Pump gas 421 SBC HP

[mt-engines]

Built a SBC for a customer and we are ready for the dyno. What kind of power should this combo make? And what should it run?

4.155 bore x 3.875 stroke 6" rod
AFR 190 heads 76 cc chamber
Flat top pistons with 7cc reliefs
Brodix HV1000 intake
270/275 cam .460" lift 108 lobe sep
We have a few different carbs to choose from, 850 and 950 hp holley.
1 3/4 to 3" headers

Engine is going into a 1970 Chevelle wagon, guy spends every weekend at different car shows and plans to put a lot of miles on this. He also wants to drive it to the racetrack to see what it will run. He wants a fun sleeper

Stock chassis Th400, 3.73 gears

[Elroy]

Hydraulic flat tappet?

[mag2555]

With that small amount of valve lift I don't see it making more then 470 hp .

[1980RS]

Built a SBC for a customer and we are ready for the dyno. What kind of power should this combo make? And what should it run?

4.155 bore x 3.875 stroke 6" rod
AFR 190 heads 76 cc chamber
Flat top pistons with 7cc reliefs
Brodix HV1000 intake
270/275 cam .460" lift 108 lobe sep
We have a few different carbs to choose from, 850 and 950 hp holley.
1 3/4 to 3" headers

Engine is going into a 1970 Chevelle wagon, guy spends every weekend at different car shows and plans to put a lot of miles on this. He also wants to drive it to the racetrack to see what it will run. He wants a fun sleeper

Stock chassis Th400, 3.73 gears

If the engine were mine and going in that wagon I would use an RPM Air Gap and a good 750 dp street carb since he will only race in once in a while a single plane will hurt performance. The engine should make a lot of torque.

[F-BIRD'88]

Advertized engine horsepower determined by internet poll.
Is there a SAE "correction factor" for that?

[rfoll]

Horsepower is just a number, and with a cam that small it wouldn't be very high. It should make decent torque. Somewhere in the 12s shouldn't be difficult if it hooks up. The combo is screaming for a good 3310, preferably one with the down leg boosters.

[rustbucket79]

Tiny cam for the displacement and cylinder heads, overall the combo appears to be focused towards a mild build suitable for a cross country trip.

I wouldn’t expect big power numbers, perhaps 1.1 to 1.2 hp/ci. Torque should be somewhere between very good and amazing, depending on F-Bird’s correction factor.

[Moparboy440]

What is the Compression ratio? What is the cam ICL and duration at 0.050"?

[rfoll]

Static compression should be in the mid 9s, depending on deck clearance.

[mt-engines]

1st pull

[steve cowan]

1st pull

Hey MT,
What carb were you using on the first pull,interesting how little fuel used initially.

[mag2555]

Do you have the uncorrected numbers?

I was assuming the heads are stock and flowing about 240 cfm@ .460” lift, that 507 hp is much closer to 250 cfm it would seem.

[Elroy]

Do you have the uncorrected numbers?

I was assuming the heads are stock and flowing about 240 cfm@ .460” lift, that 507 hp is much closer to 250 cfm it would seem.

Its that simple huh?

[mag2555]

It’s a well needed starting point with the compression this motor is built with, yes!

[FC-Pilot]

That should be a great little street engine. Throw some factory looking valve covers on and tell everyone it is a cammed 307.

Paul