Carb. an Clev. info
Re: Re: engine won't rev out -- CLVLNDLVR	Post Reply	Top of thread	Maverick Message Board

Posted by: Chris W. 02/10/2002, 03:46:04

On our 302 we've run into that same "problem". Our 302 has TFS heads, Victor Jr. intake, 230/240 solid f/t cam, about 9.5:1 comp., and Hooker 1 5/8" headers. We've tried a 600,700, and 800 Holley double pumpers on the engine. Some people will say to use a 750, but everybody always says all it needs is a 600. With the 600 and 700's, the motor can almost pull 7000 RPM's. But I don't think the motor likes the 600 very much. It seem to struggle sometimes. With the 800, it'll only pull about 6200 on a good day. But guess what, with the 800, we run about a half second quicker in the quarter mile. It even runs better on the street. Another benefit of the 800 is that if the motor doesn't turn as hard, less wear and tear. We even ran each carb long enough to make sure they were dialed in. Is the carb you have stock or modified? If your running a Torker intake and your probly running the 4V heads, right? If you are and the carb is stock then the 850 doesn't sound to big. The 4V headed motors can use a little extra carb. But, everyone's right, with that cam the motor shouldn't pull much past 6000 anyways. If that carbs modified then it may be a little big. I recently talked with a tech guy from BG about our 850 Speed Demon we have for one of our cars. He said that if you actually flow test our 800, it will never flow the 800 cfm that it is rated at. I don't remember what the actual flow was around, but I think he said it was around 700. He said that our 850 SD actually flows in the 1050-1060 range. They rate it as an 850 because it has the same basic internal dimensions (venturi dia. and butterfly size) as a Holley 850. They called the rating system an "industry standard." Whatever that means? Even though the demons are production carbs, compare them to a stock Holley, they are seriously "modified." If your carb is modified then it could be to big. If I were you, I would use the one that just "feels" best for you. Actually with a 4V headed motor, even if that 850 is a little big now, all that's needed is a cam swap. 4V Cleveland's like solids and alot of lift. Around .600" at least, no matter what the duration. There is usually never a problem with valve clearence either. In one I've built recently, I used a cam with 251/251 dur. @.050 w/ .610"/.610" lift. With the KB pistons I used, I probly could have been safe althoughway through .700". I checked the valve clearence with zero lash and no head gasket. The piston were .016" down the hole at TDC. Now this motor turns 7000 RPM's with no problem. At least so far. The motor only has about 30 miles on it and we're afraid to keep on it once it hits 7000.

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