PORT VOLUME-IS BIGGER BETTER OR IS LARGER LESS? Richard Holdener
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Wyrmrider
Well-Known Member
shape and velocity is better
bigger can kill your low end = flat spot
so unless you trailer and run high rpm only...
same with big valves, big cam , big compression
all have to work together
bigger can kill your low end = flat spot
so unless you trailer and run high rpm only...
same with big valves, big cam , big compression
all have to work together
I go by what Jim Laroy has always said. The shape is what's important.
Krooser
Building Chinese Free Engines since 1959...
Geez that guy is annoying....
B3422w5
Well-Known Member
More port volume for big inches
MOPAROFFICIAL
Well-Known Member
Depends on the rpm window and wether or not you built beyond the heads sweet spot. 'Like a 4" arm" Most stock heads can grow 15cc and 9nly make more power even if they flow 'about the same'.
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B3422w5
Well-Known Member
Anything W5 and below was pretty much designed for stock stroke, or at most, a 3.79 arm.
The advent of 4 inch plus arms left such stuff wheezing in serious even bracket level builds on the big end of the track, especially non offset stuff like eddies, Trick flows, etc
The advent of 4 inch plus arms left such stuff wheezing in serious even bracket level builds on the big end of the track, especially non offset stuff like eddies, Trick flows, etc
MOPAROFFICIAL
Well-Known Member
302 based motors come with heads that have smaller ports than a 318. This example is really just about useless to any of us...and they went over the factory designed port volume by ...oh 55+cc!?
They basically went from changing to an ideal performance head from stock..to a head that belongs on a 351 or 400cid.
That is called purposeful blundering for the sake of the argument to make a point that's really tired and common knowledge.
They basically went from changing to an ideal performance head from stock..to a head that belongs on a 351 or 400cid.
That is called purposeful blundering for the sake of the argument to make a point that's really tired and common knowledge.
yellow rose
Overnight Sensation
B3422w5
Well-Known Member
One NICE thing about about long stroke, small heads...
1/8 racing becoming the norm has masked that weakness to an extent.
I know the 418 with eddies i am putting in my Dart will “ seem” to run much better in the 1/8 than it will in the 1/4.
Block of wood.... meet under the gas pedal
1/8 racing becoming the norm has masked that weakness to an extent.
I know the 418 with eddies i am putting in my Dart will “ seem” to run much better in the 1/8 than it will in the 1/4.
Block of wood.... meet under the gas pedal
I feel obviously port volume, velocity is important but like everything people take it some times too far especially with basic builds. With SBM there's not too many 200 plus cc heads so port volume ain't a huge issue, generally only comes up when people talk about doing 318/273. I think the tunnel port 302 boss ford has scared everyone especially with small displacements running even reasonable sized ports.
Obviously there was no need going bigger than the 190 cc heads didn't really gain but on the dyno didn't really lose, don't think it was meant to be super scientific just he we have these heads and and short block lets see what happens. Lots of his dyno runs are from years ago and he just try's sometimes to see what different conclusions he can come up with the data. But to It does show ya the 190 cc where the best fit for the 302 and probably the strongest runner but I don't think the other two would of been slugs.
A great head flow guy once told me, "Velocity is torque"....
MOPAROFFICIAL
Well-Known Member
yellow rose
Overnight Sensation
I think my W5’s were 225 or close to that. The W7 is what I should have used, but at the time I couldn’t get them.
33IMP
Well-Known Member
Which of these seems the most wrong?....
1. 408 mopar stroker with 170 cc. Rpm heads
2. 302 Ford with 225 cc. Cnc ported heads
3. 396 Chevy (big block) with 316 cc. heads, stock, that flow 325 cfm.
4. 440 mopar with stock heads that flow around 220cfm, if they are pretty good ones (215 cc.? 235cc.?)
....
1
1. 408 mopar stroker with 170 cc. Rpm heads
2. 302 Ford with 225 cc. Cnc ported heads
3. 396 Chevy (big block) with 316 cc. heads, stock, that flow 325 cfm.
4. 440 mopar with stock heads that flow around 220cfm, if they are pretty good ones (215 cc.? 235cc.?)
....
1
yellow rose
Overnight Sensation
4 then 1. But a lot has to do with what it is for.
turboking15
Well-Known Member
Big thing i take away from this demo is people want to say too big of a head kills low end power when in all actuality most of the power difference is less than 10hp across the pull, up until the point where the larger head pulls away in the upper rpms. Youll be hard pressed to find someone who can tell a 10hp difference by the seat of their pants. (Read 90% of the people on this board, myself included)
yellow rose
Overnight Sensation
As mentioned by Richard, what is it doing at part throttle? I’ll never recommend the biggest head port as possible to use. Ever. The dyno is one thing, actually driving the car and how well it works is another.
There’s a reason hidden here why 351 Cleveland’s and 426 Hemis were dogs on the street.
