Reply With Quotehas anyone had luck with a edelbrock tunnel and a single carb on a bbc ? i picked one up cheap, is it worth bolting on? i'm topping out @4500 and would like to get a little more with out sacraficing too much low end....
DUCKY:
Edelbrock makes a street-ram that supposedly good for 3500-7000 rpm. You just have to make sure that the cam and manifold work together, otherwise you will end up with a dog! Tunnel-Rams are not the greatest thing on a jet, because jets like torque, and lots of it! depending on your setup, I would run either 2 600 vacuum secondaries, or you might look into a pair of the 450cfm carbs that Holley make for Nascar use. They are double pumpers, with dual inlet, center hung floats, and no choke. They actually flow about 525cfm each. They would look cool, run great, and not suck down the fuel for no reason.3k-7K RPM band.....OK.....But most jets run at 5-6K nominal. Jetboats are inherently in-efficent and that's why they need the out-of-the hole torque from BigBlocks to get going.
But a NASCAR syle carb??? Hhmm no! I wouldn't run that with the style boosters it has...NASCAR "390" Versions (which flow an actual 700cfm with 500HP motors)really don't have a bearing on manifold choice considering performance motor's carbs are choosen by: [1.2cfm per Horsepower] so 500-600HP being the average motor's horsepower comes out to about 600-720 cfm; used by the motor.
(Most of us run 1100-1200 advertised cfm. on a flow-bench @ 1.5" Merc) but the motor is only taking in 600-700cfm @ 5-6hg of vacuum (cam dependant figure). The motor itself is actually the only determining factor in carb choice, not the manifold, or me!
That NASCAR 390 (you referred to it as the 450cfm) carb straight leg boosters would actually hurt a jetboats performance. Its boosters were originaly designed for trucks so there would be a better signal at the low end.
Maybe if you were running a "prop" :::cough::: :::cough::: this carb might benefit you, but not at 7K RPM and 5-600HP. You need to soften up the vacuum signal for these motors by installing a 750 (or appropriate venturie size) Carbs w/"drop-leg" boosters or even one of Braswells Billet modified pieces.
When choosing the carbs, think butterfly size and main-body size, and your intended use of your (exact) motor.
Big Block motors should stick with the 1 11/16 baseplates and a 750 Body, provided your at 450+HP or higher. 600 Vacuum secondarys will work, but save the cash and up-grade to the "drop-leg" boosters over the "straight-leg". Maybe the 450cfm Bodied carbs would work on an Olds...but not a heavy breatheing Chevy or Ford
And once and for all to rest the little NASCAR carb subject...the metering blocks are 3 circuit versions, great for high HP motors, but the 390 Bodies were designed by Braswell/Holley to restrict air for NASCAR set-ups running high compression motors but able to fuel them accordingly. Why spend the money to convert a 390's Circuits to work, when you can spend it else where for more power potential?....
Hope I was helpful with this crediable information...
has anyone had luck with a edelbrock tunnel and a single carb on a bbc ? i picked one up cheap, is it worth bolting on? i'm topping out @4500 and would like to get a little more with out sacraficing too much low end....
norcal spectra:
has anyone had luck with a edelbrock tunnel and a single carb on a bbc ? i picked one up cheap, is it worth bolting on? i'm topping out @4500 and would like to get a little more with out sacraficing too much low end....What are the specifics of your motor. Type of carburetor, are your heads square or oval port. I would bet that the manifold you bought is square port...check your motor...
I need more info to see whether it will work or not. Cam specs? Compression ratio? Head type? Etc
-Ty
Single carb tunnel rams are generally a poor design. The air/fuel mixture has to run horizontally to the runners then make a turn down the runners, as opposed to a dual carb setup like in the picture that hack job posted where the flow basically goes straight down the runners creating a "ram" effect - tunnel "ram".
But not knowing what intake you currently have, you may not lose any speed either.
I had a single carb tunnel ram on a boat and it seemed to run fine but really sucked the fuel even with a "little" 700cfm Holley. I changed it to an old C454 low rise intake and didn't notice a difference, but I didn't have a speedometer and it was before gps's.
it's a ls6 rec. port , factory ls6 manifold, .520 lift and 280degree on the cam, 750 double pumper...never mind, i just went through the previous owners paperwork L2377 pistons that's 8.22:1 compression w/ my closed chamber heads frown
[ July 31, 2002, 07:23 PM: Message edited by: norcal spectra ]
I would go with the Holley/Weiand with a couple of the 600CFM Edelbrock Marine carbs. You need a tunnel ram with long runners for torque. You won't be sorry!
Dennis Moore
Family and Performance Boating Magazine
Dennis Moore:
I would go with the Holley/Weiand with a couple of the 600CFM Edelbrock Marine carbs. You need a tunnel ram with long runners for torque. You won't be sorry!
Dennis Moore
Family and Performance Boating MagazineLong runners will not improve torque the way you think they will. It does offer a better top end! The only way to get better torque would be to get an intake manifold that divides the runners up to each cyliner, or close that theory such as pairing them up; Holleys Dominator style manifold. I think they are the greatest in design for amuteurs running motors such as ours.
Otherwise get a sheet-metal manifold
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