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Re: Ported Ford 289 heads with port energy discussion
Posted: Sun Sep 10, 2017 7:48 pm
by hoffman900
MadBill wrote:I'm not advocating that approach, merely providing a numerical answer to your flow-based pipe size question:
"So is a flow chasing 53cc 1.6" valved exhaust that flows 170 cfm oversized for a relatively high rpm 289? Flows about 190 cfm with a 1 5/8" pipe. Thanks, Charlie"
As per my previous response, I believe pipe size comes first. Theories on the subject have certainly evolved over the years. The factory race system (developed in the late forties/early fifties) for the Vincent 61 c.i. V-twins I raced in the sixties was a pair of 2" x 54" pipes and a number of 30.5" singles in the pre-war era ran dual pipes of ~ 1.5".
This.
A friend of mine talked with his old, late friend Mark Donohue at length about the AMCs. They tried all sorts of sizes on primaries on the Javelin motors with no difference, so they used what was most easily available. We know WAAAYYY better now and engines of that size with similar power are running primaries two sizes smaller. This totally means the ports they were using back then were way too big.
Re: Ported Ford 289 heads with port energy discussion
Posted: Sun Sep 10, 2017 9:51 pm
by MadBill
FWIW, with all else equal, if you input a higher V.E. into the PipeMax program it of course estimates more power but also suggests a slightly
smaller pipe.
Re: Ported Ford 289 heads with port energy discussion
Posted: Sun Sep 10, 2017 10:00 pm
by randy331
digger wrote:MadBill wrote:Update:
I found a graph by David Vizard in his
How to Build Horsepower book; it also can be seen about 1/4 of the way through his Max Small Block book as seen here:
http://www.chevydiy.com/chevy-small-blo ... t-systems/
The chart suggests pipe size vs. exhaust flow. For a street/strip engine with 170 CFM flow, a pipe ID ~ 1.60" is shown.
that methodology for choosing pipe size would perpetuate the issues of an oversized port. i think pipe size has hardly anything to do with port flow on a flow bench.
I'd say optimum ex pipe size has nothing to do to do with what the ex port flowz on a bench.
Those types of ideas are based on theory only.
Randy
Re: Ported Ford 289 heads with port energy discussion
Posted: Mon Sep 11, 2017 4:56 am
by digger
MadBill wrote:FWIW, with all else equal, if you input a higher V.E. into the PipeMax program it of course estimates more power but also suggests a slightly
smaller pipe.
mine doesn't, an increase in VE needs more pipe size and the same size as when VE is kept same but peak hp rpm is adjusted to give same hp
e.g. 6800rpm with 110% equals same size as 7511rpm with 100% both have same predicted hp number and pipe size within 0.001". so pipemax primary pipesize is very very strongly correlated to peak hp
Re: Ported Ford 289 heads with port energy discussion
Posted: Mon Sep 11, 2017 11:46 am
by MadBill
The info I quoted is from a PipeMax v. 3.7. I've got a newer version filed away somewhere that I haven't loaded yet; guess that's one of its refinements so I better get it cranked up..
Re: Ported Ford 289 heads with port energy discussion
Posted: Mon Sep 11, 2017 12:36 pm
by CGT
mag2555 wrote:With a duel pattern Cam and compressions above 11.5 even a 68% Exh to Intake ratio as shown in flow bench testing will work well many times!
What book or article did that information come from and what is well? Absolutes spoken on very dynamically complex processes tend to trip my
b#!%&*t alarm.
Re: Ported Ford 289 heads with port energy discussion
Posted: Mon Sep 11, 2017 3:15 pm
by GARY C
Maybe time to start measuring exhaust performance with a sound frequency measurement SFM as oppose to CFM.
Re: Ported Ford 289 heads with port energy discussion
Posted: Mon Sep 11, 2017 5:01 pm
by Stan Weiss
CGT wrote:mag2555 wrote:With a duel pattern Cam and compressions above 11.5 even a 68% Exh to Intake ratio as shown in flow bench testing will work well many times!
What book or article did that information come from and what is well? Absolutes spoken on very dynamically complex processes tend to trip my
b#!%&*t alarm.
Unless things have changed very recently. The 2.9 - 3.0 HP per ci N/A NHRA (500 ci) and Australian Pro Stock (400 ci SB's) are running closer 60% Exhaust to Intake ratio.
Stan
Re: Ported Ford 289 heads with port energy discussion
Posted: Tue Sep 12, 2017 6:29 am
by mag2555
Not only that fact like Stan posted , but look at some of these great performing heads with like a 2.19" Intake valve and yet still just a 1.65" Exh.
These Heads are a built in 70% or less Exh to int ratio no matter how you slice it!
Re: Ported Ford 289 heads with port energy discussion
Posted: Tue Sep 12, 2017 6:36 am
by Carnut1
Hp/cube and rpm make a difference here. Available differential pressure makes it that the intake valve takes presidence so you see larger and larger intake valves and better c/d intake ports. The exhaust valve and ports shrink and even though pumping losses increase for the exhaust the engine still makes more power.
Re: Ported Ford 289 heads with port energy discussion
Posted: Wed Sep 13, 2017 9:30 am
by randy331
CGT wrote:mag2555 wrote:With a duel pattern Cam and compressions above 11.5 even a 68% Exh to Intake ratio as shown in flow bench testing will work well many times!
What book or article did that information come from and what is well? Absolutes spoken on very dynamically complex processes tend to trip my
b#!%&*t alarm.
Those kinda comments are about as comical as 2-3 deg of LSA is worth 30-50 pounds of TQ.
Randy
Re: Ported Ford 289 heads with port energy discussion
Posted: Wed Sep 13, 2017 10:28 am
by user-9274568
Pipemax recommendations can be spot on for headers. Lengths, and sizes....
Re: Ported Ford 289 heads with port energy discussion
Posted: Wed Sep 13, 2017 4:59 pm
by David Vizard
I mentioned this before a year or so ago but intake to exhaust ratios are entirly dependant on the CR.
DV
Re: Ported Ford 289 heads with port energy discussion
Posted: Wed Sep 13, 2017 5:04 pm
by David Vizard
cspeier wrote:Pipemax recommendations can be spot on for headers. Lengths, and sizes....
Chad,
It is really rare that I disagree with you but for the engines we most commonly deal with all the commonly used programs are far from accurate.
DV
Re: Ported Ford 289 heads with port energy discussion
Posted: Wed Sep 13, 2017 7:47 pm
by Warp Speed
Stan Weiss wrote:
Unless things have changed very recently. The 2.9 - 3.0 HP per ci N/A NHRA (500 ci) and Australian Pro Stock (400 ci SB's) are running closer 60% Exhaust to Intake ratio.
Stan
Weird huh?!? Lol