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Discussion Starter #1 (Edited)
What does it take to make 2+ horsepower per cubic inch? What does a healthy comp engine make these days? My train of thought is this...

- A healthy race engine makes about 1.5 foot pounds of torque per cubic inch. Base on that it is just a matter of turning the required RPM to reach your 2 hp/ci target.

Am I over simplifying it? I feel like stepping up from 1.6-1.8 is a pretty big leap in the components that need to be used to make it live.
 

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What does it take to make 2+ horsepower per cubic inch? What does a healthy comp engine make these days? My train of thought is this...

- A healthy race engine makes about 1.5 foot pounds of torque per cubic inch. Base on that it is just a matter of turning the required RPM to reach your 2 hp/ci target.

Am I over simplifying it? I feel like stepping up from 1.6-1.8 is a pretty big leap in the components that need to be used to make it live.
It all depends. The smaller the engine, the easier it is. The tighter you turn it, the easier it is. Comp and Pro Stock are approaching 3 hp per cube.
But, for example, a 350 Chevy with 23 degree heads takes some bucks to build 700 hp. A 350 with 15 degree heads, piece of cake. But, you still need decent parts. Especially in the valve train. Someone else will explain it all better.
 

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Srs, I think I might be partially responsible for this thread. As I've been saying that the 1.6Hp per inch motors are NOT really that difficult. We have done a few in the last couple of years. AND most of my reasoning behind that is our stuff is usually with GM OEM dual plane intakes. NOw not sure where the dyno sheets are, but we did a 468 that went over 700hp, a 475 that went 785Hp. Both of these engien are also in your 1.5Tq per inch formula. BOTH those engines had BBc GM OEM head casting and dual plane intakes on pump gas. What if we switched to race gas and compression, aftermarket heads and single plane intake, ALONG with the cam timing events that could be used?

I do agree with Randy above that the smaller engine are easier to get to 2Hp/inch. Like he posted with a 700+Hp 350 isn't hard at all. Just some nice parts, work and some $$$. BUT a 1264Hp 632 BBc is more work to get to that 2Hp/inch. It can be done, just not quite as easy as the smaller stuff.

There are many many guys on here with 2+Hp/inch. Depending one engine platform also plays into the difficulties. Much harder with a AMC or Buick, then a LS or BBc due to aftermarket parts availability. It isn't really hard for a SBc to do 2Hp/inch. Also it isn't really hard for a small to midsize BBc to do to do it. Just takes some work, nice parts and some $$$. Don't get me wrong, it's not like a stock rebuild with a cam and heads.
 

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Srs, I think I might be partially responsible for this thread. As I've been saying that the 1.6Hp per inch motors are NOT really that difficult. We have done a few in the last couple of years. AND most of my reasoning behind that is our stuff is usually with GM OEM dual plane intakes. NOw not sure where the dyno sheets are, but we did a 468 that went over 700hp, a 475 that went 785Hp. Both of these engien are also in your 1.5Tq per inch formula. BOTH those engines had BBc GM OEM head casting and dual plane intakes on pump gas. What if we switched to race gas and compression, aftermarket heads and single plane intake, ALONG with the cam timing events that could be used?

I do agree with Randy above that the smaller engine are easier to get to 2Hp/inch. Like he posted with a 700+Hp 350 isn't hard at all. Just some nice parts, work and some $$$. BUT a 1264Hp 632 BBc is more work to get to that 2Hp/inch. It can be done, just not quite as easy as the smaller stuff.

There are many many guys on here with 2+Hp/inch. Depending one engine platform also plays into the difficulties. Much harder with a AMC or Buick, then a LS or BBc due to aftermarket parts availability. It isn't really hard for a SBc to do 2Hp/inch. Also it isn't really hard for a small to midsize BBc to do to do it. Just takes some work, nice parts and some $$$. Don't get me wrong, it's not like a stock rebuild with a cam and heads.
Yes, I agree. The smaller engine, the simpler for me to get 2 hp per cube. For example, I did 592 with a 289 sbc with unported Brodix spec heads, and a stock block, single 4. Don’t ask me to get 860 out of a 427 bbc using like parts.
 

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Randy what was the RPM of that 289 sbc if you don't mind sharing.
 

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I don't know what the poster was exactly looking for, but speaking from a garage hack perspective; IF you have a good cylinder head guy, you can get to 2hp/ci without being a rocket scientist. But there is a big jump from 1.8 to 2.0 per ci. It takes careful consideration of all pieces used. I also agree that it is easier with smaller engines. It may be as simple as parasitic loss is big on larger engines.
 

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To the OP:

What cubic inch range are you dealing with ?

Do you have an RPM target ?

Are you limited on your choice of intake/carbs ?

Obviously ( as you already know) air flow, rpm, compression and ring seal are your friend when shooting for that goal.

Someday I'd like to do so with a 429-440" BBF.
 

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Mike Finnegan ( RoadKill) built this for his boat some years back:



 

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Mike Finnegan ( RoadKill) built this for his boat some years back:



Same engine, 564 ci (took some bore out of it) all freshened up.


 

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Nice.

How much compression does that thing have?

Great numbers for not having to spin the shit out of it.
 

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Nice.

How much compression does that thing have?

Great numbers for not having to spin the shit out of it.
Thanks. I think we ended up with 14.5:1. It's Mike Edmondson's engine (TN Youngblood). Jet boat engine. He bought it from Finnegan. Already ran .2 faster than Finnegan ran with no real engine or hardware tuning. Went to 8200 on the dyno, happy as a clam, hangs on real well. Right where it wants to be with that intake.
 

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Discussion Starter #15
To the OP:

What cubic inch range are you dealing with ?

Do you have an RPM target ?

Are you limited on your choice of intake/carbs ?

Obviously ( as you already know) air flow, rpm, compression and ring seal are your friend when shooting for that goal.

Someday I'd like to do so with a 429-440" BBF.
Let's assume 400 - 450 cubic inch range.

Before 8,500 rpm

Single carb, cast (no sheet metal)... just for fun.
 

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Let's assume 400 - 450 cubic inch range.

Before 8,500 rpm

Single carb, cast (no sheet metal)... just for fun.
Chevy Ford Mopar Olds Buick???

FYI there "was" a member here, did SBc (forget the size, but IIRC it was under 410) pumpgas deal, Ebay Nascar heads and intake. Designed for street style only driving and not chasing Hp #'s. Made 780Hp. Jeremy at Extreme built the motor and with shipping from Ny to Detroit, was less than 10K. This was back around 10 yrs ago.

NOT 2Hp/inch, but pretty close at 1.9Hp/inch (if it was 410, might have been more, might have been less) and pumpgas street motor.

Maybe Chris U will chime in? He might recall or know more about it.
 

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Thanks. I think we ended up with 14.5:1. It's Mike Edmondson's engine (TN Youngblood). Jet boat engine. He bought it from Finnegan. Already ran .2 faster than Finnegan ran with no real engine or hardware tuning. Went to 8200 on the dyno, happy as a clam, hangs on real well. Right where it wants to be with that intake.
Nice, figured it was close enough in Hp on different dyno's to be awash. And will smaller inch and running faster, seen that before a couple times.

Congrads
 

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Let's assume 400 - 450 cubic inch range.

Before 8,500 rpm

Single carb, cast (no sheet metal)... just for fun.
Platform ......?

Ford, Chevy, LS, Mopar, ....
 
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