Let's talk about blower drives for a minute,

Well, more so the drive belt/pulley's.

We're all familiar with the nice wide 2 or 3" belts, be it 1/2 pitch or the MM style, but some of us also really dig the V-belt drive set ups.

I have a 6-71 i'm thinking about putting on my 32, but like many would like to convert to multiple V belt. It currently has a 3" Gilmer style 1/2 pitch drive.

I'm aware of the over/under drive table for these as i've had a 6-71 on my old 32, but what i'd like to know is some details on the V-belt ratio's.

On the cogged style, tooth count is pretty much how it's broke down, which also dictates the dia of the cogs themselves i assume.
So, am i to also assume, for example, that if i am running say a 10% underdrive with a 1/2 pitch, i can make a mutiple V set up with the same dia as my current cogged pulleys, and have the same ratio????
And is my measurement transferred to the OD, or the base of the new V belt pulley to get an accurate ratio?

Am i way off?
If so, please help me understand.
I want to make my own set up, but with the amount of work involved, i want to make sure i will be making them with the proper ratio and not blow the head gaskets out of my mill.

Is there a table with specific dia for V-belt set up's out there i have not been able to find that is similar to the others offered by blower companies?

This has been wandering around my small brain for a few days and thought it would be a good topic for here.

So, what do the more knowing have to say that could assist us who want to make this change?

Thanks, looking forward to knowing so i can V-belt this thing.

Tony

 

I like v belts.

 

The dimension would technically be measured at about half the thickness of the belt when in the groove for the ratio. I'm not sure how much a 1/4" in or out would affect what you're doing though if you measured the outside diameter or the diameter at the bottom of the groove.

 

I would think with a v belt setup your only concern would be the ratio of crank pulley size to blower drive pulley size. Since the v belt isn't "locked" to any particular point on the drive pulleys like a cogged belt, as long as it's not slipping you should be good to go.

 

As long as the pulley grooves are the same width on top and bottom pulleys, you can measure the OD of the pulleys and the percentage difference will be the same as circumference.
4 X 3.14 = 12.56 (top)
5 X 3.14 = 15.7 (bottom)

12.56 / 15.7 = .8 or 4/5... (20% over)

 

I also like V-belts,planning on running twin belts on my471,y-block 292

 

Don't forget you will need to order a matched set of belts, whatever number you chose to run. Can be expensive.

I have a feeling if you do this, it won't be long until you find out why they changed to Gilmer belts as soon as they could.

 

The diameter of the pulleys will give the drive ratio, ie. a 5" lower pulley 4" upper would give you a 20 percent overdrive. 5 - 4 = 1 divided by 5 = .20 Factors I've been wondering about are belt slippage and overall belt speed, larger pulleys will give better grip but higher belt speed, how high is safe? Also a belt tensioner that would keep the same tension on all the belts indivdually might be needed.

 

I have a Cragar 4-71 setup that has 3 V belts. I think Cragar switched over to the Gilmer belts when they offered the 6-71's. Slipping might be your biggest problem. I am no expert by any means, but I suspect you might need to run a 4-belt set-up with the 6-71 to keep it from slipping. Maybe with newer better belts, the grip might be better, but I have no idea. My set-up is not up and running yet, so I can't offer any personal experience.

Maybe do a chain drive instead. That would be over the top. On off days, I toy with that idea myself.

 

You can use the same tensioner you would with a Gilmer belt, IF the v belts are a good matched set.

 

GREAT info fella's!
I figured the same tensioner could be used providing good quality matched belts were used as exwestracer mentioned.
I would make an idler pulley that would be grooved as well though.
My plan was to run 3 belts. Slippage was a concern i did think of as well considering the amount it takes to turn the blower.
The info given to calculate the drive ratios is great! I could not wrap my head around it but knew it was not too complicated. Sometimes it pays to ask 'cause when it's written in from of you it makes much more sense.

And i'm sure the reason's for the masses to switch to cogged belts has a solid foundation behind it, but, i just can't help but love the look, and quietness of the V-belts.
I know, i'm nuts for wanting it quieter..it's one of those thing's i can't explain. Ive run the 3" set up and it sounded cool, especially with a 4 speed, but, i'm going to *try* and put a full hood on my car and it'd be pretty slick to not know what was under the tin

In a nut shell, it's something i'd like to do as i said. If it turns out to not be worth the time and effort, i'll just stick with the Gilmer set up i have but switch to a 2" drive instead and just enjoy the noise as i did before.

And a chain would be wild, but i plan to drive the shit outta this car and for some reason not comfortable with that idea inside my small brain .....would be wild a hell though.

Thanks again for the info. much appreciated!


Tony

 

Slipping might only be a problem too if your have a fast and heavy foot. Might be ok if you drive it normally on the street. But, if you are planning on any big show stopping burn-out, doughnut sessions, the V belts might not be able to keep a firm grip.

 

Did you talk to Kerry?? He built all his own V belt drive and has already figured out all the hard stuff.

Good luck, -Abone.

 

Wont you lose that awesome Blower whine sound with a v belt system ?

 

i started with 2 sbc 3 groove crank pullys, then got a snout that was close to the correct lenght, then talked to my machinist buddy, he made the idler pully idler arm and made a new center for the upper pulley, now i just need to weld the new center in the upper pully in the correct spot.

i know this set up is 1-1 but its a 471 bower. i know alot of the 671s are underdriven.

oh and parts stores dont really sell "matched sets" of belts anymore, they are supose to be made to better size standards, at least thats what gates told me when i worked at the parts store.

jeff

 

Pitch diameter of a V belt.....interesting stuff. You'd probably be safe assuming it to be the same as the OD of the pulley, as long as the belt doesn't sit down in the pulley too far.

 

Squirrel has it right. Just have to figure the ratio between the diameters of the drive and driven pulleys.

I wanted to a vbelt drive setup but couldn't afford the real Cragar stuff. I whittled my own pulleys and idler and used a storebought snout and idler arm. Been running like a champ for a few years.

FWIW the matched belt thing is a load of crap. I've never bought special matched belts, just belts with the same part number. No issues.

Here are a couple of pictures.

 

I was thinking (not to much) that to tension V belts, you must keep them pretty tight. Whereas the Toothed type belt can be much less tight without slipping. Now first main bearings and crank snouts were not made to support this extra tension. I talked to some Ford foundry guys at Bonneville who were running a supercharged V6 Super coup engine before they came out. Said they were trying real world running with the motor and had sustained several failures on the dyno using a serpentine belt to drive the blower. Just a thought about why I would not use V belts

 

gilmore can run quiet you have to drill 1/8 in holes in grooves of pulleys to allow the air to escape the whistle will dissapear. but I love the sound of
my 502 on the highway especially passing a car or going under an overpass.

 

I know, thought about doing that to my last one but didn't. If i'm gonna run the Gilmer i'll let it scream like it should.
The thought was more the old timey look than anything.

More GREAT info guy's!
Kerry, thanks for the info and pics! Thats what i'm looking to do if i do it. Very nice!
Squirrel, thanks. It was very hard for me to explain but that was my concern for where measurements should be taken.

Again, thanks to all you guy's for taking the time to write and give some details/knowledge.


Tony

 

Tony,

I am a little late to this party, but here you go.

Lets say you want 10% under or 10% over and you want to run a 4 inch pulley then the matching pulley would be 4.40inches.

4.40/4.00 gives you 1.10 which is 10% over
4.00/4.40 gives you 0.90 which is 10% under

If you were talking teeth
44teeth/40teeth is 1.10 again 10% over
40 teeth/44 teeth is .90 again which is 10% under


So basically pick a pulley size that will look and fit right and then machine the other to be a ratio of what you are looking for. Being that this is for the 32 I would guess that the crank pulley size would be the limiting factor. Determine a pulley size that will comfortably fit the crank to frame clearances and then work out the blower pulley. Also make the pulley diameter as large as you can within reason, a 10 inch pulley would be really stupid looking. You want to use a large diameter for a couple reasons.

1. A large diameter pulley will offer you greater belt to pulley contact (Wrap angle)and therefor less likely to slip.

2. a smaller pulley will make the belt do more work through the bending around a small diameter and will cause early fatigue to the belts and can cause premature failure.

As some one mentioned, Order a matched set of belts, it only make sense to make sure that the belts are made from the same lot and will be same size. Also the belts will be of the same material and same amount of shelf life. I would NOT want to match up a belt that is new with one that is been laying on a parts store shelf for 3 years, would you?

 

One thing about cogged blower belts is you want to tension them a little loose when the motor is cold, because with the blower and manifold being alum, they will expand so the tension will increase as the motor comes up to operating temp.

Some of the early V belt set ups used a spring loaded tensioner pulley to compensate for this and keep tension relatively constant.

Maybe "Kerry" can comment on this, since he seems to have his V belt drive worked out.

 

Thanks Jim, much appreciated!

Tony

 

slightly off topic, but interesting to me....Kerry appears to have a fan clutch on his blown engine. It's the only one I've seen, besides mine.

On the tension thing...that's a good point. My toothed belt starts out with 3/4" side deflection when it's cold, and warming up the engine tightens it up to about 1/4". My guess is that the right way to tension a V belt drive would be to use a belt tension gage



to get the tension right when the engine is up to operating temp.

 

I agree v-belts look cool and I want them for my 6-71, but the 2" gilmer has been around a very long time, since '58 or so I believe. Squirrel will know.

 

I don't know the exact time, but i think you're right in that time period.
That's why if its too much hassle i'm just gonna swap to the 2" set up.

 

Tony, if you do decide to run V belts, just remember it is much better to get as much rap on blower and crank, with proper placing of the idlers. That allows you to not run to much tension which is much better for crank and blower snout.--TV

 

Tony do have any pics of your 2 inch setup,how was your firewall clearance?

 

They did figure it out and make it work in the Thunderbird Supercoupe. That car uses an 8-rib blower belt. There is a belt from the crankshaft to a jackshaft that has a spring-loaded tensioner. Then there is a belt from the jackshaft to the blower that also has a spring-loaded tensioner. All the other accessories are on a third, spring-tensioned belt.

The jackshaft belt pulls the crank pulley toward about 10 o'clock, and the accessory belt pulls toward 2 o'clock. So maybe that helps balance the load of the belts and takes some upward load off the #1 crank bearing.

In the end, the #1 bearing does show more wear than the others, and the crank damper can wear out as well, but that's at high mileage ... like 100k+.