Roots Blower Questions

[tortoise702001]

Dan, Dave or Mike ( Mike I think you were the one with the blown sm block in the green chevelle) or anyone who has knowledge that can answer some of my questions below.

Currently a have 5k mile 350 with 9:1 comp and 76CC head on it. Flat top pistons. Cast components in the motor.

1) Roots blower (Weiand 177) on a small block chevy 350 with 9.5:1 compression would this be okay or what is the ideal compression ratio 8.5:1?

2) Does the motor need forged parts such as crank and pistons? Is cast crank and piston okay?

3) What kind of fuel system is needed? Mechanical or electric pump? Stock fuel lines okay? Does the motor need to maintain a certain fuel pressure?

4) Can you use a regular carb. or do you need one made for blowers applications?

5) Is there a certain size cylinder head needed? 185, 190, 200 or bigger CC runners?

6) Cam suggestion?

I am asking because after seeing Mike's green chevelle with the blown small block under the hood I was thinking of doing this to the motor above.

Thanks,

Rob

[SpiderDan]

Hi Rob,

Its late and I am a bit tired, so I 'll respond tomorrow when I am firing on all eight cylinders. ;D

[SpiderDan]

tortoise702001 said:

Dan, Dave or Mike ( Mike I think you were the one with the blown sm block in the green chevelle) or anyone who has knowledge that can answer some of my questions below.

Currently a have 5k mile 350 with 9:1 comp and 76CC head on it. Flat top pistons. Cast components in the motor.

1) Roots blower (Weiand 177) on a small block chevy 350 with 9.5:1 compression would this be okay or what is the ideal compression ratio 8.5:1?

2) Does the motor need forged parts such as crank and pistons? Is cast crank and piston okay?

3) What kind of fuel system is needed? Mechanical or electric pump? Stock fuel lines okay? Does the motor need to maintain a certain fuel pressure?

4) Can you use a regular carb. or do you need one made for blowers applications?

5) Is there a certain size cylinder head needed? 185, 190, 200 or bigger CC runners?

6) Cam suggestion?

I am asking because after seeing Mike's green chevelle with the blown small block under the hood I was thinking of doing this to the motor above.

Thanks,

Rob

Hi Rob,

Sorry I am just getting back to you, I've been running around like mad lately.

Rick should probably chime here as well, but here's my limited knowledge.

The lower the compression the better, mine is 7.9:1 - with the lower compression it allows you to run higher boost, with in reason.

I used and would recommend ALL forged internals (rods, piston, crank), I believe that if you are going to build a blower engine, might as well set it as appropriately.

Fuel systems can vary, obviously high volume is the way to go. I went with high volume Cater Mechanical, either way would be fine. I also upgraded to 1/2 fuel line from the gas tank to the carbs. Not saying it has to be done, but was recommend for my set up (671 - dual 650 double pumpers)

On the cylinder heads, I actually spoke to a couple of machine shops that specialized in blower engines and pretty much got the response, just a good set of high flow heads, with a blower, (mine are LS7 Heads) I don't think the heads are critical as a none supercharged engine, with it being forced. Of course flow = power.

Don't waste your money on the blower carbs, regular will do fine, we just took the choke off mine and didn't even need to re-jet them. I would go with double pumpers though.

On the cam and again I am no expert but did some research and the idea is to have good lift and duration on the exhaust side. Mine is a solid lifter with direct lube lifters and CompCam roller rockers.

I hope this helps a little Rob. Do I see another blower Chevelle in the club?

[tortoise702001]

Dan,

I am getting ready to get my camaro back on the road and was thinking of putting a small blower on that car. I liked that guys Mike car with the blower tucked under the hood. I still need to see if I want to spend money on new heads and the blower vs. leaving the motor alone.

Rob

[SpiderDan]

Rob,

Go with the blower, you WON'T regret it.

tortoise702001 said:

Dan,

I am getting ready to get my camaro back on the road and was thinking of putting a small blower on that car. I liked that guys Mike car with the blower tucked under the hood. I still need to see if I want to spend money on new heads and the blower vs. leaving the motor alone.

Rob

[mikec]

Rob, glad to hear you are considering the Mini-blower on the chevelle. i will put my spin on your questions regarding my 177 set-up. I hope they help.

Currently a have 5k mile 350 with 9:1 comp and 76CC head on it. Flat top pistons. Cast components in the motor.

Q: Roots blower (Weiand 177) on a small block chevy 350 with 9.5:1 compression would this be okay or what is the ideal compression ratio 8.5:1?
A: The ideal c/r should be in the 8's, of course more boost equals less compression for longevity. the Weiand tech write up does not advise going ove 12-12.5 under boost. see link:
www.holley.com/TechService/Library.asp
(contains all you need to know about boost levels, etc!)



Q: Does the motor need forged parts such as crank and pistons? Is cast crank and piston okay?
A:The rule of thumb I used is anything under 5-7 psi boost would hold together with ARP studs and a good 4 bolt main block.
When I build my stroker block I will install forged pieces, more for balance and faster revs. I will be around 9 psi when complete

Q: What kind of fuel system is needed? Mechanical or electric pump? Stock fuel lines okay? Does the motor need to maintain a certain fuel pressure?
A: more is better is the rule, if you are running electric you should install the return line from the regulator. I use the 115 GPH mechanical, gives me arouns 10 psi at the carb. the benchmark i have been told several times is +6 psi for the mini's. 6-71+ would need a great deal more, unless you are running a duel set-up. Thats a whole different thread

Q: Can you use a regular carb. or do you need one made for blowers applications?
A: am using an Edelbrock 750 with all of the high flow rods anf light springs. It worked great out of the box!

Q: Is there a certain size cylinder head needed? 185, 190, 200 or bigger CC runners?
A: I am using a massaged set of 202 fullies, i love the old school stuff fitted with the latest in hardware, besides the blower the heads have been the single best improvement i have installed. I completed the stage 2 porting and polishing on the intake and exhaust, SS valve 3 angle grind, guides, comp spring(stock, no 6500+ revs for the small block so i thought the stockers would be just fine)


Q: Cam suggestion?
A: Well, again I installed the larges that would fit the application. The stock springs and rockers were the limmiter. I have the specs somewhere in the files. Its a very big cam, borderline radical. all I can say is when the cam and the blower come in at 3000-3200 RPM hang onto your hat ;D ;D
I know the blower grinds are much smoother and give you the 110 overlap. I did not even look at them because I wanted that lumpy idle and awesome hot rod sound from the begining!!!!!!!. either keep it stock or make it what you want! Thats the joy of hotrods ;D


last but not least. I highly recomend the MS pro billet dist, and the 6AL box, with a boost retard. huge improvement over the HEI. It is well worth the dollars.


I hope this helps, please feel free to give me a call if you have specific questions on the mini blower. I have attached me cell # below
Mike
916-796-5901

[Aaron]

only thing not mentioned..
is cams with 112+ LSA are best for forced induction applications. 114-116 work the greatest.


aaron

[mikec]

This stuff below is right out of the Weiand Tech Services manual. just plan your build with what you have in mind, the parts gurus will let you know when you are running on the edge of the limit.
I have no issues with the timming, just dial in the retard you want because the big cam likes a lot of initial timing. like 22-24 deg. or so! ;D





The “mildest” of Weiand’s blowers are the Pro-Street superchargers,
which are set to produce from 5 to 7 pounds of
boost. The company recommends a hydraulic cam for these
applications - where the engine will not be spun past 6,500
rpm and has several grinds available. All of these cams are
ground on a 112 to 114º lobe center line, which helps maintain
cylinder pressure to maximize horsepower at these lower
boost levels. Keeping the cylinder pressure up also gives you
excellent throttle response.
The milder cams that Weiand offers are great for street performance
enthusiasts who want to gain about 100 to 120
streetable horsepower. The company also offers slightly “bigger”
cams for the next performance level up.
For 6-71 and 8-71 blowers, Weiand again recommends running
a hydraulic cam, as long as you keep the boost level
below 10 PSI. Weiand also offers cams for these type of
applications.
For your higher boost levels in gasoline burning engines, the
company recommends running a flat tappet or roller cam
with a 110º lobe center line. This cam design provides good
overall power on pump gas and also aids in engine cooling.
Plus, the 110º center line provides even sharper throttle
response and helps lower initial cylinder pressure