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Author Topic:   Best all around motor
sledgehammer
Member
posted October 06, 2003 07:20 PM
Next year will be my first in an IMCA stock car and I am wondering what kind of motor to build. The track that I race at is tacky most of the time with occasional dry slick conditions (1/4 mile). I intend on running 6.50 gears and would like to turn 6500 to 7000 rpm's. I have a standard bore 4 bolt 350 block to start with and want to either go with a 383 or 350. Any suggestions or experiences are welcome.

Thanks

istock59
Member
posted October 06, 2003 07:40 PM
For my money, in the IMCA Stockcar class, I'll always build a 383 over a 350. Nearly the same cost for parts.

Good luck turning 7000 with the 350cfm carb. Not many I know of getting that many R's...

[This message has been edited by istock59 (edited October 06, 2003).]

sledgehammer
Member
posted October 06, 2003 08:05 PM
What would be a resonable rpm to expect?


oluck96
Member
posted October 06, 2003 09:34 PM
Dont run stock rods over 6500 or you may get a suprise. the bigger cubes will give ya more torque at lower rpm'S


racer17j
Member
posted October 06, 2003 10:21 PM
383 is the best way to go for an i stock on a 1/4


istock59
Member
posted October 07, 2003 07:30 AM
Figure on 6500, maybe 6700, as your top RPM. That little carb runs out of steam by then, so gear accordingly.


Dixon
Member
posted October 07, 2003 02:06 PM
If you're willing to drop some cash on a carb, Willy's can make you one that will flow way over 350 cfm. They make a lot of the "390" cfm Busch carbs, and those motors are making over 720 HP.


KPLugnut
Member
posted October 07, 2003 02:34 PM
I beg to differ with that....ANYONE with tooling can make a carb flow a ton more air (and maybe with some skill, the proper amount of fuel, too), but the kind of carbs you're referring to (those that flow "a lot more air") do NOT pass inspection with IMCA tech guages.
Sure Willys makes great carbs (along with many other companies), but when push comes to shove, and the venturi, boosters, and baseplate HAVE to be ONLY a certain size, there is NO physical way to get more air thru that same sized hole given the same pressure drop or signal from the engine.

And with regards to all the "best" IMCA-legal 350cfm carbs, I'd challenge anyone to prove to me that any one of them flows significantly MORE air at the same pressure drop on the flowbench and still have it legal by the tech guages.

What I'm getting at, guys, is that one cannot compare a builder's successes with 4bbls or any builder's severely modified "outlaw" carbs with that of the IMCA legal 7448 Holley 2bbl. It's too closely monitored to be a heavily modifiable piece in terms of "advertised airflow".
Now if you're talking throttle response, good fuel curves, and midrange torque-producing capabilities, well, that's a horse of a different color...

Just my 2 cents....

KP


istock59
Member
posted October 07, 2003 02:48 PM
FWIW Dixon, a 390cfm 4 barrel does NOT equal a 350cfm 2 barrel + another 40 cfm. Two barrel carbs and 4 barrel carbs are measured at different pressure drops on the flow bench, thus they are not the same scales. If I remember right, a 390 cfm 4B is about 540 cfm on the 2B scale.



sledgehammer
Member
posted October 07, 2003 04:30 PM
So with that said about the carbs, does everybody agree that the 383 is the way to go and if so if the 5.7 rod or the 6 inch rod better to use?


Wallydog9g
Member
posted October 07, 2003 05:29 PM
go with whatever your pocketbook desires...
the 5.7 rods, rebuilt are around 100 bux and dont be afraid to push them up to 7000 but the imca carb wont work up there...
build the 383 with speed pro pistons, call comp cams and have them match you a cam to your track, run 1.6 stock rockers, get yourself a set of 441 heads and port them up, port match your intake, which should be a 4 bbl intake with the center cut out, slide your carb all the way back.
you'll be impressed at what this cheap combo can accomplish


sledgehammer
Member
posted October 07, 2003 05:52 PM
what about a set of 487x heads instead of the 441's?


racer17j
Member
posted October 07, 2003 06:44 PM
why would you want to run big chamber smogger heads on a motor with no compression limit get some aftermarket heads or double humps leave the 76 cc heads for us 9-1 guys


istock59
Member
posted October 08, 2003 08:27 AM
I agree. Forget the large chamber heads. Go for a set of humps. Or Vortecs. Or if the budget allows, Dart/WP/ProTopline.

As far as rods go, Scat 6.0" are pretty reasonably priced.

Dixon
Member
posted October 08, 2003 10:22 AM
Sorry guys, I wasn't trying to start a dispute, it's just what I've seen on a dyno. I appreciate the info and I wasn't aware of the pressure differences on the flowbench. I guess it makes sense that the vacuum signals would different for a 2bbl than a 4bbl on the same motor.
I don't know a whole lot about carbs, but I've personally seen those Willy's carbs outperform a lot of others on Busch motors. Just a suggestion.


sledgehammer
Member
posted October 08, 2003 11:33 AM
I can get a set of humps set up with springs, guide plates, studs, staneless valves, 2.02, 1.6, and ported for 300.00. Would this do until I have have the money to by aftermarket.


istock59
Member
posted October 08, 2003 12:41 PM
Sledge, I'd think those hump heads would do very nicely. With those heads I'd forget about the aftermarket heads, and spend my money elsewhere. Like good shocks and more new tires. Nothing hooks up that power like a new IMCA tire on the RR....

Dixon, no dispute with me. Just want to make sure we're not comparing apples and oranges. And when you compared 4B and 2Bs... Willys probably makes a good 350cfm carb too, but if it's truly IMCA legal, it don't flow any more air than others.




sledgehammer
Member
posted October 08, 2003 03:32 PM
59 - would there be that much difference between the humps and vortecs that I would want to spend a couple hundered more for a set of vortecs?


racer17j
Member
posted October 08, 2003 05:14 PM
not for that kind of money if you went with vortcs you would have to mess with the intake and stuff plus when your talk'n 5-600 bucks for a set of stock heads that right around ther price of some aftermarkets


66jj
Member
posted October 08, 2003 07:47 PM
willys sells a carb with oval butterflies etc it is the right size in one direction only. thus its very catchable in the tech area, but most people spending 1200 on a carb only dream of making the tech area.



istock59
Member
posted October 08, 2003 10:08 PM
sledge, you won't build a set of vortec to race ready condition for a "couple hundred more". With the special intake and all the extra machine work, I'd say you're looking at 400-500 more. And that buys FOUR Bilstein shocks.

Given the choice between humps (with Bilstein shocks) and vortecs (with cheapy shocks), I'd take the humps...

But if the budget allows, Vortecs are a great head... but don't expect them to be a cheap solution.

istock59
Member
posted October 08, 2003 10:11 PM
66jj, that makes for a strange carb! Is it oval all the way thru or just the bottom? I've seen a Holley carb that is 350cfm specs from the top, but it's 500 cfm on the baseplate. Don't know much about it, but IF (big if) they only tech from the top, it'd be legal....


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