Best Exhaust To Add Torque To 283?

[GMHTP]

Hi all,

I’m in a small-cube exhaust gray area in a difficult to fit headers car, and could use some advice.

I kept my dad’s 57 Chevy 283 powered, as it was being machined when he passed and it was the engine that he wanted to build. But despite being an amazing road trip ride on long rallies, it could use a little more torque even with a 2.74 first gear and 3.89s.

The car has 2.5 ram horns now and I’ve been carb “tuning” via wideband and butt dyno so far. I’ll have access to a dyno and a tuner when I get moved to the city soon.

The combo is below, but which of these options seems better to you?

1. Would extending 2.5 ram horns’ 2.5 inch piping a ways, before necking down to 2.25 dual exhaust further back, help torque? Has anyone dyno/track tested this?

2. There’s one set of long tubes that will fit the car, but will 1 5/8 primaries to 3 inch collectors be too big and hurt a 283’s torque more? The header sizing calculator calls for 1.5 primaries and 2.6 inch collectors with 34 inch primary length.

3. Having a shop build me 1.5 primary long tubes for big $. Could probably afford an EFI setup for that kind of coin. Are there any old school 1.5 header builders I could look for?

And what are your thoughts on the cam? It was off the shelf so both the duration and the LSA seemed a touch high. Should have custom ordered it.

The combo:
1957 283, .040 over, balanced, forged crank, forged Scat rods, KB flat tops
Just under 10:1 static CR, 8.0:1 dynamic CR
Voodoo hydraulic flat tappet, 256/262 (213/219), .454/.468 with 1.5s, 112 LSA
Edelbrock EPS dual plane, 1 inch open spacer, 500 cfm AVS2 carb
Trick Flow Super 23 175cc aluminum heads, 56cc chambers, 230 cfm/170cfm flow at cam lift
2004R overdrive with 2500 stall lockup converter (might raise to 3000), 2.74 first gear
9 inch with 3.89 gears

I’d appreciate any insights you might have.

[BobbyB]

I say research, then buy a "DRAGY". It is truth serum for your butt dyno... for not too much money. With this measuring actual performance going down the road, you can know, rather than guess what happens from a given change.

Probably try going to a split or 4 hole spacer rather than open.

Ask mike jones what he thinks about the cam and what he would recommend for getting more torque where you want it.

Good luck with it.

[skinny z]

And what are your thoughts on the cam? It was off the shelf so both the duration and the LSA seemed a touch high. Should have custom ordered it.

I found that cam on Lunati's website however I couldn't find a cam card for it. Specifically, looking for the installed intake centre line. Did you degree the cam when installed?
Compression equals torque. You may find an improvement with something else however a little more info is needed for comparison.

[Walter R. Malik]

Hi all,

I’m in a small-cube exhaust gray area in a difficult to fit headers car, and could use some advice.

I kept my dad’s 57 Chevy 283 powered, as it was being machined when he passed and it was the engine that he wanted to build. But despite being an amazing road trip ride on long rallies, it could use a little more torque even with a 2.74 first gear and 3.89s.

The car has 2.5 ram horns now and I’ve been carb “tuning” via wideband and butt dyno so far. I’ll have access to a dyno and a tuner when I get moved to the city soon.

The combo is below, but which of these options seems better to you?

1. Would extending 2.5 ram horns’ 2.5 inch piping a ways, before necking down to 2.25 dual exhaust further back, help torque? Has anyone dyno/track tested this?

2. There’s one set of long tubes that will fit the car, but will 1 5/8 primaries to 3 inch collectors be too big and hurt a 283’s torque more? The header sizing calculator calls for 1.5 primaries and 2.6 inch collectors with 34 inch primary length.

3. Having a shop build me 1.5 primary long tubes for big $. Could probably afford an EFI setup for that kind of coin. Are there any old school 1.5 header builders I could look for?

And what are your thoughts on the cam? It was off the shelf so both the duration and the LSA seemed a touch high. Should have custom ordered it.

The combo:
1957 283, .040 over, balanced, forged crank, forged Scat rods, KB flat tops
Just under 10:1 static CR, 8.0:1 dynamic CR
Voodoo hydraulic flat tappet, 256/262 (213/219), .454/.468 with 1.5s, 112 LSA
Edelbrock EPS dual plane, 1 inch open spacer, 500 cfm AVS2 carb
Trick Flow Super 23 175cc aluminum heads, 56cc chambers, 230 cfm/170cfm flow at cam lift
2004R overdrive with 2500 stall lockup converter (might raise to 3000), 2.74 first gear
9 inch with 3.89 gears

I’d appreciate any insights you might have.

Personally, I would locate some 1 1/2" Shorty headers and change that "open" spacer

[GMHTP]

Whoa didn’t realize gps performance units had come so far, very cool. I’m not an expert, so I just based the 1 inch open spacer on the good engine masters dyno test results. Of course that was much bigger cubes than this engine too.

Here’s the card skinny, I gave wrong adv duration numbers above. The machine shop installed the cam, and all I know is they said they’d install based on Lunati’s recommendations.

A53BCE77-4987-4E8A-AB85-8198B4DBA2C3.jpeg

[Old School]

Leave the exhaust alone for now. The cam is about 15 degrees too large. Something about 200 @.050 on a 110-112 lobe separation will have more torque. A single pattern or a dual pattern with maybe 4 to 6 degrees more exhaust would be my choice.

Getting rid of the spacer is good. You want a dual plane induction system. The heads are large but you can't change everything. A smaller cam will be the most torque gain for the buck and effort.

[skinny z]

Personally, I would locate some 1 1/2" Shorty headers and change that "open" spacer

X2.
The spacer would be an easy enough back to back test.
With regards to headers, when I'm running a sim on a given known (raced and recorded) engine combination, I'll often substitute manifolds for headers (in simulation) to align the real world results from the virtual dyno results. There can be quite a difference between to the two styles of exhaust.
The same applies to rest of the exhaust system.
As for your calculated SCR and DCR , something isn't adding up at my end. I'll look a little deeper once I'm back in the office.

[GMHTP]

Thanks for the replies. Interesting thoughts about the spacer. I’ll have to rewatch that episode, now I’m wondering if they were testing it on a single plane manifold. Probably.

Old School, I chose the TFS heads because they were new, aluminum and a small chamber option with 1.94 valves. Heard velocity would be ok on a small bore, but this is my first small engine also so didn’t know for sure.
There was a smaller Voodoo cam option but it was in the 20X” range so I went up one size. Was hoping for good top end but only going to 6,000 or so so far.

Skinny I just checked my notes, static was calculated by machine shop at around 9.7. I did the dynamic calcs, hopefully they’re not out of whack…

[Tuner]

1.5" tri-y are probably best but 2.5 ramhorns are plenty for a 283. The open spacer isn't helping and I have not seen a 500 Edelbrock that could be made to run well with simple jet and rod changes because the idle circuit is "what are they thinking?" You would have better luck with some 600 Edelbrock carb primary clusters but even those are a crap shoot because they are not all the same. The oirginal 283 carb or similar OE carb, Rochester 4Jet or WCFB, or an original 300-340 HP 327 Carter 3721 AFB would surely run better.

The Trick Flow heads have fast burn chambers and will be picky about the distributor setup. The mechanical advance curve and vacuum advance have narrow tolerance for best performance with chambers like these. On the dyno move the timing around in steps and look at the results in 500 RPM ranges to find the mechanical curve it wants.

I say research, then buy a "DRAGY". It is truth serum for your butt dyno... for not too much money. With this measuring actual performance going down the road, you can know, rather than guess what happens from a given change.

Probably try going to a split or 4 hole spacer rather than open.

Ask mike jones what he thinks about the cam and what he would recommend for getting more torque where you want it.

Good luck with it.

Cell phones have accelerometers in them and there are free apps to measure HP and Torque. This one is $15.00 but there are some for free.
https://play.google.com/store/apps/deta ... pert&gl=US

https://duckduckgo.com/?q=cell+phone+ac ... fab&ia=web

You guys criticizing the cam, the one he has is less duration and more lift than Duntov's "12 & 18" 3736097 cam, which is the one I would use if the car were mine.

[rfoll]

I ran a simulation with the software I have and headers showed 30 more ft. lbs. more and about the same in power increase. I'm with everyone else on the spacer thing. I run 4 hole adapter on my car with a 2.73 rear gear. As an experiment I installed an open adapter and the low end torque disappeared and the mixture went very lean. I also used a 500 AFB for a while and although it ran good, I could never get it tuned to where I wanted. If it were my car, I would try a Quadrajet, but that would mean a different manifold and the aforementioned 4 hole adapter

[GMHTP]

Ok sounds like I’ll be replacing or removing the open spacer. Good info.

Tuner, the tri 5 guys claim that “good” tri ys don’t always fit well, and I’d have to change flywheel to a smaller tooth unit if I used let’s say a Patriot tri y. Might wait on that in case I raise the lockup converter stall again.

I wondered if someone would mention a different carb. Truth be told I’m an EFI guy and carb newbie (last project was a roller cam Turbo Buick), and chose the edelbrock 500 AVS2 due to the reported better drivability and easier tuning as I do long trips in it. My small town mechanic is a big Q jet guy but I’m moving soon, I’ll also ask a Chevy dyno tuner about the carb and playing with timing (MSD dizzy) when I find one in Omaha / Lincoln.

rfoll that’s interesting, did you simulate with the 1 5/8 long tubes?

[1980RS]

I just got a Draggy, can't wait to test it out this year. As for headers for that 283 use 1 1/2" tubes with a 2.5 collector. There has to be a few sets out there that you can fan to fit your car. The smaller tubes will make more torque, sure helped my 283 back in the 70's with a set of them.

[Tom68]

Rams horns are big enough but if you want more grunt go straight to tri ys or long tube headers.
1 5/8 long tubes will still be better down low than manifolds, but 34'' sounds a bit short.

[F-BIRD'88]

Cam has too much exhaust duration.
A 200 to 210 @.050 on 108/110 hyd will be better for 283 torque. A lil comp high energy or a lil Isky Hyd
Single pattern cam.
Ditch the open spacer. use a 4 hole or a combo/hybrid 2 hole and D slot spacer. "divided plenum"
Yup this car needs a Qjet. A stock GM Qjet intake and a 4 hole spacer on it is great.
On that intake a lil holley 600 VS (1850) will work.

Will any of the low buck 1 ½" pri mid length headers (2½" collector)(Flowtech etc) fit that chassis.
In tests these common 1½" Tube mid length headers made very good torque.

A DV single pattern custom grind Lunati Voodoo hyd cam will work well too. keep the duration short. VH30/VH30 on 110 lsa in on 105° 110/105 207/207 @.050"

[mt-engines]

The best exhaust for your application should have a turbo at the end of it.