stock exhaust manifolds and performance

[mopar_nocar]

i have a set of stock manifolds on my 400 in my ramcharger. i am very happy with the tone (read quieter) i have with my stock manifolds. i had been running headers on a 360 in that and this is the first 4 wheeler i have owned in a looooong time w/cast iron manifolds. well, would it be worth the noise and general pain in the a$$ it is with headers for the mighty ramcharger? it has a stock cam, eddy performer intake, 750cfm Vac. Sec. Holley, stock '78 400 truck cam, i milled the block .100 to get some compression (using stock pistons still down .010 in the hole).

how much of a gain are the headers really worth?

i have another project coming together, i am seriously considering using stock manifolds on my .030 over 360 with a 204/214 .442 lift cam. which, btw is going into a 1959 F100. gonna' make that old ford truck into a dodge!

sb

[benno318]

im sure i am going to be strongly opposed on my thoughts on this, but in my opinion, from my experience, i dont believe headers make any noticable difference on a stock to mild engine. experts will claim x hp and x lb/ft etc etc. but at the end of the day i doubt you or i could feel any difference if we swapped your manifolds on that stock cammed 400. i bet the cam stops making good grunt at 3800-4000, perhaps earlier? headers would no doubt help once revs rise, but were it my truck, it would stay with manifolds.
on the subject, in australia here, a bodys pre 67 have no off the shelf headers availiable. i have seen plenty of 360's etc jammed in tight with stock manifolds run real strong on the strip, and one that sticks out was a 63 fitted with tunnel rammed 360. this thing could lay rubber for 3-4 minutes at a time, pulling 7500 rpm in top gear with 2.75 gears, and let me tell you it ranks as one of the best burnouts i have seen to this day.

[benno318]

actually i think i remember a good exhaust test a few years or so ago in mopar muscle? from memory, a steve dulcich article, 318, 360, 340hp manifolds, then a few different brands of headers all compared on the dyno. it had a fairly well modified engine as the mule, but even so it also proved how the manifolds stacked up against the headers-not that bad.

[George G. Leverette]

Headers will not improve performance signifiantly on a street driven car. Mopar Muscle ran an article where tests were conducted under controlled conditions and the improvements in horse power ranged from 3-17 maximum header improvement over stock manifolds. I have a set of 340 manifolds with thermal barrier inside and ceramic coating on the out side, I have wondered if this improved the HP output. I have a set of Magnum exhasut manifolds on a 68 383 which will be coated and have a thermal barrier added. Headers showed an immediate HP gain years ago because they leaned out an over rich condition in cars burning leaded fuel. Todays cars must meet emission standards which have a different blend of gasoline and lower octane ratings. Its difficult to convince the old timers that old technology no longer applies.

[mopar_nocar]

well,

i'm convinced. i am staying with my manifolds on the 4x4 and my 59 F100 will get manifold treatment as well.

unlike some on this board, i like my rides quiet in the cab. don't want to hear headers.

sb

[DavidA]

When I replaced the stock manifolds on the 400 I had in my Challenger for Hooker Shorty Headers I noticed a definite improvement in power. However not sure it was worth the hassle I had with them interfering with the steering cross linkage. Keeping the stock manifolsd in case I ever want to go back to them.

[Tuff360]

What if you have the heads ported and polished, bigger cam? Is it better to stay with the stock manifolds and run duals? I want to run some stacks in my truck and I was thinking about headers, cats, x-pipe, and then to the stacks, or should I just leave the cats off run stock manifolds, x-pipe and stacks?

[benno318]

of course the more that is done to the breathing capabilities of the engine, the more responsive it will be to the addition of headers. having said that, it was surprising to read that the article i described in mopar muscle was of a decent engine, from memory approx 350hp? and i think the absolute most power gained from the poorest 318 manifold to the best header was something like 25 to 30hp. i should try to find that issue so i can be more exacting in my quotes.....check back tommorow or the next day, ill see if i can find it.

[jelsr]

If you are running a closed system (mufflers) the difference is not that great. Not familiar with SB's but the 440 HP or 383 RR manifolds (whatever you call them) with the 2-1/2" outlets work very well on BB's. Headers are designed to run open and use sound waves, mufflers wreak havok on the sound waves.

[Rods67Cuda]

as far as sound level, i just put a set of 1 3/4" TTI headers on my 67 barracuda with a 400 and it actually is quieter inside the car
i think it might be a little louder from an onlooker, but the resonation inside the car is MUCH less

[benno318]

found the magazine article, and it was actually a 360 300hp mopar crate engine. put out 311hp with small 318 manifolds, a couple more with 360 manifolds, 1 more with 340hp manifolds, up to 327hp with tti stepped headers. torque was similar increase, 10-15 lb/ft from worst to best and in my opinion not worth the bang for the buck at that power level.

[mopar_nocar]

on my 4x4 i am running the stock 1978 center dump 440 exhaust manifolds. the car is sooooo much quieter in the cab than it was with the 360 and hedman headers. AND i haven't had to get under the hood nor under it to tighten any bolts to stop exhaust leaks. that's a bonus i'm not used to. and i can check or change plugs and/or wires w/o cooking my fingers!

benno318's example is a much 'hotter' engine than my 400. i think the difference would be even less than that with my engine. as for my 360, i bet its in the same range as that 300hp crate motor if not a little milder. i'll be quite happy with 312-313hp out of mine. in fact, it might be a little scary in the old p/u!!!

sb

[gthomas]

I had a '88 Ford Bronco with a small block and single exhaust. The biggest and best modification (except for lockers on both ends) was by changing out the cat to one with 3 inch inlet and outlet as well as changing out the exhaust with a 3 inch muffler and 3 inch pipes. I couldn't beleive the difference in torque and overall performance as well as a noticeful improvement in gas mileage.