Give me some info on Roots style blowers.
 

I've got an L03 that I am working with. It's a 92, 9.3:1 compression, only real engine mod was 1.6 ratio rockers (pretty mild since it's still the stock cam).

I'm going to be running propane, which is roughly 105 octane... with 105 octane, and 9.3:1 compression ratio, I should be able to run a lot of boost without any detonation problems.

The propane mixer was too tall for the stock hood anyway, so I'm making a cowl... and I might as well make it as tall as I need for a blower :-).

My questions are as follows:

What roots blowers are available that are relatively "bolt-on"? The eaton ones look like a LOT of fabrication work. I'm just looking for something easy to make some power, that I can reuse later if I build a better motor.

What are good ones for the price?

How much boost do you think I could run comfortably with the stock bottom end?

How noisy are they at part-throttle? This is a daily driver, I don't mind some blower noise winding it up at WOT, but I don't want an whine that drives you nuts when just putting around to work and back.

Do a search on the forums. There's been a lot of discussion of the holley/wieand powerchargers. There's even a Holley 144 article in the tech articles. Good thing that you're making a cowl hood; you're gonna need it with any roots blower on a thirdgen. On a stock 350 it'll yield 100hp. Not sure about a propane injected 305 though. Good luck on your findings.

Should have mentioned, I read the tech article, it said his blower was fairly quiet at low RPM, which disagrees with what a lot of people mention from time to time... I was hoping to get some more opinions on this.

Also I read the messages in this forum but not a lot went into any great detail about comparisons between blowers.

After re-reading your first post, I'm a little confused now. I don't know anything about propane injection, but are you planning on this being your daily driver? If the propane really prevents detonation like you say it will, then the Holley/Weiand 144s are probably your best bet as far as cost/bolt-on application is concerned. That's just my opinion. Hopefully someone who has a blower will step in soon to share some info.

Ok DauntlessZ28 your off the hook :D

First off regardless of what anybody says I would not run any type of boost with cast pistons (you say the engine is basically stock) besides having to worry about detonation, they just are not strong enough to handle the strain that boost puts on them. I speak of this first hand my Z had 11K miles on it and was only a year old when I put the 144 w/7lbs boost on it within 2k miles it was actually ripping the wrist pins out of the pistons. Second any of the blowers that have a serpentine belt are not noisy at all, the blower whine with the big blowers is made because of air getting trapped between the cogged belt and the pulley.
Third I do not have any experience with propane but as a rule of thumb anything over 8.5:1 is too much and that’s with forged pistons. As far as bolt on they are all pretty straightforward hope this helps :)

Check out the 192 ci unit from the blower shop. Billet case , 192 ci gives you plenty of boost availability at lower air temperatures than a 144 or 142 or even a 177.

http://theblowershop.com

http://theblowershop.com/images/tbs192sc.jpg

They do make noise even with a serpentine belt.

Wow that is a great lookin blower....didn't mean to give the impression they don't make noise just what type and how loud sorry!

Shoot man aint no need to say sorry to me for nothing man, you got one bad 305 . They make a lil noise when you open em up , not as much as with a 1/2 pitch or 8mm like you said, but rotors twisting make that erie sound up high too , most of them anyewayz. :hail: :D

Yes, I AM off the hook:lala:

OK let me clear up the propane thing. It's not propane injection, it's 100% propane, no gasoline. Not really super-important to the supercharger discussion, I just meant to say I've got high-octane fuel. Propane can run a NA engine with 12:1 compression no detonation, so 9.3:1 is very low in comparison.

Basically, pretend I'm running 105 octane race gas all the time.

So unless superchargers by their very nature increase detonation, the higher octane of my fuel ought to make 9.3:1 totally acceptable as a base compression ratio.

OK sounds like the 144 would be an acceptably quiet blower for me, I don't mind noise high-up but just don't want it screaming at low RPM (I saw a guy who had a centrifugal blower, even at idle, you didn't want to stand next to his car with the hood open).

Anyone else want to weigh in on the durability of stock pistons? I was under the impression several people were running stock bottom ends with no problems?

Here is holleys tech site for superchargers lots of good info here:
http://www.holley.com/HiOctn/TechSer...fo/SCTech.html
Their Effective Compression Ratio Chart shows with 9.5:1 static compression and 6 lbs boost the effective compression is 13.4:1

post pics when your done have fun with it

Sure it's important…. Propane is much more detonation resistant (I was under the impression that it's between 107-108 octane). It also starts as a liquid and vaporizes somewhere between the tank and chamber dropping temperature quite a bit, acting like an intercooler. Propane also burns slower which results in slightly different engine dynamics.

This all ends up with your 9.3:1 ending up being a very sluggish engine with propane (I've seen people run in the range of 15:1 on work trucks running propane). It's probably roughly in the range of 6:1 on gas. Not only will you be able to run a lot of boost with propane, but you'll want to run a lot to make the engine street able.

Secondly, I was under the impression that propane mixers could be positioned any way you want… have you considered an adaptor mount so that it doesn't have to be on the top of the blower giving you some more hood clearance. With the fleet vehicles out there now it's also not that hard to get your hands on propane injectors and run FI if you wanted to.

Superchargers do increase detonation, they add heat to the A/F mixture which makes it more detonation prone, but the denser charge is also less detonation prone then a less dense charge then a less dense charge at the same temp and cylinder pressure.

The stock pistons, rods… will not break from boost. What will break them is detonation or rpm. If you make sure that the engine is well tuned and keep the rpm's reasonable (say under 6K, 5500 for sure) you won't break anything. OTOH, if you race it regularly, just like anything else you'll eventually break it, but that would be the case with an all forged bottom end… (just not as quickly)

From BDS:
From Holley/Weiand:
From Dyers:
Bottom line you probably can get by with cast and under 5LBS boost but for the cost/hp factor with that low of boost you probably wont be happy :driving:

Don't get me wrong here I am not trying to start anything or argue just trying to give you some first hand info and not something that I read or heard. Hopefully you won't hurt anything or have to pull the motor out and redo it like I had to

There are 9second cars out there running factory short blocks… Like I said before, if you keep rpm's down and tuning good it can be done. Is it preferred, no way. Would hypereutectic pistons be better… as long as you keep detonation under control. Would forged pistons be much better… yea that way you can make one or 2 mistakes before carrying your engine home in a bucket…

First those are recommendations, not hard rules or facts.

Been running a stock 305 on 12 lbs boost for a year.. Other than the bearing are shot, the rods and pistons, and crank are fine.

Also a buddy was running ~28 pounds on a GN with cast pistons.. Ran for years..

But reality is, you can run boost on a "stock" motor. Will it last forever? No... Will it last as long as a purpose built motor.. Hell no.. :D But with care and proper tuning.. You can get by. ;) BW