440FE = 1hp per cube?

[NIsaacs]

I have read a lot about this, that it is "easy" to get this number. I have also read a lot, that it is "easy" to get 2hp per CFM of head intake flow. However they don't seem to both add up the same. Since my 428/440 FE is on the mild side or in the "easy" category, I should have 440 hp. Or using the 2 hp head flow numbers, my ED's advertised at 270....I have read that in real life this number might be closer to 250..... so using the term "easy" I should have 500hp.

So....using my seat of the pants meter and a chassis dyno for power numbers, I would guess my 440 is more in the 400hp range. I have posted a dyno sheet that I have of this engine, before the Edelbrock top end kit and was  when a stock '08 Toyota Tundra beat my numbers, Lol. Any thoughts?

Nick

[Ford428CJ]

Well, let's see......  the prep work along with the assembly is very very important. So zero deck, file fit rings and paying attention. Yes, you could get 1.5HP per CI. also if you have Ed heads. I would do some bowl work to them and have the seats / valves redone. You could find power in that.

You also need the right combo of parts to get what you need out of it..... So there is more to it then just slapping together an engine and expecting it to perform. Also we need more information than what your posting.

[jayb]

It's not that tough to get 1 horsepower per cube these days.  It is much more difficult to get 2 HP per intake cfm; you need a really good cam and intake combination to get there.  Also, these horsepower numbers refer to horsepower at the flywheel.  The chassis dyno gives you horsepower at the rear wheels, which is usually around 20% lower than horsepower at the flywheel due to drivetrain losses.  Chassis dynos are also notorious for underreporting power, especially if you have an automatic transmission. 

[plovett]

It's not that tough to get 1 horsepower per cube these days.  It is much more difficult to get 2 HP per intake cfm; you need a really good cam and intake combination to get there. 

x2.  The hp per cube goal is fairly easy.  The hp per cfm is not.  In addition to what Jay said, any engine that gets 2 hp per cfm is likely to be a high compression deal.  Possible on high octane pump gas?  Yeah, possible, but not at all easy in my opinion.  Getting 2 hp per cfm requires everything to be optimized and sacrifices to be made, such as driveability.   We are of course talking about naturally aspirated engines. 

JMO,

paulie

[plovett]

What's your full engine combo?

paulie

[fe66comet]

That is about what I am shooting for with my 445, 1.5 per cube sounds like a reasonable number.

[plovett]

That is about what I am shooting for with my 445, 1.5 per cube sounds like a reasonable number.

1.5 x 445 = 667.5 hp.   I'd like to hear the plan for that.  Not impossible, but that won't be a simple or easy deal.

JMO,

paulie

[My427stang]

I have read a lot about this, that it is "easy" to get this number. I have also read a lot, that it is "easy" to get 2hp per CFM of head intake flow. However they don't seem to both add up the same. Since my 428/440 FE is on the mild side or in the "easy" category, I should have 440 hp. Or using the 2 hp head flow numbers, my ED's advertised at 270....I have read that in real life this number might be closer to 250..... so using the term "easy" I should have 500hp.

So....using my seat of the pants meter and a chassis dyno for power numbers, I would guess my 440 is more in the 400hp range. I have posted a dyno sheet that I have of this engine, before the Edelbrock top end kit and was  when a stock '08 Toyota Tundra beat my numbers, Lol. Any thoughts?

Nick

2x head flow is a WAG if everything is optimized, parts choices AND tuning, some can get to 2.2-ish x head flow if real good.  So it's not that you "should" have 500 hp, it's only that your heads "should be able to support" 500 if all else is right

[Joe-JDC]

Everyone OVERLOOKS the most obvious issue with cfm/hp comparison which is the average airflow at average lift of camshaft.  Yes max airflow is important, but what is the average cfm?  Take that number and multiply it by 2 and you would be closer to the actual hp of a given cubic inch engine.  A head that can flow 270cfm at .700" such as a tweaked RPM, will not flow that cfm using a .525" lift camshaft.  Now the flow of that head at .250" lift will probably only be 165cfm, and at .300"lift maybe 190cfm, and at .400" 215cfm, etc.  up to .700".  If you take flow rates at each .050" lift on a flow bench, then average that number for average flow through the port, then you can realize the net probably horsepower of a regular street engine.  It will not be the max flow possible giving the max horsepower possible.  Potential is different from actual, and very few engines reach maximum potential for a given head flow.
Another issue that the cubic inches will draw on a head differently due to different cubic inch sizes, and that is another study within itself.  That same RPM head that flows 270cfm at .700" lift and 28" hg will continue to flow more air at 30"hg, or even 40"hg, reaching maybe 350cfm due to the increased "draw" on the port.  As long as the port doesn't go turbulent and reduce flow, it will continue to work at higher cubic inches, and at higher rpms, even though the camshaft only had .525" lift.  Joe-JDC.

[NIsaacs]

It's not that tough to get 1 horsepower per cube these days.  It is much more difficult to get 2 HP per intake cfm; you need a really good cam and intake combination to get there. 

x2.  The hp per cube goal is fairly easy.  The hp per cfm is not.  In addition to what Jay said, any engine that gets 2 hp per cfm is likely to be a high compression deal.  Possible on high octane pump gas?  Yeah, possible, but not at all easy in my opinion.  Getting 2 hp per cfm requires everything to be optimized and sacrifices to be made, such as driveability.   We are of course talking about naturally aspirated engines. 

JMO,

paulie

Okay, that makes more sense, I could not understand the numbers I was coming up with. 1 hp per cube is not hard but 2hp per cfm is a work of art.... I go to a lot of chassis dynos on dyno days here and it always seems the gassers are on the low side and the diesels are high. I have never seen an engine dyno so I am not sure what goes on there. I have asked the operator what the loss differential is, but he says there are a lot of variables, so it's hard to compute. Using 20%, my 243hp would only be about 292hp at the flywheel then, kinda sick, huh? This next spring I will put my pickup on the dyno again and get a comparison with the new top end. The old combo had stock D2 heads, performer intake, 280h comp cam, and 750 edelbrock carb. I don't have the exact compression ratio, just guessing about 10.5.

Nick
 

[plovett]

I don't think the "max cfm x2 = hp" deal was ever meant to be more than a rule of thumb for maximum hp potential.  Air Flow Research (AFR) cylinder heads has posted the following "formula" and that may be the origin of it.

cfm x .25714 x no. of cylinders = hp

Take that .25714 times 8 cylinders and you come up with 2.057 x cfm = hp.  While this is in formula form it is no way an actual usable formula.  I mean that to say it does not calculate actual horsepower.  Just an estimation of potential hp in a maxed out(race?) type engine.

Joe has a good point about taking the average cfm the port sees throughout the lift curve.  That's more realistic as more data is used, but even that would be a huge oversimplification as there are many other factors affecting power.  Duration at each lift point, compression, charge temperatures, combustion efficiency, exhaust efficiency, overlap, etc, etc.  and on and on......   That is why I say it (2xcfm=hp) is just a rule of thumb for max hp given a max flow rate, and nothing more.

JMO,

paulie

[My427stang]

I don't think the "max cfm x2 = hp" deal was ever meant to be more than a rule of thumb for maximum hp potential.  Air Flow Research (AFR) cylinder heads has posted the following "formula" and that may be the origin of it.

cfm x .25714 x no. of cylinders = hp

Take that .25714 times 8 cylinders and you come up with 2.057 x cfm = hp.  While this is in formula form it is no way an actual usable formula.  I mean that to say it does not calculate actual horsepower.  Just an estimation of potential hp in a maxed out(race?) type engine.

Joe has a good point about taking the average cfm the port sees throughout the lift curve.  That's more realistic as more data is used, but even that would be a huge oversimplification as there are many other factors affecting power.  Duration at each lift point, compression, charge temperatures, combustion efficiency, exhaust efficiency, overlap, etc, etc.  and on and on......   That is why I say it (2xcfm=hp) is just a rule of thumb for max hp given a max flow rate, and nothing more.

JMO,

paulie

Of course its a rule of thumb, what else could it be?

Blairs "twins" for example

High 260's on the CJ head - 517 hp (1.988x intake flow, but probably could have went higher if not pump gas)
High 290s on the BBM head - 572 hp (1.93x intake flow, same as above)

However I am truly missing the average calculation you guys like.

From the Edelbrock site

    88    153    195    233    265    270 = Intake flow for a stock Edelbrock head

Average = 200.......I hope we can make more than 200 hp!   If 2x average flow is what you want to use for a wag to adjust, fine I could see that, but I still say it's still  low balling at 400, an Edelbrock head can support more than that out of the box

Read my post again, 2x head flow is good if everything is optimized for peak hp, that mean parts match each other and match desired RPM peak.  You can't say "If you have a .525 lift cam"  of course it isn't going to make the numbers, it's not built to take advantage of the head.

I personally build for rpm range, more than the hero numbers, but 2x peak intake flow is relatively conservative estimate for what a head can support and a decent wedge can do 2.2 with a good guy behind it.  Some good heads will lean higher, crappy heads lean lower, but it's a very old and proven WAG

Like you said though, and what I tried to tell him was it has zero do do with what someone's motor WILL make. 

[plovett]

Using 20%, my 243hp would only be about 292hp at the flywheel then, kinda sick, huh? This next spring I will put my pickup on the dyno again and get a comparison with the new top end. The old combo had stock D2 heads, performer intake, 280h comp cam, and 750 edelbrock carb. I don't have the exact compression ratio, just guessing about 10.5.

Nick
 
[/quote]

Chassis dyno's have a lot of variation between them.  Plus there are more variables involved so it's harder to calclulate your true hp.  Transmssion type (and converter) if auto), tire pressure, accessories on the engine, etc. affect the results.  They're just not as reliable a measuring device as an engine dyno.  And even engine dynos can have a fair amount of variation between them.  If you have a C6 auto in your truck for instance, your hp loss will likely be quite a bit more than 20%.  I'd guess closer to 30%.  A big fixed blade fan with no fan clutch will also eat up a lot of power between the engine and wheels.

As for you combination, what exhaust do you have?  Headers?  Pipe diameter?  Mufflers?

With the Edelbrock heads, a 280H cam, good exhaust, 10+:1 compression, a 750-850 cfm Holley,  a good intake manifold, and good tuning, I think you could top 400 hp at the flywheel.

With the D2 heads, a Performer intake (not RPM), and an Edelbrock carb, it will be a lot less.    What combination was on there when you got the 243 hp? 

JMO,

paulie

[plovett]

I don't think the "max cfm x2 = hp" deal was ever meant to be more than a rule of thumb for maximum hp potential.  Air Flow Research (AFR) cylinder heads has posted the following "formula" and that may be the origin of it.

cfm x .25714 x no. of cylinders = hp

Take that .25714 times 8 cylinders and you come up with 2.057 x cfm = hp.  While this is in formula form it is no way an actual usable formula.  I mean that to say it does not calculate actual horsepower.  Just an estimation of potential hp in a maxed out(race?) type engine.

Joe has a good point about taking the average cfm the port sees throughout the lift curve.  That's more realistic as more data is used, but even that would be a huge oversimplification as there are many other factors affecting power.  Duration at each lift point, compression, charge temperatures, combustion efficiency, exhaust efficiency, overlap, etc, etc.  and on and on......   That is why I say it (2xcfm=hp) is just a rule of thumb for max hp given a max flow rate, and nothing more.

JMO,

paulie

Of course its a rule of thumb, what else could it be?

Blairs "twins" for example

High 260's on the CJ head - 517 hp (1.988x intake flow, but probably could have went higher if not pump gas)
High 290s on the BBM head - 572 hp (1.93x intake flow, same as above)

However I am truly missing the average calculation you guys like.

From the Edelbrock site

    88    153    195    233    265    270 = Intake flow for a stock Edelbrock head

Average = 200.......I hope we can make more than 200 hp!   If 2x average flow is what you want to use for a wag to adjust, fine I could see that, but I still say it's still  low balling at 400, an Edelbrock head can support more than that out of the box

Read my post again, 2x head flow is good if everything is optimized for peak hp, that mean parts match each other and match desired RPM peak.  You can't say "If you have a .525 lift cam"  of course it isn't going to make the numbers, it's not built to take advantage of the head.

I personally build for rpm range, more than the hero numbers, but 2x peak intake flow is relatively conservative estimate for what a head can support and a decent wedge can do 2.2 with a good guy behind it.  Some good heads will lean higher, crappy heads lean lower, but it's a very old and proven WAG

Like you said though, and what I tried to tell him was it has zero do do with what someone's motor WILL make.

I agree with all of that.  I was (and am) just trying to drive home the same point you are.  I read your post correctly the first time and I still agree with it.  I don't use average flow numbers to calculate anything.  It would have to be tweaked with more info like duration at each lift point, just for starters.  I was trying to point out that even THAT extra information won't change the fact that we're still just dealing with a rule of thumb that estimates something given some ideal situation. 

I'm not knocking the old 2 x max cfm deal.  But you can see why the original poster saw the discrepancy between that and his results.

JMO,

paulie

[My427stang]

OK, we agree, sorry, you are still as cool as I thought you were before