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weiand 6-71 blower questions

38K views 27 replies 9 participants last post by  camaroman7d 
#1 ·
Hello everyone, iam new here and hope someone can help me out.
I just recently got an 82 camaro with a 30 over 350, afr heads, 6-71 blower and dual holley 600's. The rear is a moser 9" with 456's and is a mini spool. I need all the help i can get on blower engines as i have never had one before.
I don't really have any specs as what the c/r is, or cam specs, what boost its pushing etc.
Iam looking for info on how to figure out what boost iam putting out, or ways to change the boost for more power. The only thing the previous owner told me was it was running 13% underdriven, and is detuned for cruising on the streets, which is meaningless to me as i have no clue what it means.
My major problem right now is, i just don't think the engine is performing at low rpm like it should be, especially with the 456 gear ratio. Iam not getting much power until over 3000 rpm.
Sorry this post is so vage, but iam looking for a tutor in blower engines, as iam new to them.
Thanks in advance for any help anyone can shed onto me.
Daryl
 
#2 ·
Blower Motor

Theres a lot to learn about blower motors, I recently built one myself. Theres plenty of very knowledgable guys on this forum. I would recommend reading books on tuning supercharged engines, and doing research online. I would visit the Blower Drive Service website,The Blower Shop site, Mooneyham, and Don Hampton Blowers. One thing is very crucial, and thats your timing curve. I blew a headgasket in the learning process. The fuel curve is also very critical, I recently had a similar issue with low rpm power. Turned out the air bleeds were too large in the high speed circuit. Theres plenty of stuff to learn, take your time and have fun. Do your research and you'll learn fast........Borti
 
#3 ·
sounds like you have a start to a very nice little setup. there is most definetly alot to blower motors. to answer your question on the underdrive that means that you are basically not using the full potential of the blower.And how you do this is by changing pully ratios like that of a bicycle sprockets and gears. to be 13% under driven you are likely running lower boost and would result in less lower end. with it being under driven that means the blower is spinning slower. but you better know that bottom end before you start cranking up the boost. and be ready to run race gas. :thumbup:
 
#4 · (Edited)
If this is your first motor, you have alot more things to worry about than how many pounds boost it has...Your time would be better spent on other areas of tuning the motor. Seems to me theres alot of people that get real caught up about boost numbers.

Pull the motor out, put it on a motor stand and pull the oil pan off. Someone earlier said you should get to know the rotating assembly and make sure nothing is awry or out of clearance, and thats a real good point IMO.
 
#5 ·
Thanks for the info everyone. I will be looking into the websites mentioned.
I knew i would be having to pull the engine to check how the bottom end of the engine was built, The guy said it was built for the blower, but i take that with a grain of salt as its just someones word with no paper work to back it up. but just not ready to do that yet. Just picked the car up last week, so i thought i would run it until winter, then pull the engine over the winter an give it a go through.
Just trying to get as much info as i can on blower engines, and tuning them.
Is there a way i can measure my pullies, and check which size are on the car so i have an idea where iam with that? Are the pullies measures in standard inches, millimeters, or?
Thanks again for everyones help on this.
Daryl
 
#6 ·
uplateagain said:
Hello everyone, iam new here and hope someone can help me out.
I just recently got an 82 camaro with a 30 over 350, afr heads, 6-71 blower and dual holley 600's. The rear is a moser 9" with 456's and is a mini spool. I need all the help i can get on blower engines as i have never had one before.
I don't really have any specs as what the c/r is, or cam specs, what boost its pushing etc.
Iam looking for info on how to figure out what boost iam putting out, or ways to change the boost for more power. The only thing the previous owner told me was it was running 13% underdriven, and is detuned for cruising on the streets, which is meaningless to me as i have no clue what it means.
My major problem right now is, i just don't think the engine is performing at low rpm like it should be, especially with the 456 gear ratio. Iam not getting much power until over 3000 rpm.
Sorry this post is so vage, but iam looking for a tutor in blower engines, as iam new to them.
Thanks in advance for any help anyone can shed onto me.
Daryl
You need to supply a lot more information if you want help
to start with
Cam model or specs
Compression ratio
Ignition type and timing
Head type (model)

There are people here who can help but they need info.
 
#8 ·
T-bucket23 said:
You need to supply a lot more information if you want help
to start with
Cam model or specs
Compression ratio
Ignition type and timing
Head type (model)

There are people here who can help but they need info.
he bought it from a guy so I dont think he will have the specs. It doesnt sound like he gave him any info on it. I dont buy used motors especially blower motors from people. Unless you plan on tearing it down and rebuilding it. Just to much to risk. the teeth like eric said is the best way. I am not sure on the exact math but there are people here who can tell ya. If it were me I would just buy a few different pulleys and play with it. I think you can even buy them in sets. :mwink: but remember the higher the boost the higher your comp ratio will be so you depending on how high you plan on going you might have to run higher octane. have fun though. and good luck
 
#9 ·
motorhead454 said:
he bought it from a guy so I dont think he will have the specs. It doesnt sound like he gave him any info on it. I dont buy used motors especially blower motors from people. Unless you plan on tearing it down and rebuilding it. Just to much to risk. the teeth like eric said is the best way. I am not sure on the exact math but there are people here who can tell ya. If it were me I would just buy a few different pulleys and play with it. I think you can even buy them in sets. :mwink: but remember the higher the boost the higher your comp ratio will be so you depending on how high you plan on going you might have to run higher octane. have fun though. and good luck
Have you ever purchased blower pulleys in sets to "play with"?? They ain't cheap, close to $100+ each.
 
#10 ·
ericnova72 said:
Have you ever purchased blower pulleys in sets to "play with"?? They ain't cheap, close to $100+ each.
this is true!lol but if you got the cash why not?lol I would just cause you would always have them. My grandpa has had his for two blower motors now. but he has money though.lol. or just buy the ratio that you want? but they are damn expensive! :D
 
#11 ·
Thanks again for everyones replies.
I don't have any specs on the c/r, cam, or the bottom end. I know the heads are afr aluminum, so i can probably find a stamping on them to look up what they are.
Iam not looking to go nuts with the pullies, just get a little more low end out of the car as it doesn't produce much until after 3000 rpm. so i can change out the gears from the 456's to 373's or around there.
What is the math that needs to be done after countng the grooves in the pullies?
This is only a street car, its not going to be run down the track, so i would like to be able to stay with 93 octane.
Thanks again for all your help. I will check the pully size and get back to everyone.
Daryl
 
#12 ·
:thumbup:
uplateagain said:
Thanks again for everyones replies.
I don't have any specs on the c/r, cam, or the bottom end. I know the heads are afr aluminum, so i can probably find a stamping on them to look up what they are.
Iam not looking to go nuts with the pullies, just get a little more low end out of the car as it doesn't produce much until after 3000 rpm. so i can change out the gears from the 456's to 373's or around there.
What is the math that needs to be done after countng the grooves in the pullies?
This is only a street car, its not going to be run down the track, so i would like to be able to stay with 93 octane.
Thanks again for all your help. I will check the pully size and get back to everyone.
Daryl
no prob. I couldnt tell ya what the math is for the pulleys cause i do not know how either. lol. I would think with afr even the baseline would be fine for your set up. I would talk to the blower shop they could give you a ton of info. the c/r is your biggest thing to figure out. I would hope it is at around 8.5-1 to 8-1.
 
#13 ·
Divide the number of teeth on the driving (crank) pulley by the number of teeth on the driven (blower snout) pulley, like this...

Crank pulley = 45 teeth
Snout pulley = 39 teeth

45 / 39 = 1.15 or 115%

In the above example you are driving the blower at 115% of engine speed, so the blower is 15% over-driven. If you wanted to reduce boost you could swap the pullies, and then you would have...

Crank pulley = 39 teeth
Snout pulley = 45 teeth

39 / 45 = .87 or 87%

In this example you are driving the blower at 87% of engine speed, so you are 13% under-driven.
 
#14 ·
The above info is pretty good. Get the car running good and drive it around for a while before you start changing things. It has to be a fun car to drive. You will probably blow off a set of tires pretty quickly. haha BTW you can get a nasty ticket or group of tickets if you aren't carefull. :mad:

I'd take a carb off and look inside the blower. Pop the belt off too and spin the blower by hand. It should turn freely and not be scored or chewed up. If it is you will definitely be down on boost. No easy or cheap fix here. You will have to send it to one of the blower shops for a rebuild.
The things are heavy. Around 70-80 pounds.
$300 up pluss massive shipping.

You can get a vacuum/boost gage from autometer in several different styles. Get one. Install the 1/8 npt fitting in the manifold under the blower. Yes there will be vacuum in the manifold even cruising. You will only get boost when the throttle is open far enough for the blower to draw in more air than the motor can by itself. The 6-71 blower displaces 411 cu in per revolution and is quite efficient at relatively low speeds. You have to overcome vacuum before you get boost. It happens pretty quick however. Don't get too carried away with boost on the street. 5-8 psi is good for a SBC You could go to 10-11 underdrive and pick up a little but I'd be carefull. The more boost you have the more critical timing and carb tuning becomes. The first time it backfires hard will open your eyes for sure.
$60 or so

Try your converter out for stall speed. You really need about 3000 stall even with the blower in this case. I've got a 3k in mine and it really made driving it more fun.
$350 or so

The 4.56 gear are going to be a major pain on the street. I ditch them for a 3.73.
$175 +/- a little. If you install them yourself.
add another $100 minimum if you don't.

Instead of messing around with the timing light trying to figure out the advance curve just take the distributor to a good performance shop and have it run on the Sun machine. Tell them you want full advance by 2000-2200 engine rpm and about 15-16 degrees of advance. Install the dizzy and set total advance at 28-30 degrees at about 3000 rpm and let the initial fall where it might. All you need to worry about is that it doesn't kick back against the starter. It shouldn't with proper C.R. With this set up and a 3k converter you will have full advance almost anytime you step on the gass.
$50-75 about.

I put a few $$$ figures in to give you and idea of the cost of blower related items. As they say "...get used to it" :(
 
#15 ·
The very first thing you need to invest in is a boost gauge. Until you know how much boost the engine is making you will have a hard time figuring out what's going on with the power. You said the previous owner told you it is 13% underdriven. That iseasy enough to verify as mentioned above. Witha 6-71 on a 350 I would guess your boost is down around 8lbs, based on your drive ratio. You are doing the right thing by asking questions and trying to learn. What you don't know can kill that engine. I highly suggest you buy and read the book "Street Supercharging" by S/A Designs. It will really help you understand what's going on.

Ignition timing and timing curve is very impoortant and will make a major difference in performance and engine cooling.

ISince you don't know all the info on the engine, provide what you can. Verify your drive ratio, check your initial timing and total timing, install a boost gauge and verify boost.
 
#16 ·
Thanks again for all everyones help.
I counted the teeth on the pullies and they are 61 snout, and 54 crank.
not sure on the timming or the boost yet, ordered a gauge but won't be here until monday.
the heads are AFR alum. 195 runners, and 68cc.
the trans, is a th 400, with stock converter,
ignition is msd 6 al, coil msd blaster 2, and msd dist.
The rear tires are 295-50-15, bfg radial t/a.
also mentioned is the 456 gear, dual holleys.
 
#18 ·
Just so my understanding is right. If i put a say, 3000 stall converter in, doesn't that mean that everytime i take off i will be doing 3000 rpm holeshots? almost like a neutral drop at 3000rpm? Sorry for asking such dumb questions, but iam just trying to learn.
Also once i get my boost/vacuum gauge, where do i hook it up to, the intake, or somewhere on the blower?
Is there a pre drilled place, or do i have to drill and install a nipple?
also what oil should i be running in the blower, and how do you check what oil it has, and where to fill it? (i know, its something i should know before even owning a blower engine)
once again sorry for the questions, but iam in new grounds with the high hp engine group. Basic, and mild engines no problem for me, but trying to learn as i go now.

I really do appreciatte any help all you guys are giving me.
Daryl
heres a couple pics of what iam playing with.

 
#19 ·
OK, you are misunderstanding how a torque converter works. They are a load and power sensitive power transfer device. The simplest analogy I can offer is that it is similar the centrifugal clutch on a go-kart or mini bike. Just normal putting around or takeoff from a stop a 3000 stall will act just like a stock converter with about 200 rpm more slip, you have to load it up(mash the throttle) to get the stall effect to be apparent. It is nothing like a neutral drop at all, more like slipping a clutch to get areally healthy stickshift to leave a stop light without squealing the tires.

The boost gauge is to be hooked to the manifold below the blower to read pressure, you will have to look to see if there is already a spot for it.

As far as the lube, consult the manufacturer of the blower for type and fill point and oil level.

Sharp looking car!! :thumbup:
 
#20 ·
Nice ride, bud! Here are some perspectives on your questions... others may have a different perspective.

- with a loose (higher stall) converter, you will still feel some pull when you drop it in gear and you will still need to apply some brake pressure at stop lights, but when you mash the loud pedal it will spin up towards the stall rpm as you leave. It won't spin to the stall rpm unless you have a line-lock or trans-brake. You will definitely notice a difference, as the motor is winding into its power band as you leave.

- the boost/vacuum gauge tap comes off the intake manifold below the blower. There should be at least one NPT hole in your intake manifold. If not, drill and tap.

- use gear oil (70-90w) in the blower drive. There should be a filler hole in the front gear plate.
 
#21 ·
Kind of hard to suggest a stall speed without knowing the specs on the cam/engine. I would think 2500-3000 should be abour right (I would lean towards 3000). I also agree 4.56 gears are not a good combo for a blown motor unless you are planning to run 1/8 mile. Blowers make a lot of torque down low so you don't need a lot of gear. As mentioned you want the boost gauge connected to the manifold below the blower. Should have a a hole somewhere in the rear of the manifold, probably has a pipe plug in it.

Unless your blower is leaking you shouldn't need to worry about the oil, it can go many many years without needing any attention. Doesn't hurt to check though. There is a pipe plug in the front cover of your blower just to the left of the pulley, that's where you fil it.

Get a timing light on that thing ASAP and see what the initial and total timing is, this can make or break your power output and driveability. With 4.56 gears and stock conveter you should be smoking the tires just off idle.

Keep asking questions that's how you learn.
 
#22 ·
I zoomed in on the front cover of the blower in your pictures. There is a little red pushbutton valve on the right (pass side) of the blower snout. You should fill this cover up to the bottom of the hole where this valve is with gear lube. After that there is no need to ever use this pressure releif valve. The front cover will build what ever boost pressure the blower puts out. This helps the lip seals do their job. BDS is pretty emphatic about not relieving this pressure. So don't do it. Fill it and forget it. These blowers are designed to run for years without maintenance.

Otherwise start with a vac/boost gage and set the timing. then have fun.
Nice ride. The blower install looks pretty good. I'm green with envy.

I'm picking up my new blower carbs tomorrow for my new blower set up. Blower should be here next week and the drive the following week.
 
#23 ·
bentwings said:
I zoomed in on the front cover of the blower in your pictures. There is a little red pushbutton valve on the right (pass side) of the blower snout. You should fill this cover up to the bottom of the hole where this valve is with gear lube. After that there is no need to ever use this pressure releif valve. The front cover will build what ever boost pressure the blower puts out. This helps the lip seals do their job. BDS is pretty emphatic about not relieving this pressure. So don't do it. Fill it and forget it. These blowers are designed to run for years without maintenance.

Otherwise start with a vac/boost gage and set the timing. then have fun.
Nice ride. The blower install looks pretty good. I'm green with envy.

I'm picking up my new blower carbs tomorrow for my new blower set up. Blower should be here next week and the drive the following week.
I was looking for the relief valve, but didn't see it until you directed me to it. My blowers have the valve in a slightly different location. I agree the bottom of that hole is the full mark.

Interesting BDS says not to relieve the pressure. Hampton blowers told me to release the pressure when I park the car for the day. I have always done it and never had any issues.
 
#24 ·
Hello again, and really appreciate everyones help with this.
I just got my vac/boost gauge today. I looked on the manifold but only found the pictured fitting. There is one on both sides of the rear of the manifold, but not sure if this is where to hook my gauge up. Looks like it is right on top of part of the head. I drew an arrow to what iam talking about. Please let me know if i can install my fitting for the gauge in this spot.
As for the timming i didn't get a light yet, plus iam unsure of how to check it. Any info on this would be very helpful also.
As for the torque converter would it be a good choice to get the 3000 stall? should it be a 10", is there any thing i need to do to fit a 10" converter, or is it a direct fit?
Thanks again for everyones help, and for your kind comments about my car.

Here is the picture of the intake port iam wondering about for the gauge.

 
#25 ·
Well i had some time to mess around with the car today. The car would never manually shift into 1st, or 2nd gear, only drive. Whenever i would take off out of the hole it would shift so fast that 1st, and 2nd really never did anything, it would be in drive before 20 feet and low rpms. (also no kick down hooked up)
I found that the shifting cable was hooked up wrong, and that the previous owner put a pin in the ratchet shifter so it couldn't be manually put in 1st, or 2nd. I have no idea why, (maybe he was afraid of it lol).
But all i can say now is, this thing came alive now that i can get the rpms up off the line. Its a whole new beast. Now its FUN to drive.
I have put about 200 miles on it in the last 2 weeks and the wow factor was there for the looks, but it wasn't impressing me with the power factor. I can now say i have a smile on my face when i launch it. :D
I am looking into the websites, and books mentioned as i want to learn all i can, and also with the timing if anyone can break that down for me.
Still unsure of where to hook up the vac/boost gauge also.
Well just wanted to let you guys know the update.
Thanks,
Daryl
 
#26 ·
Thanks for the input. i never checked to see if the vacuum modulator was hooked up. wouldn't it shift hard, (like jolt) when it shifted through the gears if it wasn't? or if not enough vacuum?
I was told the transmission was built up, and had a shift kit installed. but thats words from the previous owner.
It always shifted fine when in drive through 1st, and 2nd, but happened very fast that you were in drive almost immediatly.
As for the kick down, there is no cable installed. with the 456 gears i can't see a need for it, but when i change to 3:50, or 3:73's i may want to hook that up.
I will check again on the manifold for a fitting, but unfortunetly i don't think there is one.
Thanks again for your input.
Daryl
 
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