Intake choice

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roadripper

roadripper

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So I'm building this 318 , 1987 block , 340 heads and manifolds, I have two intakes to choose frome one is a holley street dominator (small ports 318),the other is the factory 1977 cast 4 barrel intake (large ports). So I'm thinking cast one would be better because of larger ports? But never used a holley intake before? not sure with smaller ports? Any ideas ??

Thanks mike
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Both will work fine. If your running a TQ carb, I don't see why you wouldn't use the factory cast. If your going to sell the "left over" intake, the Holley intake will sell for more.....
But.....
I say, "try them both". It's only 17 bucks for the intake gasket set. Let the seat of your pants decide which you like better, and not us on the net :D
 
Interesting choice.
Tell us more about your build.
(I'd try them both.)
 
The Holley may be more responsive due to smaller ports, which you may need if you don't get back some of the compression lost by the bigger chamber 340 heads. Personally I'd prefer the 1.88" valves as opposed to 2.02" on most 318's.

The OEM intake limits you to a spreadbore TQ. A square bore can be adapted, but adapters usually aren't good for airflow. Can the Holley use either without an adapter? The weight savings of the Holley is nice too.
 
I think the holley would be better at lower engine speed because of the velocity will be higher but will kill it (saturate) at higher rpm.
but than again trial and error is some times the best.
 
I once did what you are now doing.On a stock 73Dart. I was very disappointed with the soggy bottom end.I used the matching factory CI intake and TQ. That combo will want a higher stall and bigger gears. Ima thinking at least 2800 and 3.55s minimum.
I would bolt on the small-port first. Good luck
 
i have that cam in my 408 (bought it for my 360)
if you are NOT running a high stall converter with it, i would go with the holley, to try and make up some bottom end
if you are running a high stall converter, use the stock intake
 
Cast Iron intake with the 340/360 heads. Should be a nice combination with that cam. .020 off the 340 heads will gain any compression you may have lost. Holley messed the choke well up on that manifold. It is too far forward to use the OEM choke without mods.
 
The problem isn't just the static compression lost. It's the Dcr in the basement around 6.6, and the 125psi of cylinder pressure.
That makes for really sluggish air flow through those big passages, at low rpm. My teener didn't wake up 'til well past 3500. Granted the teener wasn't fresh anymore (this was in the late 70s,maybe 78ish) but it wasn't an oil-burner either.
I still have that same short-block teener, now with its freshened factory heads and teener cam. It ran gangbusters in my FormulaS as a winter motor, with 3.55s and a 2800TC in a 904. Or a clutch. And/or an A999. Still with it's original short block.It is now running about 7.2Dcr and pressure is a tic over 140psi. And it runs through a smallport C.I. intake and the same TQ. I even ran it with 3.91s and 4.30s; what a treat that was.
 
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I'd go to the local chassis dyno school and test them both.
 
I used to "upgrade" 318's to 340 specs pretty often. That would include honing with torque plates, good rings bearings, windage tray, high pressure oil pump, double true roller timing set, 340 cam, lifters, 340 valve springs, milling heads .020 (max cut for the money) and .019 on the intake side of the head, tight guides, Viton valve seals, any 360 heads, cast iron 340 intake, carb, find TDC, degree the cam, quick curve distributor with 25 degrees of centrifugal advance, set timing at 10 degrees before TDC. They would run like a 72/73 340. 340's did not really take off till 3,000 rpm and pull past 6,000 rpm from the factory, that is what high performance means to me.
 
Really?? The factory cast intake hurts low end torque????? Give me a break..... I've never seen low end suffer from the factory cast.... and you can hog the center on it to more match a square bore. You only need the flat (1/8 inch) 12 dollar adapter to bolt a eddy carb on it.

Not say'n Holley or cast. I said try them both means you have them.
 
Use the cast iron intake and a Thermo Quad. Find someone who can set up the TQ and be done with it.

I can tell you from dozens of tests never make the intake ports smaller than the head. It's a power killer all over. It won't make more torque like the fools say.

Use the correct sized intake runner for the port in your head.
 
I'm bettering my money on the TQ intake and I'll double the best sum if a TQ is used.
(properly set up and tuned)

But I as well said to try them both. The worst case is wasted time and maybe gaskets if they don't come apart nicely.
Just some gasket maker at the ends is all it'll be.
 
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