carb selection???

[eastwoodad]

i am having conflicting opinions on carb selection, maybe you guys could help.

here's what i have:
81' Regal
231 N/A .030 over
9.5 to 1 compression
Forged Pistons
Port match and bowl cleanup on 8445 heads
Turbo crank
KB mark 2R cam .494in .506 ex./ 226in 232ex @ .050
KB #1 Single plane intake
Hedman Headers
TH350
3.73 gears

I am trying to find a carb that is suitable for this. Holley's site recommends a 390 but i think that will be too small. Kenne Bell recommends a 390 or 600 vacuum secondary. Demon usually recommends not using vac. secondaries on any cam over 220 duration. i'm not crazy about using vac. secondaries. Holley offers a 450 mechanical secondary carb but i think this might still be too small. I do want to drive on the street a bit but i still want it to perform at the track. Anybody have any experience on this?

 

[eastwoodad]

well after doing a little more research, i've found out that the 450cfm mechanical secondary is out of the question. apparently it isnt equipped w/ accelerator pumps on the secondary side making it useful only for dual quad tunnel ram setups.

any experience on the others??

 

[eastwoodad]

well a friend of mine is going to loan me a 600 single feed vac. secondary holley. I'll see how it works.

does anybody know what cfm the 4.1 Q-jet is?

 

[MoeJr]

QJets only come 750 or 800 cfm. Nice thing with a QJet is it will only supply what the engine wants. Better performance and gas mileage when set up properly

 

[unboostedV6]

Not knowing how much torque converter you have, I'd try the 600 vacuum secondary first. Very easy to install,tune,cheap,and easy to get rid of if you find something else better. While the 750 Q-jet that came on the 4.1 is a great fuel metering carb, in won't work well with a single plane intake(other than factory) and the cam you're running without some complicated rework. I used one from a '76 Buick 350 on my 224-224 cammed 4.1. Worked awesome until I swapped out the oem intake for the Weiand 7541. Had to drill the acc pump holes to overcome initial stumble, the ran out of pump duration. Car would move 8 ft then die. Next carb was a Holley 750 vac, q-jet replacement, set up with dual feed,secondary jets -worked well after basic Holley tuning. Then I went racing....whole 'nuther story...Hope this helps! GB

 

[unboostedV6]

By the way, the fix for the Q-jet acc pump problem is to bore and hone the pump well and replace the stock plunger with the larger one from an old Rochester 2GC. I didn't have the ambition to go forward with that one...GB

 

[fuzzyGN]

I have a similar set-up except lower compression and it is a 4.1. Anyway, the 600 Vac Sac Holley is a great performer on that combo. The single plane intake is a bit overkill if spinning it under 6500 RPM. I think I may have lost a little performance going from the Edelbrock dual plane to the Kenne Bell single but I can't really tell if it was the intake or something else I changed at the same time. Your combo should be very solid.

 

[eastwoodad]

Thanks for the advice Greg, Erik, and MoeJr!!

I haven't picked out a converter yet, but I am looking for about a 3000 stall. Maybe a little more, maybe a little less....what do you think?? It will be street driven on weekends so I dont want to go too high, but I know I will need a decent stall to get the v6 rollin'. Thanks.

Aaron

 

[fuzzyGN]

Currently I have a 4 speed and in a 2600 pound (with driver) car. I was going to go for about a 2800 stall myself once I go to the TH-350. With my new combo (11.5 to 1, 224 solid roller, alum heads) though the stall may be a bit trickey to get right. As the cars weight goes up, more stall is needed to get it rolling. At the same time the more compression and cubic inches you have, the less stall is needed. I think your target of around 3K should be about right considering the weight of the car and the engine you have.

 

[eastwoodad]

FuzzyGN,

Do you have any pics or other info on your build?? et's??

I have always loved N/A Buick V6 builds, especially the old Ron Cosner car and all the KB cars. Now I finally have the opportunity to build one.

Aaron

 

[fuzzyGN]

My current combo is actually pretty simple. I started with a .030 over 4.1 and had the block decked about .020 to square it up. I pocket ported the heads, which on the later 4.1's were the same casting as the turbo heads. I got a used cam off ebay that appears to be an old Postons cam, the agressive one. I had a Performer intake but later switched to the Kenne Bell. A holley 600 vac sac with a secondary metering block (so one can change the jets in the rear) tops it off. The headers I have are old Hooker Super Comps which are 1.5" primaries and 2.5" collectors. It is then exhausted through the short Race Magnum mufflers dumping under the car.

The car is a 1977 Vega wagon. That is why the weight is so low. I have it set-up with a 4 speed, two-step, and 4.30 gears. The rear tires are Hoosiers 26 9.5 14's. The Vega wheel wells are so small that is all I can fit without major work. It runs well for a low compression engine (~8.4). I think I have about 600 bucks total into the engine because EVERYTHING is used. An inexpensive gasket kit with new rings and that was it. The car runs 14.60's @ 94 through the mufflers with a best of a 1.97 60'. I think the engine is starting to get tired because the MPH isn't as consistant as it used to be.

Some issues with decking the block is the pushrod required length changes. I actually have to run adjustable pushrods which kills the RPM potential of the engine. Also I think the open intake is a little big for a lower compression engine. I changed from a 5 speed to a 4 speed at the same time so I can't be for sure. It is great fun dusting off Mustangs (my favorite) and then be able to tell them thy lost to a little 6 banger. My custom tag is V6POWER!

 

[eastwoodad]

Sounds like a sweet setup!! I was hoping to be in your ET range with my setup but it looks like I may have my work cut out for me. One advantage I will have is the higher compression, and the air here in VA is great in the fall/spring and the altitude is very low as well. We'll see what happens!

Aaron