FrontEngineDragsters.Org Forum
Technical => Matt Shaff's Engine Shop => Topic started by: gasserx on January 29, 2015, 11:10:05 PM
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I finally got my engine this week! Its a SBC with Hilborn injection (alky), and shorty stacks.
Short stacks will probably work good also, but i would like the taller ones for a little more nostalgia look.
I scored some 12 metres of 2.5" alu tubeing for almost free, and was thinking of making another set of taller stacks for it. What would be a good length to try?
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Stack length is another tuning parameter that is different for your engine than mine.
A lot of things affect the RPM range that a engine operates in for maximum torque.
The short story is long stacks make torque in the lower RPM ranges and short stacks let the engine
make peak HP at a higher RPM range.
Check out Pipe Max software. I do not own it but a engineer friend of mine does a lot with it.
I know it has formula's for header tubing and I think it also works with intake length.
Matt
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Matt is right, long stacks = lower RPM power, and short stacks = higher RPM power.
So if your cam/ motor combo is higher power at high RPM you'll run better with short stacks.
It's no secret that SBC's will make more power the higher you rev it, but in order to run higher RPM's you need a better lower-end and better valve train. So your questions should be what RPM should I shift at and what RPM thru the lights.
Now my guess is you don't have a 10,000 RPM Chevy, because if the tubing you just bought is 2.5" ID, then your Hilborns are no bigger the 2.5" . Most of the 10,000 RPM Jr fuel engines are using 2 7/8" injectors unless they are racing the 14° heads and are JrFuel"A" class that the rules allow 3 1/8" injectors, where a couple of teams are running 10,500 to 11,000.
My JrFuel "B" SBC 9700 to 9800 RPM is running as short a stack as we can get to fit on the injectors.
One of the JrFuel "C" teams running at around 9,000 RPM is running 4" or 5" stacks, on 2 3/4" Hilborn's. You could call Don Enriquez at Hilborn, that's what he runs.
So you need to find-out what RPM your engine is making the best power, and set-up your stacks, torque converter,shift points, and rear gears/ tires size to LET your engine run in the best RPM range. You'll have to dyno your engine if you can't find out what you need from your cam guy or engine builder.
A tuning tip about stacks is if it turns out you want 8" stacks, and you are racing a track that has a crappy start line, put your short stacks on because they will kill some of your torque/ bottom end power so you can get off the line.
Here is a picture of my 2 7/8" Hilborns, but now I run angled Kinslers with sort stacks, I can post pictures of them too, but I figure you'd like to see my Hilborn's.
Good Luck with your combo
Jon
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Thanks for your replies guys. I dont know what type of cam the motor has yet, but im about to disassemble it these days so hope to find out.
I can say for sure its not going to shift at 10.000 RPM ;D
Those are real short stacks Jon! Thanks for helping. I`ll see if i can manage to do a dyno on the engine before spring.
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STOP!!! That engine ran some low 5.20's like it is--it does not need taller stacks--now for looks...maybe you prefer taller--I can go with that but.... don't second guess a Well Tuned combo you just shelled out for--That is one heck of a SBC engine for what you are doing--get it running--drive some THEN screw around with it if you want but you need a well tuned ready to go combo--messing with success is not the way to start out--Learn the car, learn to drive then mess with it otherwise you will spend all your time fixing things that were AOK and not get to run as much. Just my two cents worth
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I agree, run it and than change it, and change one thing at a time so you know the result of the change.
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I agree, run it and than change it, and change one thing at a time so you know the result of the change.
Ditto
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I sent you the cam card with that motor? correct.
But like David says just run that thing. I only sold it for tuition $$$ for my son college. If I kept it because I knew it was and is a great back up motor. Only reason I switched it was I had Tom Martino build me a 387" motor to get into the sevens.
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I will run it like it is guys, dont worry about that :) Just going through it to ensure everything is okey.., and regarding the stacks that was mostly to have ekstra sets to test. After all, stacks is probably the easiest to swap without huge impact.
I`ll make them myself for fun, and wanted to know if there was any particular size thats a good starter.
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Well, for what’s worth… I remember seeing old pictures where engine tuners were experimenting with different stack lengths by using stacks that were cut in two pieces and linked with what appeared to be radiator hoses (making it easier/quicker/cheaper to test different lengths).
But I think you would only want to start messing with that once you have your car (and driver) running very consistently.
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I have a short set (4") and a tall set ( 8"). The tall set seemed to make a bit more torque. Skip the dyno expense and put the car on the track and go to work tuning it. Picture is 2013 with the 8" stacks.
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hey..you can see over the shortys better--that is good for rookie :)
that engine in that car will scare you to death first few runs--you will be looking to slow it down until you get your "sealegs'
You bought a great unit!!
Jim tunes all our members rides at the track and I promise that deal is on the money!!
Even with a junk converter it will scare you
Mike at Alkydigger has stacks any length made --on the shelf and is a great source for tech
start looking for some fresh alky and get it running
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hey..you can see over the shortys better--that is good for rookie :)
that engine in that car will scare you to death first few runs--you will be looking to slow it down until you get your "sealegs'
You bought a great unit!!
Jim tunes all our members rides at the track and I promise that deal is on the money!!
Even with a junk converter it will scare you
Mike at Alkydigger has stacks any length made --on the shelf and is a great source for tech
start looking for some fresh alky and get it running
(http://www.frontenginedragsters.org/forum/index.php?action=dlattach;topic=1517.0;attach=4119;image)
Do I see a new avatar picture here? Let me know and I will make it happen.
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Avatar? What's that?
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Avatar? What's that?
The little picture directly below your name on the left side of your posts.
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Avatar? What's that?
The little picture directly below your name on the left side of your posts.
Oh,I see. How about a 2014 picture?
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Avatar? What's that?
The little picture directly below your name on the left side of your posts.
Oh,I see. How about a 2014 picture?
Done
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Thanks Glen!