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Ford Windsor 408's HP Plateaus @ 5,600

General engine tech -- Drag Racing to Circle Track

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NewbVetteGuy
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Ford Windsor 408's HP Plateaus @ 5,600

Post by NewbVetteGuy »

All,

Looking for help solving a mystery. Not my engine, but I have my theory...

Ford Windsor 408: 4.030" bore, 4" stroke; 6.2" rods; 10.85:1 CR
FloTek SBF 205cc / 60cc heads 2.08 / 1.6" valves
Dual springs with dampners 150lb seat; 450 lb open
1 3/4" headers 3" collectors
FST 750 DP carb
Anderson Ford hyd roller N-111 cam: 315/325, 248/258 @ 0.050", 5.76"/5.76" lift with 1.6 Rockers; 110 LSA ICL 105
Stopped liking timing @ 36 deg
Edelbrock Super Vic intake
93 octane; Stuska dyno

.040 plugs; recommended heat range; msd something something ignition box

Guy was expecting it would pull to 6,500 but curve goes flat @ 5,500 - 5,600 and stays that way for 700 rpm...
Image

If that image doesn't resolve; I'll go post it somewhere and come back and repost...




Adam
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Re: Ford Windsor 408's HP Plateaus @ 5,600

Post by NewbVetteGuy »

maxracesoftware 876499 wrote:Tue Sep 15, 2020 8:15 pm
Just seeing if I can abuse the Quote feature to "Tag" Larry as my hunch is his magic math is very useful on this one...
Mark O'Neal
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Re: Ford Windsor 408's HP Plateaus @ 5,600

Post by Mark O'Neal »

What's the fuel pump pressure?
treyrags
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Re: Ford Windsor 408's HP Plateaus @ 5,600

Post by treyrags »

My guess is not enough intake CSA. If it was a problem with the lifters or springs I think it would dive instead of flatten.
NewbVetteGuy
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Re: Ford Windsor 408's HP Plateaus @ 5,600

Post by NewbVetteGuy »

Mark O'Neal wrote: Tue Sep 15, 2020 9:54 pm What's the fuel pump pressure?
5.5-6.5



Adam
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Re: Ford Windsor 408's HP Plateaus @ 5,600

Post by NewbVetteGuy »

Ford R302 lifters.

Heads have a min CSA of 2.165.
Solving for intake port centerline length I get 5.77” (not measured)


Adam
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Re: Ford Windsor 408's HP Plateaus @ 5,600

Post by rustbucket79 »

My thoughts would be the heads are the cork in this package. Everything else looks good, and the power carried out without falling off too much.
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Re: Ford Windsor 408's HP Plateaus @ 5,600

Post by superpursuit »

Heads too small.
I would have used 1 7/8" headers as well.


Allan.
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Re: Ford Windsor 408's HP Plateaus @ 5,600

Post by NewbVetteGuy »

rustbucket79 wrote: Tue Sep 15, 2020 10:29 pm My thoughts would be the heads are the cork in this package. Everything else looks good, and the power carried out without falling off too much.
That was my thinking, too. I haven’t been able to find a dyno showing choke to know that this is what it looks like on the dyno but Larry’s descriptions of increasing pumping losses as choke sets in made sense that this is what it would look like.

I did the CID + rpm calculator and it estimates that this much CSA should go “sonic”/ start backing up / going turbulent beyond 5,800 and its only a bit earlier than that.

These hyd roller lifters have a purported rpm limitation especially with high rpms, too. From what the owner found the piddle check valve becomes unseated at high oil temps and rpm. Ford made a modified version of the lifter (R302H), which has a lighter weight ceramic piddle check valve and a higher rate spring. Apparently gains 300-400 rpm with the same weight and temp oil.

-There’s definitely a chance that both could be an issue here, but not sure how he’ll be able to tell if the new lifters gained him anything without paying for more dyno time; if it was an EFI motor it would be easy: increasing fuel consumption / injector time as RPM increases, right?


Any way to try and diagnose whether the lifters are a factor limiting power here? No idea what lifter bleed down looks like on a dyno graph.


Adam
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Re: Ford Windsor 408's HP Plateaus @ 5,600

Post by NewbVetteGuy »

treyrags wrote: Tue Sep 15, 2020 10:02 pm My guess is not enough intake CSA. If it was a problem with the lifters or springs I think it would dive instead of flatten.
My guess too; I knew it wasn’t the springs and the heads CSA seems like a definite problem but I just didn’t know what lifters bleeding down looks like on a dynograph and I couldn’t find good examples.


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Re: Ford Windsor 408's HP Plateaus @ 5,600

Post by mt-engines »

do you have lbs/hr of fuel used per rpm? air flow through the carb? did the carb go fat? lean? did the air flow keep going up? or fall? show us the data
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Re: Ford Windsor 408's HP Plateaus @ 5,600

Post by bob460 »

Maybe too much spring pressure for these lifters?
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Re: Ford Windsor 408's HP Plateaus @ 5,600

Post by mag2555 »

In those Cam lift spec's you posted how is it that two different lobe lift numbers give the same amount of gross valve lift?
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Re: Ford Windsor 408's HP Plateaus @ 5,600

Post by treyrags »

mag2555 wrote: Wed Sep 16, 2020 6:11 am In those Cam lift spec's you posted how is it that two different lobe lift numbers give the same amount of gross valve lift?
I think those are advertised duration, not lobe lift?
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Re: Ford Windsor 408's HP Plateaus @ 5,600

Post by steve cowan »

With that bore and stroke I come up with 5800rpm for a average CSA of 2.165".

Average CSA of 2.165" x port length 5.77" x 16.387 = 204.7cc
If those heads are as cast there might be some turbulence issues like most as cast heads i have seen.
My own track testing has shown to small csa in cylinder head will limit power no matter how much rpm turned on engine.
My calculations for that cubes at peak power of 6500rpm needs approx 2.42 avg CSA which is close to 227-229 cc.
These calculations are just a starting point only.
steve c
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