[STripleduce]

HELP!!! I have been searching for info on CFM ratings for tri power setups.I have been told several ratingsfrom 920 - 1400 CFM for tripower setups.I was told my set has a 390 CFM center C# on floatbowl 7019927 & 2 430 CFM outers C# 7029683.This should be considered 1250 CFM right? I've done some polishing to all carbs in the air horn area which should increase CFM. Also I need to know if CFM rating differs at differnt RPM?

[This message has been edited by STripleduce (edited 07-27-2000).]

[Ken K]

I don't know where you got the CFM numbers for a Tri Power but I think they are a little high. I have heard that 66 Tri Powers flow about 888 CFM and a 65 Tri Power flows about 100 CFM less than a 66. I have heard that the small air cleaners will only flow about 600 cfm. I have heard that a big car dual snorkel air cleaner flows about 1000 cfm. So which Tri Power has more performance, a 65 Tri Power with a big car air cleaner or a 66 Tri power with the small air cleaners?

[BVR421]

stripled, you may or may not have the right numbers but what you need to keep in mind is that 2 barrel carb's flow is tested at a different bench pressure. I forget the exact numbers but as an example (approx) if a 2 barrel is rated at 300 cfm it flows the same as a 4 barrel rated at 250 cfm. The best stock trips do flow slightly more than a stock quadrajet but only very slightly. Personally I dont care what they flow, a tripower and a 4-speed is the essence of muscle car.

[Ken K]

I have made the offer before and I will make it again. If anybody in AZ or SoCal wants to perform a Tri Power Test I will supply the Tri Powers. I have two 1965 Pontiac Tri Powers, a 66 Tri Power, A big car air cleaner, original foam type individual air cleaners, paper type individual air cleaners. I will also buy a set of K&N air cleaners.

[STripleduce]

Ken & BVR.
Thank you for the info.There are other issues here to be answered. C#s are these the original carbs ?They do not appear to be as there are metering screws on all three.As far as I know only the center is supposed to.Also one other question that I forgot to ask before.Would cross drilling between the plenums help in top end?

[Blackcat]

A couple of years ago HPP did a Tri-power vs
4bbl comparison. It was on a 68 GTO with a 428. The 4bbl was stock 750 quad. Their estimate of the Tri-power was 800cfm.

[Ken K]

Tri Power end carbs do not have idle adjustment screws, the end carbs you have are not correct. The end carbs also don't have a power valve or chokes. There are also different size center carbs, the 66 Tri Power uses a big bore center carb and a 65 and before uses the smaller carb. Do you know what year Tri Power you have? If it is a 64 or before it won't work with the 65 and up heads. Half of the Tri Powers you see for sale on Ebay and elsewhere don't have the correct end carbs on them. The fastest way to tell if a Tri Power has the correct end carbs is to look for idle adjustment screws, if it has them the carbs are incorrect, another way is to look at the fuel inlet. The fuel inlet on the end carbs should be facing toward the passenger side of the car.

[PONTIAC DUDE]

The trouble is the manifold flow. Like any manifold, if it doesn't flow the cfm of the carbs doesn't matter. CFM of carbs is a misconception anyway. A formula devised a long time ago in a galaxy far,far away. Air flow requirements of the engine determine it's capibility. To give you an exapmle I raced a Late Model on a 1/2 mile asphalt track and switched from a 500 2bbl. to 390 4bbl. (You could use either) and picked up track times. flow related/not cfm. There's another TECH article for Jim Hand answer to. Later.

http://Pontiacdude.cc

N.O.S. is like American Express: "You don't leave home without it"

[This message has been edited by PONTIAC DUDE (edited 07-21-2000).]

[KEV]

Hey Strip! The most of the flow #s I have heard support the 800 cfm mark. Ken is right, no idel screws.

I have also read the article Blackcat referenced. In that article the tripower did outperform the Qjet in the test. (shifts were made @ 5500 rpm i believe)

PONTIAC DUDE,

Why do you say that the trouble is the intake manifold flow?? Do you by chance have a flow coefficient of a '66 tripower intake?(intake to head) I am interested in hearing your comments on this. I have heard many state that the flow of the tripower intake is poor my findings have shown otherwise. Wondering what you have experienced.

Kev

------------------
Kevin Swaney
Gold '66 GTO, 389 4 spd with Trips
13.042 @ 106.64 mph

[STripleduce]

Thank you Kev..I had allways heard that the tripower would out flow any manifold except dual quad or tunnelram.Also due to the LARGE plenum areas and relativly short runners of almost equal length they would tenb to perfom more like a Tram.Though my Question still remains ie.CFM#s for carbs I'm sorry if I did'nt specify that.I'm also wondering about modifying the manifold by cross drilling the plenums to increase top end perf.

BVR421

Thank you again.I realize that I may not have the correct CFM#s.That is why I included the C#s for the carbs.I have tried to contact GM & Pont,but they can't seem to find any thing.Pont.refered me to this site for help.All is apreciated.Thanx again.

[KEV]

Hey Strip! Well you should be able to get your answer if you are going to continue to use the end carbs with idel screws. Someone should know what a stock GM 2bbls cfm is.

Funny you seem to be doing some of the same thinking I have done recently. I did some port work on my manifold and gasket matched it as well. Need to see if there was any gain. I have not had any track time yet.

I have wondered about the modification you discuss as well. I was more thinking of cutting down the divider between the venturis . So that the passenger and driver sides of the plenum can "see" each other. I did not want to make this mod as it would be a little difficult to reverse. I have thought about adding 1/2 to 1 inch spacers with the center sections cut out to test this a bit.

If you make the mod (cutting down the dividers) let me know how you make out. I would be interested in the results.

Kev

ps. What are you running the trips on now and what kind of ET/Mph are you running?

------------------
Kevin Swaney
Gold '66 GTO, 389 4 spd with Trips
13.042 @ 106.64 mph

[Ken K]

The problem is there are different CFM ratings for different 2 bbl Rochester Carbs. I have heard there is a Cadilac 2 bbl carb that is rated at 500 cfm. I know someone who use to work in a carburator shop and I was told that regular 2 bbl carbs can be converted to end carbs, I know this can be done with the small bore Chevy carb they use on the Edelbrock Tri Power for small blocks because someone is already selling them this way. If I knew how to post pictures on here I would show you how to make a duplicate center carb from parts from other carbs, I would also show the differences between the end carbs and the center carb. They make a Chevy carb that has a shorter fuel bowl on it that when used with a 65 or before Tri Power will have all the tops of the carbs level so a long oval type air cleaner could used.

[STripleduce]

'70-400-YD block stock B&S Fgd flt top.
Fully ported angle milled #16 hds 68cc 2.18-1.77 vlvs 11.5-1 CR.
1.5/8"into3.5"headers W/stepped crossover(own design).
284D .513L 112 deg Lobe center strait up.
560+ Hp

Used to be S.P. 900 cfm holley.
3200 lb 79 F.Bird.
400 T 3800 stall 3.54 posi.
Ran 11.2 consistant 1/4

Going into 2750 lb 47 Chev.W/ 78 camaro sub frame & 2.56 spooled 10 bolt.
If calculations are correct W/ tripower should get into mid 10s

sorry it's not a47 pont. but the price was right.

[Ken K]

Smoke screen and Mirrors, what did you do cut down big block Chevy intakes and chop up the exhaust valves? Why didn't you use 670 heads? I guess the Chevy won't know the difference.

[KEV]

Hey Strip! I agree, your valve numbers look a bit off. Also, what is the duration at .050 on that cam? Have you ever run the tripower on this current setup or no? What are the heads flowing? You stated they were fully ported and I was curious as to what kind of #s they flowed.

Thanks for the info,

Kev



------------------
Kevin Swaney
Gold '66 GTO, 389 4 spd with Trips
13.042 @ 106.64 mph

[PONTIAC DUDE]

I was getting ready to reply as this is the first really free time I've had, but noticed a post futher up on the board on Tri-Power, that more or less says what I've seen. It's neat running trips, just need to make a tunnel ram type aluminum manifold for them at a little lower height and really blow some minds,,,,, and Et's. later.
http://PontiacDude.cc

[STripleduce]

The exh. are stock for '68 # 16 D port hds.The int. came from '75 # 5Cs which had been modified before I got them.I would assume that they are chev because of the shorter stems.Had to machine spring , guige & seat area to accept them.The reason I went with these heads was because of runner vol.,chamber size(72cc)& most importantly the amount of material to work with in the pocket. The pocket was re worked to a 17 deg twist to give the charge more swirl upon entry into the cylinder.The angle milling was done for 2 reasons 1.to decraese CCs from72 > 64 (after relieving the vlvs & mirror polishing.Matched to 68cc).2 To give the port a straiter shot at the cylinder(8deg versus 14deg).

KEV

They are fully ported.Never flow tested but CC matched at 265 int. 190 exh. The cam D at .050 is 228 Hyd running solids.Inregaurd to your running spacers I think that would increase plenum vol giving alittle bog at bottom.But it would probably give a good reasult at top.The reason I said cross drill was because it would easier to plug if I don't like results.If you do try the spacers let me know what happens.

[STripleduce]

SORRY forgot to say I haven't run the T.P.on it yet.I am in the process of pollishing the manifold. I did finaly find out that carbs are stock the outers were modified in the '70s. The guy who didit claimed he changed the throttle plates because the old ones were lost.He also claims that the set was originaly from '66 421 390 Hp said he wasn't sure but he thought that it was rated at 1100 CFM by the factory? Tonight I'm going to the library & I'm going to see what I can find on that eng.So far I'm guesing that I'll find the same as I've found in my manuals here.No 2GCs with matching #s From '64-'71.I am assuming that they must've been ordered special.

[Blackcat]

66 421 Tripower came in two forms 356hp and 376hp I've had a few over the years. I will still stand by my 800cfm for the Tri-power. (stock unmodified)

[STripleduce]

I'llbuy the stock unmodified 800CFM.but like I've been saying they are not normal.I cannot find a match to the #s any where.I just spent 3hrs in the library going through tech mans.and found about 2000 different 2GCs but no match to my #s. I suppose I'll have to take a guess or have them flow tested.Thanx