Blower question

enjenjo · December 18, 2009, 08:56:00 PM

How tight do you run a Gilmer belt on a blower drive?

bowtietillidie · December 18, 2009, 09:31:56 PM

Take a straight edge between the two pulleys furthest apart. Stand it on edge . Now take a nickle stand it up on it's edge, when the nickle passes thru and touches both straight edge and gilmore belt without resistance.
The belt has the right tension :!:

PS: Make this check on the drive side of the belt

kb426 · December 19, 2009, 08:33:11 AM

It makes all the difference whether it's flat tooth, 8 mm or 14 mm or if you have an all steel engine or alum. heads etc. Flat tooth belts have to be tight. each progressive mm. size is run looser. My one word description would be "snug" not tight. The amount of overdrive and the boost level also are factors. I'm pretty sure I didn't help at all.

enjenjo · December 19, 2009, 11:35:29 AM

This is a street motor, 355 SBC. It's set up 10 percent underdrive. It's a 1/2" pitch belt 2" wide.

My concern, you can turn the water pump against the belt easily with just one finger with the engine not running. The water pump drives off the back side of the belt, with the belt tight. It may be that I am worried about nothing, since the water pump drives on the loaded side of the belt, and when running there will be enough tension on that side to keep it from slipping.

kb426 · December 19, 2009, 04:20:33 PM

You're making me nervous but I worry about everything. I've never been able to measure the amount of power it takes to run a water pump, though. I'm still not much help.

wayne petty · December 19, 2009, 10:03:04 PM

water pumps create pressure behind the thermostat..

i have always wondered just how much also...

anybody got a small block chevy and a pressure gauge to screw into the front of the intake... with a thermostat in.. and the heater hoses blocked off?

everything i own right now is a ford... or a flat six corvair..

that should give everybody the idea of how much pumping the pump does require..

this would allow enjenjo.. to know how much slippage is too much...

i am thinking.. larger pulley.. so the water pump will act like an idler.. instead of a friction drive..

i was wondering a few weeks ago... if anybody had ever cast up a small block chevy timing cover.. but like a front wheel drive 3.1 timing cover.. where the water pump is out in front of the left hand valve cover.. so the whole front of the motor is clear.. its just an idea... but a 3.1 V6 belt driven pump .. or an electric pump could be mounted there.. ...

that really short timing cover and water pump housing.. could be really handy for other applications..

i seem to recall that in an engine masters article.. the difference was like 14 horsepower.. @6000 rpms.. but that number is really fuzzy...i also don't think that was against a closed thermostat.. or a cycling thermostat..

Digger · December 20, 2009, 01:38:13 PM

Not too snug. You should have at least a half inch deflection when it is warmed up. (There is quite a bit of expansion) any less than that you risk breaking the blower or crank snout.
What kind of blower drive are you using? As I recall most use accessory drive v-belt pullys for the pump. Of course my memory isn't that great anymore---where do I send this?

32coupe · December 20, 2009, 05:26:18 PM

Hi Frank
I run mine with at least a 1/2" of free play when cold, and when it warms up it's tight.

enjenjo · December 20, 2009, 06:11:27 PM

QuoteWhat kind of blower drive are you using?

This is a car that a buddy bought partly done. Some of the parts are marked BDS, but they are all pretty old, so who knows.

wayne petty · December 20, 2009, 08:52:30 PM

if most of it is from BDS.... i would bet they have an answer for you...

http://www.blowerdriveservice.com/

Jbird · December 23, 2009, 01:55:27 AM

I've done a few supercharged engines but I never had one where the Gilmer belt also spun the waterpump. On a serpentine accessory belt driven water pump it takes a bit of work to spin the pump against the backside of the belt. On an Escalade I did a few years ago the blower, and everything else, was driven off one serpentine belt using a stock GM tensioner. How full of a circle does the belt make around the H2O pump? Jbird

enjenjo · December 23, 2009, 05:15:08 AM

QuoteHow full of a circle does the belt make around the H2O pump?

Less than a quarter circle.

bowtietillidie · December 23, 2009, 01:35:14 PM

Cragar and Wiend both made blower drives like you described I have used both and both worked well
Does anyone remember when machine ran on line shafts? Those old belts flopped around all over the place ........ but the machines were able to handle a very heavy cut. The reason was ..... the area of belt on the flat pulley and an idler on the driven side of the belt .
Side note: measure the contact area on the flat pulley in question convert to square inches . You will be supprised how much flat belt you have working for you. Also try to turn the pump pulley in the proper direction of rotation,
i'll bet you have a hard time turning it. But can turn it very easy in backward rotation. Also if you have an OLD copy of Machinery's hand book you will find every thing you ever wanted to know about flat belts and flat pulleys.
When ever I run on to something I don't work with everyday tend to make it harder than it really is, So I have a sigh on the back drop of my bench.
It says KISS Keep It Simple Stupid
Works every time for me

enjenjo · December 23, 2009, 01:38:59 PM

QuoteIt says KISS Keep It Simple Stupid
Works every time for me

I tend to agree. I'm going to try it this way. It has run before, I just don't know how long.

Jbird · December 23, 2009, 10:48:48 PM

Quote from: "enjenjo"
QuoteIt says KISS Keep It Simple Stupid
Works every time for me

I tend to agree. I'm going to try it this way. It has run before, I just don't know how long.

Just make sure you have a bag of marshmellows around in case it doesn't go as hoped. No sense in letting all that heat go to waste. Jbird