Author Topic: Buick 350 supercharged  (Read 15925 times)

Offline buickfed

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Buick 350 supercharged
« on: December 04, 2014, 06:55:20 PM »
some of you know I run a 350 buick with a b&m s/c. I have to make my own intakes(340 mopars) due to nobody else does. this year we went 10.2' @ 128. I'm not a tuner so whatever works we go with it and we do it just for fun and r&d.
now I have cut up a 455 dual quad to use a Hampton 4-71. laying out everything on the engine with carbs and scoop, the thing is taller than the roll cage. I told the driver i'll buy him a periscope. lol.
anyways looking at the belt drive, instead of using a cog belt, is it possible to run a 10 rib serp belt on it?  more questions to follow.

thanks
john

Offline denverflatheader

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Re: Buick 350 supercharged
« Reply #1 on: December 16, 2014, 12:26:32 PM »
Anything’s possible : )  If it’s a clearance issue you’re concerned about with 2” or 3” wide blower pulleys/belt, might I suggest you look at motorcycle stuff.  Here’s one-off “cog” pulley made by John Buttera (his son I think is selling).  It’d be stunning, Lil John would “smile big” to see his pulley driving a supercharger…

http://www.ebay.com/itm/LIL-JOHN-BUTTERA-MADE-7-8-WIDE-60-TOOTH-PULLEY-125T-GATES-BELT-HARLEY-OR-OTHER-/151516478078?pt=Motorcycles_Parts_Accessories&hash=item234715fa7e



Offline buickfed

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Re: Buick 350 supercharged
« Reply #2 on: December 16, 2014, 04:03:22 PM »
trying to stay away from cog belts. they make numerous serp 10 and 16 rib pulleys for the 250's, etc. don't know if they would work on a 4-71. haven't figured out which combo would give me 5-6lbs of boost.
since they don't make stuff for the 350 buick, I have to make or alter parts to work. I just cut up a buick 455 dual quad intake so I can move the blower forward for the pulleys. I did a mopar d/q for the b&m blower, but won't work for the 4-71.

Offline denverflatheader

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Re: Buick 350 supercharged
« Reply #3 on: December 16, 2014, 06:15:08 PM »
No cog belt, okay.  The 16 rib serpentine will no doubt work, so now I see why you’re asking on the 10 rib.  Based on existing small b&m s/c max 6-8 lbs output with a 6 rib, on paper a 10 rib “should work” with the 4-71 driven less to meet your goal of 5-6 lbs of boost.  I’m guessing your small b&m s/c use 6 inch lower pulley and 3 inch upper pulley.  You’ll probably need upper pulley closer to 5.0 inch diameter to try on the 4-71 to reach your 5-6lbs of boost with 6 inch diameter lower pulley (lots of factors, I agree, experiment in progress).

Offline buickfed

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Re: Buick 350 supercharged
« Reply #4 on: December 17, 2014, 06:28:55 PM »
thanks Denver. its a sticky wicket trying to cross figure out the ratios and the pulleys that are available and that fit top and bottom and the idler. like I said, running an engine nobody really makes parts for can irritating, amusing, invigorating or just dumb.  ;D. but I have been doing buicks since I was a kid. too late and too old to change now.

Offline buickfed

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Re: Buick 350 supercharged
« Reply #5 on: December 18, 2014, 04:49:11 AM »
picture of what was a 455 dual quad intake

Offline denverflatheader

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Re: Buick 350 supercharged
« Reply #6 on: December 18, 2014, 07:25:05 AM »
John – my pleasure, I have a few 8mm pulleys here so was easy to measure the diameters.  A 50T is close to 5.0 inch diameter and a 60T is close to 6.0 inches… funny how that worked out.  In other words, it calculates to 20 percent overdrive with 50T on top and 60T on crank.  For how your 350 ran in quarter with the b&m s/c, I was thinking 4-71 and 20 percent should work well.  If you think 20 percent too much to start, bump it up to 5.50 inch diameter pulley on top… would change it to about 9 percent overdriven (not as much fun).  Offbeat stuff is “cool” like your intake.  I want to make one for a tiny flathead V8-60 (136ci) for a baby roots supercharger I got from France.  Alan
         
p.s. for comparison your b&m s/c with 6” bottom pulley and 3” top pulley is close to 100 percent overdrive… 


From Wiki-pedia:  positive-displacement superchargers are usually rated by their capacity per revolution. In the case of the Roots blower, the GMC rating pattern is typical. The GMC types are rated according to how many two-stroke cylinders, and the size of those cylinders, it is designed to scavenge. GMC has made 2–71, 3–71, 4–71, and the famed 6–71 blowers. For example, a 6–71 blower is designed to scavenge six cylinders of 71 cubic inches each and would be used on a two-stroke diesel of 426 cubic inches, which is designated a 6–71; the blower takes this same designation. However, because 6–71 is actually the engine's designation, the actual displacement is less than the simple multiplication would suggest. A 6–71 actually pumps 339 cubic inches per revolution (but as it spins faster than the engine, it can easily put out the same displacement as the engine per engine rev).

Here’s some comparison calculations using 6-71 information above with 4-71: 

6-71 = 426ci ~ 339ci actual 339/426 = 79.5 percent
4-71 = 284ci ~ 284 x 79.5 percent = 225.7ci actual 
b&m = 144ci x 2 = 288ci @ 100 percent overdrive

Answer:  4-71 @ 225.7ci to equal b&m 144 @ 288ci, need to overdrive the 4-71 ~ 20 percent

If a 6 rib works with the b&m s/c, a 10 rib should work for the 4-71 to output the same ci.  The belt strength/holding/breaking point would probably be doubled...


« Last Edit: December 19, 2014, 06:16:57 AM by denverflatheader »

Offline buickfed

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Re: Buick 350 supercharged
« Reply #7 on: December 18, 2014, 06:12:46 PM »
in between making chips, i'll have to sit down and try to figure the numbers all out AND then find a belt to fit.

Offline buickfed

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Re: Buick 350 supercharged
« Reply #8 on: January 03, 2015, 08:03:02 AM »
going to make a blower restraint and need to know what is the width of the blower restraint straps?

dreracecar

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Re: Buick 350 supercharged
« Reply #9 on: January 03, 2015, 08:48:12 AM »
Is the track you run at going to allow a non SFI restraint?? Call DJ Safety, they are pretty good at doing odd-ball things when there is nothing available. They have been re-strapping my "Kuhl" restraint plate for years and carry the liability if somthing goes wrong.
 Saw a video of a trans-brake launch with a serp belt with a blower-- wasnt pretty

Offline buickfed

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Re: Buick 350 supercharged
« Reply #10 on: January 03, 2015, 11:51:17 AM »
from what I've read, just the straps are sfi rated. the top plate, aluminum, and header parts are non sfi. ???

dreracecar

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Re: Buick 350 supercharged
« Reply #11 on: January 03, 2015, 04:50:44 PM »
A manufacture must be willing to sew straps onto your plate, some will not because they want you to buy their system. Their system (plate-straps-mounting hardware) is what gets sent in for testing in order to attach the SFI tag to the straps. Again talk to DJ as they are somtimes willing to do that.

Offline buickfed

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Re: Buick 350 supercharged
« Reply #12 on: January 03, 2015, 06:38:05 PM »
http://www.goodvibesracing.com/moreinfo.php
replacements straps; they weave into 2 slots on the plate like seatbelts and the other end is sewn and the pins slide thru. unless I'm missing something.

Offline buickfed

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Re: Buick 350 supercharged
« Reply #13 on: February 07, 2015, 01:42:38 PM »
if pulley ratio is 1:1, does pulley diameter, 2 big ones or 2 small ones, change anything?

dreracecar

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Re: Buick 350 supercharged
« Reply #14 on: February 07, 2015, 04:41:57 PM »
The ratio remains the same