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Old 03-27-2007, 12:31 PM   #1
1ARACE
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Default Pros & Cons of a Tri-power vs 4 barrel?

Curious of other's opinions. I have talked to quite a few people who said they used to run a tri-power, but took it off and ran a 4 barrel. Many have said they were hard to tune-in and had a lot of problems with them, so they used a 4 barrel because it's easier.
I've never used one nor seen one in action, so I don't know much about them just going off other people's experiences.

What is so problematic and difficult with them?
Is there any advantage/disadvantage compared to a 4 barrel?
Do both perform and behave the same?

Atm I have a wieand stealth intake and was thinking of using a holley 3310 750 under stock hood. I am using original motor/components and I would rather use a tri-power for originality/nostalgic aspect, but I am still learning the ropes and bit of a novice still so i'm nervous/leary about them. If they are as difficult as others have said, i'm not sure I would be able to troubleshoot it and enjoy the vette if i'm always farting with it.
Bottom line, I hate to part with $3-4k for something I may not be happy with, so I'd appreciate any feedback/comments/education on them.

Thanks much
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Old 03-27-2007, 01:06 PM   #2
gkull
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Modern tuned runner 4 barrel intake manifolds can actually cause cylinder overfilling over a certain rpm range. That is how they claim additional TQ & HP.

60's & 70's tri powers are not a tuned runner length. They produced more power by additional CFM of 6 barrels and some driveability by running on a single 2 barrel most of the time.

As for tuning. It's is just a learning courve. My 61 Vette came with two 4 barrels. Much more functional than 3X2.

If I had money to burn on an intake setup, without a doubt 4 webers in downdraft or even side draft have the highest sex appeal.
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Old 03-27-2007, 01:14 PM   #3
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During my interviews and reseach for tech articles at GM back in the late 70's, I had several discussions with GM design engineers regarding Tripower (aka "Triple Power Pak") versus 4-barrel. Here are the key comments that came from this:

Originally, the muiltiple carb setups (2x4 and 3x2) were used due to the limited cfm capacity of then-available single 4-barrels (since the Rochester 4GC and the Carter AFB were the only things the auto makers had going in the 50s and early 60s). Thus, the Tripower became associated with performance.

With the advent of large-cfm 4-barrels (Holley & Q-Jet), there was no technical justification for multi-carb setups.

Marketing liked Tripowers and could sell a performance image. Tripowers in the late 60s were marketing tools - not engineering performance tools.

A Tripower (3 2-barrel carbs) cannot feed 8 cylinders as uniformly as a single 4-barrel. Given equal cfm flow through a Tripower and a 4-barrel, the 4-barrel actually has the advantage due to more even fuel distribution.

Tripowers utilizing individual air cleaners have severe cfm flow restrictions due to air filter size. Single large air cleaners for the entire setup flow much better than individual air cleaners for each of the carbs.

Tuning is cumbersome due to the inaccessibility of the center and end carb float bowls on the Holley carbs. This makes quick track tuning almost impossible. But Tripowers still look cool and sound great...
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Old 03-27-2007, 01:27 PM   #4
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Interstingly enough the 390 HP with a Q-jet was the exact same engine that was used for the 400 HP tri power (L-68). Granted they played a lot of games with true horsepower ratings back then (often understated). The L-68 did run well but since the three two barrels opened progessively you got a better kick in the seat from a good four barrel if you hit it from a level 2000 RPM (and had the vacume built up). Even after everything mentioned above, if I could find a reasonably priced tri power set up to fit my 69 I would jump all over if cause they look really
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Old 03-27-2007, 01:32 PM   #5
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Quote:
Originally Posted by lars View Post
But Tripowers still look cool and sound great...
had a sixpack on my 69 dodge,man was that sweet
and contrary to popular belief once you get the hang of them
the setup and tuning is relatively easy.
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Old 03-27-2007, 01:39 PM   #6
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Other side of the coin. The vacumn secondery holley setup is tough to tune and make run well but if properly setup are comparable to a 4 bbl. The 67 through 69 Corvettes had a 390 HP engine and a 400 HP engine. The only difference in these 2 engines was the intake setup. The tripower produced 10 more HP at a little more rpm. The modern tripower setups "Barry Grant" are very efficient and well designed. Equal fuel distribution and on a par with similar CFM 4 BBl setups. I just built a large base rochester tripower for my car. It uses modified early 70's 2 bbl carbs for a 350 or 400 chevy with a center electric choke and side inlets. I have the Offenhause 360 degree split single plane. It has uniform, short runner lengths, about an 1 1/2 long, into a large plenum and provides equal fuel distribution. These weren't available in the late 60's early 70's. It runs on a two bbl and has a mechanical linkage that kicks in the end carbs. No power valves or idle circuits in the end carbs, they are just dumpers "secondaries". The only adjustment on the end carbs is jetting and when the linkage kicks them in. I also installed a plate nitrous system. It has 3 spray bars dumping into 6 ports. Should be better and more uniform nitrous/fuel distribution than a single spray bar set up on a 4 BBl plate, not as good as port injection or fogger. For long trips the end carb linkage can be easily adjusted to run on just the 2 bbl up to cruising speed. Got right at 20 mpg with my small base setup. 3.55 gears and a 4 speed. They look pretty cool and sound awesome when you kick in the end carbs. They are very streetable. Some of the modern 4 BBl setups will produce more power and better times, but these can be setup to be very competative. Click the image to open in full size. Click the image to open in full size.

Last edited by 63mako; 03-27-2007 at 01:44 PM.
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Old 03-27-2007, 01:42 PM   #7
Little Mouse
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In 74 I put a trypower off a 69 435 on my modded 73 454, paid
$85.00 for the complete setup and spent $15.00 for three carb
rebuild kits. With the 350 cfm center carb and 500 cfm vacumm
end carbs its as simple as any vacumm secondary holley four barrell.
I ran it for a couple yrs sold it for $125.00. I would buy another one
in a heart beat if they did not cost $2500.00 on up today.
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Old 03-27-2007, 02:06 PM   #8
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I was running the newer Barry Grant six shooter (tri power) on my small block and it was awesome, looked great, sounded great and performed great aswell (made more power than an RPM air gap and a single 4 barrel in side by side test's).
It was a breeze to tune, one screw thanks to the progressive linkage.

The only reason I am selling is that I went with a quad 48 dellorto set up with the latest motor build.

Nick
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Old 03-27-2007, 03:12 PM   #9
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The Tri-power looks great and sounds awsome. But in 1967 -69 the engineers who built the L88, and were shooting for maximum power (who isn't ) chose a 4 bbl, even though they had access to the 3x2.

Just something to keep in mind.
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Old 03-27-2007, 03:32 PM   #10
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I have run a factory 3X2 intake setup on a L88 without any problems. Total CFM wise, I believe they are more than most of the larger 4 bore carbs. The intake runners are almost directly over the ports unlike the longer runs on most single 4 bore intakes. Very little maintenance too.
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Old 03-27-2007, 03:41 PM   #11
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I can't give you any advice on 3X2 sutups, but I have run 3 different 2X4 setups and after the initial tuning, absolutely no problems at all.
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Old 03-27-2007, 04:13 PM   #12
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Quote:
Originally Posted by lvrpool32 View Post
I was running the newer Barry Grant six shooter (tri power) on my small block and it was awesome, looked great, sounded great and performed great aswell (made more power than an RPM air gap and a single 4 barrel in side by side test's).
It was a breeze to tune, one screw thanks to the progressive linkage.

The only reason I am selling is that I went with a quad 48 dellorto set up with the latest motor build.

Nick
thats not how i read the article. in recent yrs. ive never seen a muti set up out perform a single in any test. but they look cooler
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Old 03-27-2007, 04:15 PM   #13
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I have a 6-barrel set up on my 71 Roadrunner. Once you learn how to tune them they are great. If you don't want to take the time and learn or don't want to really fuss with your carbs, then stay away. The modern 4-barrel have as much if not more power than the old 6-barrel. By the way, the holleys gm and mopar use aren't much different.
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Old 03-27-2007, 04:36 PM   #14
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Quote:
Originally Posted by redc3 View Post
thats not how i read the article. in recent yrs. ive never seen a muti set up out perform a single in any test. but they look cooler


"Testing 1, 2, 3
While BG found big gains in peak power numbers, we decided to review the average power numbers between 2,500 and 6,000 rpm. Our first series of tests was performed without the Rush air filter. We altered the fuel curve to read a near-perfect 12.2:1 air-fuel ratio, while total spark timing came in at 38 degrees. It was combined with a slow advance curve to muzzle detonation in the lower rpm ranges. After reaching ideal engine-operating temps, our stroked small-block delivered a peak of 439 lb-ft of torque at 4,200 rpm and 399 hp at 5,800 rpm. The average numbers posted an even more amazing 410 lb-ft of torque and 330 hp across the board. We wanted to see the effect, if any, of the Rush air filter on the Triple D.

The custom-made Rush air filter assembly fits tightly over the three carburetors to yield hood clearance without restricting power, regardless of crankshaft speed. All other factors remained constant. Surprisingly, the air filter barely disturbed the airflow entering the carburetors and no air/fuel tuning was required. The power numbers did drop slightly, but comparing them to the previous ones reveals that such a minimal decrease would not be measurable by on-track testing. The peak numbers came in at 437 lb-ft of torque at 4,200 rpm and 397 hp at 5,400 rpm. Average numbers with the Rush filter combination were 407 lb-ft of torque and 330 hp--3 lb-ft less, on average, while posting identical average horse-power readings.

We couldn't resist putting the Triple D up against one of the industry's leading four-barrel manifolds. We swapped on a dual-plane plenum intake manifold and used a 750-cfm Speed Demon, but all the other variables were unchanged. After a few pulls, the industry leader posted less torque but more top-end horsepower. At 4,300 rpm we recorded 431 lb-ft of torque and 415 hp at 5,700 rpm. Average numbers came in at 405 lb-ft and 328 hp. While these numbers look weird, take a look at the dyno curves. This particular intake was weak on torque across the board; at approximately 4,600 rpm and below, its horsepower numbers were down as well. Above 4,600 rpm, its peak horsepower numbers climbed above the Six-Shooter's, but only slightly, causing the overall horsepower curve to fall shy of the Six-Shooter's by 2 hp on average. "
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Old 03-27-2007, 04:56 PM   #15
7T1vette
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My only experience with a tri-power setup was on a '65 Pontiac 421 with the tri-power. It was set up to run on the center carb, with hard linkage to bring the end carbs in at about half-throttle. The power came in instantaneously and without stumble or jerk, and had smooth acceleration throughout the power band. The real benefit, from my viewpoint, it that when driving normally (foot off the floor), I could get better gas mileage with that big block Pontiac than most 327 4-bbl. Chevys could get! Most folks only talk about the power of big 4-bbl. carbs....how about fuel efficiency when driving around town or on the highway? [And the tri-power setups really DO look much cooler.]
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Old 03-27-2007, 05:12 PM   #16
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Quote:
Originally Posted by 1ARACE View Post
Curious of other's opinions. I have talked to quite a few people who said they used to run a tri-power, but took it off and ran a 4 barrel. Many have said they were hard to tune-in and had a lot of problems with them, so they used a 4 barrel because it's easier.
I've never used one nor seen one in action, so I don't know much about them just going off other people's experiences.

What is so problematic and difficult with them?
Is there any advantage/disadvantage compared to a 4 barrel?
Do both perform and behave the same?

Atm I have a wieand stealth intake and was thinking of using a holley 3310 750 under stock hood. I am using original motor/components and I would rather use a tri-power for originality/nostalgic aspect, but I am still learning the ropes and bit of a novice still so i'm nervous/leary about them. If they are as difficult as others have said, i'm not sure I would be able to troubleshoot it and enjoy the vette if i'm always farting with it.
Bottom line, I hate to part with $3-4k for something I may not be happy with, so I'd appreciate any feedback/comments/education on them.

Thanks much
Late to the party here, but nonetheless, I think what has been underestimated is the advantage of the tri-power in pure cfm flow. You are talking about an intake setup that flows 1350CFM but with none of the penalties of a similar 4bbl setup of that size. It runs on the center 2 barrel until party time and then with vacuum secondaries does not overcarburete the engine. It also fits under the stock BB hood, which most intakes don't. While the L88 intake made more power, it was also 1 1/2" higher than a tri-power. As a medium to low rise setup the tri-power is a kicker.

A recent article I found in corvette enthusiast from another member showed a dyno tested 11 to 14hp top end horsepower gain (at 6300 rpm) on a very healthy (650hp) BB over an RPM air gap and single plain holley strip dominator (with a 950HP holley). They attributed most of this to the raw cfm flow of the tri-power setup allowing better breathing.

I don't think the L68 really is a strong enough motor to really show the attributes of a good tri-power setup. Granted there are single plane 4bbl setups that will ultimately out perform it, but with a much taller manifold and carb CFM than most street setups.
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Old 03-27-2007, 07:21 PM   #17
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Originally Posted by redc3 View Post
thats not how i read the article. in recent yrs. {ive never seen a muti set up out perform a single in any test}. but they look cooler
Oh you probably have and forgot. Heres one multi setup directly on the subject but of another manufacturer and does out perform a single 4 bore.

Click the image to open in full size.
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Old 03-27-2007, 09:10 PM   #18
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I have a '69 L71 427/435 and have had no problems with the carbs at all, but the engine and carbs were professionally rebuilt not long before I bought the car. The only thing I would have preferred the previous owner not have done was install an L88 cam in place of the original spec cam...it makes for one powerful, but very cranky engine...low vacuum and lousy gas mileage...about 6mpg and 125 iles to a tank. Then again, the 4.11 rear doesn't help on that either.

The L88 cam has a power band of 4400-7000 rpm's...faster than I drive the car. That big block has so much natural low end torque you don't miss the low rpm power loss due to the cam profile. When you pass 4000 rpm's, you really feel the power building up then suddenly you get a real kick in the seat when that engine really starts breathing.
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Old 03-27-2007, 09:20 PM   #19
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Roughrider-- If the "kick in the pants" doesn't outweigh the driveability, put in a cam you want. That's not a real big job, and I bet it would pay for itself [at the gas station] pretty quickly....at $3 a gallon.
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Old 03-28-2007, 10:05 AM   #20
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I really can’t think of any cons, besides the price they’re getting for the Tri-Powers these days (absurd). There is no performance disadvantage on the street (and very little at the track to certain power levels anyway) and when you pop the hood it’s just nicer with Tri-Power. I am a big fan of factory multiple carburetor set ups, in fact, of the 7 cars remaining in my collection, only 1 (74 454 Corvette) has a single carburetor (in all fairness that is a recent change as it used to sport an aftermarket tunnel ram 2X4 setup…). I am especially proud of the 2-4 factory Cross-Ram set up on my 69 Z28, but I wouldn’t have my 69 435/427 Corvette any other way than with the Tripower. I have acquired a lot of tricks through the years relating to rebuilding, tuning, maintaining, driving and racing with multiple carbs, but one thing that stands out above all that I will mention is along the lines of what 63 Mako did- I did the same with my 65 GTO’s Tri-Power, except instead of a plate system I drilled and tapped the factory cast iron Tri-Power intake to accept 8 NOS fogger nozzles. I did this a long time ago before the prices went skyrocketing on the intakes, and would not consider doing it to the Corvette setup despite the fact that the Corvette aluminum intake would be a heck of a lot easier than the Pontiac cast iron was. But the fact that the NOS 300HP hit on top of the N/A 465 RWHP brings a smile to my face every time coupled with the fact that that particular car and I will never part ways leads me to the statement that I will never regret that modification…Oh yeah- one thing I almost forgot to mention- with Tri-Powers- BE VERY, VERY CAREFUL TO WATCH OUT FOR FUEL LEAKS!!!!
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Old 03-28-2007, 10:05 AM
 
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