500hp 408 with Hi-Po 340 Manifolds?

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I don't know how many of you read the article I posted the link to, but I was surprised at the small differences in the horseower the test showed for the different cast manifolds.

318 manifolds................... 311 horsepower
360 manifolds.................. 314 horsepower
early (1968) 340 manifolds 315 horsepower

TTI headers........................327 horsepower

403 ft pounds 318 manifolds
407 ft pounds 360 manifolds
408 ft pounds 340 manifolds (1968)
435 ft pounds TTI Headers

Here's the link... http://tinyurl.com/pemfp5m

Looks like those '68 manifolds aren't worth much over 360s on a mild engine.The software is turning that eight in nineteen sixty-eight into a smiley face... that's not me.
 
dustoff440 said:
dyno test with 340 and magnum manifolds

http://www.moparts.org/Tech/Archive/exhaust/9.html

looks like 30 plus hp loss with manifolds over headers which is about 3/10 in the quarter which you should feel in the seat of the pants

I also agonized over the headers/manifolds decision and am running a 68-71 left 340 manifold and a r/t 360 magnum manifold with the 2 1/4 (92-93 only) outlet on the right side. I agree with moparmat2000 though, I will eat the loss as I want a street car with MINIMAL FRIGGING
Click to expand...

Looks like the big loser here is the driver's side 340 manifold as when the ran the engine with two of those piss poor manifolds, it made 20 horsepower less than the same engine with two passenger side manifolds...

The Magnum manifolds weren't quite as good as the early 340 manifolds (one right, one left) but they didn't use the early Magnum manifolds which have bigger outlets. What's up with that????

Headers make 'em all look bad...

You pays your money and youi takes your cherce... :cheers:
 
Bill Dedman said:
Looks like the big loser here is the driver's side 340 manifold as when the ran the engine with two of those piss poor manifolds, it made 20 horsepower less than the same engine with two passenger side manifolds...

The Magnum manifolds weren't quite as good as the early 340 manifolds (one right, one left) but they didn't use the early Magnum manifolds which have bigger outlets. What's up with that????

Headers make 'em all look bad...

You pays your money and youi takes your cherce... :cheers:
Click to expand...

I want to build a 70 DART race car after I finish this street car, Ill save the headers for it...lol

92-3 only r/t manifolds have a larger outlet than the later 1 7/8 manifolds
92-3 compared to 94 up had an additional 10 horsepower, and I believe the only difference is the exhaust manifolds
 
fast duster

[ame="http://www.youtube.com/watch?v=vaLlxFIAiJ8"]11.27 @ 120.5mph F.A.S.T. Duster - YouTube[/ame]
 
FAST cars should not be compared to anything the average (or even some above average) enthusiasts might put together. I've been involved in them an you will spend (and be willing to spend) twice the cash or more to make the power levels that are reached with mandatory stock appearing parts vs. performance aftermarket parts. Also you have to make well beyond the "normal" power range for the ET because so much is squandered through bad exhaust and not being able to jump on it out of the hole. It's not even close to Stock Eliminator.. It's a special field.
In my opinion - aside from the personal reasons for wanting one or the other - you won't make the power required with those heads or those manifolds with a hydraulic roller. You will need to use a custom solid roller, more static compression, and your power range will be at a higher rpm range than you would typically associate with a 4" engine. It can be done (and has - even been exceeded by a lot) but it takes a lot more money, knowledge, and effort to make it with manifolds than with headers.
 
Bill Dedman said:
I don't know how many of you read the article I posted the link to, but I was surprised at the small differences in the horseower the test showed for the different cast manifolds.

318 manifolds................... 311 horsepower
360 manifolds.................. 314 horsepower
early (1968) 340 manifolds 315 horsepower

TTI headers........................327 horsepower

403 ft pounds 318 manifolds
407 ft pounds 360 manifolds
408 ft pounds 340 manifolds (1968)
435 ft pounds TTI Headers


Here's the link... http://tinyurl.com/pemfp5m

Looks like those '68 manifolds aren't worth much over 360s on a mild engine.The software is turning that eight in nineteen sixty-eight into a smiley face... that's not me.
Click to expand...


For a relatively stock engine , the losses will be far less than one that has been leaned on. Allow me to reiterate.......engines are air pumps.
To make power , you need air in and out. More = more.
A FAST engine with headers and tuned for them would pick up a ton compared to slapping tubes on a 2 bbl. 318.
Now , should we get into efficiency ?
YMMV , but you will see an increase in fuel mileage with headers......if you can keep your big fat foot out of it. :D
Think of headers as Wheat Thins.........a lot of people hate them , but some think they are really good for you.
 
moper said:
FAST cars should not be compared to anything the average (or even some above average) enthusiasts might put together. I've been involved in them an you will spend (and be willing to spend) twice the cash or more to make the power levels that are reached with mandatory stock appearing parts vs. performance aftermarket parts. Also you have to make well beyond the "normal" power range for the ET because so much is squandered through bad exhaust and not being able to jump on it out of the hole. It's not even close to Stock Eliminator.. It's a special field.
In my opinion - aside from the personal reasons for wanting one or the other - you won't make the power required with those heads or those manifolds with a hydraulic roller. You will need to use a custom solid roller, more static compression, and your power range will be at a higher rpm range than you would typically associate with a 4" engine. It can be done (and has - even been exceeded by a lot) but it takes a lot more money, knowledge, and effort to make it with manifolds than with headers.
Click to expand...

Makes sense.

The original poster specs a quasi stock looking motor. A little more open than FAST rules. If I'm interpreting right?:

any intake
any carb
any cast iron head
hi po cast iron exhaust manifolds

I'm guessing street available pump 91? octane gas?

Mopar, would open aftermarket intake, carb, heads (indy x, W2?) make it a little less expensive and easier to get to 500 hp?
 
Im am more than willing to extrude hone the old dinosaurs. I currently have TTI's and column shift on my stock 74 cuda, it has been nothing but a pain. From starters to servicing not to mention linkage. The original motor is coming out in favor of an 89 based 408. I do have a set of comp solid roller lifters and the block has already been clearanced for them but something about solid roller and street just doesn't sit well with me. I think ill give IMM a call and see what he recommends. Houston has 93 octane pump gas so that's a plus.
 
Does anyone know the recipes of some of those F.A.S.T small blocks? Just curious of where they get the power from. Thanks for all the suggestions. The parts for this build will be ordered in the next week or two regardless of exhaust choice. It will be dyno'd!
 
It would be much easier to make the power - but you then have to pump it through those manifolds... That's the problem. Then head work is critical regardless of the head design used, and the camshaft will be just as critical because the exhaust will only be working against you. If you think about it as having to make 550hp with headers in order to make 500 with manifolds, you'd be thinking in the right direction.
The FAST guys will not be easy to get info from. For a camshaft once the head package is known (and I don't think RHS are the way to go - you need more head) give Dwayne Porter at Porter Racing Heads in VT a call. He does some amazing head work and camshaft development for the FAST guys.
Jake - your problem is the column shift - but you knew that.
 
Hey that's a nice video of my car. New motor combo should make some more steam this year, has proven to be alittle harder to hook up on the polys though.

The combo that ran 11.27 was pretty mild really. It was a 4 in bore, 4 in stroke (mopar forged crank) 402cu in. 11.8 comp. .550lift solid roller, hand ported 71 intake, hand ported 71 exhaust manifolds, T/A j heads w/stock size valves, Harland sharp rockers...
I dropped 30lbs off the nose of the car this winter and picked up some hp. Hoping to make it alittle harder for Jeff to catch up. lol
 
500hp with the factory parts and manifolds is not going to be anything you are going to be driving on the street... My old motor made less than 500hp on the dyno, and the new one isn't much above it.
 
Scampin can you elaborate on not being able to drive on street ? with stock parts ...
 
This is what headers are all about. Air in, air out. I run a 408 with eddy heads, rpm air gap, etc.. and it originally dyno'd at 498 hp and 528 ft/lb torque. It's a little more now, but if I took the TTi's off and ran straight manifolds I hate to think what would happen. It would choke off a ton of horsepower. If you already have the TTi's, why are you considering anything else? I love my headers. Two years now and clean as a whistle. Good sound, good power.
 
Scampin said:
500hp with the factory parts and manifolds is not going to be anything you are going to be driving on the street... My old motor made less than 500hp on the dyno, and the new one isn't much above it.
Click to expand...

Forced induction make it possible to have a streetable combination because the cam specs for turbos and blowers don't like or need much duration or overlap. This results in a lot of low-end torque and a smooth idle.

The big problem is, building an engine that is happy on 93 octane when running boost. My own 360 Magnum made 445 rwhp (about 525 at the flywheel) with 10 pounds of boost from a Vortech centrifugal, belt-driven supercharger, and is happy with pump gas if I use a MSD Boostmaster ignition timing retard.

Idles at 475 rpm, smoothly, with 12 inches of vacuum...
 
Oldmanmopar said:
Did I read this correctly that all tests were done with 2 inch down pipes. except for the headers
Click to expand...

From the article: "or our baseline test, we fitted the 360 with the lowest of exhaust low,a set of stock small-passage 318 iron exhaust manifolds. Bolted to the manifolds was a set of 21/4-inch head pipe extensions 24 inches long. So equipped, the 360 put out a respect- able 311 hp at 4,600 rpm and 403lb-ft of torque."

Looks like they used 2 1/4" pipes...
 
To build a high horsepower FAST motor, you need to focus on making torque and maintaining it as high of an rpm as possible. Which sucks for a tire limited car.
Doesn't matter who does the heads, they all flow about the same, same goes for the intake and carb and exhaust manifolds. The only way to make more power is to focus on the bottom end and make as much toque as possible, then using the cam to keep it up as high as possible. If I were to put a set of slicks, headers, intake, and a cam to work with headers my duster would run in the 9's.

Jeff P built a guy a FAST legal pump gas stroker smallblock, somewhere around 430+cu in, solid cam, etc. Made around 475hp, and Jeff knows his chit. The only thing we can do to make more power is to up compression, and more aggressive cam. The heads flow what they flow, there is no magic.
 
so let me throw into the mix, how about modern 5.9L mag manifolds. are they any better then LA 360 manifolds?
 
jake17201 said:
Think its possible? I already have TTI's but just love the stock look with the early style manifolds. I plan on using hydraulic roller cam, rpm air gap and RHS heads. Just wondering if it would still be streetable in a daily driver automatic cuda. Open to suggestions!
Click to expand...

I would just use the TTI's I your case, the engine would not look stock anyway with the air gap, and RHS. I'm considering the F.A.S.T. Look for my demon but I have the t- quad, ported stock heavy intake, etc.. Still kills me to use the exh manifolds but I'm not going to compete in fast just want to screw with the Chevy and ford guys with a stock looking demon hopefully running 11.90's with some big polyglass tires out back.
 
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