The "perfect" cam for swirl port heads
Joined: Jan 2005
Posts: 10,450
Likes: 508
From: Hurst, Texas
Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears
Re: The "perfect" cam for swirl port heads
GMPP Crate engine--300 hp 350.
Horsepower.................. 300 @5300 RPM
Torque........................ 356 ft. lbs. @ 3700
One year, a long time ago, we discover the 300 hp 350 had the swirl-port junk heads removed, and it's now being sold with Vortec heads instead. With the Vortec heads on the same old short-block, they're calling it the 330 hp 350.Horsepower ..................... 330 @ 5000 RPM
Torque .......................... 380 Ft. Lbs. @ 3800
Add thirty horsepower at 300 fewer RPM.
Add 24 ft/lbs of torque at 100 additional RPM.
That pretty much tells me everything I need to know about swirl-port heads.
Horsepower.................. 300 @5300 RPM
Torque........................ 356 ft. lbs. @ 3700
One year, a long time ago, we discover the 300 hp 350 had the swirl-port junk heads removed, and it's now being sold with Vortec heads instead. With the Vortec heads on the same old short-block, they're calling it the 330 hp 350.Horsepower ..................... 330 @ 5000 RPM
Torque .......................... 380 Ft. Lbs. @ 3800
Add thirty horsepower at 300 fewer RPM.
Add 24 ft/lbs of torque at 100 additional RPM.
That pretty much tells me everything I need to know about swirl-port heads.
Don't knock the old 300 HP 350, its worlds better than the 290 HP offering they have now. I have worked with one of those old 300 horse 350 crate engines, installed in a 1972 ElCamino SS. I got my hands on it with an ancient holley spread bore carb on a square bore intake with a stock HEI that had way too much centrifical advance and nearly 40* of total timing. It was leaking oil from the valve covers and intake and ran like hell. Pull the valve covers, intake off, etc. Adjusted some loose rocker arms. Swapped on a new set of headers, a performer RPM intake, a tweaked Q-Jet and a DUI HEI and new wires. Reduced total timing to 35* BTDC and 13* initial. It runs better than the 300 HP rating would lead a person to believe.
Last edited by Fast355; Apr 10, 2014 at 11:14 AM.
Supreme Member
Joined: Apr 2010
Posts: 1,027
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From: Modesto, California
Car: 88 Firebird Formula
Engine: LO5 5.7 TBI/Ebl Flash
Transmission: 700R4
Axle/Gears: 2.73 stock rear end
Re: The "perfect" cam for swirl port heads
I have swirl port heads and my car pulls hard until 5300. i hate this "fall on their face at 3500 - 4000" crap. It's not true. I'm sure my car would make more power on vortec, dart, or NKB heads but the swirl port heads aren't nearly as bad as what people say. 
here's an older video, its the only one i have showing the tac. pre 3.70 gears and tune. 10* advance (14* now), with a l79 cam, shorty headers, etc. I
will say after i did the 3.70's it pulls WAY easier. i think the 3.08's were killing it. but that's not really on point. haha
1987 Trans Am Acceleration with Tach 5500 RPM Shifts - 357 V8 Demon Carb - YouTube
here's an older video, its the only one i have showing the tac. pre 3.70 gears and tune. 10* advance (14* now), with a l79 cam, shorty headers, etc. I
will say after i did the 3.70's it pulls WAY easier. i think the 3.08's were killing it. but that's not really on point. haha
1987 Trans Am Acceleration with Tach 5500 RPM Shifts - 357 V8 Demon Carb - YouTube
Supreme Member
Joined: Feb 2011
Posts: 1,589
Likes: 89
Re: The "perfect" cam for swirl port heads
Yup, YOU ARE RIGHT. The text claims that the heads are "non-swirl". There's a service parts list with a cylinder head part number--but I don't remember what it was, and the part number may be entirely different from the casting number anyway.
I guess this means the swirl-port heads are EVEN WORSE than I originally thought.
I agree. The 300 hp 350HO was intended to be a performance engine; the 290 is more of a stock-replacement.
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