Thread: header size

Tweet

Wondering what would be the preferred header and collector sizes for a 383 stroker with a hydraulic roller, aluminum heads, and a single four barrell operating in the 2500-7000 RPM range???? I've looked at everything from 1 5/8" tubes with a 3" collector to 1 7/8" with a 4" collector....and just got confused on what might be the best size to boost the power (especially the torque) on an SBC.....

Take a look at this:

http://www.rbracing-rsr.com/runnertorquecalc.html
or this
http://www.autolounge.net/calculator...dersizing.html

I had a better version, which of course I can't find again, when I did my exhaust system calcs and hope it's right. I ended up with 1.5 header tubes, 3" collector and 2.25 pipes. But mine is 81 cid less then your 383.

(That must be a Chebbie - can't be yours, or...... )

Dave,
My rule of thumb has always been, torque comes from small diameter tubes and long primary's. Horsepower is large tubes and short pipes. I used 1 5/8 stepped to 1 3/4 36" long 3" collectors and 3" exhaust, with 427 Cu. In. Small block (LS 7).
My 2 cents.
Ken

I always heard and it makes sense to me that in general large tubes will produce more torque at elevated rpms but smaller tubes are mo better at lower rpm.

I might be inclined to split the difference and go with 1-3/4. The tech section at Sanderson is good reading.

Kitz

Ah, headers................books have been written about this subject. My Cad (4600 Lbs 454 Chubby, 440HP) uses 1 3/4" promary pipes with a 3" collector that's fourteen and a half inches long. It then flows through 2 1/2" mandrel bent pipes out the rear through Dynomax super turbos. When building (or buying) headers that will be used for a mufflered system it is far less costly (HP wise) to err on the small side. My system makes 2 HP less through tje mufflers than it does with open headers.

Having said that I reccomenf 1 5/8" pipes into a 3" collector thats at least 16 inches long, and 2 1/2" pipe from there back.

Thanks guys!!!!~ This old Ford guy needs all the chebbie help he can get!!!!

Same engine, wondering if thie AFR head would work ok, or what would??? might be putting a 150 shot of spray to the engine, too. Here's a link to them on eBay.... The info and flow charts are there, too.

140237094954

Thanks again!!!!!

Ok, so I'm a Ford guy..... I've always liked the results of Tri-Y headers on a Windsor, seems the more cubes, the more torque the Tri-Y's will make.... Same hold true for a chebbie????

Here's a pic of a set of Tri-Y's for an sbc.... I was contemplating the cylinder pairings----if I go to the 4-7 swap cam, which tubes get paired?????

I think that on the 4-7 swaps the cylinders then are duplicates of the fords so you header cylinder pairings would be similar to the fords

Thanks Jerry!!!! Kind of how I had it figured... Guess I'll plot it out like I do the Fords.... Curious to see if the Tri-y's help the sbc's like they do a Ford.....

and for size---go for exhaust valve size plus 1/4 in----1.600 valve-1 7/8 tube
I like .065 wall tube for welding but will use .049 or even .035 to save some weight for race stuff---

Hey Dave, just finished my 383 build. Most everything matches your specs. 1 5/8 headers 3" collectors 481 torque @ 4300 479 hp @ 5800. 1 7/8 headers
4" collectors 490 torque @ 4400 503 hp @ 5900

Originally Posted by Rgtrough

Hey Dave, just finished my 383 build. Most everything matches your specs. 1 5/8 headers 3" collectors 481 torque @ 4300 479 hp @ 5800. 1 7/8 headers
4" collectors 490 torque @ 4400 503 hp @ 5900

Did you do the cam with the 4-7 cylinder swap????

That's some very encouraging torque numbers!!! What do you have the engine in? Should be a good runner!

Hey Dave, thanks I was very, very pleased with the results. Though I have built engines in the past this is the first time I did all the work (including all the machining) myself. The cam is a Comp Cams extreme energy hydraulic roller cam. 230/236 duration .510/.520 lift. Also I'm using 1.6 roller rockers. The engine will be installed in a '74 Corvette coupe. I think the key to the numbers are in the heads. I used the AFR 195 Eliminator heads. These units flowed 277 cfm @ .600 intake and a huge 223 cfm exhaust.

I've looked at the Eliminator heads, goot to see the numbers actually match the advertising hype..... and basically a mild cam, at that!!!! Wonder what a bit more cam would do to the torque??? I keep looking at the 4-7 swap on the firing order....specs I've seen show increased torque....

Hey Dave, I too am curious about the 4-7 swap. Then I think why mess with 50+ years. I see you are thinking of using a 150 shot. I saw numbers on a set up very similar set up using a 150 shot. 642 torque/630 hp. I'm worried about my 1/2 shafts without the nitrous let alone diesel like torque numbers