Pump gas 421 SBC HP
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Pump gas 421 SBC HP
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
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
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Re: Pump gas 421 SBC HP
With that small amount of valve lift I don't see it making more then 470 hp .
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
Re: Pump gas 421 SBC HP
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.mt-engines wrote: ↑Tue Jun 01, 2021 9:04 am 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
Re: Pump gas 421 SBC HP
Advertized engine horsepower determined by internet poll.
Is there a SAE "correction factor" for that?
Is there a SAE "correction factor" for that?
Re: Pump gas 421 SBC HP
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.
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Re: Pump gas 421 SBC HP
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.
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.
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Re: Pump gas 421 SBC HP
Static compression should be in the mid 9s, depending on deck clearance.
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- mt-engines
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Re: Pump gas 421 SBC HP
1st pull
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Re: Pump gas 421 SBC HP
Hey MT,
What carb were you using on the first pull,interesting how little fuel used initially.
steve c
"Pretty don't make power"
"Pretty don't make power"
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Re: Pump gas 421 SBC HP
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.
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.
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
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Re: Pump gas 421 SBC HP
It’s a well needed starting point with the compression this motor is built with, yes!
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
Re: Pump gas 421 SBC HP
That should be a great little street engine. Throw some factory looking valve covers on and tell everyone it is a cammed 307.
Paul
Paul
"It's a fine line between clever and stupid." David St. Hubbins