347 hp?
04-27-2011, 01:25 PM
#22
Banned
Join Date: Dec 2005
Location: Lil' Rhody
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04-27-2011, 03:01 PM
#23
Join Date: Apr 2011
Location: CA
Posts: 33
Are you running a dual or single plane manifold with that?
Did you try changing up the carb to 675 or 725 before you went to 750??
My grandfather has a tote full of used carbs. Carter, Holly, Webbers. Single, two and four barrel. he also has a shoe box full of jets. I, in the past have try'ed several carbs on a set up. 25cfm can be a drastic change. when you get your cfm & jet size just right it can make a world of difference.
Did you try changing up the carb to 675 or 725 before you went to 750??
My grandfather has a tote full of used carbs. Carter, Holly, Webbers. Single, two and four barrel. he also has a shoe box full of jets. I, in the past have try'ed several carbs on a set up. 25cfm can be a drastic change. when you get your cfm & jet size just right it can make a world of difference.
04-27-2011, 09:37 PM
#24
D.R. THE PATHETIC DORK
Join Date: Jun 2007
Location: West Virginia
Posts: 30,863
^^^it's running a rpm air gap ported by fti, I may switch to a single plane in the near future for giggles......but it has excellent low and mid pull that I'm not sure I'm gonna mess with it right now, my 89 s/c project is more priority right now 
06-28-2011, 01:32 AM
#25
Join Date: Apr 2011
Location: CA
Posts: 33
.....
It's too hard to say without knowing more about the heads. Ported to the max by a pro that 347 could make decent power, but not any more than a 302 with decent heads and a cam.
And the Edelbrock carbs aren't really a performance carb. And the 4150 Ultras are a way overpriced variant of the 4150 with the same tuning options as other carbs. You can do the same thing with a Quick Fuel etc, but for a lot less money.
And a 750 is fine for a 347, a 650 would strangle the life out of a properly built 347. Which by the way, would need a hell of a lot more head than GT40anythings. I wouldn't put anything less than AFR 185 comps or TFS 190's etc on a 347.
It's too hard to say without knowing more about the heads. Ported to the max by a pro that 347 could make decent power, but not any more than a 302 with decent heads and a cam.
And the Edelbrock carbs aren't really a performance carb. And the 4150 Ultras are a way overpriced variant of the 4150 with the same tuning options as other carbs. You can do the same thing with a Quick Fuel etc, but for a lot less money.
And a 750 is fine for a 347, a 650 would strangle the life out of a properly built 347. Which by the way, would need a hell of a lot more head than GT40anythings. I wouldn't put anything less than AFR 185 comps or TFS 190's etc on a 347.
They used a 650 Demon.
They strapped on the 850 and picked up less than 7tq & only 10hp.
Thats off the shelf, on hand, test unit. They didn't even jet the 650. If they had jetted the 650 they could have pulled bigger low end and hp numbers.
06-28-2011, 10:15 PM
#26
5th Gear Member
Join Date: Aug 2004
Location: Arizona
Posts: 4,103
I've seen that story n the magazine.
I've got sort of a tendency to believe my E.T. slips from the 'strip instead of magazine dyno stories.
I kind of have trouble with the general lack of ethics I've seen over the years from the writers/editors of most automotive magazines........
I've got sort of a tendency to believe my E.T. slips from the 'strip instead of magazine dyno stories.
I kind of have trouble with the general lack of ethics I've seen over the years from the writers/editors of most automotive magazines........
06-29-2011, 12:48 AM
#27
6th Gear Member
Join Date: Apr 2007
Location: California
Posts: 10,468
What Tinman said. Also, there's a difference between dyno numbers and actual performance....assuming the dyno they use is even accurate.
That said, you can get a crapload of power out of an undersized carb. Back under older rules they had 358cid engines making over 500hp at the crank at 6,500rpm through 390's. And even the Cup engines, ~800hp from 358's using 830cfm....on an engine that should be using 1,150 single or a pair of 550+ duals.
You can be sure they're playing around with cam design a lot to do that though. You can still get good performance out of a "too small carb," but for the typical build up for most people with ots parts(heads, intake etc) a 650 on a larger engine with larger heads is sub optimal. Especially depending on the cam.
That said, you can get a crapload of power out of an undersized carb. Back under older rules they had 358cid engines making over 500hp at the crank at 6,500rpm through 390's. And even the Cup engines, ~800hp from 358's using 830cfm....on an engine that should be using 1,150 single or a pair of 550+ duals.
You can be sure they're playing around with cam design a lot to do that though. You can still get good performance out of a "too small carb," but for the typical build up for most people with ots parts(heads, intake etc) a 650 on a larger engine with larger heads is sub optimal. Especially depending on the cam.
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