New aluminum heads and extended RPM range

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blackford
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New aluminum heads and extended RPM range

Post by blackford »

I'm putting ported Promaxx 180s on a 331 SBF. I'm replacing ported DOOE 351w heads that were 155cc. I've used EA 3.3 for years and it did a very good job estimating HP when compared to dyno results. Within the last year, I got EA Pro to model the engine, and the HP improvement at high rpm is rather dramatic. The usable rpm range has been extended from 7000 to 7500+ rpm. I had to go back and make sure I didn't overestimate anything when I saw this, but all EA Pro inputs looked correct.

I’m using a Comp 282S SFT cam with 1.7 shaft rockers. It's advertised for 2000-6000 rpm, but it's always been higher than that. With the old heads and on a dyno it peaked at 6500 with about 410 HP at the crank and dropped 30 HP at 7000 (I’m sure the heads were starting to choke). I’m surprised that the same cam is producing power up in the 7500 rpm range with the new heads, but maybe part of the reason for the cam to rpm higher is threefold; I run the lash .006 tighter (.016), I have 1.7 rockers and I have a single plane ported Victor Jr intake.

According to EA Pro, the HP improvement above 5000 is +34HP@5500, +61HP@6000, +75HP@6500, +101HP@7000 and +106HP@7500. Intake flow is 280@.500 and exhaust flow is 195@.500. Peak HP went from 410@6500 to 491HP@6800. High RPM HP is 483HP@7000 and 459HP@7500. Could these heads have increased the usable range to over 7500 with a 282S cam?

My bottom end consists of a Scat 9000 hi-nodular iron crank that was lightened (counterweights were trimmed about 1/8” to clear piston), 289 length H beam rods and 383 Windsor stroker pistons. Piston and pin are 643 grams, rod total weight is 610 grams, rod rotating weight is 424 grams and total bobweight is 1814 grams. I revved this engine to 7100 all the time for 18 years. It runs like a clock...no problems at all.

Can anyone tell me if 7500 rpm is reasonable for this bottom end or should I compromise with 7300 or stick with 7100? Piston speed and Piston G's are 3792/2970 at 7000 and 4063/3410 at 7500.

The valve train integrity at 7500 is a topic for another post. Thanks

Here is a pic of the new heads ready to be installed
Promaxx heads ready.jpg
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65 Mustang FB, 331 custom built with 289 H beam rods and 383W piston, 282S cam, Ported Maxx 180s, T5z, 9" 3.89 gears. ~460HP@6500

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Re: New aluminum heads and extended RPM range

Post by F-BIRD'88 »

If you want it to last don't shift it any high rpm than needed according to ¼ et slips.
The extended new head flow and port size will love more rpm more gear. You can try even tighter valve lash for effect on the ET if you want. A even bigger duration cam will make more top end still, now with the larger heads and vic JR.
Let the et slip be your guide. But don't twist it any higher than what gives the best track ET.
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Re: New aluminum heads and extended RPM range

Post by blackford »

Yea, but can I spin it that high? That's one question. There must be a similar setups out there that I could compare my bottom end to.

The other is if the heads really could extend the usable RPM range of the engine well past 7000 with the same cam.
65 Mustang FB, 331 custom built with 289 H beam rods and 383W piston, 282S cam, Ported Maxx 180s, T5z, 9" 3.89 gears. ~460HP@6500

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1980RS
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Re: New aluminum heads and extended RPM range

Post by 1980RS »

If you are looking to spin your engine higher and make more power, you will need to change the cam timing events. Adding as little as 10°of duration on both sides of the cam will help get you there. If I am correct a 282-S cam is 236° of duration and the 294-S is 248°
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Re: New aluminum heads and extended RPM range

Post by Walter R. Malik »

blackford wrote: Mon Mar 20, 2023 1:27 pm

Can anyone tell me if 7500 rpm is reasonable for this bottom end or should I compromise with 7300 or stick with 7100? Piston speed and Piston G's are 3792/2970 at 7000 and 4063/3410 at 7500.

The valve train integrity at 7500 is a topic for another post. Thanks

Here is a pic of the new heads ready to be installed

Promaxx heads ready.jpg
A 7,500 rpm limit should not be a problem for those rods & crank as long as it does not get into detonation at any time; if it actually makes good power that high.
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Re: New aluminum heads and extended RPM range

Post by mag2555 »

I don’t see any issue with taking that bottom end to 7500, but if the rod bolts have not been replaced due to having 4 torque up sessions on them then your starting to play with fire, and if they have 5 stretch out sessions on then then you are for sure playing with fire!
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
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Re: New aluminum heads and extended RPM range

Post by blackford »

mag2555 wrote: Mon Mar 20, 2023 7:32 pm I don’t see any issue with taking that bottom end to 7500, but if the rod bolts have not been replaced due to having 4 torque up sessions on them then your starting to play with fire, and if they have 5 stretch out sessions on then then you are for sure playing with fire!
What is a torque up session or stretch out session? Does it have something to do with every time the rod bolts are torqued during assembly or every time the engine is revved to redline?
65 Mustang FB, 331 custom built with 289 H beam rods and 383W piston, 282S cam, Ported Maxx 180s, T5z, 9" 3.89 gears. ~460HP@6500

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Re: New aluminum heads and extended RPM range

Post by 289nate »

I think you will be pleasantly surprised with the difference Tracy. Can’t wait to hear how it goes.
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Re: New aluminum heads and extended RPM range

Post by steve cowan »

100 hp is a great gain for your combination, well done.
The added cross section is where the power is at.
Cam events must be very close,I don't know much about Ford engines but on SBC with moderate cam,heads etc they don't respond the best with a higher rocker ratio on the exhaust.
Intake yes,exhaust likes a bit more duration. Got to ask yourself do you want to blow down the cylinder fast or slower?.
Moving the cam around would be my first test,if not on dyno you can test at the track .
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Re: New aluminum heads and extended RPM range

Post by F-BIRD'88 »

What is the current ¼ trap MPH and engine rpm?
I bet this car can use more gearz so it traps high enough to use all the engine power band to accelerate the car.
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Re: New aluminum heads and extended RPM range

Post by BobbyB »

What is the mcsa of old vs new heads?
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Re: New aluminum heads and extended RPM range

Post by blackford »

F-BIRD'88 wrote: Tue Mar 21, 2023 3:19 am What is the current ¼ trap MPH and engine rpm?
I bet this car can use more gearz so it traps high enough to use all the engine power band to accelerate the car.
Well, this is a street car. I've gone to a road course a few times. It's mainly a project thing that keeps me out of trouble. I had 3.50s and then put 3.89s in it. I have an ailing T5z in it now that's getting replaced with a Gordon Levy T5 after the engine is done. I could track it with this trans.

This thing just keeps evolving over the years. I was planning to port my heads some more this time, but I hit water and went to plan B. The triple digit gains in HP took me by surprise. I just thought this cam would be too small to make power at 7500. Like I said though, the cam is behaving bigger and I set lash .006 tighter and I use 1.7 shaft rockers. I also have a ported single plane intake. I've had big blocks before this engine, and I have to say that I like screaming small blocks better now, and the prospect of being able to twist it higher is very appealing.
65 Mustang FB, 331 custom built with 289 H beam rods and 383W piston, 282S cam, Ported Maxx 180s, T5z, 9" 3.89 gears. ~460HP@6500

2013 Corvette 427 Convertible daily driver
blackford
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Re: New aluminum heads and extended RPM range

Post by blackford »

BobbyB wrote: Tue Mar 21, 2023 7:45 am What is the mcsa of old vs new heads?
1.9 vs 2.20

The old heads after porting 20 years ago were about 1.9 at the pinch and in the runner before the short turn. I ported them nearly 20 years ago, and since then I learned the importance of CSA. I ported a spare DOOE head 6 mos ago and got the MCSA to 2.05 (got nearly 250 cfm out of the intake port). I then took the DOOE heads off the engine and copied the porting I did to the spare head and on the 3rd intake port I hit water. On to plan B.

The MCSA of the Promaxx heads were also 1.9 out-of-the-box. An AFR Enforcer 185 head that I had for a short time was the same way. Seems odd they would have a bigger port with poor CSA at the pinch. Anyhow, after porting the Promaxx heads, the CSA at the pinch is almost 2.20. There was a lot of material around the pushrod hole and I widened the port about .100 there. I made one of those pushrod hole tools that show how much material is remaining in the wall. I also raised the roof about 1/16" to match the Felpro 1262. A few more minor cleanups to the intake and exhaust were done.
65 Mustang FB, 331 custom built with 289 H beam rods and 383W piston, 282S cam, Ported Maxx 180s, T5z, 9" 3.89 gears. ~460HP@6500

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Re: New aluminum heads and extended RPM range

Post by BobbyB »

blackford wrote: Tue Mar 21, 2023 11:57 am
BobbyB wrote: Tue Mar 21, 2023 7:45 am What is the mcsa of old vs new heads?
1.9 vs 2.20

The old heads after porting 20 years ago were about 1.9 at the pinch and in the runner before the short turn. I ported them nearly 20 years ago, and since then I learned the importance of CSA. I ported a spare DOOE head 6 mos ago and got the MCSA to 2.05 (got nearly 250 cfm out of the intake port). I then took the DOOE heads off the engine and copied the porting I did to the spare head and on the 3rd intake port I hit water. On to plan B.

The MCSA of the Promaxx heads were also 1.9 out-of-the-box. An AFR Enforcer 185 head that I had for a short time was the same way. Seems odd they would have a bigger port with poor CSA at the pinch. Anyhow, after porting the Promaxx heads, the CSA at the pinch is almost 2.20. There was a lot of material around the pushrod hole and I widened the port about .100 there. I made one of those pushrod hole tools that show how much material is remaining in the wall. I also raised the roof about 1/16" to match the Felpro 1262. A few more minor cleanups to the intake and exhaust were done.
Thanks, I am watching this one closely. I have a similar car with similar history & similar smallish mcsa heads that might need more porting... old hot rods never die..thay just get tweeked!
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Re: New aluminum heads and extended RPM range

Post by Joe-71 »

I hate to be the "naysayer" but, what is the average gain in airflow with your camshaft lift? That will be more in line with how much horsepower you can expect to gain. It has been my experience that if you don't change the camshaft, you will only gain 1 hp per cfm of airflow increase. I have yet to see the dyno results for the so called 2hp/cfm increase unless you have over 13:1 compression, and tunnel ram intake. JMO, but to see triple digit increase will not happen unless you change more than the heads. Joe-71
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