing open a huge four bbl, and the two outer carbs came in smooth as silk, so smooth you never knew they were in.

Totally unscientific, but running on a section of road in front of the refinery, the car could start from the railroad tracks and be going 115 mph when it passed the main gate a quarter mile away.

Now I have seen more tripowers set up wrong than ever set up right, and they surged, bogged, and did everything wrong. But when right, they just kept bringing on the power.

[Stephen W.]

Re: Purpose of 3x2 setup *NM*

[Craig S.]

Re: Purpose of 3x2 setup

You hit the nail on the head.......marketing.......love the look of it. 4 barrel simplicty rules. Having said that, I have a 67 tripower for my play 74 LS6 crate engine just for the look of it....Craig

[Dan M.]

Re: Purpose of 3x2 setup

I have to agree with Mike Cobine's comments on functionality. My (complete stock) 69 435 4sp has no bog and with the 3.70 gears once the cam comes in it's nothing but power and a blast to drive. FYI it took me about a month to get the tri power setup just right but have not had to touch it since. By the way it looks nice too.

Dan

[Donald W.]

Re: Purpose of 3x2 setup

I have to agree with Dan,my 67 427/435 tripower is a rush to drive. After spending some time tuning it in, it's not in need of anything but a size 11 shoe on the accelerator pedal. 1200 cfm ,i think is better than the 1-4 barrel 850 (that's my opinion),my 55 chevy i used to have had an 850 cfm carb and the response was not as strong (my opinion). Took it out last evening (first time since before Hurricanes Francis and Jean came a calling)for a 2-hour cruise and truly had a BLAST from the past, you should have been there, just one awesome ride!!!!.

Keep driving em,
Don

[Warren F.]

Re: Purpose of 3x2 setup

I had read that the cfm rating on Tri-powers were 950 total. I thought that the six pack mopars were rated at 1050 cfm, as a comparison.

[Mark #28455]

center carb 350CFM ends 500 CFM each *NM*

[Clem Z.]

350 CFM center and 466 CFM end carbs

for the corvette for a total of 1166 CFM BUT to get a 2 barrel rating equal to a 4 barrel rating you need to multiply by .71 so the real total was 827.86 even smaller than a L-88 4 barrel

[Clem Z.]

racing the 3 X 2 setup

one year SCCA said that the BBC corvette had to run certain size restrictor plate to make it even with the SBC corvette. i forget the size but with ed lowther driving we set up a 3 X 2 carbs with the correct size restrictor plate under each of the 3 carbs which gave us more CFM than the BBC corvettes that ran a 4 barrel with the same size restrictor plate. ed won every race that year but they stopped us next year by a rule change

[Clem Z.]

PS

4 barrel carbs air flow rating is done at 1.5"Hg pressure drop across the carb and 2 barrel carbs are rated at 3"Hg pressure drop so to equalize the carbs you need to do the .71 deal.