4.3 Stroke Discussion

BOSS 429 wrote:I have a 4,300 makes 840 ,but its done by about 6800 we have ran it with all kinds of diff intakes,carbs,etc all the way to 8200.port plates,different headers etc.from 27 deg of timing to 45 total

its just done

another great test is that it was in a pull truck for 3 years, now its going in a drag car,and we will test it some more

Thanks thats more of what I was looking for. I didnt want to seem like a smart ass, but My 4.3 revs fine is a very relative answer, fine compared to a diesel, sure. Ive had a 427 windsor w/ solid roller and victor heads, but with that stroke and relatively small bore, it was a great torque producer and street motor, not so good N/A as a drag motor. I have been looking around and one thing Ive found is that the 4.3 stroke motors seem to all make power in a small window. For example most that produce good power(800 plus) may have good peak power and fall off quickly, so if it makes 850 at 6700 it will only make over 800 from say 6450 to 6900 which to me is a small window. The same goes for torque if a Motor peaks at 6100 but is done making torque by 6500 its probly ok for a dyno, but in real world testing Im not sure I would be happy. My 460 went 5.6s-5.7s @123 with a flat tappet cam and iron D0VES( granted it had a single plate on it)at 3120#. I would have a hard time telling a customer to spend the money on a combo like that with solid roller, 70+ cubes aluminum SCJs, and then have my stock junk be faster or even close to it, regardless of spray or not. So when all of you say your 4.3 revs fine and makes good power, what do you mean 6500, 7000, 8000, more? Dont get me wrong Im not trying to be a D@#K, Im just trying to understand what we are talking about here. But to say stroke doesnt effect rpm and acceleration rate is absurd by any stretch.

Here's some Dyno Numbers from a SAM Built 532 BBF 4.44 bore and 4.3 stroke 775 Horsepower at 6,500 and 6,600 rpm and 673 lb.ft. of torque at 5,300 and 5,400 rpm.10.9:1 Compression Ratio,Comp Solid Roller cam .787-.791 lift 273 int.-280 exh. duration at .050,P51 Cylinder Heads ported 420 cfm Int. at .700 lift and 265 cfm exh at .700 lift,Victor Intake and 1,150 cfm Dominator.
Don't know if this helps you much but figured i would post it since they were using a 4.3" stroke crank.

Later Mark.

Barney wrote:

BOSS 429 wrote:I have a 4,300 makes 840 ,but its done by about 6800 we have ran it with all kinds of diff intakes,carbs,etc all the way to 8200.port plates,different headers etc.from 27 deg of timing to 45 total

its just done

another great test is that it was in a pull truck for 3 years, now its going in a drag car,and we will test it some more

Thanks thats more of what I was looking for. I didnt want to seem like a smart ass, but My 4.3 revs fine is a very relative answer, fine compared to a diesel, sure. Ive had a 427 windsor w/ solid roller and victor heads, but with that stroke and relatively small bore, it was a great torque producer and street motor, not so good N/A as a drag motor. I have been looking around and one thing Ive found is that the 4.3 stroke motors seem to all make power in a small window. For example most that produce good power(800 plus) may have good peak power and fall off quickly, so if it makes 850 at 6700 it will only make over 800 from say 6450 to 6900 which to me is a small window. The same goes for torque if a Motor peaks at 6100 but is done making torque by 6500 its probly ok for a dyno, but in real world testing Im not sure I would be happy. My 460 went 5.6s-5.7s @123 with a flat tappet cam and iron D0VES( granted it had a single plate on it)at 3120#. I would have a hard time telling a customer to spend the money on a combo like that with solid roller, 70+ cubes aluminum SCJs, and then have my stock junk be faster or even close to it, regardless of spray or not. So when all of you say your 4.3 revs fine and makes good power, what do you mean 6500, 7000, 8000, more? Dont get me wrong Im not trying to be a D@#K, Im just trying to understand what we are talking about here. But to say stroke doesnt effect rpm and acceleration rate is absurd by any stretch.

The intakes we run on the conventional headed BBF dictates what rpm the peak at as much as cam or stroke does. Nobody gives a shxx enough to produce an intake that will peak above 6700 for our engines.

That's why I did extensive mods to my intake on my 580 engine to get it to peak at 7200 and hold to 7400.
You can add cam to these engines and hp will increase, but just move the torque peak higher in the rpm range but not peak the hp any higher.

If you look back at all the dyno results hear and on the other board most all BBF engines regardless of cubic in will peak some where close to 6700 rpm with a single plane intake.

Most Chevys peak higher than our engines, and even if the make the same hp they will be quicker at the track because of the extra usable rpm available.

Rev ability has as much to do with cross sectional area, port velocity and like Boss 429 said bore also.

My 557 had TFS Streets on it that flowing on an average of 380 cfm with a less than 300 cc intake runner was a fast reving and fast accelerating engine.

It's all about the package not so much the stroke alone.

IDT-572 wrote:

Barney wrote:

BOSS 429 wrote:I have a 4,300 makes 840 ,but its done by about 6800 we have ran it with all kinds of diff intakes,carbs,etc all the way to 8200.port plates,different headers etc.from 27 deg of timing to 45 total

its just done

another great test is that it was in a pull truck for 3 years, now its going in a drag car,and we will test it some more

Thanks thats more of what I was looking for. I didnt want to seem like a smart ass, but My 4.3 revs fine is a very relative answer, fine compared to a diesel, sure. Ive had a 427 windsor w/ solid roller and victor heads, but with that stroke and relatively small bore, it was a great torque producer and street motor, not so good N/A as a drag motor. I have been looking around and one thing Ive found is that the 4.3 stroke motors seem to all make power in a small window. For example most that produce good power(800 plus) may have good peak power and fall off quickly, so if it makes 850 at 6700 it will only make over 800 from say 6450 to 6900 which to me is a small window. The same goes for torque if a Motor peaks at 6100 but is done making torque by 6500 its probly ok for a dyno, but in real world testing Im not sure I would be happy. My 460 went 5.6s-5.7s @123 with a flat tappet cam and iron D0VES( granted it had a single plate on it)at 3120#. I would have a hard time telling a customer to spend the money on a combo like that with solid roller, 70+ cubes aluminum SCJs, and then have my stock junk be faster or even close to it, regardless of spray or not. So when all of you say your 4.3 revs fine and makes good power, what do you mean 6500, 7000, 8000, more? Dont get me wrong Im not trying to be a D@#K, Im just trying to understand what we are talking about here. But to say stroke doesnt effect rpm and acceleration rate is absurd by any stretch.

The intakes we run on the BBF dictates what rpm the peak at as much as cam or stroke does. Nobody gives a shxx enough to produce an intake that will peak above 6700 for our engines.

That's why I did extensive mods to my intake on my 580 engine to get it to peak at 7200 and hold to 7400.
You can add cam to these engines and hp will increase, but just move the torque peak higher in the rpm range but not peak the hp any higher.

If you look back at all the dyno results hear and on the other board most all BBF engines regardless of cubic in will peak some where close to 6700 rpm with a single plane intake.

Most Chevys peak higher than our engines, and even if the make the same hp they will be quicker at the track because of the extra usable rpm available.

Rev ability has as much to do with cross sectional area, port velocity and like Boss 429 said bore also.

My 557 had TFS Streets on it that flowing on an average of 380 cfm with a less than 300 cc intake runner was a fast reving and fast accelerating engine.

It's all about the package not so much the stroke alone.

That goes a long way in explaining why big bore, dual 4 tunnel ram fords seem make horsepower and sustain it so much better.

If one is not c.i.d. limited by rules the answer is real simple.........run a big bore and a big stroke. If the details of the engine package are well thought out it'll rev just fine.

IDT-572 wrote:

You can add cam to these engines and hp will increase, but just move the torque peak higher in the rpm range but not peak the hp any higher.

This is not making a lot of sense to me..... unless you are saying that you can move peak torque higher in the RPM band, but then the torque decreases more quickly as you continue increasing RPM.

Not being a smart@@@, just trying to learn.
Thanks.

Lem Evans wrote:If one is not c.i.d. limited by rules the answer is real simple.........run a big bore and a big stroke. If the details of the engine package are well thought out it'll rev just fine.

I missed this RODEO by a mile...

Mr. wrote:

IDT-572 wrote:

You can add cam to these engines and hp will increase, but just move the torque peak higher in the rpm range but not peak the hp any higher.

This is not making a lot of sense to me..... unless you are saying that you can move peak torque higher in the RPM band, but then the torque decreases more quickly as you continue increasing RPM.

Not being a smart@@@, just trying to learn.
Thanks.

What Blake is saying makes perfect sense.
Putting in a larger camshaft will change the point of peak torque and it will occur higher in the RPM range. That will make it closer to the horsepower peak RPM which doesn't get much higher, if any, therefore narrowing the RPM band of power.

'65 T-BOLT wrote:

IDT-572 wrote:

'65 T-BOLT wrote:I have the FMS 4.3 cast crank, revs as quick as my 427 windsor!

Never thought stroke had anything to do with how fast an engine revved...................

Im sure it don't Blake! but my stock stroke 460 will not rev as quick as the 521

I would make a bet with you that your stock stroke with a 4.625" bore giving about the SAME cubic inches would rev just as fast with that shorter stroke, if not even quicker than your longer stroke 521.

rmcomprandy wrote:

Mr. wrote:

IDT-572 wrote:

You can add cam to these engines and hp will increase, but just move the torque peak higher in the rpm range but not peak the hp any higher.

This is not making a lot of sense to me..... unless you are saying that you can move peak torque higher in the RPM band, but then the torque decreases more quickly as you continue increasing RPM.

Not being a smart@@@, just trying to learn.
Thanks.

What Blake is saying makes perfect sense.
Putting in a larger camshaft will change the point of peak torque and it will occur higher in the RPM range. That will make it closer to the horsepower peak RPM which doesn't get much higher, if any, therefore narrowing the RPM band of power.

Ive never had anyone ask for a narrow RPM window. Maybe if your just looking for a HP number on a dyno, or running a very, very light car. If you have 2 850 horsepower engines. The first peaks at 6800 rpm and makes over 800 from 6400 - 7100 rpm, and the second makes 850 @ 7400 and makes over 800 from 6200 - 8000 the second motor will be faster I guarantee it.

rmcomprandy wrote:

'65 T-BOLT wrote:

IDT-572 wrote:

'65 T-BOLT wrote:I have the FMS 4.3 cast crank, revs as quick as my 427 windsor!

Never thought stroke had anything to do with how fast an engine revved...................

Im sure it don't Blake! but my stock stroke 460 will not rev as quick as the 521

I would make a bet with you that your stock stroke with a 4.625" bore giving about the SAME cubic inches would rev just as fast with that shorter stroke, if not even quicker than your longer stroke 521.

It would rev ALOT quicker and make horsepower extremely high.

Barney wrote:

rmcomprandy wrote:

Mr. wrote:

IDT-572 wrote:

You can add cam to these engines and hp will increase, but just move the torque peak higher in the rpm range but not peak the hp any higher.

This is not making a lot of sense to me..... unless you are saying that you can move peak torque higher in the RPM band, but then the torque decreases more quickly as you continue increasing RPM.

Not being a smart@@@, just trying to learn.
Thanks.

What Blake is saying makes perfect sense.
Putting in a larger camshaft will change the point of peak torque and it will occur higher in the RPM range. That will make it closer to the horsepower peak RPM which doesn't get much higher, if any, therefore narrowing the RPM band of power.

Ive never had anyone ask for a narrow RPM window. Maybe if your just looking for a HP number on a dyno, or running a very, very light car. If you have 2 850 horsepower engines. The first peaks at 6800 rpm and makes over 800 from 6400 - 7100 rpm, and the second makes 850 @ 7400 and makes over 800 from 6200 - 8000 the second motor will be faster I guarantee it.

The only racers I know of who shoot for the peak horsepower number at the cost of a shorter RPM band is the NHRA ProStock guys. That's why they use a five speed trans and would use a six speed if it was legal.

My best quess is that if the NHRA pro-stock guys could keep their present bore and put another 1/4" stroke in it they would.

Barney wrote:

rmcomprandy wrote:

Mr. wrote:

IDT-572 wrote:

You can add cam to these engines and hp will increase, but just move the torque peak higher in the rpm range but not peak the hp any higher.

This is not making a lot of sense to me..... unless you are saying that you can move peak torque higher in the RPM band, but then the torque decreases more quickly as you continue increasing RPM.

Not being a smart@@@, just trying to learn.
Thanks.

What Blake is saying makes perfect sense.
Putting in a larger camshaft will change the point of peak torque and it will occur higher in the RPM range. That will make it closer to the horsepower peak RPM which doesn't get much higher, if any, therefore narrowing the RPM band of power.

Ive never had anyone ask for a narrow RPM window. Maybe if your just looking for a HP number on a dyno, or running a very, very light car. If you have 2 850 horsepower engines. The first peaks at 6800 rpm and makes over 800 from 6400 - 7100 rpm, and the second makes 850 @ 7400 and makes over 800 from 6200 - 8000 the second motor will be faster I guarantee it.

I haven't either, but what I'm talking about is an engine with a rpm limited intake. You can keep adding cam to a point and gain more hp but with a higher peak rpm for torque.

And I agree with you an the higher rpm engine will be faster. More usable RPM. Gear will get the torque back at the tire.

But with a single plane Victor your stuck at about 6700 peak. Obviously Mr Edelbrock could have cared less if he gave us Ford guys an intake to compete with the Chevys or not.............. He advertizes it to 8000 RPM, he just failed to mention it don't make any power up there at 8000 out of the box..................

sometimes you gotta cut stuff up and "make" it work.............

I'd think we'd need to get over the 'VICTOR' thing and move on.
The so called 'mafia' tfs thing is much better than a ported vic. thing.
J.Y. Kelly's 562" deal :
951Hp @ 6,700 RPM
951Hp @ 6,800 RPM
951Hp @ 6,900 RPM
951Hp @ 7,000 RPM
It should have been pulled higher i.m.o. Not that I think It'd made more....just to see how it was past peak.

I have ran both the 4.3 stroke with the 4.44 bore and the 4.5 stroke with the 4.44 bore with the same cams and same heads just diferent blocks same style cranks and rods and same compression pistons. and the 4.3 stroke was faster than the 4.5 stroke maybe heads maybe cams, but when it come time to sell them the 4.5 stroke motor sold first becuase of cubic inches. i was it did i switched the 4.3 motor over to N20 and had lem grind me a cam and i went 530s in the 1/8 on 350 hit of n20 and went threw 3 different converters trying to get one to hold the motor. If i built another stock block style motor it would have the 4.3 stroke and the .080 over bore again. it did not seem to scuff the cylinder walls up as bad as the 4.5 stroke and i just liked it better. hope this helps

IDT-572 wrote:

Barney wrote:

rmcomprandy wrote:

Mr. wrote:

IDT-572 wrote:

You can add cam to these engines and hp will increase, but just move the torque peak higher in the rpm range but not peak the hp any higher.

This is not making a lot of sense to me..... unless you are saying that you can move peak torque higher in the RPM band, but then the torque decreases more quickly as you continue increasing RPM.

Not being a smart@@@, just trying to learn.
Thanks.

What Blake is saying makes perfect sense.
Putting in a larger camshaft will change the point of peak torque and it will occur higher in the RPM range. That will make it closer to the horsepower peak RPM which doesn't get much higher, if any, therefore narrowing the RPM band of power.

Ive never had anyone ask for a narrow RPM window. Maybe if your just looking for a HP number on a dyno, or running a very, very light car. If you have 2 850 horsepower engines. The first peaks at 6800 rpm and makes over 800 from 6400 - 7100 rpm, and the second makes 850 @ 7400 and makes over 800 from 6200 - 8000 the second motor will be faster I guarantee it.

I haven't either, but what I'm talking about is an engine with a rpm limited intake. You can keep adding cam to a point and gain more hp but with a higher peak rpm for torque.

And I agree with you an the higher rpm engine will be faster. More usable RPM. Gear will get the torque back at the tire.

But with a single plane Victor your stuck at about 6700 peak. Obviously Mr Edelbrock could have cared less if he gave us Ford guys an intake to compete with the Chevys or not.............. He advertizes it to 8000 RPM, he just failed to mention it don't make any power up there at 8000 out of the box..................

I guess thats why they make die grinders, welders, and epoxy. Your powerband shouldnt be COMPLETELY dictated by your intake. Its a shame.

Barney wrote:

IDT-572 wrote:

Barney wrote:

rmcomprandy wrote:

Mr. wrote:

IDT-572 wrote:

You can add cam to these engines and hp will increase, but just move the torque peak higher in the rpm range but not peak the hp any higher.

This is not making a lot of sense to me..... unless you are saying that you can move peak torque higher in the RPM band, but then the torque decreases more quickly as you continue increasing RPM.

Not being a smart@@@, just trying to learn.
Thanks.

What Blake is saying makes perfect sense.
Putting in a larger camshaft will change the point of peak torque and it will occur higher in the RPM range. That will make it closer to the horsepower peak RPM which doesn't get much higher, if any, therefore narrowing the RPM band of power.

Ive never had anyone ask for a narrow RPM window. Maybe if your just looking for a HP number on a dyno, or running a very, very light car. If you have 2 850 horsepower engines. The first peaks at 6800 rpm and makes over 800 from 6400 - 7100 rpm, and the second makes 850 @ 7400 and makes over 800 from 6200 - 8000 the second motor will be faster I guarantee it.

I haven't either, but what I'm talking about is an engine with a rpm limited intake. You can keep adding cam to a point and gain more hp but with a higher peak rpm for torque.

And I agree with you an the higher rpm engine will be faster. More usable RPM. Gear will get the torque back at the tire.

But with a single plane Victor your stuck at about 6700 peak. Obviously Mr Edelbrock could have cared less if he gave us Ford guys an intake to compete with the Chevys or not.............. He advertizes it to 8000 RPM, he just failed to mention it don't make any power up there at 8000 out of the box..................

I guess thats why they make die grinders, welders, and epoxy. Your powerband shouldnt be COMPLETELY dictated by your intake. Its a shame.

Just be glad TFS will help us when we need it. As we untap the power these engines are capable of they seem willing to make what we need to continue on.

It seems Edelbrock is afraid to piss the Chevy guys off if they develop something that out does the Chevy camp.
Look at the 460 crate engine, compare it to the equal 454 crate engine package in their catalog It makes almost the same power as the 454 , but they choke it with a smaller cam so it won't make more.

Lem Evans wrote:My best quess is that if the NHRA pro-stock guys could keep their present bore and put another 1/4" stroke in it they would.

They ran that 1/4" longer stroke at one time in the past however, the bore HAD to be smaller to stay under the 500 cubic inches.
If the engine had more cubic inches ... then it wouldn't be a fair "apples to apples" comparison.

rmcomprandy wrote:

Lem Evans wrote:My best quess is that if the NHRA pro-stock guys could keep their present bore and put another 1/4" stroke in it they would.

They ran that 1/4" longer stroke at one time in the past however, the bore HAD to be smaller to stay under the 500 cubic inches.
If the engine had more cubic inches ... then it wouldn't be a fair "apples to apples" comparison.

I know the rules are 500". Notice I said "if the NHRA pro-stock guys COULD". My point is....in the context of a racing engine...very few of "us" have c.i.d. limits so using a longer stroke with a big bore is a good option.

Lem Evans wrote:

rmcomprandy wrote:

Lem Evans wrote:My best quess is that if the NHRA pro-stock guys could keep their present bore and put another 1/4" stroke in it they would.

They ran that 1/4" longer stroke at one time in the past however, the bore HAD to be smaller to stay under the 500 cubic inches.
If the engine had more cubic inches ... then it wouldn't be a fair "apples to apples" comparison.

I know the rules are 500". Notice I said "if the NHRA pro-stock guys COULD". My point is....in the context of a racing engine...very few of "us" have c.i.d. limits so using a longer stroke with a big bore is a good option.

When thinking only of the bracket or index drag racer that is true. However, lots and lots of other drag race classes have a cubic inch limit to weight to adhere to.
Most truck pulling engines have to adhere to cubic limits to meet certain rules.
Class hydroplane racing has to adhere to maximum cubic inch rules; (7 liter and such).

I get your point, lol. Mine is that there isn't only this "pigeon holed" venue in racing which can use a big block Ford. Most others are cubic inch limited.

If its just a stroke length issue alone that's being debated would it not be a problem until the actual piston speed got out of control ?

I think I see what Blake is saying with the manifold, if you say took a 466 and ran the same heads as you did with a bigger engine 557 for instance , the 466 should be able to attain the same or close power level at a much higher rpm all things being equal manifold and head wise.

Different Strokes for Different Folks.........

KY JELLY wrote:If its just a stroke length issue alone that's being debated would it not be a problem until the actual piston speed got out of control ?

I think I see what Blake is saying with the manifold, if you say took a 466 and ran the same heads as you did with a bigger engine 557 for instance , the 466 should be able to attain the same or close power level at a much higher rpm all things being equal manifold and head wise.

Horsepower...? Yes, with the limited intake system. Maximum torque however, wouldn't even be close.