Salter Racing Engines rule of thumb, port 90% of Valve ?

[273]

I'm finding him interesting most what he says falls within what others have said with obviously his own take on it.

Seem like he's given the full boggie point of view though, eg. standard 4.03" bore with intake valve at 52.5% = 2.12" intake and 1.61" exhaust (76%) with 90% port size 1.91" throat 2.86" sq pinch which would put you around 358 cfm at 300 fps (mid range fps) ( cfm = ave csa x fps x .4166667), 2.86" sq (pinch) x 1,100,000 / 408 cid = 7,711 rpm or for a 365 = 8,619 rpm.

 

[MOPARMAGA]

I'm finding him interesting most what he falls within what others have said with obviously his own take on it.

Seem like he's given the full boggie point of view though, eg. standard 4.03" bore with intake valve at 52.5% = 2.12" intake and 1.61" exhaust (76%) with 90% port size 1.91" throat 2.86" sq pinch which would put you around 358 cfm at 300 fps (mid range fps) ( cfm = ave csa x fps x .4166667), 2.86" sq (pinch) x 1,100,000 / 408 cid = 7,711 rpm or for a 365 = 8,619 rpm.

One thing I was impressed with was how easy he made some of those formulas to understand.
I'm not dumb but something's are hard to grasp until it's explained differently.
The person I choose to call my mentor and friend is the same way, he can make it make sense.

 

[Newbomb Turk]

I'm finding him interesting most what he says falls within what others have said with obviously his own take on it.

Seem like he's given the full boggie point of view though, eg. standard 4.03" bore with intake valve at 52.5% = 2.12" intake and 1.61" exhaust (76%) with 90% port size 1.91" throat 2.86" sq pinch which would put you around 358 cfm at 300 fps (mid range fps) ( cfm = ave csa x fps x .4166667), 2.86" sq (pinch) x 1,100,000 / 408 cid = 7,711 rpm or for a 365 = 8,619 rpm.

The only thing I disagree with is the percentage of exhaust valve size.

NA stuff doesn't need to be that big.

Other than that the math is good.

 

[273]

One thing I was impressed with was how easy he made some of those formulas to understand.
I'm not dumb but something's are hard to grasp until it's explained differently.
The person I choose to call my mentor and friend is the same way, he can make it make sense.

Lot frown on formulas and rules of thumb, but are necessary for understanding the basics to give you a place to work from, but obviously some get to married to them as unbreakable rules and how/if they relate to the level of build their doing.

 

[Earlie A]

The math may work on paper, but what happens when the valve is larger than the port can handle? For round numbers, let's say the throat is 3 sq inches and the area over the apex is 2.75 sq inches? What is going to happen on the short side?

 

[273]

The math may work on paper, but what happens when the valve is larger than the port can handle? For round numbers, let's say the throat is 3 sq inches and the area over the apex is 2.75 sq inches? What is going to happen on the short side?

He said run a smaller valve.

 

[273]

I imagine if doing say a J heads and it's only got enough volume when ported to handle a 1.94" 2.02" etc.. whatever maybe that's what you run even on a 4.03" bore.

 

[33IMP]

I'm finding him interesting most what he says falls within what others have said with obviously his own take on it.

Seem like he's given the full boggie point of view though, eg. standard 4.03" bore with intake valve at 52.5% = 2.12" intake and 1.61" exhaust (76%) with 90% port size 1.91" throat 2.86" sq pinch which would put you around 358 cfm at 300 fps (mid range fps) ( cfm = ave csa x fps x .4166667), 2.86" sq (pinch) x 1,100,000 / 408 cid = 7,711 rpm or for a 365 = 8,619 rpm.

358 cfm? I'd be happy as heck if ANY of my big block heads flowed that!
(Considering a 906 bbm starts at around 225).
I'm not sure my big port bbc will flow that much. Pretty sure my big oval port bbc don't.

 

[MOPARMAGA]

Lot frown on formulas and rules of thumb, but are necessary for understanding the basics to give you a place to work from, but obviously some get to married to them as unbreakable rules and how/if they relate to the level of build their doing.

The horsepower chain formula is what my camshaft is based from.
Luckily I must have known that before I got the book...and the cam is used so it was cheap lol.

 

[MOPARMAGA]

He said run a smaller valve.

Like the trickflow big block heads, run a 1.780 vs almost everyone else's standard 1.810

 

[273]

358 cfm? I'd be happy as heck if ANY of my big block heads flowed that!
(Considering a 906 bbm starts at around 225).
I'm not sure my big port bbc will flow that much. Pretty sure my big oval port bbc don't.

These guys generally aren’t talking about average guy builds or even a step or two above that.

 

[33IMP]

Like the trickflow big block heads, run a 1.780 vs almost everyone else's standard 1.810

And my iron maxies run 2.08, 1.88. 60.year old tech, I guess, lol.

 

[MOPARMAGA]

And my iron maxies run 2.08, 1.88. 60.year old tech, I guess, lol.

Oh yeah I always thought that was weird.
I was just coming back to edit my post 1.76 valve size.

 

[273]

 

[273]

One thing might be a problem (ish) with his 90% rule is most heads could only use pretty small valve, which might not be a problem if it makes the hp.

Port CSA at 90% of valve

1.78 x 90% = 1.60 which = CSA 2.01" sq which = 230 CFM @ 275 FPS - 268 CFM @ 320 FPS
1.88 x 90% = 1.69 which = CSA 2.25" sq which = 258 CFM @ 275 FPS - 300 CFM @ 320 FPS
1.92 x 90% = 1.73 which = CSA 2.35" sq which = 269 CFM @ 275 FPS - 313 CFM @ 320 FPS
2.02 x 90% = 1.82 which = CSA 2.60" sq which = 298 CFM @ 275 FPS - 347 CFM @ 320 FPS
2.08 x 90% = 1.87 which = CSA 2.75" sq which = 315 CFM @ 275 FPS - 367 CFM @ 320 FPS

2.60-2.75" sq CSA especially at the push rod pinch is fairly big area, I imagine even 2.35" sq (1.92" valve) is hard to get and is good enough for 6400 rpm with a 408 or 7100 rpm with a 365, according to the calculations.

 

[273]

Port volume

1.78 = CSA 2.01" sq which = 163 cc
1.88 = CSA 2.25" sq which = 183 cc
1.92 = CSA 2.35" sq which = 191 cc
2.02 = CSA 2.60" sq which = 211 cc
2.08 = CSA 2.75" sq which = 223 cc

Fairly big volumes for those valve sizes, and that minimum would be larger if went more than 90% here and there.

 

[MOPARMAGA]

One thing might be a problem (ish) with his 90% rule is most heads could only use pretty small valve, which might not be a problem if it makes the hp.

Port CSA at 90% of valve

1.78 x 90% = 1.60 which = CSA 2.01" sq which = 230 CFM @ 275 FPS - 268 CFM @ 320 FPS
1.88 x 90% = 1.69 which = CSA 2.25" sq which = 258 CFM @ 275 FPS - 300 CFM @ 320 FPS
1.92 x 90% = 1.73 which = CSA 2.35" sq which = 269 CFM @ 275 FPS - 313 CFM @ 320 FPS
2.02 x 90% = 1.82 which = CSA 2.60" sq which = 298 CFM @ 275 FPS - 347 CFM @ 320 FPS
2.08 x 90% = 1.87 which = CSA 2.75" sq which = 315 CFM @ 275 FPS - 367 CFM @ 320 FPS

2.60-2.75" sq CSA especially at the push rod pinch is fairly big area, I imagine even 2.35" sq (1.92" valve) is hard to get and is good enough for 6400 rpm with a 408 or 7100 rpm with a 365, according to the calculations.

That's more like a safe common practice, rather than his rule. He repeatedly says that some stuff is different but 90% is safe for most heads.

 

[273]

That's more like a safe common practice, rather than his rule. He repeatedly says that some stuff is different but 90% is safe for most heads.

I get that but that, but leaves us using fairly small valves if we were to try to get close to 90% nevermind more, I doubt a set of speedmaster could do a 2.02 valve at 90% nevermind a 2.08, I'm not saying that's necessarily a bad thing. But most seem get there flow from using 2.02-2.08 in a set of speedmasters not 1.92 or less.

Wouldn't be bad if 1.92 say @ 275 cfm out performs 2.08 at 320 cfm, but would it ?

Could a set of J heads handle 1.88 valves at 90% ?

And to keep velocities up (300+ fps) at 90% got to be moving a lot of air, more than people generally get for those valve sizes.

 

[273]

Not try and or saying he's wrong, just point out possible problems if trying to use his 90% with generally used mopar heads.

 

[MOPARMAGA]

I get that but that, but leaves us using fairly small valves if we were to try to get close to 90% nevermind more, I doubt a set of speedmaster could do a 2.02 valve at 90% nevermind a 2.08, I'm not saying that's necessarily a bad thing. But most seem get there flow from using 2.02-2.08 in a set of speedmasters not 1.92 or less.

Wouldn't be bad if 1.92 say @ 275 cfm out performs 2.08 at 320 cfm, but would it ?

Could a set of J heads handle 1.88 valves at 90% ?

And to keep velocities up (300+ fps) at 90% got to be moving a lot of air, more than people generally get for those valve sizes.

I don't know the answer to any of those questions off the top of my head. However I do know what happens when I didn't know what I was doing, several years ago I ported my brand new eq heads bigger than I should have and they really suffered below 3000 rpm. This was in a daily driver Dakota r/t and honestly it sucked to drive in Seattle lol.

 

[MOPARMAGA]

Not try and or saying he's wrong, just point out possible problems if trying to use his 90% with generally used mopar heads.

I understand, I honestly don't consider many factory or factory styled Mopar heads worth messing with and the ones I would are too expensive for me. I do like the trickflows and I'm hopeful pretty soon going to port my 240s out further to a 2.610 by 1.380 gasket and match my tunnel ram after I get a gallon of splash zone.

 

[MOPARMAGA]

I will be doing a deep blend, I'll 40 grit the ports and burr finish them. The trickflow big block heads are really good, so I'm not trying to change them drastically.

 

[Newbomb Turk]

I get that but that, but leaves us using fairly small valves if we were to try to get close to 90% nevermind more, I doubt a set of speedmaster could do a 2.02 valve at 90% nevermind a 2.08, I'm not saying that's necessarily a bad thing. But most seem get there flow from using 2.02-2.08 in a set of speedmasters not 1.92 or less.

Wouldn't be bad if 1.92 say @ 275 cfm out performs 2.08 at 320 cfm, but would it ?

Could a set of J heads handle 1.88 valves at 90% ?

And to keep velocities up (300+ fps) at 90% got to be moving a lot of air, more than people generally get for those valve sizes.

That’s the problem with these rules. You can only do what the original architecture allows you to fit, so you do what you can.

There is theory and real world. Sometimes they meet. A lot of times they don’t.

 

[fishmens67]

I understand, I honestly don't consider many factory or factory styled Mopar heads worth messing with and the ones I would are too expensive for me. I do like the trickflows and I'm hopeful pretty soon going to port my 240s out further to a 2.610 by 1.380 gasket and match my tunnel ram after I get a gallon of splash zone.

I was once told it was cheaper to go faster because you always are going to want to go faster.
You should of got the 270's.
Herb McCandless told me that back in the early 90's, he also told me to fly cut for at least 650 lift. lol

 

[MOPARMAGA]

I was once told it was cheaper to go faster because you always are going to want to go faster.
You should of got the 270's.
Herb McCandless told me that back in the early 90's, he also told me to fly cut for at least 650 lift. lol

Yes I agree I should have done that for the street strip 451 I was going to build.