small block + blower=?

[ncgamedog]

I am about to start putting a 350ci together for my tow rig (85 silverado lwb 4wd 3/4t sf14 and 10b). it came w/ a 305, 700r, 208. all that is going out for the sm465/205 from my blazer. the 305 is in good shape just not enough to pull 7000lbs worth of blazer and trailer. i wanted a 4bt but seems like a lot of work and $ i dont have. so i have been tossing the idea around of building the small block w/ one of the small "under hood" roots style blowers on it. i've seen them in summit and i think they would make between 5-10lbs of boost. that doesnt sound like alot but considering going from vaccumn to boost should increase hp and efficency, and maybe fuel economy. its been explained to me that w/ just mild boost the roots style blower should make great low end tourqe plus let it stroll on out in the top end. also make it more efficent b/c the engine dosent have to work as hard to pull the load. have i been misinformed? or do you guys think that is a viable option? if so what compression ratio should i look for when building the engine? thanks - justin

 

[thedrip]

pretty much got the right line of thinking. As for compression, lower is better in this case. 8.5:1 would be as high as I would consider.

 

[4X4HIGH]

I seen what those can do with only 6lbs. of boost and 9:1 compression. Can you say pick up pieces of crank and main webbing from the ground.

This happened to a friend of mine years ago. I would stay in the 8:1 compression range with the least amount of boost. I would recommend blower pistons, steel crank, after market rods (with ARP bolts), 4 bolt block and a blower friendly cam and heads. Get ready to spend close to 5K to do it right and not explode on you.

 

[southernspeed]

I seen what those can do with only 6lbs. of boost and 9:1 compression. Can you say pick up pieces of crank and main webbing from the ground.

This happened to a friend of mine years ago. I would stay in the 8:1 compression range with the least amount of boost. I would recommend blower pistons, steel crank, after market rods (with ARP bolts), 4 bolt block and a blower friendly cam and heads. Get ready to spend close to 5K to do it right and not explode on you.

He's not wrong. Doing it 'properly' will be expensive. I looked into this before I rebuilt my '91 last time. Due to not wanting to spend thousands on an engine and then even more beefing up the drive train I opted for a warmed over 355.
However, before I settled for the 355 I'd decided I'd be better of buying a 'hot' crate motor with warrenty than going the time bomb blower route. GMPP ZZ383s make good power or you can go really mad and go for other builders (World etc) offerings of small block 454 etc, all with warrenty.
I still really like the idea of running a blower, but I think I'd reserve that for a hotrod or similar!

 

[HarryH3]

Blower and "tow rig" are not a great combination. Blowers build heat in the combustion chamber, towing heavy loads builds heat in the combustion chamber. The two don't mix well in a gasoline engine. Too much heat creates detonation which is a very bad thing in a pressurized engine...

 

[makovai]

i have different reasons, but i'm putting this in my rig next winter.
Been building it for bout 6 months now.
I'm not sure why i want to do this but it keeps me entertained.

 

[HarryH3]

Mmmm, Evil, Wicked, Mean & Nasty!