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Old 11-17-2010, 05:56 PM
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Circle track engine options, need some insight!!

*long post ahead....beware*

Ok, IMCA stock rules changed this year, and I'm wondering about a few things. There are two different options we can go after, and I'm stuck on what I need to do.

Here are the two options...

(A) 350 cfm CARBURETOR ENGINE: No cubic inch or compression limit. Flat tappet cam/lifters and stud-mounted rocker arms only. No shaft or pedestal rocker arms. No titanium engine components. No stud girdles. No mushroom lifters, lifter diameter and configuration must match OEM passenger block. Full roller rocker arms allowed.

(B) 500 cfm CARBURETOR ENGINE: Maximum 361 cubic inches (GM); 363 (Ford); 370 (Chrysler). GM approved block numbers are: 3892657, 3914660, 3914678, 3932388, 3932386, 3956618, 3970000, 3970006, 3970010, 3970014, 10066033, 10066036, 10243880, 14010207, 14010209, 14010287, 14016376, 14016379, 10054727, 14088528, 14088548, 14088552, 14093638, 14101148. Stroke must match block. No 400 or larger cubic inch parts allowed. Violation of cubic inch limit must be verified by removal of head and will result in disqualification, loss of all IMCA points for the season, $1,000 fine and a 30-day suspension. No compression limit. Flat top or dished pistons only, no gas-ported pistons. OEM or OEM replacement steel crankshaft only cannot be lightened. No aerowing, bullnose, knife edge, undercut or drilling of second or third rod throws. OEM or OEM replacement steel rods only GM 5.7 or 6-inch rod allowed. Cap screw allowed. Conventional flat tappet cam and lifters only, cannot alter lifter bores. Mandatory one inch inspection hole in all pans no obstructions to crank and rods. CYLINDER HEADS: Steel only. Must be unaltered approved OEM and minimum 76 cc combustion chamber. Only GM OEM approved head numbers are: 14079267, 3986336, 3986339, 3986339X, 3986388, 3932441, 376445, 3928454, 3932454, 3876487, 3973487, 3973487X, 3973493, 3951598, 468642, 330862, 333882, 3998920, 3998991, 3998993, 3998997, 3970126. Maximum size valves on these heads are 2.02 inch intake and 1.60 inch exhaust. May use Engine Quest (EQ) Stock Replacement (SR) cylinder head, part number CH350I, head must remain as produced, seat angles and valve sizes can not be changed: three angle valve job only (absolutely no casting removal in valve pocket of EQ head, for any reason). No porting, polishing or unapproved alterations allowed to ANY cylinder head. Guide plates, screw-in shouldered studs (0.375-inch max) and polylocks allowed. No stud girdles. Full roller rocker arms allowed. GM 1.250 inch maximum O.D. valve springs, no beehive valve springs allowed. Unaltered OEM type harmonic balancer only.

The first HAS to use a 350 cfm 2 barrel, and the second can use a 500 cfm 2 barrel.

What option would make more power/torque? Any help or questions apreciated!

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Old 11-17-2010, 06:43 PM
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Hmmmmmm... Will a 454 bbc with a 350cfm carb work?
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Old 11-17-2010, 06:51 PM
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too much weight, need to keep it light, so that means a small block is the only choice.
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Old 11-17-2010, 07:06 PM
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Or an aluminum big block. Same weight as a small block usually. Look up the zl1 engine, it's a 427 big block but weighs less than a 327.
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Old 11-17-2010, 07:34 PM
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have to use cast iron....
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Old 11-17-2010, 09:05 PM
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More cubic inches will in most cases make more torque,we have spec sprints 360 ci in northern cal that require a 4412 carb,steel block,steel heads flat tappet cam, horse power of some of these is in the low 500 range. Is this dirt,what kind of track ,full body cars. Need more info.
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Old 11-17-2010, 09:13 PM
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what about using a 6.0L aluminum LS block? that's getting you close to BBC territory w/o the weight

hrm.. you'd have to find a way to run flat tappet lifters tho.../
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Old 11-17-2010, 09:18 PM
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What are the fast guys using?
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Old 11-17-2010, 09:35 PM
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its a full bodied dirt car, IMCA stock car, 2900 pounds, 8 inch spec tire.

I won track points this year, and im running a 355, scat crank/rods, KB flat tops, double hump heads with a .516/.524 cam, roller rockers, weiand intake, 350 cfm B&B 2 barrel, stepped headers with about 48 inch tubes...dynos around 420-430.

everyone else either runs a 355, or a 383/377, with a couple 412's and 434's. The 434's are rumored to make over 500 hp, but they just burn the tires off all the way around the track, yes....burn, seen them smoke tires on dirt before.

Once again, cant use aluminum.

Just trying to get a jump on this since these rules changed last week. Wondering if the bigger carb would be worth sacrificing a bit of compression, and a little bit on the head.
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Old 11-17-2010, 09:43 PM
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Quote:
Originally Posted by BigRoy1978
its a full bodied dirt car, IMCA stock car, 2900 pounds, 8 inch spec tire.

I won track points this year, and im running a 355, scat crank/rods, KB flat tops, double hump heads with a .516/.524 cam, roller rockers, weiand intake, 350 cfm B&B 2 barrel, stepped headers with about 48 inch tubes...dynos around 420-430.

everyone else either runs a 355, or a 383/377, with a couple 412's and 434's. The 434's are rumored to make over 500 hp, but they just burn the tires off all the way around the track, yes....burn, seen them smoke tires on dirt before.

Once again, cant use aluminum.

Just trying to get a jump on this since these rules changed last week. Wondering if the bigger carb would be worth sacrificing a bit of compression, and a little bit on the head.

IMO i would go with the 500cfm carb, I race at TOYOTA SPEEDWAY in southern california, and they recently changed the Late Model rules saying instead of the 2bbl engine that can be rebuilt by specified engine builders(+20-40 more hp after a rebuild) you can run a completely sealed motor straight from GM and run a 4bbl on it. not sure on the cfm =/ ANYWAYS the guys that have changed to the 4bbl motors are consistantly 1-2 tenths quicker than anyone.
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