castillo70

I am building a 440 hp. the builder engine came without the exhaust manifolds. every time I find the manifold they are a small fortune. can someone fill me in why they are so expensive? are they worth the money/performance or should I stick with throwing headers at it?

moe7404

my experience with headers is . they are louder , hard to get the starter out. put more heat in the engine compartment. the stock HP manifolds are expeseive cause only so many was made, i was able to get a 4,200 LB, 1965 300 L 413 with non-HP ext, mild cam, 3.23 gear, it used just 1 st and 2 nd gear, small carb, to go 16.13 ET. totaly stock. i would never go to headers, for a street driver.

castillo70

thanks moe. I wonder if anybody has put these to a dyno vs headers, it would be nice to know how well they perform or not perform.

Zoomer59

yep your gonna shell out some $$$ to buy a pair in good condition.
you maybe able to piece meal a set togather if your not in a hurry. I.E sometimes there is some one who has just manifold and will let it go cheaper.

1970-300 Convertible

castillo70 what kind of price were they asking for the manifolds? Oh I I think stock is best, over headers.

Moparbob

Headers DEFINATELY unlock power as the rpm increases, conversely, as you rpm the Engine higher manifolds kill horsepower.
That is not to say good "useable" power can not be attained using the HP Manifolds on mildly worked performance engines, just saying, as the engine is built to higher output levels with BIGGER Camshaft etc., , the manifolds become a greater restriction.

I'll go digging for some DYNO sheet comparisons, but the last hp manifold Engine we did here was a "stock" type 440-6pack resto Engine, only changes were a 274H Flat Tappet Hydraulic Cam, ARP Rod Bolts and some mild Bowl blending on the stock 906 Iron Head Castings.....
was somewhere around 440hp@ 5300rpm, but more importantly was about 525 ft/lbs Torque I believe ??? but maintained above 450 lbs pretty much EVERYWHERE !
The thing is a monster with 3.55's in a '69 GTX, and NO SLOUCH at any light !

Kern Dog

The manifolds are expensive because of the guys restoring musclecars. They NEED them to make their cars "correct".
You can make power with iron manifolds. The guys racing in F.A.S.T and Pure Stock are required to maintain an unaltered factory appearance and that includes Iron Exhaust manifolds. These engines are tuned to within an inch of their lives with 14 to 1 compression, roller camshafts, internally ported intakes and exhausts, etc...
To understand performance, you need to understand that headers allow an engine to make power because of 2 things: 1) They are LESS restrictive than manifolds, allowing the exhaust gasses to pass through with less back pressure. 2) The equal length pipes merge into a single area known as a collector. In this collector, a series of pressure pulses occur that have a vacuum effect on the exhaust flow. In other words, the exiting gases tend to pull exhaust from the next header tube to flow. Headers actually extract the exhaust out while a manifold merely shows it where to go.
GOOD headers do not add to underhood heat. They will allow the engine to run cooler because due to their thinner materials, they dissipate heat quicker.
GOOD headers do not always trap the starter if you are using any one of the new mini starters. Who changes starters on a regular basis anyway? Get a good one and be done with it.

moe7404

some of the early 60s new yorker 413 ext manifolds was quite big for a non-HP manifold. it was kind of like a log manifold with the exit going down in the middle. my old brain thinks that some MIGHT have been on the right and lift sides of the engine. they look a little like a 440 truck manifold except the truck down pipe is longer. i think this is right, all 413 and 440 had a 4 bbl carb, most if not all early 60s was a Carter AFB. 1967 is last year for AFB. and the only year that had a air valve above the secondary plates. 1968 started using the Carter AVS, and is the first year for the lean idle that some times gives you a flat spot off idle. in the late 60s some 440s had Holleys. all imperials , new yorkers had the biggest engine for what year they are made, i think that all so goes for the 50s. i am pulling this from my memory i hope its right

Yohomopar

The stock manifolds have a way better flow than any header you can buy.
They are so expensive because the dudes in the 60's tried headers and threw the stock manifolds away. Seriously, I would go with the stock manifolds. I have been building Mopar engines since I could hold a wrench. You can not mess with perfection. Just look at all the GM parts. They are cheap and there are more clones than you can count. You can get more HP for your dollar with a GM motor, but a Mopar motor is all about balancing and blueprinting. If you have a Carter carb, take it off and get a Holly. Only because the Carter is prone to warping if the motor gets hot and that is kind of the point with a muscle car.

moe7404

AND dont for get to use anti-seize compound on ALL exhaust system threads. with iron manifolds on the first torquing only to 70-80% of full torque. then after 4-5 full heat cycles take to full torque. if it leeks before then go ahead and take to full torque.

TVLynn

I have never tried these.. http://www.ebay.com/itm/Dodge-Shorty...cdb771&vxp=mtr

moe7404

i think the shorty's would be good. but may need custom pipes to get out of the engine compartment. but would be worth the trouble.

Road Chicken

Like you said Moe, go with the headers. I put headman headers on my 70 440, and I LOVE THEM!!!!

moparted

if you like exhaust leaks