Factory manifolds.....just how good were they?

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Captainkirk

Captainkirk

Old School Mopar Warrior
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I have two factory cast-iron 340 manifolds...one off a '69 340 with a very slight spreadbore to fit the stock Carter AVS, and the other off a '72 340 made to fit the factory Carter ThermoQuad.
A little research tells me 'back in the day' these were considered very, very good manifolds. Other than the weight consideration (49#!!!!) does anyone know how these flow compared to other aftermarket or modern manifolds (e.g. Air Gap, etc) for a street motor application (1500-6000 RPM)?
Just curious......
 
I don't know the numbers right off but the spreadbore could hang with the best of them in most any and all comparisons.
 
Both were great for there intended purpose. I loved the AVS intake back in the day. I even had one milled to accept a 440/750 carb many moons ago. The TQ intake made more power in stock form, but how much of that was attributed to the TQ carb is questionable.

With all that said, the dual plane Weiand/Rpm intakes are better overall and lighter then any of the stock iron pieces. As far as flow numbers, I have none, but the "real" performance from many, many user's kind of speaks for itself?
 
Not very. Mike at MRL did a manifold comparison and found that there was no difference between stock and HP manifolds. I think that was on a big block though. Probably the same for a small block. That thread is floatin around here somewhere.
 
RustyRatRod said:
Not very. Mike at MRL did a manifold comparison and found that there was no difference between stock and HP manifolds. I think that was on a big block though. Probably the same for a small block. That thread is floatin around here somewhere.
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..................RRR he is asking about intake manifolds.................kim..........
 
Captainkirk said:
I have two factory cast-iron 340 manifolds...one off a '69 340 with a very slight spreadbore to fit the stock Carter AVS, and the other off a '72 340 made to fit the factory Carter ThermoQuad.
A little research tells me 'back in the day' these were considered very, very good manifolds. Other than the weight consideration (49#!!!!) does anyone know how these flow compared to other aftermarket or modern manifolds (e.g. Air Gap, etc) for a street motor application (1500-6000 RPM)?
Just curious......
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I remember, back in the day, guys would change carbs and intakes on their 340's and would not see any difference. The weight difference is over rated, 25 lbs on a 3,000 lb vehicle? What's that a .83 % gain? Unless you aren't strong enough to lift it on. It will take a real good manifold to see a performance difference, like an Air Gap, LD 340, probably a Stealth. I would expect a performer to not make as much power as any 340 intake. Both of what you have are great manifolds. What do have to loose, you already have them, an intake gasket and a couple of hours at most. I'd get a factory AVS or early TQ, put a kit in it and give it a try. Or as stated above keep your eyes open and see what becomes available.
 
66fs said:
I remember, back in the day, guys would change carbs and intakes on their 340's and would not see any difference. The weight difference is over rated, 25 lbs on a 3,000 lb vehicle? What's that a .83 % gain? Unless you aren't strong enough to lift it on. It will take a real good manifold to see a performance difference, like an Air Gap, LD 340, probably a Stealth. I would expect a performer to not make as much power as any 340 intake. Both of what you have are great manifolds. What do have to loose, you already have them, an intake gasket and a couple of hours at most. I'd get a factory AVS or early TQ, put a kit in it and give it a try. Or as stated above keep your eyes open and see what becomes available.
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It's all in relation to the overall combo.

Slap a base model, out of the box Performer on an otherwise stock engine and you might gain 10-20 hp, take that same intake and do a cam swap to match the power band, you might gain 75.

The performer intake was designed to be a slight upgrade to a stock, key word slight. No when you start getting into Airgaps, Holley street doms and others, that's where you'll start seeing more difference, especially if the combo all matches each other.


I will agree that mopar factory intakes weren't too shabby in their days, neither was that big TQ, by pass all the emissions stuff and you had you an 880 cfm carb with massive secondaries
 
RS23VOA said:
How's an LD340 rate with these others?
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I think the LD 340 are still pretty good, If you have one not worth changing. I doubt a Performer would gain any power over a 340 or 360 cast iron manifold with 340 or 360 heads. I think the Performer would be perfect for 273 or 318 heads.
 
I have one on a 70 340 with a voodoo cam and probably be running an avs.
 
IMO the 71 TQ manifold was the best factory piece. Next is the 72 then 73 and up. The 72 had EGR bumps in the floor of the primary side and the 73 and up had EGR. The 73 used EGR jets in the manifold floor instead of an exterior valve. I think even the 73 and up pieces are still pretty dang good. There have been a LOT of stock eliminator races won and records set with them. That should say something. Where is Paul on this? He should have some in depth information. Drag strip times and he might even have some flow numbers. Paul, you out there?
 
66fs said:
Should be good to go. What choke? The LD 340 does not have an OEM choke well.
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Someone down the road drilled some holes in the dash for toggle switches so I think I'm going to use a manual choke.
 
The 71-2 TQ intake will crush the early AVS manifold. The TQ has a large open plenum and the runners are actually about a 1/4 larger. One of the things that really hurts the AVS intake is the sharp edge on the deep side.
 
I have one of these TQ intakes. Maybe I'll do a comparison!
 
I'd love to see a test with a AVS intake and large (440) carb vs a 71'/73' manifold with a TQ? I'll bet there wouldn't be 5/8 horsepower difference between them.....even then, I bet any benefit was at peak power.

The modded intake for the big carb I spoke of earlier sadly never made it on a engine, but the stock AVS intake on a bud's car with a 750 Holley & adapter ran some serious numbers with a 3.23 gear, G60 belted tires, a stock converter, factory exhaust and nothing but a .*** cam. I'm old, but 13.80's @ 103 was serious to me with nothing but a mild cammed 70' 340 street Duster :).
CORRECTION on the cam ^^^^^. It was a DC Street Hemi grind.....

I'd love to see a full torque curve between the two in my first paragraph?


I know regular members here a sick of seeing my old pics, but this was it...
 

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And I agree with that ^^^^^^, but mileage would be the bigger advantage handed to the TQ and spread bore intake.
 
OldmanRick said:
I know regular members here a sick of seeing my old pics, but this was it...
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I'm not sick of them! What a trip down memory lane! I have those exact valve covers with t-handle hold-downs out in the garage right now! I remember the foamy-pie-plate filters, too! Didn't filter much air, but they looked cool! I had the velocity stack version....
 
Vizard took a stock GM QJ intake and smoothed the inlets a little and shaped the corners and the thing "ran better than ANY performance intake he put it up against" His words, not mine. Its in one of his HP series of books. Stock intakes are designed with 0-4500 RPM in mind, so of course a Strip Dominator will shine above 5000 RPM...and they do!
 
hi, the 340 intakes are very good manifolds. period. in stock , you have to use them. those cars are fast, damn fast!!!! they do NOT go out the back door at 4500 RPM!!! most are at 7000 RPM and up!!! 71 340 dusters can run 10.70's 72 340 dusters can run 10.90's on kill!!!!! MPH is in the 120 range. I don't think the intake affects them??? just things to consider.
 
I personally watched a factory cast intake/TQ go 10.90's in a 3200 lbs. steel Demon
 
ir3333 said:
I'd like to see some actual tests,then we would have the evidence
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Why would they test anything that would not sell their product. Would you buy a Performer, Torker or whatever for your 340 or 360 that would lose you 15-20 HP or make the same HP? Sorry, I'm a bit cynical... Figures don't lie, but liars can figure. Look at what people were running in "Stock Class" years ago, when everything had to be stock and unported. Why do you think 340's and 360's were factored so heavily?
 
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