Opinions on carb and manifold setup

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SalC

SalC

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Hello all (first post),

I have a '75 Duster with a 426 wedge that I just bought. Has 12.5:1 pistons, .557 mech lift cam, 2800 stall, & 4.10 gear. It has a what appears to be a somewhat conservative carb & manifold setup, a Holley Street Avenger with vacuum secondaries (looks like a 650 or 750 - no double pumper) & Offenhauser low rise type manifold.

I'm thinking more in the lines of a Edelbrock Torker II & Holley 4150 850cfm Street HP DP (part# 0-82851)? Comments? The only thing I see in Holley's comments for this carb that questions me is it says "Intended for lightweight vehicles w/ manual trans or automatics with high stall & low gearing". Low gearing? I have a 4.10...

Thanks,
Sal C
 
If it runs good, why change it?

Street Avengers are well liked from the posts of people that have them.

Why not figure out just exactly what you have. What list # is your carb? Exactly what Offy intake are you running? Single plane? Dual plane?


Congrats on your first post, welcome to FABO.

I'm about 1/2 hour from you.
 
Thanks for the reply...

Well the issue is it runs ok but for the powerplant in it I would expect a little more. The manifold appears to be dual plane, I haven't removed the carb yet. Nothing on the carb I can see as far as part number, maybe when I remove it.

Talked to the local speed shop this afternoon (Joliet), they ran the calcs and said between a 750 & 850 on the carb.
 
I would try tuning it first. Do you know how much initial and total timing it has? A vacuum secondary is a good choice for a car with an automatic. Sounds to me like somebody may have known what they were doing building it. Look on the front of the choke tower and get the List number and tell us what it is. If it's a 750, that's probably right on the mark. I wouldn't change the carburetor until I was damn sure everything else was tuned and adjusted right.
 
I have a 440 that I run a 750 Demon double pumper with a performer rpm intake. The car has run 12.12@110 an 850 was too big. Had a Torker II ,but changed it to the performer rpm. Seemed to pick up some on the launch, but I haven't made it back to the track to test it. I would go 750dp and performer rpm.
 
krazykuda said:
Also, give Rustyratrod the info he ask you and he can help you get it tuned in. He's real good at setting them up.
Click to expand...

Thanks for the kind words, Karl, but there are a lot more qualified folks here than I am, I believe.
 
Looks like it's a 80870, 870cfm Avenger vacuum secondaries...
 

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Big enough carb,it's doable. What do you expect ,when it's sorted out? More driveability?/more E.T? That 2800 stall seems soft,for a Mopar solid .557. We need more information,what would set it satisfactory for you?
 
That's plenty of carb Sal, the 12.5 pistons may not actually have 12.5cr usually they are a lot lower with stock heads and the thicker gaskets it's posible it's under 10 to 1 there are a lot of variables on what exactly was done to the engine and how it was machined. Do you know what heads are on it? Older 426 may have vert restrictive heads? I'm in Aurora Il right of I -88 and 59 if you need some tuning help. Just PM me
 
SalC said:
Looks like it's a 80870, 870cfm Avenger vacuum secondaries...
Click to expand...


Yup, that should be enough... :cheers:

The first thing to do is make sure that the accelerator pump linkage is adjusted properly .015" clearance at WOT (wide open throttle). :burnout:

Then get the vacuum secondary spring kit Holley P/N 20-13 and put the white spring in your secondary vacuum pod. This will get the secondaries opening sooner. You'll feel a difference. :thumleft:

Remember when tuning a carb, one change at a time. Then if it gets worse, you know how to go back to where you were.... :-({|=
 
But now after you do the accelerator pump adjustment and secondary spring, you should make sure that your timing is tuned in first.

If your timing is not set at its optimum, you are wasting your time trying to tune the carb.

Timing first, then carb...
 
Thanks for replies guys. Thanks for the PM's too. RRR, you asked some good questions and made some good comments. I called the prev owner and asked if he degree'd the cam, he said yes.

What am I expecting? I guess I'm expecting much better jump from a dead start, the wheels barely squeal, I would expect better (I'm allowing the stall too). This is a light car and with the 426 (and described components from the previous owner) it should smoke. I have had the car opened up on a rural road, I'm able to get the rpm up to over 6000 which I would expect with the described rear end. Something just isn't right, it should be much better. I'm thinking the carburetor.

Based on the specs and what I know of the owner it sounds like he knew what he was doing. Improvements were made over time for the better.

Here's what the previous owner gave me (of course I know I have to verify everything - which I intend to do).
Engine 1964 426 Wedge - verified by casting number and date stamp
Bored .060 oversized
Stage IV heads ported by Motorsport Performance, Addison IL - Verified casting #3614476
Cam mechanical lift .557 - Isky?
Pistons Forged TRW - 12.5 to 1
Windage Tray
High volume oil pump
8 qt Moroso oil pan
Carburation Holley Avenger - Confirmed #80870 870cfm
Trans HD 727 with reverse manual shift & shift kit - Cheetah valve body from Mopar, BM shift kit
2800 stall converter HD flex plate
fluid damper - front balancer
Springs SS with extra main leaf added
Pinion snubber
Radiator -BeCool
Water pump Alum - Summit
Heavy duty front torsion bars - ordered from Mopar made for BB conversion
4:10 sure grip read end - 8 1/4 mopar sure grip
Estimated HP over 500
Estimated ft lbs of torque over 500


As I said without the documentation / receipts I have to verify the components.

????
 
A "yes" to degreeing still tells you nothing. Where did he put it? Did he get specific? Did he degree it per the cam card? Unless he can answer that, that bad boy would be comin back down so I could verify it myself. You gotta start with a KNOWN combination. That sounds vague to me anyway so I would tear it down anyway. You simply cannot be too sure.
 
Well I wouldn't tear it apart, check cranking psi for starts that would tell us a lot, sounds like good heads. Going to have to check timing, and carb, fuel delivery, what fuel you using? My brother might have a eddy performer intake cheap.
 
All valid questions. Yes he said he degree'd it but I will have to check it. I have to verify the cam make and size, hope there is a part number stamped on the front somewhere. Also have to verify the pistons. Could be junk gas, the tank was full but I burned about 1/2 and filled it with Speedway racing fuel.

I'll most likely have to tear it down some to get at the cam, and the pistons. Have to be sure.
 
Well after a busy summer and still wanting to drive the car I decided not to rip it apart (yet). I did try the paper clip test to see if the secondaries were opening. First I ripped around the local streets opening it up and checked, didn't move. So next I took it on the expressway and opened it wide open and got off the next exit, the clip moved about a 1/4 inch so the secondaries were barely opening.

Since I already bit the bullet and bought a new Torker II and Holley 850 Street HP I figured just toss it on. I'm not an expert on tuning but dialed it as best I could for now. I must say BIG difference. Much better off the line response, tires squealed through all of 1st gear. Will post some video links this week once I shoot some. Still have some verifying to do but for now I'm satisfied...
 

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