401 sbc ready for the Dyno

[HQM383]

Progression Ignition distributor,

Not to derail but this caught my attention. Is this the programmable model that's been in discussion here?

As for HP and TQ?
I like this guess...
"560hp @ 6100rpm and 530ft/lb @ 5000rpm".

Good luck.

Yes it is!

[HQM383]

I don't have a guess on power and torque, but I have a set of those original Twisted Wedge 13/23 degree heads that I ran a cartridge roll through back 25 years ago. We left the big ledge in the bowl which I'm assuming the fellow who ported your heads did also.

They were on a factory block Lunati 408 kit engine, with dish pistons to clear the intake valve, and with a stock Edelbrock 2925 and a stock 750 double pumper carb (4779-9).

The cam was a Lunati 40146 solid flat tappet ground on a 102 LCA and installed on a 98 degree ICL. The rockers were and still are the matching Summit Racing 1.5/1.5 rockers intake/exhaust. These heads have a pushrod tube, and the 1.6 Harland Sharps I wanted to try on the intakes moved the pushrod cup toward the rocker stud too far and ran into that tube. So they weren't tried of course.

The rest of it was a Performance Distributor's HEI, 1 3/4" Hooker Super Comps with no collector extensions and no exhaust, TCI Streetfighter Turbo 350, a Streetfighter 10" 3800 converter, 4.56 gears, and 26x10 MT slicks in a 3200 lb race weight 72 Nova street machine.

It ran 6.90's at 98+ mph in the eighth with 36 degrees total timing and stock jetting when it was 100 degrees and one million percent humidity back in 2001 at Jackson Dragway in Jackson, Tennessee.

Anyhow, I said all that to say this: you should run 10.90's quite easily with your setup.

Thanks for that. You got some good results from cartridge roll clean up.

Those pushrod tubes create limitations as you say. I have the Comp Cams 1.6:1 ratio set-back intake rocker that helps align pushrod in the head, however the limitation with the +.600" lift is 5/16" pushrods. I have .110" wall 5/16" that should do the job.

The porting on these heads have the ledge removed. Something the porter didn't do is widen the bowl area more than stock or take much material from the long side radius. I have one factory std one to compare. The older pair I have been using for the past 25 years were ported around the same time you did yours. Comparing with an untouched port the roof had been raised and bowl enlarged. Flowed on the same bench as the new heads they would both have similar 'area under the curve' with the older pair being more peaky with flow numbers but no doubt newer pair more velocity.

[HQM383]

Ill guess 580HP@6200 / 530Tq@5100
Really interested to see the results.
All the best.

Thanks. I’d be very happy with that. It would be over achieving from what the original goal was.

[HQM383]

Carbs to be tested:

Race Demon 1050cfm (silver sleeve) 1.590” venturi x 1.75” throttle bore with 16 hole BLP annular boosters
Mighty Demon 850cfm 1.56” venturi x 1.75” throttle bore with 12 hole BLP annulars
Race Demon 975cfm (gold sleeve) 1.500” venturi x 1.75” throttle bore with Braswell downleg boosters
Race Demon 825cfm 1.425” venturi x 1.75” throttle bore with BLP machined downleg boosters

Probably not a big stretch to predict the 1050cfm will make best peak hp, but will it make best peak tq?

It’s not so much the cfm that will be tested but trialing some emulsion and air bleed changes with each cfm for cause and effect.

[treyrags]

The 1.59/16-hole will make the best peak and average above 4000

[1980RS]

Carbs to be tested:

Race Demon 1050cfm (silver sleeve) 1.590” venturi x 1.75” throttle bore with 16 hole BLP annular boosters
Mighty Demon 850cfm 1.56” venturi x 1.75” throttle bore with 12 hole BLP annulars
Race Demon 975cfm (gold sleeve) 1.500” venturi x 1.75” throttle bore with Braswell downleg boosters
Race Demon 825cfm 1.425” venturi x 1.75” throttle bore with BLP machined downleg boosters

Probably not a big stretch to predict the 1050cfm will make best peak hp, but will it make best peak tq?

It’s not so much the cfm that will be tested but trialing some emulsion and air bleed changes with each cfm for cause and effect.

I thought that too with my Race 1000cfm race Demons but the one with the down leg boosters was the better of the 2 at the track I found out one day. Will be interesting to see what those heads make for power.

[408 Nova]

I don't have a guess on power and torque, but I have a set of those original Twisted Wedge 13/23 degree heads that I ran a cartridge roll through back 25 years ago. We left the big ledge in the bowl which I'm assuming the fellow who ported your heads did also.

They were on a factory block Lunati 408 kit engine, with dish pistons to clear the intake valve, and with a stock Edelbrock 2925 and a stock 750 double pumper carb (4779-9).

The cam was a Lunati 40146 solid flat tappet ground on a 102 LCA and installed on a 98 degree ICL. The rockers were and still are the matching Summit Racing 1.5/1.5 rockers intake/exhaust. These heads have a pushrod tube, and the 1.6 Harland Sharps I wanted to try on the intakes moved the pushrod cup toward the rocker stud too far and ran into that tube. So they weren't tried of course.

The rest of it was a Performance Distributor's HEI, 1 3/4" Hooker Super Comps with no collector extensions and no exhaust, TCI Streetfighter Turbo 350, a Streetfighter 10" 3800 converter, 4.56 gears, and 26x10 MT slicks in a 3200 lb race weight 72 Nova street machine.

It ran 6.90's at 98+ mph in the eighth with 36 degrees total timing and stock jetting when it was 100 degrees and one million percent humidity back in 2001 at Jackson Dragway in Jackson, Tennessee.

Anyhow, I said all that to say this: you should run 10.90's quite easily with your setup.

Thanks for that. You got some good results from cartridge roll clean up.

Those pushrod tubes create limitations as you say. I have the Comp Cams 1.6:1 ratio set-back intake rocker that helps align pushrod in the head, however the limitation with the +.600" lift is 5/16" pushrods. I have .110" wall 5/16" that should do the job.

The porting on these heads have the ledge removed. Something the porter didn't do is widen the bowl area more than stock or take much material from the long side radius. I have one factory std one to compare. The older pair I have been using for the past 25 years were ported around the same time you did yours. Comparing with an untouched port the roof had been raised and bowl enlarged. Flowed on the same bench as the new heads they would both have similar 'area under the curve' with the older pair being more peaky with flow numbers but no doubt newer pair more velocity.

Very very nice setup

[Tom68]

Probably not a big stretch to predict the 1050cfm will make best peak hp, but will it make best peak tq?

Well peak torque is the peak of efficiency per cycle, a single cylinder and IR manifold needs as much carb there as it does at peak horsepower, manifolded 8 cylinders, maybe not ?

[steve cowan]

I think 1.30 - 1.35 ft lbs per cube is achievable and I agree peak torque around 5000rpm.
I also think 560hp,the problem will be torque will fall of fast above peak,as mentioned small valve and MCSA and average CSA for the cubes.
With the hp equation you need a certain amount of torque to make peak hp.

[steve cowan]

A couple of easy equations for MCSA @ 6000rpm using 0.55 - 0.61 mach.
4.125 x 4.125 x 3.75 x 6000rpm
X 0.00353 = 1351/613 (0.55 mach) = 2.20" MCSA
1351/690 (0.61mach)
= 1.95" MCSA.
Peak hp rpm will determine what speed the port can handle at the pinch.
If the peak hp number is lower than 6000rpm say 5800rpm it says its going into sonic choke earlier due to the smaller csa.

[steve cowan]

I always test my cylinder head at the highest depression possible on my bench with and without intake manifold.
The reason why is I calculate piston demand at max piston speed at around 76 deg ATDC .
For a 401 cubes at 6000rpm it is asking for 294 cfm.
Alot of intake manifolds need runner work and this shows when flowing with the head.
Not uncommon to lose 20 - 30 cfm and every runner will be different due to length, csa,shape.
I am not saying to make them all the same just saying it's another thing to look at.

[steve cowan]

I know on those twisted wedge heads the pinch is tight with minimal pushrod clearance so without extensive amount of work not alot you can do.
Something to consider.
A 2.02 " valve @ 90% throat has a area of 2.50" with stem removed.
If you have 2.0" at the pinch there is a lot variation in csa through the port and airspeed will change fast/ slow/ fast etc.
In a 23 degree head it is difficult to get round this unless you raise port alot and get better line of sight and more consistent CSA.

[steve cowan]

Just a reminder that I am not been critical towards Jamie (OP)
or his combination, just throwing my thoughts out there for guys to consider for there own engine combos and application.
All my own 383 stuff is small cam / induction tract deals as well that only turn 7500rpm.
I calculated the curtain area
Of a 2.02" valve 45 deg seat at 0.050" width at 0.640" lift to be
3.919" just something else to think about.

[steve cowan]

Carbs to be tested:

Race Demon 1050cfm (silver sleeve) 1.590” venturi x 1.75” throttle bore with 16 hole BLP annular boosters
Mighty Demon 850cfm 1.56” venturi x 1.75” throttle bore with 12 hole BLP annulars
Race Demon 975cfm (gold sleeve) 1.500” venturi x 1.75” throttle bore with Braswell downleg boosters
Race Demon 825cfm 1.425” venturi x 1.75” throttle bore with BLP machined downleg boosters

Probably not a big stretch to predict the 1050cfm will make best peak hp, but will it make best peak tq?

It’s not so much the cfm that will be tested but trialing some emulsion and air bleed changes with each cfm for cause and effect.

Between my 950hp carb and 1050 QFT with 16 hole annular boosters was 11 hp at peak using the drop base on the bigger carb.
Just for reference for yourself.
I run the 255/60/15 MT radial with 4.1 rear gear with 8" converter.
My car cross finish line at 7300 rpm.
126.5 mph or so .
As I have mentioned to you before, I think your engine will run well,you drive your car alot and it spends a fair amount of time below 6000rpm.
I am looking forward to your results with carb testing, I am interested in how much timing your combination needs.
I think carb spacers can be a eye opener when testing.
Once you have found peak hp don't be shy to get them to turn engine 500rpm higher and test because sometimes there can be a dip at peak and come back up .
I run a projected nose NGK 7 spark plug in my stuff.

[HQM383]

A couple of easy equations for MCSA @ 6000rpm using 0.55 - 0.61 mach.
4.125 x 4.125 x 3.75 x 6000rpm
X 0.00353 = 1351/613 (0.55 mach) = 2.20" MCSA
1351/690 (0.61mach)
= 1.95" MCSA.
Peak hp rpm will determine what speed the port can handle at the pinch.
If the peak hp number is lower than 6000rpm say 5800rpm it says its going into sonic choke earlier due to the smaller csa.

I think 1.30 - 1.35 ft lbs per cube is achievable and I agree peak torque around 5000rpm.
I also think 560hp,the problem will be torque will fall of fast above peak,as mentioned small valve and MCSA and average CSA for the cubes.
With the hp equation you need a certain amount of torque to make peak hp.

I know on those twisted wedge heads the pinch is tight with minimal pushrod clearance so without extensive amount of work not alot you can do.
Something to consider.
A 2.02 " valve @ 90% throat has a area of 2.50" with stem removed.
If you have 2.0" at the pinch there is a lot variation in csa through the port and airspeed will change fast/ slow/ fast etc.
In a 23 degree head it is difficult to get round this unless you raise port alot and get better line of sight and more consistent CSA.

I spent a lot of time choosing an exhaust lobe to help increase area under the torque curve between 4.5k and 6.5k. It was Billy Godbold in his book and other media and UDHarold's historic post on ST refering to the effects of exhaust opening that had me exploring and giving more consideration to exhaust lobe (net valve motion) effects on overall engine power production and characteristics. With your math and insights on the induction limitations I am very interested to see if a carefully tailored exhaust - starting with lobe and rocker ratio can help in extending the output beyond the mathematical expectation of the induction system. If not then it solidifies the math used going forward.