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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......:HMMM: :LOL: )
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.:cool:
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
Did you do the cam with the 4-7 cylinder swap????Quote:
Originally Posted by Rgtrough
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
We do 4/7 swap on almost all the chev engines we build for customers
and use bigger/shorter headers to move the curves higher in the power band--if you are building for more power the engine will compromised with smaller longer headers!!!!!
Use as big as primary tubes as you can and still get a sparkplug and socket to clear---you can pair cylinders into 2 different primary lengths to spread the tuned rpm range of the engine--especially with tri - ys
Jerry
i used the bigger size tube when i build headers for small blocks a 383 is not that small cid 1 3/4 or 1 7/8 you may have to use a stall plates for the 1 7/8. i buy all the sbc stuff from a guy i know that cuts the header plates on a cnc mill you can go to 1 7/8 with no stall plates if you work the tube and going to a small head bolt head and a small bit of work on the tube and go to a 28+long primarys and go with a X tube ex cross. as for the 4/7 swap i use them all the time there not that much more money were i get my cams there not any more then buying a stock firing cam from jegs or summit. i run them for less crank twist then the small amount of power you may see .i think you will see more power with a good built headers and ex then the cam but it all adds up i doing a 4/7 swap on two bbc blower engines for a boat i going to have the new firing order on stickers on the valve covers so some one will not try wire it with the stock firing order.if i go to a custom grind i use the 4/7 swap all the time on rollers cams
For you chebbie guys again...HELP!
I was looking at the arrangement and tube size on some 4 into 2 into 1 stepped headers for a small block, here's what I found for a sbc with a 1-8-4-3-6-5-7-2 firing order:
On the left bank, the first two clinders are paired, and the back two cylinders are paired, same thing on the right bank. Tube at header is 1 3/4" stepped to 1 7/8" 10" out from the header flange...... If I change the came to the 1-8-7-3-6-5-4-2 firing order, what is the best way to pair up the tubes on the 4 into 2 collector to maintain the same scavenging effect as the standard firing order??????
If all this confuses you, join the club!!! I spend a lot of time confusing myself!!!!!:LOL: :LOL: :LOL:
Maybe I'm just playing with something that doesn't matter a whole lot, but it IS a chebbie, and needs all the help it can get in the horsepower department......;) :LOL: :LOL: