Blower Expert Needed

I got a question for whoever can offer some advice. I got a 420 small block chevy that has custom Ross pistons for a 9.0 compression with a 0 deck height and a .039" head gasket. I got a 400 block with a 4.155 bore and a 3.875 stroke crank and 6.0 rods. I just aquired the blower off EBAY and just in time because my pistons were ordered two days before for 10:1 compression. No refund or exchange on custom $800 pistons. Now that I'm trying to tune this blower, I don't want to over do it. I have about 5-6 lbs boost when I first get on it but after about 4500 rpm my boost is falling to about 3-4 lbs. Should I adjust this setup to provide six pounds on the top side or leave it at the bottom side At cruise it has low boost which I was told is good because you dont need any boost under about 2000 rpm. This motor is built to shift a 6500 with a 7200 redline. Also this motor is topped with 215cc iron eagles, solid roller comp cam custom grind .590in. .608ex. lift and 248in. 258ex. duration@.050 tappet lift with a 112 lobe centerline. And last of all a Proform 850 double pumper. This motor runs hard but that boost loss at high rpm is troubling me. I think if I build the boost a little higher at first it could sustain 5-6lbs up high. But don't want to fry it.



Thanks, Ray

Hi Ray:
First of all, I'm not a blower expert, but assuming that you have a good sealing 6-71 & are running it at 1:1, you should be able to make about 10 lbs. of boost at 6000 rpm's. A 10:1 static compression motor with 10 lbs of boost requires some HIGH octane fuel to combat detonation, not the crappy 93 stuff & "O" ringing the block may not be a bad idea. Why is the boost falling off? Well, the single 850 DP carb maybe restricting the amount of fuel (or air) you require & most importantly, you could be leaning out the motor (you usually do this just one time). HEAT is your biggest enemy & you are building lots of heat in that motor. What do your plugs look like? Any backfiring?
Maybe Pat McCarthy can throw out some other ideas.... Don

Quote:

---

Originally posted by camaro_fever68
I got a question for whoever can offer some advice. I got a 420 small block chevy that has custom Ross pistons for a 9.0 compression with a 0 deck height and a .039" head gasket. I got a 400 block with a 4.155 bore and a 3.875 stroke crank and 6.0 rods. I just aquired the blower off EBAY and just in time because my pistons were ordered two days before for 10:1 compression. No refund or exchange on custom $800 pistons. Now that I'm trying to tune this blower, I don't want to over do it. I have about 5-6 lbs boost when I first get on it but after about 4500 rpm my boost is falling to about 3-4 lbs. Should I adjust this setup to provide six pounds on the top side or leave it at the bottom side At cruise it has low boost which I was told is good because you dont need any boost under about 2000 rpm. This motor is built to shift a 6500 with a 7200 redline. Also this motor is topped with 215cc iron eagles, solid roller comp cam custom grind .590in. .608ex. lift and 248in. 258ex. duration@.050 tappet lift with a 112 lobe centerline. And last of all a Proform 850 double pumper. This motor runs hard but that boost loss at high rpm is troubling me. I think if I build the boost a little higher at first it could sustain 5-6lbs up high. But don't want to fry it. Thanks, Ray

---

you didn't say what size blower you have. if its a small blower you're probably playing out of air. as far as adj. the boost, i didn't know you could adj. the upper boost without changing the lower boost also. to me the boost sounds ok if you have 9:1 pistons. the reason you don't have boost at cruise is because, the carb has to be opened about 1/2 way for the blower to have any air to blow. you should have boost anytime you are at WOT. if you are running 9:1 pistons, 5 lb. of boost. 850 carb. and turning it 6500 prm's and not breaking nothing then i would leave it alone. i cant believe you're not impressed with that. sounds like a nice blown st. motor to me. not sure you need all that cam though. :HMMM:

what dyno don said sounds good . one carb one this? two afb 650 cfms or holleys i wound do. sounds like it is botteleneck. at 10 to 1 and 671 with 112 centers. 10 psi it should make easy . how good is blower sealing on intake and what is the vauuum on the top. the carb when the boost drops and is the blower in good shape?? a nosealed could take more than 1 to1 but i think it is the carb and air cleaner and i hope you have a big ex

I am no experts, but a few things that are important are, cam without to much overlap, ie stuff more air and fuel in the cylinder, exhaust which is free flowing to get rid of the gases, ignition which is boost referenced, to set fire to the air and fuel. A blower takes horsepower to drive, if combustion is not happening efficiently, then boost would drop off as well. But that combo must put a smile on your face.

Im not an expert on blower motors yet, but have been doing research cause i'm going to be buildiing one next fall. From what I have gathered thus far is that blowers can tame a big camshaft, it is the wider LSA's and narrower overlaps that help the blower maintain good boost levels throughout the intake and comresion strokes.Your camshaft has a 112 LSA, and nearly 250 Degrees @.050, pretty big overlap for a small blower. Blowers like wider LSA's the wider the LSA the less overlap, and this alone will help maintain a higher cylinder pressure. I am under the opinion you are running either a 144 or a 177 ci mini blower. The only way you can increase the boost levels is changing the pulleys, now keeping in mind that more cylinder pressures are going to increase heat, you are already running 10:1 pistons, so higher octane gas is going to be a must. You might try a smaller camshaft, I am not sure if a pulley change will be enough to maintain a higher boost level with the current cam in your set up. Just my opinion

Who manufactured the blower? What size? What pulleys?

Sounds like all good information and I thank yall all. You gave me some direction to look in. The blower I'm running is a Weiand 177 with a stock drive of 1.45:1. Holley emailed me back and said that the reason my boost is falling is because its being used good. As long as I don't go into a vacuum at high rpm the blower is working well. The more efficient the intake and exhaust the better, and boost being used up like so is better than building up high manifold pressure. I could gear the pulleys a little more and maintain a boost of about 6-7 psi down low and 5-6 up high. PS. THIS ENGINE IS 9.0:1 The cam may also be a problem like someone mentioned earlier. I'm looking into that also. And just to say THIS ENGINE DOES RUN!!!!!!!!!! The only reason I'm tinkering is just to make sure I'm not leaning it or hurting it when my psi droops. This is a big engine for a small blower but I like it because it stays under the cowl hood. STEALTH ATTACK!!!

"Holley emailed me back and said that the reason my boost is falling is because its being used good."

So, I assume that if the boost fell to 1 psi at the top, the blower would be doing an exemplary job???? Sounds like lip service to me. :whacked:

My take on it, the blower is too small for the application.

tech, your idea sound more like it. What do you think about me gearing it a little bit more. I only need about 2psi to be optimum at high rpm It is set a stock psi for stock 350, they do use this blower on big blocks If I could maintain 5-6 psi I would be happy. It only spikes 5-6 psi when I first jump on the throttle.



Ray P.

Quote:

---

Originally posted by camaro_fever68
tech, your idea sound more like it. What do you think about me gearing it a little bit more. I only need about 2psi to be optimum at high rpm It is set a stock psi for stock 350, they do use this blower on big blocks If I could maintain 5-6 psi I would be happy. It only spikes 5-6 psi when I first jump on the throttle.



Ray P.

---

if the blower is not big enough it dont make no dif. what you do to it, you are still gonna use it up. the blower cant move enough air. you need a bigger blower.

Overdriving the blower will give you more top end boost, and low end too. Can you stand more at lower rpm? That blower would be better on a 350.

Quote:

---

Originally posted by R Pope
Overdriving the blower will give you more top end boost, and low end too. Can you stand more at lower rpm? That blower would be better on a 350.

---

how can overdriving the blower give him more boost, he is down to 1 lb. at top end. if you speed the blower up its just gonna get to 1 lb. quicker. his blower is not big enough. in this case i cant see where speeding up the blower will do anything. :confused:

I just back from Thunder Racing, I have a new drive and driven pulley. Thunder says this should put me at about 7psi initial and maintain 5-6psi on up to 6500 rpm. I'm going from 1.45:1 to 1.90:1 which is near the max my rotors can spin and still be in the safe zone for wear and tear. It'll take me about an hour to install and test. My boost should not build up down low till the throttle is wide open according to Thunder. This design and blower set-up should come into affect above 2200rpm. Guess we'll see!!!




Ray

WER

Well if anybody is interested, I changed the pulleys on the blower and you talk about a difference. I start making boost at about 2050, got full 6psi at 2150 and it stays at 5-6 all the way to about 5500rpm and then holds about 6-7 up to 6800 and I let off. This motor is really running now. I have never felt so much power. And I just got rid of a '78 chevy luv stepside with a 383 10.5cr roller comp .630/.630 252in/258ex 106 LSA victor jr intake and the same dart 215cc heads. 10.80s ETs 1/4 @127. This engine feels a lot stronger and definitly more streetable than that 383. I thinks I like it a lot.

W.F.O. Ray

Quote:

---

Originally posted by lt1s10
how can overdriving the blower give him more boost, he is down to 1 lb. at top end. if you speed the blower up its just gonna get to 1 lb. quicker. his blower is not big enough. in this case i cant see where speeding up the blower will do anything. :confused:

---

beat the hell out of the air and make alot of heat. if you are looking in to more boost i would get a big blower. the cam i think for this small blower is a bit to big. so is the cid of the engine somthing like 112 500 510 at 0.050. 235./240 this is a howards cam i did build a engine for a guy that had a 177 blower on a 350 he used the BM cam for it the idea is to go past vacuum and go boost . boost is a measured amount of force. the thing that is getting force this fuel /air this make heat and bad thing can happen at wot it would be nice to see say 3to 4 this make having the blower worth be on the car:whacked:

The 177 blower moves 177 cu. in. of air per revolution. If the engine normally uses less than that amount of air per rev, the blower will make pressure at 1:1. Since 177X2 is 354, a 350 will be marginal at that ratio. A positive displacement blower does NOT compress air, it just moves it. The pressure comes when the engine is not taking the air away as fast as the blower is pushing it in. Nit-picking maybe, but it helps to understand the process.

now someone cane explane how it picked up 5 lb. of boost at 6800, and stayed the same up to 5000 rpm's.

Ray:
Glad it seems to be working out for you, but like Pat said, a bigger blower & maybe a couple of 750 DP's will work less to make the same power (there is a point of diminishing returns by overdriving the blower) I changed from a 15% over driven 6-71 to a 8-71 straight up on my 502 (also changed the cam & went to aluminum heads..mostly for a heat sink) Results: motor made 800 HP & 725 lbs of torque @ 5800 RPM on crapo 91 octane pump gas..with NO detonation. This was an increase of 80 HP and no more screwing with $$$114 octane race gas.

Quote:

---

Originally posted by R Pope
The 177 blower moves 177 cu. in. of air per revolution. If the engine normally uses less than that amount of air per rev, the blower will make pressure at 1:1. Since 177X2 is 354, a 350 will be marginal at that ratio. A positive displacement blower does NOT compress air, it just moves it. The pressure comes when the engine is not taking the air away as fast as the blower is pushing it in. Nit-picking maybe, but it helps to understand the process.

---

you are rigth. BUT there is many variables . a big blower running it not as fast is the way to go . smaller bower will make more Heat . and they eats drive belts at more boost and run them to hard and you will melt down the engine watch out for this

Well, according to Holley/Weiand I am running my blower safe at 1.90:1 over-drive. The 177 is a big block blower and runs at 1.98:1 on a 454 big block to maintain 6psi. The stock pulleys I had were for a 350. I understand that a bigger blower would work less and make more HP, but I don't want a hole in my hood.
The pulley change made the difference I needed. I'm happy.
Holley says it will hold up to that because if you ordered the same set-up out of Jeg's for a big block you would get the same pulley ratio.


It1S10- I NEVER HAD ONLY 1LB BOOST, I ONLY WAS LACKING 1-2PSI FROM HAVING THE 6PSI THAT I WANTED IN THE FIRST PLACE. YOU MISREAD THE ARTICLE SOMEWHERE, PLEASE CHECK BACK AGAIN. MY BOOST WAS FALLING TO ABOUT 4PSI AT HIGHER RPM.

I understand that a bigger blower would work less and make more HP, but I don't want a hole in my hood.

HOOD.. We don't need no stinkin hoods :LOL:

Quote:

---

Originally posted by DynoDon
I understand that a bigger blower would work less and make more HP, but I don't want a hole in my hood.

HOOD.. We don't need no stinkin hoods :LOL:

---

yes i hear that. i do not have a hole in my hood they think i have a gear drive :LOL:

Pat, that is one mighty fine engine you got there.

It1S10- I NEVER HAD ONLY 1LB BOOST, I ONLY WAS LACKING 1-2PSI FROM HAVING THE 6PSI THAT I WANTED IN THE FIRST PLACE. YOU MISREAD THE ARTICLE SOMEWHERE, PLEASE CHECK BACK AGAIN. MY BOOST WAS FALLING TO ABOUT 4PSI AT HIGHER RPM. [/B][/QUOTE]


==============================================

you said, holly said........ As long as I don't go into a vacuum at high rpm the blower is working well.

tech said..........So, I assume that if the boost fell to 1 psi at the top, the blower would be doing an exemplary job???? Sounds like lip service to me.

you said........tech, your idea sound more like it. What do you think about me gearing it a little bit more. I only need about 2psi to be optimum at high rpm.

for some reason i read into that you was looking for 2 lbs. of boost at 6000 rpm's. :whacked:

Quote:

---

Originally posted by DennyW
:LOL: I read it like Mike read it. Frankly, I'm a little confused now. The one thing I'm thinking about, is if you increase the boost, or maintain a 5-7 pounds at the upper rpm's, are you considering the massave load at that rpm's on all moving parts ? Do you have extra parts like the racers that are sponsored does laying in the trailer ? I hope so. :LOL:

---

that makes you a dumb a%s like me. used to i couldnt spell, now i cant read. :rolleyes: :LOL: :LOL:

Quote:

---

Originally posted by DennyW
:LOL: Oh well. :LOL: I can't hardly wait to see how many runs he gets when he beefs it up.

---

sounds like he has some good stuff, 6800 is getting a little tight. :cool: :LOL:

Quote:

---

Originally posted by DennyW
:LOL: Oh well. :LOL: I can't hardly wait to see how many runs he gets when he beefs it up.

---

Denny, I'm only running 6psi on 9.0:1 Forged Ross Inverted Dome pistons, I got a 4340 Eagle crank, 4340 H-beam Eagle rods completely balanced assembly, competion oil pan with uni-directional windage screen, blue-printed oil pump, solid roller Comp H bar pop-up lifters custom comp cam Iron Eagle 215cc heads with Pro magnum roller rockers and Hi-tech 5/16 push rods

Quote:

---

Originally posted by DennyW
:) Ok, so at 7 pounds boost at that rpm, 13.5 is ok with you ? Just use good fuel of course. And make sure that timing and richness is right. :)

---

I am also running a timing retard for every pound of boost my ignition retards 1 degreee. I also blended and polished my combustion chamber to help eliminate hot spots. My boost timing is 32 degrees at full 6 psi boost. I'm running pump gas and haven't seen any problems And I did my homework on my piston selection and block height and headgasket to give me a good quench area. And last of all it is a little rich. If you got any other ideas to keep it out of detonation share em.



Ray

it will take it give it hell:whacked: dont run out of fuel on the top end:(

Quote:

---

Originally posted by pat mccarthy
it will take it give it hell:whacked: dont run out of fuel on the top end:(

---

THANKS PAT, I'm new to this blower stuff but I'm trying to get the hang of it. I've been around it but never owned or run my own and it makes a difference.

Whattaya think?

Quote:

---

Originally posted by camaro_fever68
THANKS PAT, I'm new to this blower stuff but I'm trying to get the hang of it. I've been around it but never owned or run my own and it makes a difference.

---

my engine some people say should of not worked. but it works great and i have 10to1 and run 10 of boost i have the msd btm on mine and it all work and this been this way for 5 years and i am not easy on it. the cam this big and is on 110 this kills some static cr and at idle at the intake my vacuum is 2 inchs but when it runs in to boost hang on .but it sound like your on the edge. like i am to but it will work. i think i would of used the multi-layer steel head gaskets but that what i would have done .O rings are out the new head gaskets work good unless you run top fuel

BLWN31 yes it look good and think all the money you saved by not having to paint the block:LOL:

What multi-layer gasket,??? I used the felpro pre flattened embossed steel ring race head gaskets. 0.039"

Quote:

---

Originally posted by blwn31
Whattaya think?

---

um um ug uh ugu umm pretty stunning **) :p

they are used in the ls1and6 small block fel-pro makes them and cometic make them i have been told that they can take 20+ boost they are the way to go. the gaskets is flat plates of steel an can not move out like the fire ring on the old type of head gaskets

[QUOTE]Originally posted by camaro_fever68
[B]I am also running a timing retard for every pound of boost my ignition retards 1 degreee. I also blended and polished my combustion chamber to help eliminate hot spots. My boost timing is 32 degrees at full 6 psi boost. I'm running pump gas and haven't seen any problems And I did my homework on my piston selection and block height and headgasket to give me a good quench area. And last of all it is a little rich. If you got any other ideas to keep it out of detonation share em.

Ray, you certainly have done your homework. You've handled detonation with the proper quench, polishing, rich mixture and ignition retard. Good job!!!

Hey Pat, I'm with ya about the MLS head gaskets. Unfortunately for me, I had the block O Ringed. The new gaskets had just, just came out and didn't know anything about them. Oh well. Is your block O Ringed?**)