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Marv D · 09-08-2017, 10:26 AM

Port velocity is what supports low RPM torque over high RPM power. Biggest key in that is the port that keeps the intake charge moving quickly to the chamber keeps the fuel 'mist' in suspension. That was the idea in the late 90's GM 'swirl port' head. (keep turbulence's in the intake charge so the fuel can't drop out of suspension at low speeds) Althought not a 'performance' head by ANY term,, they did make good torque from idle to around 3800 (which is 99.9% of the truck motor operates)

That's why a 'Large by HUGE' intake runner is not as good at low RPM power,,, as it is at flowing massive amounts of air to support high RPM. It's a compromise of keeping the A/F mixture in check at high speed with a small runner,, vs. a large runner that will flow more A/F when there is demand at high RPM.

The 170cc vortec is a good head for low RPM torque (in stock form or the E-tec Edelbrock), no denying that. BUT so is the AFR 180cc standard 23° / standard SBC intake configuraton that ROCKS in a heavy truck.There are a number of decent small runner aluminum heads out there right now, just don't fall in to the evilbay No-name import JUNK heads. Those appeal to the unsuspecting. Do your homework on ANY off-brand or house brand aluminum head. There are good and bad,,, and WORSE!

BUT with the head, consider a valve train upgrade to a nice hydraulic roller that will take advantage of the low lift flow. You can not achieve valve action with a flat tappet like can be had with a roller. It's a significant cost to upgrade but the risk of loosing a cam to poor oils or cam breakin disappear!!. You start it up and let it idle. WAY better on the new engine (and the nerves)

I have a set of 170 E-tecs on a 327 in my El Camino with Holley MPFI and a custom hydraulic roller,,, and had a set of iron RHS vortecs on a 383 in my 94 4x4 also a hydraulic roller motor. The ONE thing I can tell you after many miles on both,, I've built my LAST Vortec head motor. Not worth the BS of intake and rockers and rocker covers and re-routing the plug wires / looms. Today there is JUST AS GOOD out there in standard SBC form as the vortec

09-08-2017, 10:26 AM	#3
Marv D Registered Truck Offender Join Date: May 2008 Location: hells training ground (aka Ariz) Posts: 3,118	Re: SBC Alu Heads Designed for Torque Port velocity is what supports low RPM torque over high RPM power. Biggest key in that is the port that keeps the intake charge moving quickly to the chamber keeps the fuel 'mist' in suspension. That was the idea in the late 90's GM 'swirl port' head. (keep turbulence's in the intake charge so the fuel can't drop out of suspension at low speeds) Althought not a 'performance' head by ANY term,, they did make good torque from idle to around 3800 (which is 99.9% of the truck motor operates) That's why a 'Large by HUGE' intake runner is not as good at low RPM power,,, as it is at flowing massive amounts of air to support high RPM. It's a compromise of keeping the A/F mixture in check at high speed with a small runner,, vs. a large runner that will flow more A/F when there is demand at high RPM. The 170cc vortec is a good head for low RPM torque (in stock form or the E-tec Edelbrock), no denying that. BUT so is the AFR 180cc standard 23° / standard SBC intake configuraton that ROCKS in a heavy truck.There are a number of decent small runner aluminum heads out there right now, just don't fall in to the evilbay No-name import JUNK heads. Those appeal to the unsuspecting. Do your homework on ANY off-brand or house brand aluminum head. There are good and bad,,, and WORSE! BUT with the head, consider a valve train upgrade to a nice hydraulic roller that will take advantage of the low lift flow. You can not achieve valve action with a flat tappet like can be had with a roller. It's a significant cost to upgrade but the risk of loosing a cam to poor oils or cam breakin disappear!!. You start it up and let it idle. WAY better on the new engine (and the nerves) I have a set of 170 E-tecs on a 327 in my El Camino with Holley MPFI and a custom hydraulic roller,,, and had a set of iron RHS vortecs on a 383 in my 94 4x4 also a hydraulic roller motor. The ONE thing I can tell you after many miles on both,, I've built my LAST Vortec head motor. Not worth the BS of intake and rockers and rocker covers and re-routing the plug wires / looms. Today there is JUST AS GOOD out there in standard SBC form as the vortec __________________ Still playin with trucks, even at my age! When you're dead, it's only a problem for the people around you, because you don't know you're dead. .....It's kinda the same when your STUPID. I just did my taxes and reviewed my SS statement. Thanks to the current administration it looks like I will only have to work till noon on the day of my funeral. Last edited by Marv D; 09-08-2017 at 10:35 AM.