SBC head?

[88bluestar]

So rules dictate no porting, and have to use open chamber SBC heads per rules. I gather 441, 487, and 993 are the ideal castings.
2 bbl rochester on a 2701 Edelbrock intake, 1/2" spacer per rules. Exhaust manifold(likely either the 1998 5.7 truck manifolds or Camaro LT1 manifold), rams or center type not allowed. Rules allow 1.94 or 2.02 int, 1.50 or 1.60 ex valves.

Since no porting is allowed, what is the ideal valve job, and/or tricks for this situation?

[rebelyell]

local rules similar; require production GM heads but chamber no smaller than 70cc ... thus allowing milling heads to 70cc. No porting allowed. Flattops, no domes. our cam rule max FT valve lift .480"
I prefer 487 as they have plenty meat allowing milling to 70cc while still sealing well and not hitting water. Suggest valve face angles larger than typical 45* ... e.g. 50* or 52*

[88bluestar]

Going to stay with 1.94/1.50 more than likely because I'll be racing against 602 crates and really don't want to lose any torque.

[mag2555]

You want to run valve and seat angles that provide the highest level of average flow within the lift range your stuck to run in, and angle steeper then a 45 degree seat do not provide that!
Since your limited to that .480” lift and stock heads then by half of that .480” lift( .240” lift ) you want to have the biggest flow numbers taking place that you can get.

In league with this take note that especially with a stock head that the flow that you have up to about .325” lift is totally determined by the valve and seat angles ( the size and shape of the runner from the flange to the crown of the short turn have little to do with the flow numbers) , and to me angles steeper then 45 degree have no place in a limited motor like your building, not to mention that using steep angle will greatly limit how many times you can freshen up the valve job if that matters to you?

Also on a side note , never trade off flow for compression as long as you have the minimum needed for your Cam pick.

[dannobee]

Use a 75 degree cutter to open up the throat. Too much and a tech might bitch though. The "best" jobs replicate the factory chatter marks in the bowl. If the 75 is shiny and pretty, you're more likely to get thrown out if they're inspected. Seat angles are important, and unless you have a flow bench and can try different angles, the usual 60,45,30 worked. 0.060" 45 degree seat for durability. Cut the valve at 45 and back cut at 30 and 22. Dykem the valve and see where the seat touches, then back cut the 30 to within 0.030 of that line. Then cut your 22 degree angle.

50 degree seats *might* work a little better, but won't last as long if you're a set-it-and-forget-it kinda guy. There is more maintenance in the higher seat angles.

On the exhaust, keep the ski jump on the valve to help with reversion if you're restricted to exhaust manifolds. Same tricks on the intake apply (radius under the 45 might make more power but likely isn't legal). Carefully inspect the factory chatter marks and practice on a scrap head until you can replicate them. 0.080" 45 degree seat for durability.

Start with the 1.94/1.50 and as they wear, step up to 2.02/1.60 after a few valve jobs.

[mag2555]

I would step right up to the 2.02” intake valve even if you just go with a basic 30/45/60 valve job .

It does not sound like much, but you will pick a 5% larger curtain area which will mean 5% more flow in the lift range where your valve is spending the most open time.

Your port velocity will also pick up and the motor will pull harder out of the turns and your peak hp will come in at a slightly lower rpm which should all be a plus for this type of motor.

[steve cowan]

Going to stay with 1.94/1.50 more than likely because I'll be racing against 602 crates and really don't want to lose any torque.

What rpm do these engines operate in?
I also like the steeper than 45 seat.
It does kill low flow including flow at overlap which will lower combustion contamination
Steeper seats fatten up mid lift as well.
Are you allowed to modify throat area ?
I like good cfm/ in2 at the valve/throat area hence the smaller valve BUT the bigger intake valve/throat could make more torque but chamber shrouding could be an issue.
Like everything you have to try different set ups
Eg - valves, seat angles, top cuts,throat size and shapes etc or just set and forget and have fun
And also if you valve float any valve job it will wear out regardless of seat angle.
Just took my 383 sbc apart that has 50deg seats, they look good after several months and dozens of passes.
Blued,back blued,bounce test etc
Only came apart as steel shim head gasket leaking water.

[Elroy]

You want to run valve and seat angles that provide the highest level of average flow within the lift range your stuck to run in, and angle steeper then a 45 degree seat do not provide that!
Since your limited to that .480” lift and stock heads then by half of that .480” lift( .240” lift ) you want to have the biggest flow numbers taking place that you can get.

In league with this take note that especially with a stock head that the flow that you have up to about .325” lift is totally determined by the valve and seat angles ( the size and shape of the runner from the flange to the crown of the short turn have little to do with the flow numbers) , and to me angles steeper then 45 degree have no place in a limited motor like your building, not to mention that using steep angle will greatly limit how many times you can freshen up the valve job if that matters to you?

Also on a side note , never trade off flow for compression as long as you have the minimum needed for your Cam pick.

How many lift limited, restricted engines have you built using your theories and how well did they do? So have the highest average flow always, with no regard given to piston position in relation to opening or closing points, or vacuum level present in the intake?

That sounds pretty easy. Im surprised everyone hasn’t figured that out by now.

[88bluestar]

My rules are 360 max cid. 9.9:1 compression ratio. E-85 fuel.
There is no rpm max. No max lift on the cam. hyd or solid cam.
3/8 dirt track, American racer tire. roughly 3000 lbs car, and powerglide trans.

[steve cowan]

My rules are 360 max cid. 9.9:1 compression ratio. E-85 fuel.
There is no rpm max. No max lift on the cam. hyd or solid cam.
3/8 dirt track, American racer tire. roughly 3000 lbs car, and powerglide trans.

Are you able to talk to anyone at your track who runs that class?
I would want to know rpm parameters to look at gearing, then you can look at cam events etc
Cylinder heads are the cork being unported.

[88bluestar]

Would a 3 angle or a 5 angle job be better for this type of engine?

Class is new to the track next year, so not really anyone to bounce ideas off of there.
$500 claim on heads, and intake. $50 claim on rochester carb.

Cam, lifters etc recommended already through Mike Jones, specifically for competing against 602 crates.

Running 5.7 rods
I gather the LT-1 camaro exhaust manifolds are the closest thing to running headers from a flow standpoint. It doesn't say anything in regards porting the exhaust in the rules so maybe a gray area there.

Just wondering if a 2.02 is worth it at all since there is no porting allowed, and I believe a bowl cut can not have any blending done.

RPM range is roughly 3,000-6800. There is no gearing limit, no rpm limit. carb and heads being the biggest restrictions.

Short block will have the lightest rods and pistons my budget will allow, and plan to run low tension thinner rings to cut down on friction.
simple sbc stock oil pump, and whatever other friction saving things I can mustard.

[dannobee]

When you first posted, I figured it had to be a claimer class. Do the bowl work with the cutters as I suggested. The angles that I suggested will work fine. Keep the stock 1.94's for now until you have a few races in the class and can better gauge what you'll need. The 2.02's will likely need to be unshrouded on the chamber side, so that'll be something you'll have check on the flow bench (and check legality)

Don't forget the back cuts on the intake valves. It really makes a difference.

[88bluestar]

Class rules are sealed 602 crates(6200 max rpm) or open 360/9.5:1 max, no max rpm. Both have to use a 2 bbl Rochester carb with only slight booster mod and nothing else. USRA HOBBY STOCK RULES. Mike Jones had recommended a cam in-line with what is needed to accelerate on restarts to compete with the 602. I prefer the open option but the heads and intake have a $500 claim so I don’t want to spend to crazy. No porting is allowed and I gather any valve size change to 2.02 the rules allow only the bowl cut and absolutely no blending.

[dynoflo]

does the 602 have to run a rochester. Solid or hydraulics? neck down valves ok piston out of hole a bit? I have probably built 50 of these type but need to know more. SMI has the best carbs . The big rpm is out of the question. Build tq not hp. The 602 will still make 400 tq with rochester. Stay away from 993.

[88bluestar]

does the 602 have to run a rochester. Solid or hydraulics? neck down valves ok piston out of hole a bit? I have probably built 50 of these type but need to know more. SMI has the best carbs . The big rpm is out of the question. Build tq not hp. The 602 will still make 400 tq with rochester. Stay away from 993.

Have to run rochester 2bbl on both.
Hydraulic or solid is allowed.
What is the issue with the 993 heads?


GM five and seven-tenths (5.7) inch or six (6) inch rods are permitted. Must be stock appearing I-beam
non-polished rod. Aluminum or light weight is not allowed. Cap screw rods are permitted
13.6.8 A minimum one (1) inch plug above the oil level in the side of the oil pan is recommended. If not utilizing
a plug, oil pan will have to be removed at time of inspection.
13.6.9 Only stock, unaltered two-barrel low-rise cast iron intake manifolds or Approved aluminum intakes are
permitted. Approved aluminum intakes are GM – Edelbrock (#2101 or #2701) or Weiand (#7547 or
#7547-1); Ford – Edelbrock (#2121 or #2181 or #2665) or Weiand (#7515 or #8023 or #7516);
Chrysler – Edelbrock (#2176) or Weiand (#7545 or #8022). Porting, polishing or port machining is not
allowed. Bowtie, aftermarket, SVO and W2, marine, VORTEC or other special production intake manifolds
are not allowed. Spacer between carburetor and intake may be no more than one-half (0.5) inch total
with one-tenth (0.1) inch maximum thick gaskets and may not be throttle bore adjustable. External
cooler lines from back of intake to front of intake is not allowed.
13.6.10 Cast iron stock production or aftermarket steel stock replacement heads are permitted. Porting and/or
polishing is not allowed. GM cars must utilize 76cc heads (approved head numbers are 336, 339, 388,
441, 454, 487, 624, 813, 882, 991 and 993). Aftermarket head numbers are: GM – EQ Part #CC167ES2
or #CH350I; Dart Part #10024267 or #10024360; World Products Part #043600 or #042670; Ford
– World Products Part #53030; Chrysler – EQ Part #CH138B; RHS/Indy Part #20300 or #20301. Heads
may be flat milled to reach the 9.5:1 compression rule. Valve size no larger than 2.02 intake and 1.60
exhaust. VORTEC heads are not allowed. Beehive valve springs are not allowed.
13.6.11 Screw-in studs, guide plates and poly-locks are permitted.
13.6.12 Roller cams and lifters are not allowed. Roller Rocker arms are not allowed (stock-type stamped steel
rocker arms or cast steel rocker arms only). Roller tip rocker arms are permitted. Chryslers may utilize
OEM steel shaft rockers but may not exceed one hundred twenty (120) pounds of valve spring seat
pressure and must maintain OEM valve spring dimensions. Under valve cover pressurized valve train
oiling systems are not allowed.
13.6.13 Mushroom lifters are not allowed (stock diameter only). Must match make and model.
13.6.14 Stud girdles are not allowed.