Headers on my 383 'vette!

[Roscoroo]

a 383 cu chev is a 350 w/a 400 crankshaft.

[rpm]

Originally posted by Roscoroo
a 383 cu chev is a 350 w/a 400 crankshaft.

Ah, that explains it. I had never in my life heard of a GM 383. My Dad had a '66 Plymouth Sport Fury with a 383 Commando. Very strong motor.

[lazs2]

You can buy a "crate" 383 chevy engine right from GM now.  Most of the 383's people build are nothing more than a 350 with a 400 crank but there are other combos including destroked 400 small blocks.

lazs

[Steve]

Lazs, they might be block huggers.. I really don't know.  They weren't called  block huggers in the summitt catalogue.  They were called... umm oh ya... Super competition headers.   They make those, fortunately for me, specifically for my car.  It was a PITA getting them in but I didn't have to do any cuttin/welding.

[Steve]

I looked at the crate chevy motor as well but it used short rods and they were hyper instead of forged. Friends advised me that this motor might not hold up to heavy loads of sauce.

I ended up building a much stronger motor for about the same price plus I used my orignal block so, if I ever sell it, I can still say "all numbers match".  

Thanks for the advice Rosco... I'm goin w/ Flowmasters.

[Steve]

Beet, headers are exhaust manifolds that are designed to allow for ideal airflow.  This allows the engine to breathe better, producing more horsepower.*



* experts, feel free to chime in if my definition is inaccurate.

[Steve]

And... what will be the fuel consumption of that thing? Will it be any more than 8mpg?

I think it will get about 12 to 15 MPG.(It's a pretty light car). I won't ever know though because I don't care. I also don't care/believe in global warming(as far as  man having a major influence).
Finally, I don't care about gas prices either, as long as it's available.

[beet1e]

Originally posted by Steve
Beet, headers are exhaust manifolds that are designed to allow for ideal airflow.  This allows the engine to breathe better, producing more horsepower.

Ah! Well why didn't you say exhaust manifolds! Now I know what you're talking about, are yours of a certain shape to allow more rapid outflow? Polished ports and all that?

[Roscoroo]

when we say exhaust manifolds we all see these heavy cast iron ... very few flow decient junk .. Headers is a 15-35 hp gain on a stock v-8 ussually . and as long as you buy a quality set  they seldom have problems .  

I myself make my own flanges and adapter plates for all the headers i build .
(i even was autherized to build race headers for hooker years ago )  but my headers arnt cheap .. i just finished a set for a 3 ltr v-6 thats droped into a MR2 w/ out being coated they cost the guy 580.00
but there also built in a way that he can install a turbo later if he wants to .
my v-8 race headers steped ,clocked, built full tilt are 1000+ and they ussually gain 5+ hp on the pro stock cars over most of the other guys . (probly because I Argon purge the tubes when welding them)

On the big car show nights up here I can say that close to 40% of the cars that show up have had my hands on there exhaust , roollbars , and other mods from back halfs ect...

[Steve]

are yours of a certain shape to allow more rapid outflow? Polished ports and all that?

Well the ports in my heads are polished, yes.  but there is a difference between heads and headers.

Rosco or lazs, explain about tube curves, same length tubes for all cylinders, long tubes and stuff like that please.  I am confident that you would do a much better job than I.  

Rosco, maybe I should have gotten a set from you.  I paid $559.00 for my headers.

[Steve]

Oh ya., rosco:  The cut outs aren't for performance really.  They are for setting off other car alarms, and assisting my stereo in drowning out the rap music emanating from the ricer's cars.

[Roscoroo]

Your running the dart 2 heads on your 383 ?  the non spacer plate ones from what i see in the pic's which is ok .

the secret of good headers is amount of bends vs tube lenth vs size  . For my 383 thats in my chevelle wag . ive got 1 3/4's primarys that are 24-26 inches long with 9 inch collectors .... then i added 10 inches of 3 inch  to give me a tuned collector then i steped it down to 2 1/2 inch  thru a set of dynomax flowthru mufflers then out in the stock location . now this is a mild stroker and grocery/kid hauler mostly . but with the 700r4 and 3.73 gears on 28 inch slicks it ran a 12.86  just babyin it, no nitrous and pump gas . not real fast but not to shabby for a car that gets 19-21 mpg ...

For your set up id probely go with 1 7/8's or  2  inch primarys . and perhaps 3 inch to the mufflers then 2 1/2  or 2 3/4's tails on it  the tails will keep the noise level respectable and the 3 inch will give it low pressure for faster r's ... exspecially when you hit the n20. For extreame go
with 2 1/4 primarys but the bottem end "pull" starts to drop out and the milage goes in the gutter around this size.
i did a 71 chevelle this way and it turns 9.90's with turn downs after the mufflers , and 10.20's/.30's with the 2 1/2 tail pipes on .   2-3 tenths of a sec diff with that much tailpipe  isnt too bad .

as for ported / polished heads .. polish on the exhaust side .. match porting is a must .  for the intake i ussually match port the intake and just polish the bowls ... most of the new alum heads are nicly done and need just alittle work to make great performers .

now long tube vs short tube ..
Long tube,
ok emagine a  bunch of pulses of pressure going thru a pipe ..    you try to keep them even the longest so they stay smooth ... now add 3 more pulses  (this is what we call clocking a collector)  we try to bring them in evenly and get a timed spiral flow thru the collector so it will increase speed by going into a low pressure area . (this causes the pipe to scavage )  this creates faster rpm in the engine buy pulling the exhaust out of the head ports .  see less work for the engine.

hard Bends will vary the speed of the pulses thats why we make them shorter lenth primarys (it takes tons of trials to get what lenth is right or wrong)


Short tubes ...
these are great for limited space and do increase power , but they dont have the ability to scavage like long tubes will because the timing /clocking and long collector just isnt there..


Hope i explained this well enough for you all to understand ... i tried to keep it simple but i kinda think backwards sometimes .

[Geary420]

Lookin good Steve!!  When u gonna post up some pics of the whole car??

Geary

[lazs2]

header theory is extensive..  rosco didn't say anthing that is not correct.. but..

In most street applications... the headers available will all make about the same HP when hooked up to a street exhaust system..  15-40 hp is about reasonable to expect out of the entire package..  

Big blocks probly (99% of the time) gain a little more than small blocks.  

I run dynomax... I am kinda tired of hearing "that flowmaster sound" from every new pickup that goes by.  I do run two chamber flowmasters on the Healey but they don't sound anthing like what you know as "that flowmaster sound".

Friend of mine who ownes a shop ran 3 sets of headers and mufflers on his Chevelle and he dynoed every set..  there was probly more difference in the HP readings caused by outside air temp than by the different headers..  

lazs

[Siaf__csf]

Bah.. forget it. I cant link it safely sorry Rightfoot..