Im starting to put together A 440 Dual 450 mechanical secondary Holleys double pumpers on a Weiand Hi Rise Tunnel Ram, and an Intake .507 Lift & .284 duration cam with Automatic 3 speed 727 with a 2800 stall, In a C Body 1968 Plymouth Fury weighing in at about 2 tons. Anyone know how this is going to act or any issues in going to run into? I'm also putting on 1 3/4 headers to 3 in collector to 3 in out the back through a set of super 10s. Only thing is I may not be able to change yet is the 2.76 rear end on the peg legged rear. Any and all responses with be greatly appreciated thank you!

I wouldn't run the 450's. Dual 650's minimum. Wait for other opinions though.

Compression?
I ran a tunnel ram,ran great.
Agree on more carb.
Might consider a little more cam depending on other components.

personally I would go less cam. that fury is heavy. small tube headers and a smaller cam would be your best bet. I think 450s would be fine, if your just cruising it.

Weiand makes a great tunnel ram, but I wouldn't use carbs with mechanical secondaries on that heavy car and those gears. I'd suggest 600 carbs with vacuum secondaries, if not you're looking for a bogging engine when you get on the go pedal.

Why is it the guys with the motors that could use a tunnel ram use a large singal four barrel and the guys that sould be useing a 750 want to use a tunnel ram?

You need a cam with 280@.050 + duration, 5000 stall converter, 4.88 gears and a lite car.

The 450 CFM carbs are a good choice BUT mechanical secondaries are not. Go with 2 450's with vacuum secondaries.

I've run vacuum secondary 600's and I think the 450's would be a much better choice.

Small blocks that rev high and fast like bigger carbs and mechanical secondaries - lumbering big blocks do not!

People suggesting BIG carbs consider this ... opening the primaries on twin 650's is like opening the throttle on a dominator - the off-idle response will be terrible.

I bought the engine trans combo as is with some specs on the cam and knowing it has 2800 stall, supposedly I was told its all blue printed but I don't know. He said it should be 9:1 compression it's a 1971 440. Also doing some research I was seeing that the 450's work better If they are double pumpers, I don't know never messed with tunnel ram set up. Also low on the funds so changing parts is not very easy option haha. I may be able to get a 4.10 for the rear if that will help the throttle responsiveness at all.

Also thanks for the responses everyone!

I think it's 9:1, that's what the cam requires too so giving its supposedly blue printed I hope it all matches right haha.

What makes the mechanical secondaries such an infamous choice? I keep see this same response to other people's tunnel ram questions. Makes me wish I was able to choose the carbs haha.

I don't mean to be a poop about the tunnel ram, in truth aways thought it would be fun, and back in the 70s I had a freand with one on a 440 that worked pretty good.

And back in the 70s to get 650 hp from a 440 you would have needed a tunnel ram but not today, a 950 or 1050 Holley and a M1 or Eldelbrock will get you there.

So the old tunnel ram is definitely OLD SCHOOL COOL and will Make power if you have the parts under it but be slug and no fun at all if you can't make it work!
Otherwise you can put dog collar around each stack you have on the carbs.

With the mechanical secondaries, once you floor it all the throttle blades open right up, you lose air velocity and vacuum signal to the carbs and they don't meter fuel properly, worse at low rpm. A higher stall converter and a lighter car with steeper rear gear help offset this problem.

The 440 weiand hi rise tunnel ram is a great intake, works much better on a 440 than on most other engine platforms. It will run great once it's all dialed in and on a 440 those intakes make for a nice driving car, however as stated, you should consider selling those mechanical secondary carbs.

Would a 4.10 rear help counteract some of that or just try to change the carbs?

"mechanical" secondaries mean they're controlled with the pedal. Vacuum secondaries are controlled by manifold vacuum so they kick in when the engine tells them too.

Either route needs some fine tuning but generally the vacuum secondaries will give you better cruising.

At a minimum, it is the last you could do, your going to need more gear.

I have dual 500 AFB's, B-Body runs like the wind.

The mech sec 450 Holley #9776 is not a double pumper The lean tip in has to be covered by the single pri acc pump. These may be hard to tune on a tunnel ram that often needs a big acc shot.

For a heavy C body, I'd run a pair of (in order of preference)
500 Edelbrock AVS with dual quad calibration #1804
390 vac sec Holley #8007
600 vac sec Holley #1850

I'm also in the 500AVS or 600 VS camp.

I never really liked the 450 single pumpers.

Myself...... I'd probably try and hunt down a couple of clean used slightly older 1850 Holleys, since I don't really care for the new version with the non-adjustable floats.
I just can't imagine spending $300+ each for a pair of those.

I'd probably step up to the QFT 1857 instead, but then you're at over $750 for the pair.
About the same $$$ as a pair of new AVS's.


Obviously if you already have the 450's..... I'd try it and see how they work.

Really their not double pumpers? It's nearly the first thing on the box they're sitting in, in gray bold "double pumpers" but I could be wrong, I'm not sure cause it is the #9776. Can you send pictures on here?

add pics thru the "file manager" below the text box