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.

 

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.

 

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.

 

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

 

9,600. We took it about 700 above on the gear change.

 

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.

 

Here's a engine that makes a little over 2 hp/cuin that will cost a little over 100k$.

1005.8ci Godfather Big Block Engine - Popular Hot Rodding Magazine - Hot Rod

Check out the biggest big-block on the planet! It measures at 1,005.8ci and has an unreal 5.220-inch bore and 5.875-inch stroke! Pictures and further details can be found at Popular Hot Rodding Magazine.

www.hotrod.com

 

This 500” Pontiac made 1060@7800. Quite simply it took about $40 per cubic inch. Lol

 

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.

 

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.

 

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

 

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

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

 

Nice.

How much compression does that thing have?

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

 

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.

 

Not a max effort by any means but pump gas built ( 11.7to1 comp ) and drag week tested 1.82hp/ci 402ci 23* heads

1967 Chevelle - It's Big To Be Small - Hot Rod Magazine

"This engine was designed with Drag Week in mind from the get-go." - Jake Stelter - Hot Rod Magazine

www.hotrod.com

 

Not a max effort by any means but pump gas built ( 11.7to1 comp ) and drag week tested 1.82hp/ci 402ci 23* heads

1967 Chevelle - It's Big To Be Small - Hot Rod Magazine

"This engine was designed with Drag Week in mind from the get-go." - Jake Stelter - Hot Rod Magazine

www.hotrod.com

LOOKS FAMILIAR

 

When I started this thread I wasn't looking for a specific recipe to produce 2 hp/ci in a specific type of engine. I apologize of I was too vague. Rather, I am trying to determine the thought process that goes into planning a 2+ hp/ci build. There has got to be more to it than just finding the biggest, baddest head/cam/intake available and blindly hoping for the best. For example, ENGINE AIRFLOW by Harold Bettes (there are other good publications available as well) contains a lot of theory and formulas that can be used to determine how much air an engine must move to produce a given amount of power. Given a specific displacement, we can then determine how many rpm that engine must turn to move the targeted amount of air. Using these two numbers (airflow and rpm) we could select a head that will fit the bill (airflow and cross section). Am I over thinking this? I assume that putting as much compression ratio as the fuel will allow will help torque production, especially as rpm continues to climb.

Alternatively, post your proven 2+ hp/ci build details and let's reverse engineer the build(s) and look for trends.

 

When I started this thread I wasn't looking for a specific recipe to produce 2 hp/ci in a specific type of engine. I apologize of I was too vague. Rather, I am trying to determine the thought process that goes into planning a 2+ hp/ci build. There has got to be more to it than just finding the biggest, baddest head/cam/intake available and blindly hoping for the best. For example, ENGINE AIRFLOW by Harold Bettes (there are other good publications available as well) contains a lot of theory and formulas that can be used to determine how much air an engine must move to produce a given amount of power. Given a specific displacement, we can then determine how many rpm that engine must turn to move the targeted amount of air. Using these two numbers (airflow and rpm) we could select a head that will fit the bill (airflow and cross section). Am I over thinking this? I assume that putting as much compression ratio as the fuel will allow will help torque production, especially as rpm continues to climb.

Alternatively, post your proven 2+ hp/ci build details and let's reverse engineer the build(s) and look for trends.

Again, it’s far easier to produce 2 hp per cube for me, with a small, say, 300” engine then a large, 400” engine. That is using standard 23 degree heads. A head that flows 269 out of the box, and flows 289 after a superior valve job will support 600 hp on a 285 to a 300” sbc. Picking the right cam, and carburetor, and angle milling to get all the compression you can get, (which ain’t much with this combo) and getting a carburetor that actually works, is a piece of cake after you figure it out. Now, all these engines had good pistons, gas ported, and lightened, titanium valves, good valve train, and a good oil pan, with a great vac pump. Does this help?

On the larger engines, you need a lower valve angle head to make it easy. A 400” which I’ve never done, would be easy to get 800 hp out of with a good 15 degree head, but hard, I think, to do with a 23 degree head. Although others on this board have done it, and more.

 

454 BBC + .070”, Edelbrock head 2.190” valve 320cc port, 10.5-1 compression, 780 vacuum secondary Holley. Went 8.50’s at 2900 lbs. with a 3sp automatic. Never got on the pump with it, maybe 1.8-1.9 hp per ci ?

 

That's stout. Were the heads the rectangular RPM version? Also what RPM?

 

Roughed a couple examples into pipemax, never mind the VE , look at the cfm needed, rpm and compression. Pipemax has no care what engine is called. If you can provide the cyl with that cfm at that rpm you may be able to make that HP.

397.216 Cubic Inches @ 8000 RPM with 110.00 % Volumetric Efficiency PerCent

Required Intake Flow between 329.2 CFM and 348.8 CFM at 28 Inches
Required Exhaust Flow between 206.7 CFM and 239.4 CFM at 28 Inches

600 RPM/Sec Dyno Test Lowest Low Average Best
Peak HorsePower 744.2 774.8 790.1 805.4
Peak Torque Lbs-Ft 536.0 558.0 569.1 580.1

HorsePower per CID 1.874 1.951 1.989 2.028
Torque per Cubic Inch 1.349 1.405 1.433 1.460

BMEP in psi 203.5 211.9 216.0 220.2
Carb CFM at 1.5 in Hg. 1011 1125 1182 1239


397.216 Cubic Inches @ 8500 RPM with 105.00 % Volumetric Efficiency PerCent

Required Intake Flow between 329.2 CFM and 348.8 CFM at 28 Inches
Required Exhaust Flow between 206.7 CFM and 239.4 CFM at 28 Inches

600 RPM/Sec Dyno Test Lowest Low Average Best
Peak HorsePower 759.9 791.1 806.8 822.4
Peak Torque Lbs-Ft 514.5 535.7 546.2 556.8

HorsePower per CID 1.913 1.992 2.031 2.070
Torque per Cubic Inch 1.295 1.349 1.375 1.402

BMEP in psi 195.3 203.4 207.4 211.4
Carb CFM at 1.5 in Hg. 1026 1141 1199 1257

 

397.216 Cubic Inches @ 9500 RPM with 100.00 % Volumetric Efficiency PerCent

Required Intake Flow between 344.9 CFM and 365.6 CFM at 28 Inches
Required Exhaust Flow between 216.6 CFM and 250.8 CFM at 28 Inches

600 RPM/Sec Dyno Test Lowest Low Average Best
Peak HorsePower 774.1 805.9 821.8 837.7
Peak Torque Lbs-Ft 465.1 484.2 493.8 503.4

HorsePower per CID 1.949 2.029 2.069 2.109
Torque per Cubic Inch 1.171 1.219 1.243 1.267

BMEP in psi 176.6 183.8 187.5 191.1
Carb CFM at 1.5 in Hg. 1092 1215 1276 1338

 

Here's a nice pump gas build, not quite 2 per, but I think it would be fun.

 

Could be 780 vac carb per part number but somebody has had to open it beyond that or def choke point.

 

Cant’t figure out how to quote and rely on my new phone.

Yes, Edelbrock RPM head, Book 780 had stock sized throttle bores and venturies. HP peaked at 7500, Sniper Jr. intake, cam 270’s/280’s 111 sep in at 108, .900” lift

 

What RPM?

to quote tap the reply button under the comment, lower left.

 

Wasn’t scienced out, was the first build of a new combo.
Didn’t care for the Kaase comment, I’m just a guy in a garage doing the best I can with what I have. I will say I’ve been around some individuals over the years that I consider real sharp, and I learned from them.

 

Mr.Kaase isn’t known for doing anything 1/2 way. He has tons of resources and plenty of input from the custom cam guys at Comp Cams and elsewhere.

His BBC was the highest scoring BBC there, so he was doing something right. It would be interesting to see what he’d do differently if given another two weeks to work on it.

 

It's easier to make HP with RPM. With that in mind you'll want something with a small stroke and big bore. Take your choice.

 

The fundamentals...

Big bore = big intake valve = bigger intake flow potential.

There are a few ways to achieve 427”. It would be interesting to see the potential of the “best” practical over-squared combination vs the Square bore stroke combo.

 

I know who Jon is and what he does, one of those sharp individuals I was talking about.

Your snide comment was about him learning something from me, I doubt it.

 

Sarcasm doesn't always come across on the Net. ... There's at least 1 Phuckstick BBC fan who reads threads in here, who has the belief that Kaase "threw the competition" and didn't give it his best effort. The comment was for his consumption more so than anyone else. As I stated, Kaase doesn't do anything 1/2 way.

By the way ... I was on my Iphone and read your " Wasn't scienced out" comment as a comment about the Kaase build. My mistake.

Yes he knows his stuff, but the limitations on the specs of that competition apparently limited the BBC performance. If he didn't get more than 1.41 hp per cubic inch out of one ...Apparently it's much harder than some people think it would be.

And even the Experts can learn new things. Happens all the time.

lastly, I haven't had the opportunity to talk with Kaase for quite a few years, but met him years ago at the 2004 EMC event and then talked with him on the phone a couple times after. He is wealth of information and outside of his EMC builds while they are going on he will share just about anything he knows with you about making Your build better. Just an all around great guy from my experience.

 

The 10.5 CR/.550 lift limit/rpm limit, all played in the deal, I'm sure that the FE was a mix of stocker and super stock engine builds that the builder does all the time and for many many years,

 

They removed the cam lift rule, but the BB's still had an intake valve size limit to deal with. Take the total curtain area of the valve divided by the cly size. ........ and you'll see one big limitation for starters

 

Callies Magnum 8 cw crank, Carrillo 1.850” journal rods, .650” wide rod bearings @ .0017”-.0018” clearance. Gibtech guided box pistons @ .0065” clearance, Trend .787” DLC pins, Total Seal .65mm ring set w/ 5 lb. oil ring, .015”, .055”, .055, .012” ring gaps, Jesel belt, box oil pan, Schumann 45 psi oil pump, Maxima PS0, T&D 2.0/1.85 steel rockers, Trend 7/16 pushrods.

 

OK, now we're getting real. Sounds like a Super Stock. Nice build. Put an intake valve and some compression in that thing and it would be a beast.

 

What did you rev it ? Edit... Saw where you stated 7,500. Chassis dyno ?

That's a hell of a combo.

 

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.

A healthy Comp Engine these days makes between 2.80 to 2.95 HP per cubic inch. A few have made 3.00

 

General math I use, 2hp per cfm on pump gas, 2.4 for race gas. 4% more power per point of compression.

You can use math to calculate torque from displacement, CR and volumetric efficiency. High engine speed and higher vol eff is what separates the winners from the losers.

 

General math I use, 2hp per cfm on pump gas, 2.4 for race gas. 4% more power per point of compression.

I would think this is a general statement for a small CID engine.