On the Fence
Thread Starter
Le Mans Master
Joined: May 2008
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2022 C3 of the Year Finalist - Modified
On the Fence
Another cylinder head question:
Given the limitation of a set of 2-1/2 inch rams horns, with 2-1/2 mandrel bent Magnoflow exhaust system, (headers are not something I want, and understand I am taking a power penalty):
I am down to selecting from two heads, Performer RPM (185 cc) OR AFR 180 (180 cc). No question the AFR heads flow better.....BUT, can it flow better with the exhaust manifold restriction?
I guess bottom line question, would there be more seat of the pants torque with the AFR heads over the RPM heads, with all else the same? and especially without headers?
Given the limitation of a set of 2-1/2 inch rams horns, with 2-1/2 mandrel bent Magnoflow exhaust system, (headers are not something I want, and understand I am taking a power penalty):
I am down to selecting from two heads, Performer RPM (185 cc) OR AFR 180 (180 cc). No question the AFR heads flow better.....BUT, can it flow better with the exhaust manifold restriction?
I guess bottom line question, would there be more seat of the pants torque with the AFR heads over the RPM heads, with all else the same? and especially without headers?
Race Director
Joined: Jan 2000
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From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
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2017 C2 of Year Finalist
Not sure what cubes etc you're dealing with...but the AFR's would win. Hopefully it's no more than 350 or so cubes for heads that small.
Cam choice will need to be carefully selected for either head...'cause they will be different.
Good head flow is good head flow.
JIM
Cam choice will need to be carefully selected for either head...'cause they will be different.
Good head flow is good head flow.
JIM
Thread Starter
Le Mans Master
Joined: May 2008
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2022 C3 of the Year Finalist - Modified
Head FLow
Not sure what cubes etc you're dealing with...but the AFR's would win. Hopefully it's no more than 350 or so cubes for heads that small.
Cam choice will need to be carefully selected for either head...'cause they will be different.
Good head flow is good head flow.
JIM
Cam choice will need to be carefully selected for either head...'cause they will be different.
Good head flow is good head flow.
JIM
As for cam my understanding of a good head like the AFR is that you may want a single pattern cam versus dual since the dual pattern is meant to deal with the handicap of a poor exhaust port, etc. With the RPM head I have been thinking Comp Cams XE264HR ro XE270HR. I want bottom end torque and don't care about 6000 RPM HP.
Race Director
Joined: Jan 2000
Posts: 13,018
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From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
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2017 C2 of Year Finalist
It's not just max airflow you have to look at. At probably every lift point you check the AFR will be moving more air. So even at .100, .200" etc there will be more flow. The manifolds aren't going to choke it too bad. You can certainly take a grinder to them and open them up as much as possible. Steve(632C2) was running high 11's with is 383 using cast iron manifolds and a whole motor disguised to look like a 327/250 HP.
Certainly headers will help...but the better flowing heads will let you get the most out of the manifolds.
Cam choice is going to come down to cubes, rpm, trans/converter, compression, gearing, weight, intake manifold and carb, remaining exhaust system and what your idea of street manners is.
The better the head flow...the less cam you need to achieve "X" goal. Having exhaust restriction can skew things and require a little added duration as long as we don't get too much overlap.
Tell us more about the whole combo. Flat tappet, Hyd roller, solid lifter, solid roller?
JIM
Certainly headers will help...but the better flowing heads will let you get the most out of the manifolds.
Cam choice is going to come down to cubes, rpm, trans/converter, compression, gearing, weight, intake manifold and carb, remaining exhaust system and what your idea of street manners is.
The better the head flow...the less cam you need to achieve "X" goal. Having exhaust restriction can skew things and require a little added duration as long as we don't get too much overlap.
Tell us more about the whole combo. Flat tappet, Hyd roller, solid lifter, solid roller?
JIM
Team Owner
Joined: Oct 2004
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From: altered state
St. Jude Donor '05
Youl pick up across the board with the AFRs even with those manifolds. Ive ported the daylights out of the rams horn saw no gains.
If there were any it would only show on a dyno...or maybe the track not the butt o meter though. Some 1-5/8 shorties would help, anything would lol. Stock heads are puke
What about some Sandersons?
Burning Brakes
Joined: Apr 2007
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From: Kona Hawaii
Another head option would be the Trick Flow 56cc heads with roller cam valve springs.They flow well and will give a nice boost to the CR.FelPro 1094 head gasket,& hyd roller cam will give that 350 some bottom end grunt..The smaller intake ports will increase port velocity helping low end performance.Also read this article on carbs and intake manifolds.Closing up that open plenum divider & using a 4 hole carb gasket did wonders for the low end torque.http://community-2.webtv.net/mattgru/carb/
Thread Starter
Le Mans Master
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2022 C3 of the Year Finalist - Modified
Here is the rest of the package so far:
ZZ4 350 Short Block brand new
Chevy Hydraulic Roller Lifter set
Performer RPM intake OR possibly RPM Air Gap
Holley Avenger Carb - 660 or 750
Comp Cams Magnum Roller Rocker 1.52 or maybe Scorpion rollers 1.5?
Cam - thinking about Comp XR264HR or XR270HR, maybe Magnum 270 with the AFR head. I do not want to over-cam it.
Going into my 4-speed 77 Corvette in the avatar. Rear end is a 3.55 ratio. The car will be much lighter due to aluminum heads, intake, radiator, composite spring, aluminum wheels, no radio, no spare tire.
I am a beginner at all of this, but trying to build a solid, high quality and reliable engine that will be torquey down low and up to 5500 RPM. I really am not as concerned about high RPM nor high speed.
So now the question is about the heads, and cam. The AFR 180's are less than $200 difference from the Performer RPM heads, so cost is not a real big deal. And I think the quality if equal. Tell me what you think.
ZZ4 350 Short Block brand new
Chevy Hydraulic Roller Lifter set
Performer RPM intake OR possibly RPM Air Gap
Holley Avenger Carb - 660 or 750
Comp Cams Magnum Roller Rocker 1.52 or maybe Scorpion rollers 1.5?
Cam - thinking about Comp XR264HR or XR270HR, maybe Magnum 270 with the AFR head. I do not want to over-cam it.
Going into my 4-speed 77 Corvette in the avatar. Rear end is a 3.55 ratio. The car will be much lighter due to aluminum heads, intake, radiator, composite spring, aluminum wheels, no radio, no spare tire.
I am a beginner at all of this, but trying to build a solid, high quality and reliable engine that will be torquey down low and up to 5500 RPM. I really am not as concerned about high RPM nor high speed.
So now the question is about the heads, and cam. The AFR 180's are less than $200 difference from the Performer RPM heads, so cost is not a real big deal. And I think the quality if equal. Tell me what you think.
Thread Starter
Le Mans Master
Joined: May 2008
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2022 C3 of the Year Finalist - Modified
Plenum Divider
Another head option would be the Trick Flow 56cc heads with roller cam valve springs.They flow well and will give a nice boost to the CR.FelPro 1094 head gasket,& hyd roller cam will give that 350 some bottom end grunt..The smaller intake ports will increase port velocity helping low end performance.Also read this article on carbs and intake manifolds.Closing up that open plenum divider & using a 4 hole carb gasket did wonders for the low end torque.http://community-2.webtv.net/mattgru/carb/
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Verdad Gallardo
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From: New Or-leens Loo-z-anna
Being a rookie....I "read-up" & ground the intake & head ports (on my'93 pickup 350 SBC) to open them and to match the size of the internal ports where they joined (which were up to 1/8" different in size).
I also trimmed the port I.D.s (mis-use of the term) of the intake gaskets where needed.
I immediately noticed a 75 rpm increase at idle....(with carb/etc untouched)....I re-adjusted the idle down.
I am hoping to get similar results when I grind the I.D.s of the head/exhaust manifold internal ports/trim I.D. of exhaust gaskets.
I should be able to notice a slight difference in acceleration.
I also trimmed the port I.D.s (mis-use of the term) of the intake gaskets where needed.
I immediately noticed a 75 rpm increase at idle....(with carb/etc untouched)....I re-adjusted the idle down.
I am hoping to get similar results when I grind the I.D.s of the head/exhaust manifold internal ports/trim I.D. of exhaust gaskets.
I should be able to notice a slight difference in acceleration.
Last edited by doorgunner; Nov 18, 2013 at 09:14 AM.
Thread Starter
Le Mans Master
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2022 C3 of the Year Finalist - Modified
Match AFR
Anyway, thanks for the input. Ultimately, a 400 HP, 400 Ft Lbs torque is what my goal is, as long as it is in the 1200-500 RPM range.
Safety Car
Joined: Jan 2009
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From: New York
Can you clarify what you posted above. You said Match the AFR heads to the GM Fast Burns. I am not following what you are saying. The Fast burns are GM and the AFR heads made by Airflow Research. Are you saying pick an AFR head with similar specifications to the GM Fast burns. If so, I understand. I think it will be difficult to see an apples to apples comparison, as there are lot of specific fact, i.e. valve sizes, intake volume, valve springs, etc. I don't believe there will be an exact match.
Anyway, thanks for the input. Ultimately, a 400 HP, 400 Ft Lbs torque is what my goal is, as long as it is in the 1200-500 RPM range.
Anyway, thanks for the input. Ultimately, a 400 HP, 400 Ft Lbs torque is what my goal is, as long as it is in the 1200-500 RPM range.
AFR is the head every one insists on , so I was trying to say what you did . match as close as possible to the GMPP Fast Burn .. I chose the fast burn over the others because it is not just flow that matters it is a multitude of things and having GM already tried and tested with the ZZ430 I wanted to match that so I had confidence in the numbers.
Now that being said , I can say this .. It is a very strong set up , that has great idle and manners and makes that 350 ci as powerful as a lot of the 383 stokers out there.. An it is very affordable I got a new in box complete set of fast burns for 985.00 .. It was off ebay or racing junk I forget which. And the fast burns unless your going to 600 and up lift are as good as any head out there no matter the brand. PLUS you have a blue print from GMPP with the specs ensuring the power advertised because it is all built off the ZZ4 short block