I was reading about it apparently anything above .3 MACH = 338 fps is where choke starts and since these fps are based off calculated fps you might actually be in it above 321 fps why calculated 321 fps is considered highest useable.
What would it take to make 1.44 lbs-ft per cid ?
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I've been told there should have been a little more in the E85 but I don't know for sure. I wanted to play with jetting some but we were safe where we were and I'm kinda green. That was my first time having anything on the dyno so I was happy it went home in one piece lol
A guess of the top of my head, need less gas to make same hp so less fuel in the system better overall mixture atomization etc.. Better burn. Alcohol more Torque more fuel lower intake temps maybe.
RAMM
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Yes the alcohol cools the intake charge which is why TQ production is better, but when you factor in the fuel volume req'd because stoich is 9.7-1 with E85 but in reality it is probably more like 6.5-7.0-1 that is alot more fuel you have to make room for in the induction tract. So you have the fuel displacing the air which is why upper RPM HP usually suffers compared to race fuel. Basically you need a larger intake tract to take advantage of alcohol. J.Rob
Newbomb Turk
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One thing I think I've learnt from this is too little velocity is a lot harder to get than people make it out to be most heads seem to be in the acceptable range calculated 260-310 fps with 285 fps being considered optimal.
And examples of 260 fps the lowest recommended fps and would give the largest ports for a given cfms is very unlikely to come across 225 cfms = 170 cc, 250 cfms = 190 cc, 275 cfms = 205 cc, 300 cfms = 225 cc, those are some very large ports for each given cfm and there still would be considered very acceptable velocities for very good hp and torque. You would have to add like 15+ cc to these to be considered slow port with possible reversion, it seems like too high of velocity is far more likely above 310 fps being the highest recommended, 225 cfms = 140 cc, 250 cfms = 155 cc, 275 cfms = 170 cc, 300 cfm = 190 cc. Any thing like 5+ cc smaller and run the risk of too much velocity.
It seems like ports generally for a given cfm automatically fall in the ranges acceptable velocities as long you build for the right rpms range for a given cid for each head. Which might be why we generally focus on cfm numbers.
Minimum csa might be more of an issue.
Calculated recommended head flow cfm for a given cid and rpm.
RPM. 4,500.....5,000....5,500....6,000....6,500....7,000
273. 150.........167......184.......200........217......234 cfm
318. 175.........194.......214......233........253......272 cfm
340. 187.........208.......229.......250........270......291 cfm
360. 198.........220.......242.......264........286......308 cfm
408. 225.........250.......274.......299.........324.....349 cfm
And examples of 260 fps the lowest recommended fps and would give the largest ports for a given cfms is very unlikely to come across 225 cfms = 170 cc, 250 cfms = 190 cc, 275 cfms = 205 cc, 300 cfms = 225 cc, those are some very large ports for each given cfm and there still would be considered very acceptable velocities for very good hp and torque. You would have to add like 15+ cc to these to be considered slow port with possible reversion, it seems like too high of velocity is far more likely above 310 fps being the highest recommended, 225 cfms = 140 cc, 250 cfms = 155 cc, 275 cfms = 170 cc, 300 cfm = 190 cc. Any thing like 5+ cc smaller and run the risk of too much velocity.
It seems like ports generally for a given cfm automatically fall in the ranges acceptable velocities as long you build for the right rpms range for a given cid for each head. Which might be why we generally focus on cfm numbers.
Minimum csa might be more of an issue.
Calculated recommended head flow cfm for a given cid and rpm.
RPM. 4,500.....5,000....5,500....6,000....6,500....7,000
273. 150.........167......184.......200........217......234 cfm
318. 175.........194.......214......233........253......272 cfm
340. 187.........208.......229.......250........270......291 cfm
360. 198.........220.......242.......264........286......308 cfm
408. 225.........250.......274.......299.........324.....349 cfm
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Newbomb Turk
Well-Known Member
He said it. An engine bolted to a power glide will rpm slower than a stick.
Most engine dyno’s can’t measure an engine’s ability to make rpm.
That’s why two engines making 500 hp will have two different mph even if both cars are identical.
One will rpm quicker that the other. That means that engine is making more power cycles sooner. That’s more go sooner and the car is quicker.
Since there are far fewer stick cars out there, they get screwed the hardest on tuning and **** like that.
They are two totally different animals and that includes a transbrake car. It’s not even close to tuning like a stick.
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Again I said It's kool little engine, But the only really impressive thing about is not it's hp or torque but that it did it with a 195 cfms, Doesn't change the fact that it stop picking up power for the last 1000 or so rpms it's just an observation. But you got to make a big thing about it cause your Cult of the Small depends on this and that Ford 650 vs 750 carb shootout where they end up picking the 750 anyways.
Even if this engine kept making power to 6500 rpms with the 195 cfm head, it would just be kooler engine, wouldn't change anything for me. The take away from that build ain't if your looking to make 435 hp @ 6000 rpm and 430 lbs-ft, the obvious answer is you need a 316 ish engine with a 195 cfm 145cc head, it's if you pay attention to details that generally there's more to be squeezed out if one so chooses.
But most will just choose the 340/360 route for a 435/430 hp/tq with a 230-250 cfm head.
This engine doesn't prove anyone one wrong, cause no one is arguing if you dump a lot of time and effort and money into an engine that you can't get results like this. You only think that's what people are arguing again strawman
Even if this engine kept making power to 6500 rpms with the 195 cfm head, it would just be kooler engine, wouldn't change anything for me. The take away from that build ain't if your looking to make 435 hp @ 6000 rpm and 430 lbs-ft, the obvious answer is you need a 316 ish engine with a 195 cfm 145cc head, it's if you pay attention to details that generally there's more to be squeezed out if one so chooses.
But most will just choose the 340/360 route for a 435/430 hp/tq with a 230-250 cfm head.
What records ?
For you.
This engine doesn't prove anyone one wrong, cause no one is arguing if you dump a lot of time and effort and money into an engine that you can't get results like this. You only think that's what people are arguing again strawman
I don't think much of this thread is actionable for the average Mopar guy.
I'm not going to go to a cylinder head guy and be like "hey I wanna target x fps please make that happen"
I think a few good "reproducible" engine recipes would be great. And honestly, most of the engine master challenge builds aren't representative of what an average guy can reproduce.
I'm not going to go to a cylinder head guy and be like "hey I wanna target x fps please make that happen"
I think a few good "reproducible" engine recipes would be great. And honestly, most of the engine master challenge builds aren't representative of what an average guy can reproduce.
Well it seem from what I can tell most heads seem to fall in the 260-310 fps which from the sound of it is considered the acceptable velocity range. So basically you just got to match cfm/hp with the right cid/rpm which is basically how most do it, so for the most part unless your doing something special and or above 7,000 rpms it probably not a thing most got to worry about. Maybe the only thing that might hold the average guy back is possibly the push rod pinch which is ballpark cid x rpm / 1,100,000 = min csa which is usually the pinch.
I Totally agree, It's generally easier to make a bigger slightly less efficient engine for the power and rpm your after.
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My bad, the 12 hr gap, I thought It was the Olds engine you were saying that won records.
Did he win records by running less air flow than the other guy's ?
What those guy's can do is amazing, but again your take away is bizarre, the goal ain't to make hp with ridiculously small ports flowing low cfm at super high velocities with the smallest carb, headers, intake runner, cid etc.. You can get And go tah dah and marvel at the magical feat you accomplished.
Here this book might help you.
Highly doubt it, I'm pretty sure one of those chev engines had a VE of a 116% so he was getting air in, I'm sure the Dodge was similar and you don't turn a 371 to like 8000 rpms without moving air. Hp is mostly airflow.
Efficiency ain't everything, we live in a world of cheap relatively inefficient hp, you could easily out do these engines in a afternoon with a catalog and a credit.
Don't make these engine any less impressive but it not the only way and it's really not the most popular way to make power.
Look at this thread very few care or see no point in trying to build higher lbs-ft per cid.
Pretty sure I've read it and others from the local library, when I was 12, probably make more sense to me now.
My god your dense, I've never argued that he didn't flow less air on the bench that cfms didn't go down, that wasn't the important point (your always focusing on the wrong aspect). The point wasn't that he didn't need less airflow he needed less velocity (was the point) and to get less velocity you either make the port bigger which he couldn't or flow less air on the bench but obviously on the engine like I stated he was flowing more air. But I bet though that him and all the other racer squeezed every last useful cfm they could get out of the heads cause like I also stated, the goal wasn't to run the least cfms possible like you like to think.
If that what does it for ya, yes less cfm on the "bench" went faster in the car and yes they only did it all with 161.5 cc.
Does this engine make the shrine ?
What does any of this conversation with YOU got anything to do with making power, talking to you is like talking to a flat earther all you care about spreading your Cult of the Small
Not saying these formulas work but to me they seem like there in the ballpark.
Trying on the original reasonably efficient Trick Flow 408 example from post #1.
https://www.motortrend.com/how-to/408-inch-budget-mopar-westech/
514 hp @ 5,900 rpm 1.26 hp per cid.
526 tq @ 4,000 rpm 1.29 lbs-ft per cid.
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According to these formulas a 408 that peaks at 6000 rpm, needs a minimum push rod pinch csa of 2.23" sq and 299 cfm heads with an average csa of 2.52" sq and port volume of 204 cc for a 285 fps.
Trick Flow say the flow 300 cfm with a port volume of 190, not sure of pinch csa probably a little shy of 2.23" sq. The calculated csa average is 2.34" sq which gives a calculated 308 fps which according to the chart is the "highest usable port velocity with very good hp and tq but with possible hp loss"
This is at 100% ve more ve and or rpm is gonna run these heads at a higher velocity and obviously less ve and or rpm a lower velocity etc..
As for minimum csa it seems to be design to happen at peak hp.
300 cfm x 2.4 / 2.23" min csa = velocity at peak hp 323 fps @ 6000 rpm.
To me It seems like average csa is supposed to happen around peak torque, there's a formulas for intake and header average csa to tune for 260 fps at peak torque (cid / cylinders) x peak torque rpm / 88200 = average csa.
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These formulas are based on 100% ve and we'll use 100% in this example.
VE% x cid = usable cid = 408.
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First is to figure out need head flow, cfm = usable cid x rpm x .0009785 / 8
Cfm 299 = 408 x 6000 rpm x .0009785 / 8
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Next minimum csa which is usually push rod pinch.
Min csa = cid x rpm / 1,100,000
Min 2.23" sq = 408 x 6000 rpm / 1,100,000
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Next average csa and port cc for desired fps (velocity) which we'll say is 285 fps.
Based on 4.95" port length and port flow of 299 cfm and port average csa.
Port volume cc = port length x 16.387 x csa.
Fps = cfm x 2.4 / csa.
300 fps = 2.39 csa = 195 cc
285 fps = 2.52 csa = 204 cc
260 fps = 2.76 csa = 224 cc
If you look at these calculated recommended fps with very good hp and tq you got a range of 260-300 fps with 285 fps being in the halfway between the two, and seems like 240-320 fps is considered the maximum usable range. Which is a port size of 243 cc to 182 cc for 299 cfm head.
I'm sure there's circumstances to use out side of 240-320 fps.
Trick Flow 408
Trying on the original reasonably efficient Trick Flow 408 example from post #1.
https://www.motortrend.com/how-to/408-inch-budget-mopar-westech/
514 hp @ 5,900 rpm 1.26 hp per cid.
526 tq @ 4,000 rpm 1.29 lbs-ft per cid.
------------------------------------------------
According to these formulas a 408 that peaks at 6000 rpm, needs a minimum push rod pinch csa of 2.23" sq and 299 cfm heads with an average csa of 2.52" sq and port volume of 204 cc for a 285 fps.
Trick Flow say the flow 300 cfm with a port volume of 190, not sure of pinch csa probably a little shy of 2.23" sq. The calculated csa average is 2.34" sq which gives a calculated 308 fps which according to the chart is the "highest usable port velocity with very good hp and tq but with possible hp loss"
This is at 100% ve more ve and or rpm is gonna run these heads at a higher velocity and obviously less ve and or rpm a lower velocity etc..
As for minimum csa it seems to be design to happen at peak hp.
300 cfm x 2.4 / 2.23" min csa = velocity at peak hp 323 fps @ 6000 rpm.
To me It seems like average csa is supposed to happen around peak torque, there's a formulas for intake and header average csa to tune for 260 fps at peak torque (cid / cylinders) x peak torque rpm / 88200 = average csa.
-----------------------------------
These formulas are based on 100% ve and we'll use 100% in this example.
VE% x cid = usable cid = 408.
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First is to figure out need head flow, cfm = usable cid x rpm x .0009785 / 8
Cfm 299 = 408 x 6000 rpm x .0009785 / 8
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Next minimum csa which is usually push rod pinch.
Min csa = cid x rpm / 1,100,000
Min 2.23" sq = 408 x 6000 rpm / 1,100,000
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Next average csa and port cc for desired fps (velocity) which we'll say is 285 fps.
Based on 4.95" port length and port flow of 299 cfm and port average csa.
Port volume cc = port length x 16.387 x csa.
Fps = cfm x 2.4 / csa.
300 fps = 2.39 csa = 195 cc
285 fps = 2.52 csa = 204 cc
260 fps = 2.76 csa = 224 cc
If you look at these calculated recommended fps with very good hp and tq you got a range of 260-300 fps with 285 fps being in the halfway between the two, and seems like 240-320 fps is considered the maximum usable range. Which is a port size of 243 cc to 182 cc for 299 cfm head.
I'm sure there's circumstances to use out side of 240-320 fps.
Trick Flow 408
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Newbomb Turk
Well-Known Member
I like to take things with a grain of salt, but as I calculate different engines out they all seem to be within the charts ballpark numbers.
From what I understand you generally want intake, port, headers to be tuned around 240-260 fps at peak torque and peak hp be no higher than 338 fps measured, 321 fps calculated.
Came across this formula for estimatung VE% = (hp x 4235) / (cid x rpm)
Seems closely related to the so called carb formula cfm = ( cid x rpm / 3456 ) x VE% it's seems to estimate 1.225 cfm per 1 hp, imagine based on a middle of the road bsfc.
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Take the above 408, 514 hp @ 5,900 rpm, 401 hp (526 lbs-ft) @ 4,000 rpm.
Estimated VE%
VE% @ peak hp = (514 x 4235) / (408 x 5900) = 90% VE
VE% @ peak tq = (401 x 4235) / (408 x 4000) = 104% VE
Seems closely related to the so called carb formula cfm = ( cid x rpm / 3456 ) x VE% it's seems to estimate 1.225 cfm per 1 hp, imagine based on a middle of the road bsfc.
--------------------------------------------
Take the above 408, 514 hp @ 5,900 rpm, 401 hp (526 lbs-ft) @ 4,000 rpm.
Estimated VE%
VE% @ peak hp = (514 x 4235) / (408 x 5900) = 90% VE
VE% @ peak tq = (401 x 4235) / (408 x 4000) = 104% VE
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Update...After digging around the internet and talking to some of the guy's on speed talk, forgot I opened an account over there too as well as here back in the day.
From what I can tell most of the time you want mach/fps choke point at peak hp, before peak obviously your engine gonna want peak sooner and nose over and kill top end and after peak hp your wasting velocity throughout the power curve.
And what port fps gets choke point at peak hp seems to vary with port design obviously each engines different. So to me unless you know for that particular head, cid and rpm etc.. combo what you can get away with you want to caution with lower velocities, eg.. like calculated 260-285 fps especially with poorer head designs.
I may be wrong, hard to get a straight answer on this, but seems to fit with what everyone is saying.
From what I can tell most of the time you want mach/fps choke point at peak hp, before peak obviously your engine gonna want peak sooner and nose over and kill top end and after peak hp your wasting velocity throughout the power curve.
And what port fps gets choke point at peak hp seems to vary with port design obviously each engines different. So to me unless you know for that particular head, cid and rpm etc.. combo what you can get away with you want to caution with lower velocities, eg.. like calculated 260-285 fps especially with poorer head designs.
I may be wrong, hard to get a straight answer on this, but seems to fit with what everyone is saying.
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