Switch to 2bbl

Dwight Southerland · 12-16-2017, 09:28 AM

Quote:

Originally Posted by Coleydog

Thanks, but finally figured out where to find that.

You're not using http://www.classracerinfo.com?? Shame on you!!

Chipper Chapman · 12-16-2017, 10:54 AM

If you were to get a proper 2bbl camshaft ground how much would it differ from a 4bbl grind? I’m under the assumption that you’d want less duration when you go from a 800cfm q jet to a 350cfm 2bbl. Thought hard about doing this with 350/255 before selling, I didn’t think there’d be much difference in the 69-71 350 going from 750 to 500 cfm but these later engines loose a lot more airflow capability

Coleydog · 12-16-2017, 11:38 AM

Quote:

Originally Posted by Dwight Southerland

You're not using http://www.classracerinfo.com?? Shame on you!!

I've used it many times, just didn't look in the right place, now I know. Great info and very helpful.

rboyle · 12-17-2017, 04:10 PM

So am I looking at about .5 slower for my 1973 Nova 350/175/287 horse set up? .390/.410 lift cam, good 882 heads, Boburka 207 quadrajet, dish pistons, metric 200 trans with 5.13 rear. Car weighs 3470 in H/SA but would weigh 3418 in L/SA with a 2 barrel setup. I figured it at .90 better minus the .5 tenths loss on a carb swap so overall about .4 tenths better class for my combo? Does this sound right?

rboyle · 12-17-2017, 04:13 PM

The index is .85 better and 50 lbs less so about .90 better but car slows up about .5 because of restrictive 2 bbl carb.

Billy Nees · 12-17-2017, 05:07 PM

I think that you would probably slow down more than .5. You can't use the big 2V on your combo and the L index is tough.

rick winchester · 12-17-2017, 07:02 PM

At 3418lbs your car would be n/sa with a 13 flat index. 3418 -170 for driver devided by 224 hp =14.5 n/sa Rick

rboyle · 12-18-2017, 10:40 AM

Quote:

Originally Posted by rick winchester

At 3418lbs your car would be n/sa with a 13 flat index. 3418 -170 for driver devided by 224 hp =14.5 n/sa Rick

Sorry, my mistake on the classification. Yes 3418 is 52 lbs less than my current minimum and .85 less than my current index so about a .90 difference, right?

Coleydog · 12-19-2017, 10:03 AM

Quote:

Originally Posted by rick winchester

At 3418lbs your car would be n/sa with a 13 flat index. 3418 -170 for driver devided by 224 hp =14.5 n/sa Rick

I'm totally confused now, I thought the drivers weight was added to the shipping weight? The shipping weight was divided by the HP

12-16-2017, 10:54 AM	#2
Chipper Chapman Member Join Date: Jan 2004 Location: Belmont N.S. Canada Posts: 473 Likes: 246 Liked 166 Times in 71 Posts	Re: Switch to 2bbl If you were to get a proper 2bbl camshaft ground how much would it differ from a 4bbl grind? I’m under the assumption that you’d want less duration when you go from a 800cfm q jet to a 350cfm 2bbl. Thought hard about doing this with 350/255 before selling, I didn’t think there’d be much difference in the 69-71 350 going from 750 to 500 cfm but these later engines loose a lot more airflow capability __________________ Chris Chapman 1969 Chevelle NHRA F-G/SA 1090

12-17-2017, 04:10 PM	#4
rboyle Senior Member Join Date: Jan 2015 Posts: 604 Likes: 1,454 Liked 586 Times in 162 Posts	Re: Switch to 2bbl So am I looking at about .5 slower for my 1973 Nova 350/175/287 horse set up? .390/.410 lift cam, good 882 heads, Boburka 207 quadrajet, dish pistons, metric 200 trans with 5.13 rear. Car weighs 3470 in H/SA but would weigh 3418 in L/SA with a 2 barrel setup. I figured it at .90 better minus the .5 tenths loss on a carb swap so overall about .4 tenths better class for my combo? Does this sound right?

12-17-2017, 04:13 PM	#5
rboyle Senior Member Join Date: Jan 2015 Posts: 604 Likes: 1,454 Liked 586 Times in 162 Posts	Re: Switch to 2bbl The index is .85 better and 50 lbs less so about .90 better but car slows up about .5 because of restrictive 2 bbl carb.

12-17-2017, 05:07 PM	#6
Billy Nees VIP Member Join Date: Oct 2002 Location: On a hilltop in Pa. Posts: 4,494 Likes: 3,600 Liked 7,734 Times in 1,739 Posts	Re: Switch to 2bbl I think that you would probably slow down more than .5. You can't use the big 2V on your combo and the L index is tough. __________________ Billy Nees 1188 STK, SS I'm not spending 100K to win 2K

12-17-2017, 07:02 PM	#7
rick winchester Member Join Date: Mar 2003 Location: cincinnati ohio Posts: 209 Likes: 307 Liked 207 Times in 34 Posts	Re: Switch to 2bbl At 3418lbs your car would be n/sa with a 13 flat index. 3418 -170 for driver devided by 224 hp =14.5 n/sa Rick __________________ Rick Winchester Stk 3277

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