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Old 11-15-2010, 12:42 AM   #1
gearslammer
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Default roots supercharger engine build

My buddy and I are preparing to build a roots blown engine and we could really use some help! He's a pro engine builder, but has never fooled with superchargers...I'm a schmuck.
This is a 2700 lb street driven car that I would like to at least get into the mid 10's (small time stuff for you guys). Running 4.86 gears with a TKO 600. Here is what we are thinking so far.

To minimize wear and tear on the tranny we prefer to run the low gear and just turn the engine up a bit say 7000-7300 shift point with max 8000 rpms. I'm getting a Little M block (350 mains) destroked with 4.125 bore and 3.48 stroke (377 ci). Probably try to shoot for 7:1 compression. Thinking about a Littlefield 8-71 blower from reading this forum. Here are my questions:

1. What are the best aluminum heads for the buck? Runner size gets pretty complicated with blowers I have found. What size exhaust valve is good?

2. I read here that Isky makes oddy cams and they apparently do an awesome job on custom grind blower cams. What are your thoughts? Any other cam folks you like?

3. Is this the correct sized blower for this mill? Is Littlefield the way to go on roots?

4. What's the best way to do the ignition. Old school mechanical advance or lock it out (say at 37*) and use a system that retards the spark as boost increases.

THANKS if your still reading! LOL! Sorry, but I really want to get it right this time.Tired of chasing my tail and blowing $$$$. Any help is appreciated!
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Old 11-15-2010, 10:19 AM   #2
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Default Re: roots supercharger engine build

3500 lb's, 400 block, half filled with Rockblock, really small solid roller, AFR 210's, Weiand 177 supercharger with a Holley 950, runs low tens@129mph without the nitrous. Don't know how you could possibly underdrive an 8/71 enough to only run 9's? Maybe shift from 1st to 6th and run two barrel carb's?

Last edited by allend43; 11-15-2010 at 10:21 AM.
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Old 11-15-2010, 11:56 AM   #3
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Default Re: roots supercharger engine build

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Originally Posted by allend43 View Post
3500 lb's, 400 block, half filled with Rockblock, really small solid roller, AFR 210's, Weiand 177 supercharger with a Holley 950, runs low tens@129mph without the nitrous. Don't know how you could possibly underdrive an 8/71 enough to only run 9's? Maybe shift from 1st to 6th and run two barrel carb's?
WOW! Ok, wel that's good to hear! Thanks, guess it shouldn't be any problem then even if we don't get it just right!
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Old 11-15-2010, 12:32 PM   #4
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Default Re: roots supercharger engine build

LOL yeah you won't have a problem running only 10's!
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Old 11-15-2010, 12:34 PM   #5
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Default Re: roots supercharger engine build

Since roots style blowers are volume movers, you size the blower to be able to move a little more amount of air than needed to make the power you're looking for. The difference in power between two identically blown engines is the difference in blower drive power to make either low or high boost. If you build a 377ci motor that'll spin to about 7200rpm, you're probably going to end up around 500hp n/a and a 2700lb car only needs around 600hp to make a 10.5 pass. In your case, you're looking for a blower capable of flowing air for around 750hp so that final measured power at the crank comes to about 600hp. To get 600hp out of a 500hp n/a motor, you're talking boost of something like 3-5psi. You could make the car much more driveable at 350hp and need 10-14psi to stay in the mid 10's. Saying all this and allend43's statement, a 177 supercharger is PLENTY big for just about any engine you attach it to and still achieve your goals, just a matter of how much boost is needed to get there.
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Old 11-15-2010, 01:01 PM   #6
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Default Re: roots supercharger engine build

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Originally Posted by fast82z View Post
Since roots style blowers are volume movers, you size the blower to be able to move a little more amount of air than needed to make the power you're looking for. The difference in power between two identically blown engines is the difference in blower drive power to make either low or high boost. If you build a 377ci motor that'll spin to about 7200rpm, you're probably going to end up around 500hp n/a and a 2700lb car only needs around 600hp to make a 10.5 pass. In your case, you're looking for a blower capable of flowing air for around 750hp so that final measured power at the crank comes to about 600hp. To get 600hp out of a 500hp n/a motor, you're talking boost of something like 3-5psi. You could make the car much more driveable at 350hp and need 10-14psi to stay in the mid 10's. Saying all this and allend43's statement, a 177 supercharger is PLENTY big for just about any engine you attach it to and still achieve your goals, just a matter of how much boost is needed to get there.

Good stuff! Gave me plenty to consider for sure. I don't mind going faster! LOL! As far as drivability concerns are we mostly talking about over heating issues?
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Old 11-15-2010, 01:26 PM   #7
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Default Re: roots supercharger engine build

With my half filled 400 block I had a serious heating issue, I had a had time getting it up to 170 unless it was a really hot day. Griffin aluminum radiator with duel electric fans.
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Old 11-15-2010, 01:28 PM   #8
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Default Re: roots supercharger engine build

why build, just buy this...


http://www.racingjunk.com/category/9...S-amp-S-A.html
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Old 11-15-2010, 01:33 PM   #9
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Default Re: roots supercharger engine build

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Bet that would get you in the ten's
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Old 11-15-2010, 01:42 PM   #10
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Default Re: roots supercharger engine build

I'm at work (don't tell) so I can view the link, but I really want to learn about building engines and this is my chance to learn. Plus I know I could save big $$$ doing it ourselves.
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Old 11-15-2010, 01:43 PM   #11
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Default Re: roots supercharger engine build

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Originally Posted by gearslammer View Post
Good stuff! Gave me plenty to consider for sure. I don't mind going faster! LOL! As far as drivability concerns are we mostly talking about over heating issues?
Maybe I should've said street manners instead of driveability. If you build a lower n/a hp engine and run higher boost, you can run less rpm, converter, and gear. In other words, the car will be much more fun to drive on the street and still be capable of the same 1/4 mile performance of the higher n/a hp engine.
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Old 11-15-2010, 02:23 PM   #12
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Default Re: roots supercharger engine build

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Originally Posted by fast82z View Post
Maybe I should've said street manners instead of driveability. If you build a lower n/a hp engine and run higher boost, you can run less rpm, converter, and gear. In other words, the car will be much more fun to drive on the street and still be capable of the same 1/4 mile performance of the higher n/a hp engine.
Oh I see...well, it is a 5 speed stick if that makes a difference.
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Old 11-15-2010, 02:27 PM   #13
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Default Re: roots supercharger engine build

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Originally Posted by allend43 View Post
3500 lb's, 400 block, half filled with Rockblock, really small solid roller, AFR 210's, Weiand 177 supercharger with a Holley 950, runs low tens@129mph without the nitrous. Don't know how you could possibly underdrive an 8/71 enough to only run 9's? Maybe shift from 1st to 6th and run two barrel carb's?
1st to 5th then! lol
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Old 11-15-2010, 05:33 PM   #14
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Default Re: roots supercharger engine build

Well I'm fine with going faster than intended, but any suggestions about heads and such or maybe something I haven't even mentioned that I should consider?
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Old 11-15-2010, 06:39 PM   #15
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Default Re: roots supercharger engine build

The better the heads, the faster you go, pretty much same as N/A (in general). Boost will go down but power way up.

Last edited by allend43; 11-15-2010 at 06:43 PM.
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