I think when they bolted the manifolds on and the motor lost 90hp........ that’s when it became pretty apparent the overall combo may not have been fully “optimized” for exhaust manifold use.

I think the slow hydraulic roller ramps and pretty big seat timing hurt that motor's manifold potential. It had like 83° overlap at the seat. I target 55° or less depending on the motor. Bracket guys successfully live and die buy a cam's 0.050" numbers. Manifold motors seem to care about actual seat timing.


And certainly you cannot argue with the header advantage in that example. I just don't think you're going to get 680 HP out of any manifold motor with any cam and a bunch of Summit Racing parts slapped together like you could do with a header motor.

Hanlon's Razor. The subject video was for fun, not to be an exhaustive peer-reviewed study on the subject.

Was hoping this thread would have disappeared after the new server came up.

A hundred years ago my street car was a 63 Plymouth with a low mileage 67 R/T 440.

It had a Max Wedge exhaust system. I loved it even though I had to replace the gaskets in the factory exhaust cutouts from time to time.

Two problems with the Max Wedge exhaust however.

Weight, I bet it cost a tenth on the track over tube headers.

Under hood heat, there was a lot of it.

Would I build the same car again?

Absolutely!

So, if you had replaced the cam(and nothing else) with another hyd roller that would have brought the power numbers between the headers and manifolds closer together........ would it make more power with manifolds....... or just make less with the headers?

From my perspective, if they were in the 580hp range on pump gas, with a hyd roller cam, 6bbl induction, thru ex manifolds......... they really weren’t doing too bad at all.
Imagine your old 505 with a 6bbl and hyd roller cam, compared to the configuration it was in during your dyno test.
580 would have been a pretty good number.....no?

i pulled out an old september 1970 popular hot rodding mag where they did a chassis dyno/drag strip test on a '70 4spd 6pak dodge. car made 244hp@4250rpm at the tires stock. car ran 13.95@100.78 with 4.10 gears. they dyno tuned the car and got 272hp@4250rpm and ran 13.74@105.63mph. then they took the car to a header shop and put on some 2 inchers. car made 318hp@4750rpm an ran 12.92@108.42mph. 74hp gain in total; pretty cute. i think the car could've 110+ if it hadn't been over geared.

i really don't have much of a dog in the manifold/header fight; i use both. but, this has been going on for decades. i remember hanging out at the chassis dyno shop in '68 and '69 and it was the same argument. seems like nothing is solved but if your a manifold lover then power isn't as straight forward as the common culture dictates. otherwise, you'll have to use your head rather than your gonads. this is also got me thinking back to the late '90's and chassis dynoing my r/t. it made 325hp between 3900rpm and 4300rpm and then fell off a cliff. what would a few hundred more usable rpm (like the '70 dodge) have netted me with a better exhaust? or, would the automatic transmission ate up all the gain?

Could be both. Although not exactly the same, but increasing the lash in mine (i.e. making the cam look smaller to the motor) made a bunch more power everywhere.

And yes, if it's 580 hp on the dyno I use.

That was with ex manifolds, correct?

The increased lash making more power if there were headers installed on the motor may or may not have played out the same.

Yes.

Correct, That is why I said that with a smaller cam in your example, the manifold motor's power might go up, and in the header application it might go down. But maybe not.

Some of the horsepower gain can come down to how well the HP exhaust manifold port is matched to the cylinder head port (and gasket). Guess how much hp you gain by just doing that on a stock '69 440 6BBL to a stock HP cast iron manifold and nothing else? Nick's a good......make that a great guy

First mod I did to my new '69 383 Road Runner back in the summer of '69 was put a set of Hooker Headers on it and they never came off even after "cooking" I don't know how many starters. Never dyno'd it but seat of the pants there was never any doubt there was a performance and HP gain and more than a few tenths better at the drag strip.

Thanks for posting Nick's video! Enjoyed it and all of the other videos he does, stand up guy IMO ..............................Nick should have done a special Moparts only version and LOST horsepower with the headers,

Mike

just to stir the pot.... who can supply an engine to go on this dyno that will not have much if any gain from headers ? i think i could......

And... I think my 413 MH engine wouldn't care a whole lot. With 233HP @ 4000 it only needs 390CFM, and max torque is ~2000.
Maybe a little better flow-tune with 4-2-1 and small tubes?

One oddity I recently found was that the VIN plate doesn't match other published figures; VIN says 233@4000
Mopar chart says:
Dodge 1971/72 V8- 413-1 4 BBL 4.188 X 3.75 7.5 to 1 265 @ 4000 445 fp @ 2400 Sodium Ex. Valves
Dodge 1971/72 V8- 413-3 4 BBL 4.188 X 3.75 7.5 to 1 238 @ 3600 407 fp @ 2000 Sodium Ex. Valves

It has the huge heads and MH manifolds, so it is a -3, but what is the definitive value for factory power?
Eric Bannerman on the FB Travco group I think has straightened me out, and I do have a 413-1 after all (I rechecked the frame # while matches the VIN and block stamping.)
"in my experience the number on the tag is only found in a couple places in factory literature as each engine has both a net and a gross HP and other publications often list the gross instead of the net that is listed on the tag. Even the stickers on the engines listing the HP are normally the gross number.
The factory 1971 salesman book lists the 413-1 HP as
Net 233 @ 4000
Gross 265 @4000
The same book lists the 413-3 as:
Net 215 @ 3600
Gross 238 @ 3600

the salesman book is just a source for both the factory net and gross HP ratings. Those are the books a Salesman used to look up options and such. The same information might be in the factory service manual. The 413-1 is listed as an option for the M375 and that's the only 1971 application it was used in as far as I know. The motor homes used or were available with the 413-1 through 1973 when the 440 replaced it.
All the truck 413 engines in 1971 used the truck style parts like the exhaust manifolds and such instead of the car version of those parts. So what you have is probably the original engine."

The important #s to me are 445 fp @ 2400 if I'm going to re-gear the drive train.

I'm still not certain what the -1-2-3 models are; if the -1 is in motorhomes and the -3 is in D500s and the like, is the -2 the car model?

Nick actually has a video that evaluates go fast goodies but in reverse. He started with a healthy street built 440 that had an RPM intake, headers and a holley carburetor. He dynoed it as such. Then he swapped headers for manifolds and tested it. Swapped RPM for iron OEM intake. Then a carter in place of the Holley. With stock parts the engine made noticeably less power but he said he would prefer the lower output with factory parts over higher output with aftermarket parts. I like him and his channel.

Hi Folks, the replies are getting more wacky by the day, but its still a good thread!

I only got interested because its the COMBO that I want to run!
1971 sixpack 'all-iron' engine with a sixpack, exhausting through them AWFUL HP manifolds...

So will someone out there PLEASE tell me the BEST COMBO???

Basically what I'm saying, who's got the best 'ALL-IRON' set-up, WITH HP manifolds and what's the CAMSHAFT choice...???

Obviously the 'supposed' SIXPACK naughty Nick was running, was a POO motor with low comp pistons, 516 heads (probably) and a lumpy 'OLD SCHOOL' cam...

Easy response - call the people that do it regularly, either Bob K (Mr. Six Pack racing) or Dwayne Porter. Buy their recommend camshaft and parts, take their advice, or have them build you an engine. They've done the development and make a few bucks for their effort. Bob K has helped us with a pure stock hemi and 440-6, and his advice has matched up with the results. If I remember correctly, you said earlier you wanted 450 HP, which won't be a problem with a six pack setup and stock manifolds. There have been similar builds on this forum with dyno results as well.

"best all iron set-up"? best would be race gas. pump gas being more practical for dual purpose. i think the most economical pump gas would have a good set of heads (i'd use KB184 pistons for open chamber), something like a summit 6401 cam, straight thru mufflers, and not over geared or over converter. race gas would open things up some power wise but would be a higher cost.

There are articles in the tech section that cover this. I did several articles 10 to 15 years ago on camshaft selection with HP manifolds as well as engine design for HP manifolds so this info has been out there for a long time.
http://www.moparts.org/Tech/Archive/bb/550hp.html

The thing I learned way back when was that the camshaft is the key. You need to be very careful picking a cam when running HP manifolds. If the cam is too small you lose top end power. If the cam is too big you lose power everywhere. The cam needs to be "just right" and then it works great with HP manifolds. Do not call the camshaft tech line to get a cam for manifolds. They have no idea. Do not ask for cam advice on the internet, you'll just get a bunch of nonsense replies. The only person I'd call for a manifold cam is Dwayne.

Dwayne is the go-to guy in this case. And most other cases for that matter. He has always came through for me.

Just like any other motor. Maximize cylinder pressure for the heads and gas you have available, good heads, good exhaust, the right type of cam.

Any number of part combinations can get you there. The difference between the 450 HP and 475 HP engine with the things I mentioned above is going to be in the tune and tweaking the details.

Assuming std stroke.
915, or 906, or 452 Head? It does not matter. Any of them can flow 270 cfm. Match it up with the right piston. I'm not a reverse dome piston fan. I use the 915, with a dish. So much cleaner. 915 availability and cost to make them right might be higher than the others.

Solid lifter, fast rate cam and decent rocker set up. Wide lsa, probably would not go over 240°@0.050 on the intake.

2 1/2" mandrel bent exhaust with a straight through muffler.

Full street trim should run 12.50s @ 112 mph in full weight B body. Add tires, gear, and converter, 12.00.