Correct GT class

Ed Carpenter · 04-18-2008, 10:59 PM

What would be the correct GT class for my car? I'm currently running SS/I with the 327/275hp combo with a 207 q-jet. I believe with a 4GC it will be the 250hp combo. Thanks. ED

66 Chevy II

3120 lbs including driver

327 with 4GC carb

Bill Harris · 04-21-2008, 02:15 PM

If you have Excel you can use my calculator to tell you what classes you can run. Just enter the shipping weight, factored HP and trans type and it will tell you the legal classes and appropriate weights.

Remember that the rulebook says that for GT classes you have to use the shipping weight for the body style with the largest available gas engine.

www.employees.org/~bhracing/gt_class_calculator_1p1.xls

If you don't have Excel I can run the numbers for you.

Ed Carpenter · 04-21-2008, 04:12 PM

Bill,

I'm not on a computer now with excel. I can do it tommorow when I get home. Do you use the shipping weight of the car your claiming? A 66 never came with the 327/250hp combo. The 65 did. Do it calculate with the 65 car? Thanks.

greg fulk · 04-22-2008, 01:14 AM

Ed use the 66 weight.

John Mason · 04-22-2008, 12:08 PM

Ed,
You need to change heads as well as the carb to make it a 1963 250 HP. 1.72 intake valve and smaller chamber in the 520 (250 HP) head. Also, it's 250 HP in S/S but 258 HP in GT.
I run GT/IA (12 lb/HP) @ 3266 minimum with that combo.
The 1965 250 HP uses your 275 HP head but it's factored to 260 HP. Maybe the Q-jet is worth the 15 HP. It's got to be close.

John Mason · 04-22-2008, 06:49 PM

That's what I said, but it's factored to 260 HP in SS with the 041 heads or 265 HP using the World heads. I don't think 15 HP less and the bigger intake valve offsets the much smaller carb.
JMHO.

04-18-2008, 10:59 PM	#1
Ed Carpenter Live Reporter Join Date: May 2006 Location: Dripping Springs, Tx Posts: 2,709 Likes: 186 Liked 520 Times in 132 Posts	Correct GT class What would be the correct GT class for my car? I'm currently running SS/I with the 327/275hp combo with a 207 q-jet. I believe with a 4GC it will be the 250hp combo. Thanks. ED 66 Chevy II 3120 lbs including driver 327 with 4GC carb __________________ Ed Carpenter 2005 Chevy Cobalt A/SM Race Engine Development

04-21-2008, 02:15 PM	#2
Bill Harris Member Join Date: Mar 2002 Location: Ooltewah, TN Posts: 421 Likes: 13 Liked 26 Times in 13 Posts	Re: Correct GT class If you have Excel you can use my calculator to tell you what classes you can run. Just enter the shipping weight, factored HP and trans type and it will tell you the legal classes and appropriate weights. Remember that the rulebook says that for GT classes you have to use the shipping weight for the body style with the largest available gas engine. www.employees.org/~bhracing/gt_class_calculator_1p1.xls If you don't have Excel I can run the numbers for you. __________________ Bill Harris ex 2172 STK ex 2272 S/S

04-21-2008, 04:12 PM	#3
Ed Carpenter Live Reporter Join Date: May 2006 Location: Dripping Springs, Tx Posts: 2,709 Likes: 186 Liked 520 Times in 132 Posts	Re: Correct GT class Bill, I'm not on a computer now with excel. I can do it tommorow when I get home. Do you use the shipping weight of the car your claiming? A 66 never came with the 327/250hp combo. The 65 did. Do it calculate with the 65 car? Thanks. __________________ Ed Carpenter 2005 Chevy Cobalt A/SM Race Engine Development

04-22-2008, 01:14 AM	#4
greg fulk VIP Member Join Date: Jan 2003 Location: jackson Posts: 1,165 Likes: 0 Liked 5 Times in 3 Posts	Re: Correct GT class Ed use the 66 weight. __________________ Greg Fulk 308 308X P/SA "ALL AMERICAN"

04-22-2008, 12:08 PM	#5
John Mason Member Join Date: Apr 2002 Posts: 147 Likes: 0 Liked 0 Times in 0 Posts	Re: Correct GT class Ed, You need to change heads as well as the carb to make it a 1963 250 HP. 1.72 intake valve and smaller chamber in the 520 (250 HP) head. Also, it's 250 HP in S/S but 258 HP in GT. I run GT/IA (12 lb/HP) @ 3266 minimum with that combo. The 1965 250 HP uses your 275 HP head but it's factored to 260 HP. Maybe the Q-jet is worth the 15 HP. It's got to be close. __________________ John Mason 7743 SS Last edited by John Mason; 04-22-2008 at 12:20 PM. Reason: dropped last paragraph

04-22-2008, 06:49 PM	#6
John Mason Member Join Date: Apr 2002 Posts: 147 Likes: 0 Liked 0 Times in 0 Posts	Re: Correct GT class That's what I said, but it's factored to 260 HP in SS with the 041 heads or 265 HP using the World heads. I don't think 15 HP less and the bigger intake valve offsets the much smaller carb. JMHO. __________________ John Mason 7743 SS

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