Head selection for street performance sbf

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travis
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Head selection for street performance sbf

Post by travis » Wed Aug 08, 2018 5:29 pm

351w, roughly 10:1 compression, 218/222 hydro roller on a 112 lsa, dual plane, etc, 2500 stall C-6, 4500-ish pound F-150 with 3.55’s. Strictly street performance usage.

I pretty much had my mind made up to use a small aftermarket head (AFR165, dart 170 pro1, Brodix 171, etc), but after reading through tons of dyno tests, even mild engines generally show better results across the board with bigger heads, all else being the same, at all points in the test range.

I’m looking for a wide powerband from 2500-6000, with excellent part throttle performance in street use rpm range but that will still pull hard at WOT. Would the next size (or 2) up be better? Something like AFR185’s or 195’s, Dart 195’s, Brodix 195’s, etc? I’m afraid I may be thinking too conservatively, but I’m also trying to accommodate the heavy weight and desired usage with a mild converter and gear.

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Re: Head selection for street performance sbf

Post by Walter R. Malik » Wed Aug 08, 2018 5:44 pm

travis wrote:
Wed Aug 08, 2018 5:29 pm
351w, roughly 10:1 compression, 218/222 hydro roller on a 112 lsa, dual plane, etc, 2500 stall C-6, 4500-ish pound F-150 with 3.55’s. Strictly street performance usage.

I pretty much had my mind made up to use a small aftermarket head (AFR165, dart 170 pro1, Brodix 171, etc), but after reading through tons of dyno tests, even mild engines generally show better results across the board with bigger heads, all else being the same, at all points in the test range.

I’m looking for a wide powerband from 2500-6000, with excellent part throttle performance in street use rpm range but that will still pull hard at WOT. Would the next size (or 2) up be better? Something like AFR185’s or 195’s, Dart 195’s, Brodix 195’s, etc? I’m afraid I may be thinking too conservatively, but I’m also trying to accommodate the heavy weight and desired usage with a mild converter and gear.
Bigger heads will definitely produce more horsepower at Wide Open Throttle at the expense of transient response and torque below the torque peak RPM. You did say STREET.

Exactly how often do you intend to run your vehicle at Wide Open Throttle ...?

That should make your decision.
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Re: Head selection for street performance sbf

Post by travis » Wed Aug 08, 2018 6:23 pm

Thanks Walter. That pretty much validates my original thinking...I’m just really bad about 2nd guessing my decisions sometimes.

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Re: Head selection for street performance sbf

Post by BigBlocksOnTop2 » Wed Aug 08, 2018 7:06 pm

4500 lbs. 3.55:1 gears and 351 cu.in., that's a lot . The C6 is a power robber too....Maybe a really good bottom end and a blower!

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Re: Head selection for street performance sbf

Post by travis » Wed Aug 08, 2018 8:32 pm

BigBlocksOnTop2 wrote:
Wed Aug 08, 2018 7:06 pm
4500 lbs. 3.55:1 gears and 351 cu.in., that's a lot . The C6 is a power robber too....Maybe a really good bottom end and a blower!
I wish it was in the budget. Some day...

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Re: Head selection for street performance sbf

Post by mag2555 » Thu Aug 09, 2018 7:54 am

You will not get a hp power band topping out at 6K with a head port volume that will give you the best overall average drivablity with that weight vehicle period!!
Error on the small side and you can always port them up!
Last edited by mag2555 on Thu Aug 09, 2018 8:09 am, edited 1 time in total.

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Re: Head selection for street performance sbf

Post by My427stang » Thu Aug 09, 2018 8:03 am

I have had very good results in the past with AFR 165s on 347s, I'd expect them to do real well on yours too. Might be able to gain a little snap with a little cam advance too. I assume you are near 108 ICL now, depending on the rest of the cam specs you may be able to crank it forward a bit

However, that goes against your 6000 RPM peak. I think that is the wrong peak for a build like that and you should be shifting it way down, or change gears and let her rip :)

Which dual plane and exact compression matters too, although there are some options when you buy new heads to adjust where you are
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Re: Head selection for street performance sbf

Post by turbo2256b » Thu Aug 09, 2018 8:08 am

just what is your desired usage

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Re: Head selection for street performance sbf

Post by travis » Thu Aug 09, 2018 8:53 am

Strictly street performance but still useable as a truck on occasion. I don’t expect it to peak at 6k but want it to still pull well on top, with as much power in the 2000-5500 range as possible.

Compression will be somewhere between 9.6 and 10.1, and planning on trying the Weiand Stealth that I already have first, along with a 650-750 vac sec carb.

Cam should be here in the next few days...the parts pile is growing!

I’m copying this build posted by Mike Jones a while back, but on a 351w platform.

355 SBC
10:1 compression
ported 492 heads
Performer RPM
Holley 600cfm "top-loader"
LS firing order hydr roller cam: 216/220 @.050" .340"/.340" Lobe Lift, 112 LSA, 108 ICL
1.6 rockers
Morel #4602 lifters
PAC 1218X springs

RPM---TQ--BHP
3200--439--267
3400--443--287
3600--445--305
3800--444--321
4000--443--337
4200--440--352
4400--440--368
4600--441--386
4800--441--403
5000--432--411
5200--422--418
5400--412--423
5600--400--426

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Re: Head selection for street performance sbf

Post by Carnut1 » Thu Aug 09, 2018 10:18 am

I think the gt-40 aluminums with some porting would work well on this project. Thanks, Charlie
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Re: Head selection for street performance sbf

Post by travis » Thu Aug 09, 2018 7:56 pm

Carnut1 wrote:
Thu Aug 09, 2018 10:18 am
I think the gt-40 aluminums with some porting would work well on this project. Thanks, Charlie
If I had much of a clue on real porting (not just improving on weak flowing OEM heads), and access to a flow bench, I would certainly try it. I’m just afraid I would do more damage than good.

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Re: Head selection for street performance sbf

Post by My427stang » Sat Aug 11, 2018 12:49 pm

Do you have all of your cam card information? Also, how did you calculate you current compression (parts you used, measured or manufacturer specs, etc)
70 Mustang, 489 FE, TKO-600, Massflo SEFI, 4.11s
71 F100 SB 4x4, 445 FE, hot rod 4x4

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Re: Head selection for street performance sbf

Post by travis » Sat Sep 08, 2018 12:39 pm

Cam is 218/222@.050, 264/268@.006, 112 lsa, 109 ica if installed straight up. I can tweak from there if needed.

Compression calculations are based on different combinations of parts...I haven’t locked into anything yet. Just got the block back from the machine shop...it cleaned up at .030” over.

I got a bit sidetracked with a couple of large unexpected expenses and trying to finish up some other honey-do’s.

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Re: Head selection for street performance sbf

Post by MTENGINES » Sat Sep 08, 2018 2:22 pm

Walter R. Malik wrote:
Wed Aug 08, 2018 5:44 pm
travis wrote:
Wed Aug 08, 2018 5:29 pm
351w, roughly 10:1 compression, 218/222 hydro roller on a 112 lsa, dual plane, etc, 2500 stall C-6, 4500-ish pound F-150 with 3.55’s. Strictly street performance usage.

I pretty much had my mind made up to use a small aftermarket head (AFR165, dart 170 pro1, Brodix 171, etc), but after reading through tons of dyno tests, even mild engines generally show better results across the board with bigger heads, all else being the same, at all points in the test range.

I’m looking for a wide powerband from 2500-6000, with excellent part throttle performance in street use rpm range but that will still pull hard at WOT. Would the next size (or 2) up be better? Something like AFR185’s or 195’s, Dart 195’s, Brodix 195’s, etc? I’m afraid I may be thinking too conservatively, but I’m also trying to accommodate the heavy weight and desired usage with a mild converter and gear.
Bigger heads will definitely produce more horsepower at Wide Open Throttle at the expense of transient response and torque below the torque peak RPM. You did say STREET.

Exactly how often do you intend to run your vehicle at Wide Open Throttle ...?

That should make your decision.
This is BS...

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Re: Head selection for street performance sbf

Post by groberts101 » Sat Sep 08, 2018 4:32 pm

MTENGINES wrote:
Sat Sep 08, 2018 2:22 pm
Walter R. Malik wrote:
Wed Aug 08, 2018 5:44 pm
travis wrote:
Wed Aug 08, 2018 5:29 pm
351w, roughly 10:1 compression, 218/222 hydro roller on a 112 lsa, dual plane, etc, 2500 stall C-6, 4500-ish pound F-150 with 3.55’s. Strictly street performance usage.

I pretty much had my mind made up to use a small aftermarket head (AFR165, dart 170 pro1, Brodix 171, etc), but after reading through tons of dyno tests, even mild engines generally show better results across the board with bigger heads, all else being the same, at all points in the test range.

I’m looking for a wide powerband from 2500-6000, with excellent part throttle performance in street use rpm range but that will still pull hard at WOT. Would the next size (or 2) up be better? Something like AFR185’s or 195’s, Dart 195’s, Brodix 195’s, etc? I’m afraid I may be thinking too conservatively, but I’m also trying to accommodate the heavy weight and desired usage with a mild converter and gear.
Bigger heads will definitely produce more horsepower at Wide Open Throttle at the expense of transient response and torque below the torque peak RPM. You did say STREET.

Exactly how often do you intend to run your vehicle at Wide Open Throttle ...?

That should make your decision.
This is BS...
The hell it is. Port velocity at part throttle is greatly controlled by cross sectional area even though that cross section isn't anywhere near saturated during closed throttle scenarios. And larger CC heads GENERALLY have larger cross sections which do and always have hurt transient response and torque production WELL below the engine torque peak. Not everything can be fixed or compensated with a smaller cam and shorter timing. Just because some here don't pull their dyno's down to 1,200 rpm or really care about torque production at that low an rpm doesn't mean that the potential losses aren't real.

I've seen many combinations of bigger ports and bigger valves lose torque way below their peaks but especially so immediately right off idle during smaller light throttle stabs. I once opened up the small pushrod pinch on my Edelbrock RPM headed 383. No other porting or tuning changes at all, no it would not take any different spark/fuel tune whatsoever from its already gnats assed dial in, and the motor went from abruptly spinning the tires a 1/2 turn while rolling along at 850 rpm idle and slightly just barely jabbing the throttle to about 1,200-1,300 rpm.. to a paltry little tire scrub of barely 1/16 rotation afterwards. This same thing can happen with the old 96+ Vortec heads too. Sure power rises up near peak and beyond but not everyone cares about bigger peak numbers at the expense of more easily moving a heavier and taller geared vehicle from a stoplight at part throttle.

And I know of no even somewhat later model F150 that only weighs 4,500 lbs. Even the smaller spartan rubber matted shortbox's can easily creep past 5,000. And many are 5,500lbs or well more depending on options. Then add driver and gear to go higher yet.

Travis.. IMO, you already answered your own question with the vehicle and drivetrain spec's. Smaller higher velocity heads and induction system will be better all around and you will only give up 20 - 30 peak horsepower in that tradeoff.

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