Switch to 2bbl
 

I currently have a dish piston 305 how much slower can I expect it to run with a 2 Barrel. Thanks for the input.

Re: Switch to 2bbl
 

My 69 Chevelle wagon ( 3865 lbs) slowed .5 or so from a Q-jet to a 2GC.
Mike A114

Re: Switch to 2bbl
 

Mike, Much bigger 2 bbl. on a bigger engine...Probably can't read too much into this.


Mr Money, Not enough info here. Depends on who built the 2 bbl, the 4 bbl, and the engine, itself.

Maybe the wizard on the hill in Pa. will take a WAG at it?

Re: Switch to 2bbl
 

Motor ran. 80 under with 4bbl. Having Dean Oliver build my 2gc. Not sure how good the intake is. It's going in a 77 Buick skylark that will fall into R/SA.

Re: Switch to 2bbl
 

Thanks Mark
Al Peters told me the difference between the small 2GC and the big one, is also about .5

Mike A114

Re: Switch to 2bbl
 

I run the same combo in 1978 nova: reasonable motor, deano carb, cam was ground for a four barrel. Ran mostly mid 13.8's in fair air, 13.7's in good air, mph mid 93 at 3450 weight in R - when HP was 180 in 2016 season. Running stock aluminum intake, not tried the cast intake as yet, for 1978 both are legal. Don't know how this will compare to your 4 bbl numbers.

Re: Switch to 2bbl
 

Jmoneyfoot, 305 dish piston motor, intake valves are different size, on 2 barrel & Q-jet. on 350 Q-jet & 2 barrel motor have same size valves, easer to switch 2 barrel to Q-jet.plus 2 barrel on 350 are bigger size than 305.

Re: Switch to 2bbl
 

Mr. Billy uses the SWAG method. With Billy it's science!

Re: Switch to 2bbl
 

Really good intake, really good head (don't worry about the small intake valves), bigger cam than 4V and carb flows about 325 CFM (before Deano).
There's a very good one here in Div.1 in a Malibu wagon that runs R and T and when it pops up it's usually a second under car. Much better combo than my 307.

Re: Switch to 2bbl
 

Billy, same cam 78 Malibu 2 barrel & 79 Malibu Q-jet, I thought about useing 2 barrel on my Malibu, but you had to change heads.

Re: Switch to 2bbl
 

Well you got me thinking, just checked on a 318 mopar in 70 & 69, 70 was 185, 69 - 172. Really, was there that much difference between the two? Hope someone who runs one can chime in.
Sorry if I jumped rails here.
Mike
The factor for the 70 is 15.32 and the 69 is 16.70. What class are these?
Mike

Re: Switch to 2bbl
 

its funny the 318 in 68 is rated higher, even though its the same engine. I am going to asdk the powers that be to get the lower rating on the 68

Re: Switch to 2bbl
 

70 would be O/S and the 69 would run P/S

Re: Switch to 2bbl
 

Thanks, but finally figured out where to find that.

Re: Switch to 2bbl
 

Mr Money, It really doesn't matter what the exact number is. Both will run way under.
They run J and K/SA with a 4 bbl ,and R and T with a 2bbl, and you're better off being in R and T.

Re: Switch to 2bbl
 

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

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

Re: Switch to 2bbl
 

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

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?

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.

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.

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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

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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?

Re: Switch to 2bbl
 

I would expect more than a .5 drop off, if you can`t use the big (1.375) 2GC.
Only 1 L car (-.617) at 1-7 LODRS @ E-town. A few N`s, and at least one of them used to be in L.
See Billy`s post above.
Mike A114

Re: Switch to 2bbl
 

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

Re: Switch to 2bbl
 

Rich said his car weighed 3418. One would assume that's with the driver weight added. So, the 170 needs to be removed to find the natural factor for the car. Then you would adjust to the lightest possible weight for that class. Then add the the driver weight for the total weight with the 2 bbl .combo.

Re: Switch to 2bbl
 

I’m still wrapping my head around the 350cfm for the 305 2bbl and 500cfm for the 350 2bbl.

302 is 287cfm and 351 is 356cfm. Only wish Ford had 350cfm on the 302.

Re: Switch to 2bbl
 

305 uses "medium sized" 2bbl, about 325 CFM.
69-70 350s use "really big" 2bbl, about 400 CFM.
All other 350s use "big" 2bbl at about 350 CFM.

FFFFord put 350 CFM carb on 82 manual trans Mustang GTs only.