2 barrel circle track engine build recommendations

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Dirt_Racer
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2 barrel circle track engine build recommendations

Post by Dirt_Racer »

Hello all,
Just curious as to what would be a build for the following rules. 2500 lb sport mod running 1/2mile slicker than usual track

Max cranking compression 175 lbs hot
390 ci limit
Gauge legal 4412 (alcohol permitted)
Flat tappet cam hyd or solid
Roller tip rockers only
350 block only
Any iron head and aluminum intake
Flat top or dish pistons
Any suggestions welcome
Thanks
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Re: 2 barrel circle track engine build recommendations

Post by Walter R. Malik »

Dirt_Racer wrote: Thu Sep 09, 2021 10:13 pm Hello all,
Just curious as to what would be a build for the following rules. 2500 lb sport mod running 1/2mile slicker than usual track

Max cranking compression 175 lbs hot
390 ci limit
Gauge legal 4412 (alcohol permitted)
Flat tappet cam hyd or solid
Roller tip rockers only
350 block only
Any iron head and aluminum intake
Flat top or dish pistons
Any suggestions welcome
Thanks
Don't use alcohol with a restricted engine & Use a high velocity, single plane intake manifold.
Use a smaller engine with more gear, (if the driver can handle it).
Get flat-top pistons and use whatever chamber size & solid cam profile combination which will give you 174 lbs. of compression, (Hot).
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Re: 2 barrel circle track engine build recommendations

Post by econo racer »

I have a vic jr 2bbl intake excellent clean condition fixing to go on craigs list. $150
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Re: 2 barrel circle track engine build recommendations

Post by barnym17 »

I am thinking alcohol might be viable because it brings its own oxygen to the party.
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Re: 2 barrel circle track engine build recommendations

Post by CamKing »

Bore: 4.030-4.060"
Stroke: 3.48"
Rod: 6"-6.125"
Flat Top pistons
Heads: Bowtie, Vortec, Vortec L31, Vortec Bowtie
Cam: Mechanical Flat Tappet, 248/252 @.050", .359"/.359" Lobe Lift, 108 LSA
Rockers: 1.6-1.5
Manifold: Vic Jr, Vic Jr 2bbl
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Re: 2 barrel circle track engine build recommendations

Post by KnightEngines »

CamKing wrote: Fri Sep 10, 2021 10:07 am Bore: 4.030-4.060"
Stroke: 3.48"
Rod: 6"-6.125"
Flat Top pistons
Heads: Bowtie, Vortec, Vortec L31, Vortec Bowtie
Cam: Mechanical Flat Tappet, 248/252 @.050", .359"/.359" Lobe Lift, 108 LSA
Rockers: 1.6-1.5
Manifold: Vic Jr, Vic Jr 2bbl
Yeah, that's a front runner.
I'd run it on meth, it's not port csa limited, only carb limited, so meth with show dividends in tq with no loss of hp.
I'd go 4 barrel Vic jnr with a tall tapered 2 barrel spacer to bump up plenum volume. With a carb limited engine more plenum volume reduces pulsing through the carb, evening out the draw & boosting mass flow.
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Re: 2 barrel circle track engine build recommendations

Post by Dirt_Racer »

I know one engine is a 4.030 bore 3.75 stroke dart 49 cc 215 runner small dish, calculated compression was 13.2 weiand team G intake KB gauge legal carb, solid lifter don’t know the cam specs. It made 450hp 450 Tq
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Re: 2 barrel circle track engine build recommendations

Post by CamKing »

With the same cam, when you go to a larger stroke engine, you will need you to reduce the mechanical compression ratio to keep under the 175 cranking compression.
You don't want to give up compression ratio.

You also want the flatter torque curve of the 3.48" stroke x 6" rod for a "slicker than usual track".

The 500cfm carb, and compression ratio are what will limit the max HP.
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Re: 2 barrel circle track engine build recommendations

Post by PRH »

Ported heads and intake are legal?
Somewhat handy with a die grinder.
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Re: 2 barrel circle track engine build recommendations

Post by Dirt_Racer »

Sorry I forgot to mention no ported heads
OEM steel block only. Block must be Chevrolet 350, Ford 302 or 351W, or Mopar 340 or 360. Maximum 390 cubic inch.
175 lbs. max compression(Hot). No Tolerance.
Pistons must be dished or flat top. No domed or gas ported pistons.
Hydraulic or flat tappet cams only. No roller cams. No 4-7 swaps.
SFI Harmonic balancer required.
Steel Heads Only.
Must have stock diameter valve spring.
No beehive or barrel springs or stud girdles.
No porting or polishing.
No canted valve/Cleveland style heads.
No spacers between head and intake.
Any 4 barrel open plenum intake.
No porting or gasket matching.
Max 1 ¼” between intake and carburetor.
One 2 barrel Holley 4412 Carburetor.
No modifications with the exception of removal of choke plate.
Straight open hole spacer allowed.(NO Super sucker type spacers allowed.)
Jets, power valve and accelerator pump may be changed.
Must use stock metering blocks.
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Re: 2 barrel circle track engine build recommendations

Post by Walter R. Malik »

Dirt_Racer wrote: Fri Sep 10, 2021 5:46 pm Sorry I forgot to mention no ported heads
OEM steel block only. Block must be Chevrolet 350, Ford 302 or 351W, or Mopar 340 or 360. Maximum 390 cubic inch.
175 lbs. max compression(Hot). No Tolerance.
Pistons must be dished or flat top. No domed or gas ported pistons.
Hydraulic or flat tappet cams only. No roller cams. No 4-7 swaps.
SFI Harmonic balancer required.
Steel Heads Only.
Must have stock diameter valve spring.
No beehive or barrel springs or stud girdles.
No porting or polishing.
No canted valve/Cleveland style heads.
No spacers between head and intake.
Any 4 barrel open plenum intake.
No porting or gasket matching.
Max 1 ¼” between intake and carburetor.
One 2 barrel Holley 4412 Carburetor.
No modifications with the exception of removal of choke plate.
Straight open hole spacer allowed.(NO Super sucker type spacers allowed.)
Jets, power valve and accelerator pump may be changed.
Must use stock metering blocks.
I know you want a Chevrolet combination so, I would have a 4.020" bore x 3.400" stroke with "offset ground" crank and 2" journal 6" rod.

If it was mine, Getting weight off the front end of the car is probably more effective that any small power increase so, it would get a small block Ford 345.
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Re: 2 barrel circle track engine build recommendations

Post by CamKing »

Walter R. Malik wrote: Sat Sep 11, 2021 6:40 pm
I know you want a Chevrolet combination so, I would have a 4.020" bore x 3.400" stroke with "offset ground" crank and 2" journal 6" rod.

If it was mine, Getting weight off the front end of the car is probably more effective that any small power increase so, it would get a small block Ford 345.
Most circle track 2bbl classes won't allow you to go with a 302 block, and a larger then 3" stroke. We did that a lot in the 90's, with the 351N heads, and all the Chevy guys got tired of getting their butts kicked.

If he can go with a Short deck 345 Ford, with 351N heads, there's nothing faster.
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Re: 2 barrel circle track engine build recommendations

Post by brandonu »

Dirt_Racer wrote: Fri Sep 10, 2021 5:46 pm Sorry I forgot to mention no ported heads
OEM steel block only. Block must be Chevrolet 350, Ford 302 or 351W, or Mopar 340 or 360. Maximum 390 cubic inch.
175 lbs. max compression(Hot). No Tolerance.
Pistons must be dished or flat top. No domed or gas ported pistons.
Hydraulic or flat tappet cams only. No roller cams. No 4-7 swaps.
SFI Harmonic balancer required.
Steel Heads Only.
Must have stock diameter valve spring.
No beehive or barrel springs or stud girdles.
No porting or polishing.
No canted valve/Cleveland style heads.
No spacers between head and intake.
Any 4 barrel open plenum intake.
No porting or gasket matching.
Max 1 ¼” between intake and carburetor.
One 2 barrel Holley 4412 Carburetor.
No modifications with the exception of removal of choke plate.
Straight open hole spacer allowed.(NO Super sucker type spacers allowed.)
Jets, power valve and accelerator pump may be changed.
Must use stock metering blocks.
This is the same set of rules I'm working around for a guy here in Ohio. I'm just in the parts gathering phase right now. with the current supply chain, I hope everything is off the dyno by spring. He will be in the 385CI area, with a 2.00 pin and light rotator.
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Re: 2 barrel circle track engine build recommendations

Post by Walter R. Malik »

CamKing wrote: Sun Sep 12, 2021 10:49 am
Walter R. Malik wrote: Sat Sep 11, 2021 6:40 pm
I know you want a Chevrolet combination so, I would have a 4.020" bore x 3.400" stroke with "offset ground" crank and 2" journal 6" rod.

If it was mine, Getting weight off the front end of the car is probably more effective that any small power increase so, it would get a small block Ford 345.
Most circle track 2bbl classes won't allow you to go with a 302 block, and a larger then 3" stroke. We did that a lot in the 90's, with the 351N heads, and all the Chevy guys got tired of getting their butts kicked.

If he can go with a Short deck 345 Ford, with 351N heads, there's nothing faster.
The rules around here allow the 345 but, the newest rules say valve angles must remain within 1 degree of production so, we were forced to use Windsor Jr. heads ... it still is very fast and the Chevy boys complain all the time.
They now allowed them the "Bow Tie" Vortec's and the power is about the same ... but, they just cannot match the lighter front end weight.
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Re: 2 barrel circle track engine build recommendations

Post by bob460 »

Why do Ford's always get screwed over #-o ..........these chevy boy's need to become Men and stop complaining [-X .....LOL
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