Porting sbc heads?

[6.50camaro]

No claim rule. The car only has so much weight that can be removed, it’s already gutted quite a bit. For this type of car it’s at its ideal percentages to get proper bite and forward traction.

It has been quite a few years since I played with a circle track car but, is not that what weight jack bolts are for? I had a four coilover car and could shift weight for side to side, front to back, corner to corner with adjusting preload on the springs or by raising or lowering where the shock mounted to the chassis. Even with a hobby stock car where jack bolts are not allowed you can use spring buckets and put solid shims under the spring to move weight.

[Tom68]

No claim rule. The car only has so much weight that can be removed, it’s already gutted quite a bit. For this type of car it’s at its ideal percentages to get proper bite and forward traction.

It has been quite a few years since I played with a circle track car but, is not that what weight jack bolts are for? I had a four coilover car and could shift weight for side to side, front to back, corner to corner with adjusting preload on the springs or by raising or lowering where the shock mounted to the chassis. Even with a hobby stock car where jack bolts are not allowed you can use spring buckets and put solid shims under the spring to move weight.

Not front to back and side to side, you can only play unequal table legs (corner weights) with weight jackers.

[Walter R. Malik]

No claim rule. The car only has so much weight that can be removed, it’s already gutted quite a bit. For this type of car it’s at its ideal percentages to get proper bite and forward traction.

Shocks, springs, stagger and wheel offset will be the difference between being in the back or the front.

[88bluestar]

All those exist on this car already. Already has been scaled, and set ride heights. Have numerous offsets for fine tuning on track conditions.

[SoCalDave]

Youtube channel Horsepower Monster compared a set of mildly ported 882s to Dart Iron Eagles. The 882s did ok, and the work on them seems to be stuff a newbie can handle except for the valve job.

https://youtu.be/hv3ZkqZiMjI

[steve cowan]

Youtube channel Horsepower Monster compared a set of mildly ported 882s to Dart Iron Eagles. The 882s did ok, and the work on them seems to be stuff a newbie can handle except for the valve job.

https://youtu.be/hv3ZkqZiMjI

That's the problem with these so called budget dirt track rules,spending the time money on junk heads for little returns.
The as cast out of the box iron eagle was 50hp up over the reworked junk head.

[novafornow]

Agree, i have spent quite a bit of time figuring out how to make stamped rockers live. Could have just bolted on roller rockers and been done!

[Tom68]

I'm surprised there's no love for the 2.02 valve, since this engine will be 4412 restricted it will have high manifold vac at high valve lift, assuming a 2.02 flows more at low lift than a 1.94 (it bloody better) that's one way of getting some fill from a week port flow situation, I'd have thought.

Charles Servedio makes mention of running big valves in small port 307 heads with good results in his latest video.

[mag2555]

This is how you assist stamped steel rockers to live.
These are factory baffles for a Pontiac, but you could make up the same for a SBC or SBF.

Once again it’s just time and little materials.

[mag2555]

Since this string was started on the subject of porting, why has there been no talk about the important factor of how adding air flow and the velocity changes that such brings about effects the motors power band, and in turn cam factors?

[88bluestar]

Have to update this a bit. We are allowed vortecs.

Now I must ask this question, purely with the difference being either a 487/993(hump head as well) type head vs vortecs,
as comparison first in stock form and then modified specifically for my rules, what would the power difference be for hp/tq between the different heads?

vacuum rule 14hg@900 rpm
cranking compression of 150 psi
4412 gauge legal Holley carb with 1" spacer to a 2701 Edelbrock or vortec equivalent 2716.
3,000 lbs car minimum weight
kk704 american racer tire
stock automatic or manual trans with stock size and weight clutch or converter.
pump gas(e-85 can be used)

[barnym17]

with 2bbl likley 20 to 30 hp if both are massaged about the same if for no other reason than the chamber is just better thats with flow being equal which it likely won't be.

[Erland Cox]

I have built some budget 355:s with the L98 aluminum heads.
Stock they flowed 180 CFM in and I got them up to 240CFM at .500" using 1,94-1,50 valves.
I don't remember the exhaust flow.
With a Victor JR and a 750 dp and a Crane hydraulic FT cam 228-.480-107 I got 445 hp with 1-5/8 headers.
With a Megathumper 235-249-.520-107 i got 502 hp and 665 NM:s.
Wonderful power curves without any dips.
The engines are for my road race Camaros.

Erland

[88bluestar]

I have built some budget 355:s with the L98 aluminum heads.
Stock they flowed 180 CFM in and I got them up to 240CFM at .500" using 1,94-1,50 valves.
I don't remember the exhaust flow.
With a Victor JR and a 750 dp and a Crane hydraulic FT cam 228-.480-107 I got 445 hp with 1-5/8 headers.
With a Megathumper 235-249-.520-107 i got 502 hp and 665 NM:s.
Wonderful power curves without any dips.
The engines are for my road race Camaros.

Erland

We have to use cast iron heads.

[vortecpro]

Ok, I must preface this question by saying this is a budget class so I’m trying to use what I have but make as much power as I can. Rules are:
Engine must be vacuum-pumped and measure no less than 14 inches of vacuum at 900 rpm. Must have a 3/16-inch port in the intake manifold to hook up vacuum gauge. 4412 Holley gauge legal allowed.

6,200 rev limiting device and must weigh a minimum 3,000 lbs., including driver after race. Must run factory cylinder heads (no aftermarket race heads allowed). Must run flat top or dish pistons. Must have a cranking compression no higher than 150. Must run factory-style stamped steel rocker arms.

What I have is an 350(010) block, 4340 used 3.750 stroke crank(20 main/30 rod main, and 991 open chamber heads.
3/8 mile dirt track. Using pump gas but eventually will be running E-85 fuel.

What porting would I need to do and other mods to make the 991 work as efficiently as possible within these rules?

I would use a 441 casting.