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Old 03-26-2008, 08:21 PM
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carb risers

i just heard of these wood risers today from a buddy. anybody ever seen or used them? i heard they are better then the metal ones since they dont transfer heat as well as metal does.gimme some feedback pls.

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Old 03-26-2008, 08:25 PM
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Wood does insulate from heat..however wood can wick fuel. I live in the desert..dried wood..soaking fuel..so not for me..

Phenolic gaskets are great insulators..

I just ordered the heat shield and phenolic Holley set..$25 Jegs
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Old 03-26-2008, 08:25 PM
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I have one made out of hard plastic. I have heard that they will also help if you have vapor lock issues.
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Old 03-26-2008, 08:32 PM
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Stay away from the wooden spacers for the reasons already mentioned, use Phenolic.

Vince
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Old 03-26-2008, 09:01 PM
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which kind of riser do you all think would be good for my stock monte ss 86 305 with the 670 street avenger holley?
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Old 03-26-2008, 09:04 PM
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Summit SUM-G1405
http://store.summitracing.com/partde...5&autoview=sku
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Old 03-26-2008, 09:06 PM
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about how thick should it be? just the 1in. is good enough for it?
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Old 03-27-2008, 07:08 AM
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Depends on your hood. 1 inch is good for my car, any higher and I would have to rework the hood scoop.
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Old 03-27-2008, 07:15 AM
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I'd run a 4 hole spacer if it were mine but then again I would have chosen the 570cfm instead.
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Old 03-27-2008, 10:26 AM
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Quote:
Originally Posted by 6426yy
I'd run a 4 hole spacer if it were mine but then again I would have chosen the 570cfm instead.
Why is that?
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Old 03-27-2008, 11:32 AM
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read this for the basics of what a spacer does:

http://www.gnetworks.com/v4files/bar...h%20images.pdf

only sure way to know if a spacer will help at all for a particular motor combo is on a rear wheel dyno....it may want only a 3/8" thick heat insulator spacer or may want 1.5" thick or it may want none at all...

only "shade tree" way I know of to find out what is the best thickness is buy some assorted $5? junk yard spacers and and try them...

I do disagree with adding up to a 2" spacer mentioned in that article...unless it is strictly a race motor

Last edited by red65mustang; 03-27-2008 at 11:47 AM.
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Old 03-27-2008, 07:26 PM
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Thanks Red.
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Old 03-27-2008, 07:52 PM
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well my hood is a 3 in cowl, i think i have a few more inches till my filter starts hitting.im trying to decide between the open or the 4 hole riser. maybe i will just go out and find one of each for a cheap price and try them out to see what they are like and what i like
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Old 03-28-2008, 06:33 AM
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malibus,
you have a relatively heavy car, and maybe tall gears with that small motor....

you need every last ft/lb of TQ you can get for acceleration power driving normal...

depending on which intake and cam and timing is in the motor...a 4 hole spacer to build more TQ at low rpms might help your car a tiny tiny bit....a spacer is not a "magic bullet" for building power.....if you have very tall gears you may not "feel" any difference

Jake,
your 670 cfm question didn't get answered so here's my bare basic's answer....
the actual cfm thru a 300 cubic inch motor at a 5500HP peak rpms is only about 525cfm....
so a 570cfm carb is way plenty of cfm capability (unless you build a 7,000rpms HP peak "mega" cam motor)
by using a more correct size 570cfm carb with smaller venturi's the air/fuel velocity thru the motor will be much higher and closer to the "ideal" over the whole rpm's range...
that means more "pep and response" driving normal due to more TQ and and max HP power possible at any rpms WOT (for passing a truck?)....
a 670cfm carb is better suited for a roughly 400 cubes street motor which is very roughly 650cfm into and out of the motor at 5500rpms...
this link happens to be sbf's but "cubes is cubes" and as you can see you don't want a 670cfm carb unless you are building a really serious motor...

http://www.jason.fletcher.net/tech/combos/combos.htm

Last edited by red65mustang; 03-28-2008 at 06:45 AM.
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Old 03-28-2008, 06:41 AM
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Quote:
Jake,
your 670 cfm question didn't get answered so here's my bare basic's answer....
the actual cfm thru a 300 cubic inch motor at a 5500HP peak rpms is only about 525cfm....
so a 570cfm carb is way plenty of cfm capability (unless you build a 7,000rpms HP peak "mega" cam motor)
by using a more correct size 570cfm carb with smaller venturi's the air/fuel velocity thru the motor will be much higher and closer to the "ideal" over the whole rpm's range...
that means more "pep and response" driving normal due to more TQ and and max HP power possible at any rpms WOT (for passing a truck?)....
a 670cfm carb is better suited for a roughly 400 cubes street motor which is very roughly 650cfm into and out of the motor at 5500rpms...
Thanks red, I couldn't have said it better, He said his car has a stock 305, thats why I would have chosen a smaller carb.
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