F-BIRD'88 wrote: ↑Thu Mar 02, 2023 11:54 pm
I am going to suggest that the mid length headers my friend has on his sbc 57 is Flowtech #31108FLT
Or something real close.
Curious why you'd go to something that whilst free flowing isn't tuned for any useable rev range ?
I'd have thought he'd need 40 odd inch primaries to give it a kick in the middle.
You won't get much from exhaust, but if you're spending money you might as well get some of what you want.
This looks like a job for PipeMax.
I've got an older version tucked away and if someone doesn't beat me to it, I'll run the OP's specs through it and see what it churns out.
F-BIRD'88 wrote: ↑Thu Mar 02, 2023 11:54 pm
I am going to suggest that the mid length headers my friend has on his sbc 57 is Flowtech #31108FLT
Or something real close.
Curious why you'd go to something that whilst free flowing isn't tuned for any useable rev range ?
I'd have thought he'd need 40 odd inch primaries to give it a kick in the middle.
You won't get much from exhaust, but if you're spending money you might as well get some of what you want.
In a dyno test shootout of various headers on a moderate 350 sbc these 1½" tube pri Mid Length headers made suprizing good torque right where yiu need it. You can source it online...
Hedman has similar MID LENGTH headers that are 1 ⅝" primary also.
These lil 1½" tube headers work on mild moderate small cid engines.. (exhaust velocity).
They tested only slightly less HP than the best of the long tube headers tested.
All much better than chev 2½" Ram Horn manifolds.
With your specs, depending on the amount of block decked I get a range of CR of 9.4. to 9.8:1.
I mho the 9.8:1 is still short for this lil engine, the alum heads and the cam as is. Id like to see it @ or very near but not over 10.50:1 CR.
The 9.4:1 is too low. You're giving up torque.
92 ocane gas....
On the RAM Horn Manifolds I would fabricate a Split collector exhaust extension 2½" off the manifolds.
The pipe is cut right down the middle "split" A divider plate is welded in to re join the 2 pipe halfs creating Split D shaped collector pipe off the manifolds.
The divider plate has a tongue extending out the front end that extends up into the Manifold aa far as possible to create a "Split" in the manifold between the center exhaust ports.. This fools the exhaust into acting like the primaries are much longer and creates exhaust VELOCITY SCAVEGING to boost low/ mid range torque with these manifolds. Make the divider plate sheet metal quite thick so its strong. The longer the length of this Split D exhaust collector off the manifolds the better...
The longer and better fit the tongue extension into the manifold to "Split the flow" the better.
This will boost the torque output of the Ram Hiorn manifolds over stock.
Not near as much work or $$$ as custom built Tri Y headers but most of the intended effect.
GMHTP wrote: ↑Thu Mar 02, 2023 2:18 pm
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?
My simulation showed options of stock or hp manifolds. Small tube, large tube, and stepped headers with or without mufflers and catalytic converters. Using the hp manifolds and switching to small tube headers gave me the results. Losing the spacer and adding headers should get you all you want without the nuisance of buying and breaking in a new cam. There is something to be had by changing the cam, but it does look like a decent cam for a small engine.
This is incredible info and good ideas, thanks so much. Learning a ton.
Real quick, I’ve seen 2300 on the converter stall, not 2500. Could easily ask for a 3500+ unit to replace it, especially with the lockup.
And car is with mechanic to finish a couple things, I’ll ask him to do compression test when he can.
Been loading the moving truck all day then headed to Omaha tomorrow, so I’ll follow up on some of the other comments when I get settled. Much appreciated!
Yup usually on a small cid engine the stall you get will be less than advertized. "2500 stall" cause thats based on the engine torque of a typical 350.
If your converter is a 9.6" lockup they can cut it open and get the stall where you want it. On a cammed 283 more is better. I was going to post some dyno tests to show where the torque curve is going to be with that cam.
The converter is very critical on a small cid sbc..
Your trans Co. looks like they have the tech and hard parts sorted. They are getting their converters built from another suplier. . Not a bad thing just got to communicate whats is needed now that you have a baseline.
I hate to say this, but that 283 will never make appreciable torque . More stall converter is a waste of money. Replace the short block with a minimum of 350 cu in. if you want more torque.
Low end torque comes primary length. Controlling reversion is where the torque comes from. Pick up the long tube headers you can get and modify the collectors. It easy to cut the collectors and take a peice of 2.5" and flare it a bit and reweld it with new flanges.
I did a 347 for a truck, small cam 9.5:1 compression. We dynoed it with JBA shorties and adapter pipes correct for the truck. We threw a set of
1 3/4 long tube fox body headers at it to see if it would pick up some hp. Result was 10% low end tq and "1" pk hp.
4 hole spacers work good for low end tq.
Mummert Machine and Development 4 stroke hp
Mummert Y-blocks
I'm going to agree with Mummert. I add a choke or anti reversion devise at the collectors/ merge on everything because I've seen it work on the dyno many times. Double check your timing marks, the older motors had them around 8 degrees different than later stuff. I've mixed and matched balancers and timing covers and had problems
A quick update: just got the 57 back from mechanic, and two things really helped the 283.
Removing the open spacer for a 4 hole spacer, and mechanic double checking and adding 2 degrees of timing. Trick flow heads call for 38 degrees total, so now with 14 initial and 24 advance it pulls hard and low end is much better. You know, for a 283…
I’m still going to pursue the headers with modded smaller collectors, and a good dyno tune. When done I’ll post an update. Thanks for all your help.
If you're up for modifying your carb you could also check out what you can do for the primary booster signal. DV has a few good articles floating around about that, on one engine apparently going from a conventional booster to a detailed annular discharge nozzle got back much of the low end lost when going to a single plane.
Also exactly what header design are you going for? 4-2-1, 4-1, what length and choke size? And how much power is this expected to have? A properly designed 4-2-1 focused on low end could very easily be running a choke the size of some people's primary pipes...
I just don’t think those little street engines will have to pull after 3rd gear even Ford had a problem getting them to feel right to the mustang base back in the eighties and nineties with there 5.0’s so they just installed high 1st and 2nd gears in the manual transmission cars and they would pull decent and then just fall off from there in acceleration pull.So if you really want it to pull in all gears the transmission ratios need to be high and the rear gear but you will have to sacrifice that low rpm type of engine are throw in a couple of overdrives in 4,5 and 6.That’s what all the manufacturers are doing even some of the cars 8 speed transmission to compensate for no real torque in the engines.
