6-71 on a 302
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6-71 on a 302
I finished my 302 build and was really pleased with the results, but it got me thinking how much more power I can squeeze out of it. I was looking on Summitt racing and found a 6-71 that is made for a 302. I got a set of World cast iron 180 heads and a Holley 570 feeding the engine. Is this carb going to be enough when it has a supercharger on it or will I have to bump it up. Any suggestions on size? Also does anybody have any cam suggestions? I'm running a Crane 272 energizer now and don't really want to get rid of it unless I have to. Thanks
Sanders
Sanders
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From: Ohio
Well, if it IS a real 6-71, then it will fit anything that has a manifold made for it. The only real difference is the length of the drive assy out front. It varies depending on application and how long it needs to be to line up pulleys.
If it is one of the "mini" versions, it too will fit anything that has a manifold for it.
As for carb size, a call to any of the big companies will get you recommendations. BDS, Holley(mini blower set ups), Weiand, Hampton, etc. Cam suggestions are also available.
I don't think your 272 is too bad for a blower motor. The big thing is NO overlap. Lots of lift. You want air in, but not let it escape because both valves are open. A lumpy stick is not good for a blower. It sounds neat, but is not effective. It completely removes all the cylinder pressure you are trying to build using the blower.
What kind of compression ratio do you have now?? This is very critical when adding boost. You don't want 9:1 +, it will not survive long. Most motors are near 8:1. It depends on how much boost you want to add. If you keep it under 6-8 lbs it will okay. Once you want 12+ lbs, get ready for some upgrades.
If it is one of the "mini" versions, it too will fit anything that has a manifold for it.
As for carb size, a call to any of the big companies will get you recommendations. BDS, Holley(mini blower set ups), Weiand, Hampton, etc. Cam suggestions are also available.
I don't think your 272 is too bad for a blower motor. The big thing is NO overlap. Lots of lift. You want air in, but not let it escape because both valves are open. A lumpy stick is not good for a blower. It sounds neat, but is not effective. It completely removes all the cylinder pressure you are trying to build using the blower.
What kind of compression ratio do you have now?? This is very critical when adding boost. You don't want 9:1 +, it will not survive long. Most motors are near 8:1. It depends on how much boost you want to add. If you keep it under 6-8 lbs it will okay. Once you want 12+ lbs, get ready for some upgrades.
Lead Driver
Joined: Jan 2003
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From: Ohio
The boost all depends on the pulley size. The faster you turn it, the more boost. I run 6 lbs on my 390. It is a plain jane stock piston '68 motor. It is more show than go right now until I can afford some better pieces.
I know a fellow that ran the same basic stock motor parts and put 12 lbs to it. Granted it was just a race car and not driven daily(like mine). The big thing is watch your fuel, lean condition will destroy it quick. Just like a nitrous motor.
Have fun.
I know a fellow that ran the same basic stock motor parts and put 12 lbs to it. Granted it was just a race car and not driven daily(like mine). The big thing is watch your fuel, lean condition will destroy it quick. Just like a nitrous motor.
Have fun.
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What's the part#, brand and size. I could'nt find it. I have always thought an sc on a 302 truck would be the tops! A 347 with boost. Holy cow!
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davenjai,
All I have been able to find is this part# HLY-77-174FSB-1, it is not a 6-71 though. I'm sorry for any confusion, but I was wrong when I said it was a 6-71. After research I found it was a 174 "mini". Still I think it would be a nice addition to any motor.
All I have been able to find is this part# HLY-77-174FSB-1, it is not a 6-71 though. I'm sorry for any confusion, but I was wrong when I said it was a 6-71. After research I found it was a 174 "mini". Still I think it would be a nice addition to any motor.
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Sanders,
Just kidding! I thought it was to good to be true. I went back and read the posts above. Your 8.2 cr should handle the 174. Extra fuel a little less timing and "a different cam" should work well. I'm not an expert but a blower usually needs more overlap. I doubt the mini has blow off's otherwise too high revs and the blower will seperate from the intake,block by whatever means neccesary. one more thing, if your pistons are cast you HAVE to keep the revs down.If you do it should work. Comp or crane can reccomend a grind to work with goals and psi. Freight liner what are you running and where does the power come in at.
Have fun and post what you do.
David
Just kidding! I thought it was to good to be true. I went back and read the posts above. Your 8.2 cr should handle the 174. Extra fuel a little less timing and "a different cam" should work well. I'm not an expert but a blower usually needs more overlap. I doubt the mini has blow off's otherwise too high revs and the blower will seperate from the intake,block by whatever means neccesary. one more thing, if your pistons are cast you HAVE to keep the revs down.If you do it should work. Comp or crane can reccomend a grind to work with goals and psi. Freight liner what are you running and where does the power come in at.
Have fun and post what you do.
David
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