IMO you are in that area where 1 5/8 is restrictive and 1 7/8 is too big.
I think the smaller primary tube headers will be the better choice.

 

Chevy hi-performance did a test a few years ago on a 383 buildup.

They installed a set of shorty headers with 1 1/2 primarys and were shocked when the dyno showed no drop in HP.

I would go with the 1 5/8 primary tubes.

 

It really depends on other varibles such as carb, intake, cam size, so we will have a more accurate pool of factors to play with... you cannot accuratly give out a header size and you don't know the rest of the combination...... Converter... etc..... the cam and converter would let me know what your potential power band would be....and where you want your power.....

But here is some advice until you provide the rest of the info on the combination DO NOT PUT 1 5/8 HEADERS on a 383 stroker.....

 

You don't know 'the rest of the combination' but you're giving header advice? When it comes to advice, I'd take the advice of a professional header builder, like Jack Burns of Burns Stainless, Mark Lelchook of Performance Welding Racing Headers, or Ed Henniman of Headers by Ed. On the advice of Ed Henniman, I used 1-5/8" primaries with 2-1/2" collectors on my 406" daily driver Nova. In addition to towing trailers and getting 18 mpg on the open road, it ran 11.75 @ 117 in the quarter. I'll stick by Jack Burns statement about the primary and collector size, and Mark Lelchook offers the following advice:

So being very general, a low horsepower 350 CID V8 engine making only 1.5 horsepower per CID ( that's 525 hp ) may only require a primary tube size of 1 5/8" stepped to 1 ¾". This particular engine would only require a merged collector throat size of approximately 2 ¼" with a 3" outlet. The primary tube length is dictated by what RPM the engine is run at to obtain these power levels, with the vehicle weight, transmission, torque converter, and type of racing playing a dominating role.

 

One of the largest errors street enthusiasts make is in running too large of a primary pipe, and too large of a collector. For example, NHRA and IHRA Stock teams using Burns' headers in H/SA in traditional small-block powered musclecars are running 1.5-inch diameter primary pipes- much smaller than many street machines are trying to use.

http://www.popularhotrodding.com/tech/0310phr_jack_burns_exhaust_manifold_header_tech/index.html

My 11-second tow car had 1-5/8" primaries.

 

No offense Ono, but that article was written 11 years ago, and the NHRA class this guy is talking about is H/SA. Our stroker street motors today, with their much improved heads, are certainly much powerful than what was allowed in SE class racing.

1.5" tubes? No thanks.

 

Whenever the first word out of someones's mouth is something quoted from a magazine article or test runs vs real world data........ run..
Magazine articles, dyno'd in controlled environments, with less real world parameters..... vs an actual chassis dyno and best ET.......

Everyone knows that header size should be taylord to your combination.....Not because it worked for Tom, Dick, and Hank?
out:

 

You can always build a set of headers with 1-11/16 primaries if it makes you feel smarter.

 

If I were considering buying headers and I had a 383 .. I'd go 1 7/8". No telling where you'll be a year + down the road. Better to have them and not need them .. and IF they're killing any power, it'll be minimum. Quality headers aint cheap and they don't re-sell very well.

The performance/expectations of the engine should be seriously be considered. A moderate 383 would not need that much flow.


my .02 FWIW

 

If I were considering buying headers and I had a 383 .. I'd go 1 7/8". No telling where you'll be a year + down the road. Better to have them and not need them .. and IF they're killing any power, it'll be minimum. Quality headers aint cheap and they don't re-sell very well.

The performance/expectations of the engine should be seriously be considered. A moderate 383 would not need that much flow.


my .02 FWIW

I agree junior, pending his combination at minimum 1 3/4ths..... if he is going to wind that bad boy up to 6500+rpms...... 1 7/8ths

But as I stated, we don't now the rest of his combo so I am throwing a disclaimer out there.....

We still don't know his exhaust pipe size, mufflers, heads, cam timing events to examine the exhaust stroke timing and intake opening timing....etc..... to make a recomendation......

The 1 5/8s should have excellent velocity to excuvate the gases out the cylinder at low - mid rpms, but upper rpms may limit the cylinder ability to clean out the cylinder, and leaves some exhaust in the cylinder. This may affect the peak horsepower and torque numbers.. So with that said the header diameter can also shift the power band.... left or right......

Now I know some guys are going to say well I did this and that with a certain diameter or certain product.... Not to say it didn't happen but its not optimal..... Physics is Physics..... But not to say that cars with short peak numbers cannot run.... Caroll shelby said it best "Horsepower sells cars, but torque wins races" An engine making 400lbs or TQ at 2500-5900 can be just as effective as a one makine 400lbs of torque 3500-6200 rpms...... now were getting into converters and stall or manuals and shifting...

 

Here is a header calculator to size primaries/collectors based on your engine:

http://www.wallaceracing.com/header_length.php

I couldn't find your exact cam, but inputed the spec from a 284/296 comp cam.

Engine rpm for peak torque = 5000
383 cubic inches
80 degrees BBDC exhaust valve opening

Using these inputs, primary tube should be 1.62".

 

I went from Thorley TriY 1.50 to Dougs D368 1.75 , did not tell any differance other than torque band at a lower rpm. Both fit well.

 

I went from Thorley TriY 1.50 to Dougs D368 1.75 , did not tell any differance other than torque band at a lower rpm. Both fit well.

OT - Don angle plug heads? If so, how were number 3 and 6 cylinder plug wire clearance? I've got the Tri-Y's with Dart angle plug heads and have issues with the plug wires (with shorty plugs).

 

1-3/4" primary tubes, right about 32-34" long. Collectors should be 3" diameter and about 16" long.

Keep in mind that collector diameter and length is more important than primary tube diameter. So is primary tube length . . . that is the least important factor.

 

1-3/4" primary tubes, right about 32-34" long. Collectors should be 3" diameter and about 16" long.

Keep in mind that collector diameter and length is more important than primary tube diameter. So is primary tube length . . . that is the least important factor.

x2

 

I am having the same trouble with burned wires on a 383. I purchased it and do not know the brand of headers but with the shorty Accel plugs #3 is right up aginst the header. I just replaced and rerouted the plug wires, gained tremendious power, don't know for how long.
gene68ss

 

I cut and paste the below from a previous post I made. It seems relevant.


"For anyone interested, I previously said I'd post results when I changed out headers. Okay, I know it's not a scientific comparison but I think it's pretty conclusive.

Last time out ran 11.65-67's in 2600-2800 DA. Before that ran some 11.60-11.64's in 2000-2300 DA.

Swapped out summit brand 1 5/8 inch headers for new Dynatech 1 3/4 stepped to 1 7/8. No other changes.

Ran 11.55-59 in 3100-3300 DA. Worst air of the year, new best time.

Previous best of 11.57 was run in about 1500-1800 DA.

I was a little worried they might be too big and hurt my et but wanted to give them a try. I think I can safely say they were worth at least a tenth and given the higher DA maybe .15

I'm very happy with the results, the Dynatechs fit and look awesome. Good ground clearance also. Your results may vary!

My previous best was 11.57 @ 115. I ran an 11.55 and 11.57 both at 115 with the new headers but in much worse air. Actually every pass was 115 mph. I'd been runnng 113-114 in the 11.60-67 range, depending on air.

60 ft's were right on par with a best of 1.60, same as before. I guess now I'll have to wait till the fall for some nice cool air and see what it'll do."


I hope this is real world enough for everyone. I was surprised actually, I don't have a high revving engine. I shift between 6000 and 6500.
__________________

 

Swapped out summit brand 1 5/8 inch headers for new Dynatech 1 3/4 stepped to 1 7/8. No other changes.

How do these headers compare?

 

hi ,guess you are getting lots of response from your post and may not need my $.25 but ill toss it in anyway!
i have 67 4spd with a 383 10.2:1,edelbrock perf rpm heads,intake,comp cams 276HR,pro mag rockers,750 demon. strong little street engine with nice manners.had full length 1 5/8 x3" hedmans they were ok. swapped on 1 3/4 x 3" hooker super comps and i could feel more power in mid range and higher rpm.......it still has more power than the tires can use if i mash it off idle.
also,as an aside.....if smaller tubes are better,why was my car faster with 3"x18" collector extentions and no mufflers compared to my full length 2 1/2 " magnaflow system? kinda wish i opted for the 3" kit but tech said i would lose power...... i think listen to everyone then do what YOU think is best...your car/cash

 

I like my Hedman Hedders #65104 1 3/4" primaries.
They fit GREAT and have tons of room around the plugs, even Angle plugs.

 

hello Camaro world. I have a question about header size. ive built a 383 sbc , im using a dual plane intake, I have a quick fuel 750 cfm carb, 190cc 64cc aluminum heads, with stainless steel full rollers, cam is .488/.507 valve lift and DOD 289/297. I have 6.0 rods with probe pistons with negative 8.5 dish pistons. need help knowing what size headers to buy for this beast. please help. this is only the second engine ive built. newbe

 

i have the dynotech 1 3/4 to 1 7/8 step headers on my nova. the fit is the best i have ever saw unless custom built for the car! it uses a stock sized starter with all kinds of room. they are nice and close to the floor as well. the ball and socket collectors are really nice too! the coated ones use Nitroplate coatings. very easy to keep looking nice.

 

with small heads , some 1 5/8" will work. 1 3/4" would be on the large side for a mild 383. do you spin it past 6000?

 

in an ideal world (and engine design) headers would be on the conservative side. but sometimes the car will be faster with the bigger header, weather its because its light or have a bunch of stall or its just a bandaid fix for another issue.
Ford Cleveland engines usually like large headers... why?
maybe because the intake side and valve size work very well, but the exhaust port isn't so good, and the larger header is a bandaid fix for it.

peak HP should also be a consideration when choosing headers,
a 450hp SB isn't going to be using the same header as a 600hp SB.
my 420sb picked up over 1mph going from 1 3/4" to 1 7/8" headers
but the opposite would be true if I did that to my 383.

 

at only 400hp, you could run 1 5/8", even on a 383 thats got a bit more piston speed. I bet on a low rpm / low hp deal like that the diff between 1 5/8" and 1 3/4" would be a wash.

the other thing is... what are you lookin for.
if its a car that you want to 60fts hard, the smaller header may help at the expense of mph.
and the larger header should mph better but may not 60ft as well.

and you aint gonna 60ft nothin on the street, so I'll take the bigger header and the mph in a streetcar anyday.