Gilmer Belt Throwing! - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Hotrodding Basics
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 01-03-2010, 05:08 PM
454headache's Avatar
Registered User
 
Last photo:
Join Date: Apr 2009
Location: Washington
Age: 34
Posts: 237
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Gilmer Belt Throwing!

So I bought one of those Pro-Comp gilmer belt drive kits for my 454 because I thought it would look cool, and it does. The problem is that the belt either starts to fray or gets thrown off all together. I have a March alternator bracket setup.

It appears that even the slightest amount of tension on the belt causes the alternator to bend toward the center of the engine ever so slightly. This makes the belt start to fray rapidly but it stays on. I am talking about 1/2" to almost 1" of freeplay on the belt at its longest point. This is enough freeplay to let me move the belt back and forth with my hand on the water pump or crank pulleys with not much resistance. If I set it even looser, then the belt doesn't fray but just throws itself off. Set any tighter and the fraying gets even more intense. I am at a loss here and will be going to a v belt setup as I am tired of replacing frayed,lost, and thrown belts. I know the issues maybe the Pro-Comp "quality" but I fail to see how a higher quality gilmer setup would fair any better and do not want to spend $300 on a "maybe". The only difference I can see between the different brands is that the pro-comp only has a flange on the alternator pulley while the other brancds have them on the crank as well.

I am starting to think that the whole issue is the gilmer drive itself as it causes to much leverage on the front of the alternator, but other people have similar gilmer drives and have no issues.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 01-03-2010, 05:34 PM
Rickracer's Avatar
ASE Master Tech, Fabricator
 
Last wiki edit: Taurus 2-speed fan control wiring diagram Last photo:
Join Date: Jan 2010
Location: Kissimmee, Florida
Age: 55
Posts: 937
Wiki Edits: 8

Thanks: 0
Thanked 3 Times in 3 Posts
Something is not right if your alternator is deflecting, I'd find out why.

P.S. Yet another reason I won't buy Chinese made junk....
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 01-03-2010, 05:36 PM
eloc431962's Avatar
Evil Wicked Mean And Nasty
 
Last wiki edit: Pilot bearing and bushings
Last journal entry: roof repair
Last photo:
Join Date: Nov 2008
Location: back in the garage.
Posts: 13,762
Wiki Edits: 37

Thanks: 50
Thanked 28 Times in 24 Posts
Got any pics of your set-up on the engine? Those belts are not suposed to throw.

Cole
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 01-03-2010, 06:49 PM
OneMoreTime's Avatar
Hotrodders.com moderator
 
Last wiki edit: Health and safety in the shop or garage
Last journal entry: Yard Dog pic
Last photo:
Join Date: Jul 2004
Location: Washington State
Age: 70
Posts: 7,431
Wiki Edits: 3

Thanks: 60
Thanked 163 Times in 152 Posts
It appears that even the slightest amount of tension on the belt causes the alternator to bend toward the center of the engine ever so slightly. This makes the belt start to fray rapidly but it stays on. I am talking about 1/2" to almost 1" of freeplay on the belt at its longest

That is the issue as I see it..you need a stronger alternator mounting that does not deflect under load..any deflection or misalignmant of the pulley system will result in the problems you are having..

Sam
__________________
I have tried most all of it and now do what is known to work..
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 01-03-2010, 07:49 PM
454headache's Avatar
Registered User
 
Last photo:
Join Date: Apr 2009
Location: Washington
Age: 34
Posts: 237
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I agree with the deflection issue. That is why I had ditched the stock stamped bracket set up and went to the March deal. I don't think anyone makes any thing more substantial then they have for a long water pump.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 01-04-2010, 05:55 AM
Rickracer's Avatar
ASE Master Tech, Fabricator
 
Last wiki edit: Taurus 2-speed fan control wiring diagram Last photo:
Join Date: Jan 2010
Location: Kissimmee, Florida
Age: 55
Posts: 937
Wiki Edits: 8

Thanks: 0
Thanked 3 Times in 3 Posts
I still say if it's deflecting, there's something wrong. Bushing or brace missing, too small a bolt somewhere, something....
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 01-04-2010, 10:25 AM
Registered User
 
Join Date: Dec 2004
Location: San Jose Ca
Age: 62
Posts: 472
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Ron at Black mountain makes a set up like that but has no problems with belts. He gets call all the time from pro comp buyers about the problem. There is a problem in the machining I believe.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 01-04-2010, 11:44 AM
454headache's Avatar
Registered User
 
Last photo:
Join Date: Apr 2009
Location: Washington
Age: 34
Posts: 237
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
A couple of things to add...

My mounting hole which the long bolt goes through in my alternator is for a 3/8 bolt. The hole in the head for that bolt is for a 7/16" bolt. I had to enlarge the hole slightly for the bolt to fit through the alternator. I don't know if that would cause this deflection as the there is no room for the bolt to wiggle around, but maybe it's just slightly drilled off center. I'm gonna try to take this out of the equation so...

Are there any over the counter alternators (as in something I could get from Shucks which btw I'm on warranty alternator 4 from them) that have a 7/16" hole or are there any type of reducers that would make the hole in the head into a 3/8"? I know I could drill it and put a Helicoil in there but I'm trying not to go that far.

Also, the crank pulley maybe slightly off machining wise as it seems to to wobble up and down at idle.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 01-04-2010, 12:41 PM
Rickracer's Avatar
ASE Master Tech, Fabricator
 
Last wiki edit: Taurus 2-speed fan control wiring diagram Last photo:
Join Date: Jan 2010
Location: Kissimmee, Florida
Age: 55
Posts: 937
Wiki Edits: 8

Thanks: 0
Thanked 3 Times in 3 Posts
Can you post a pic of the setup? Might help us come up with some ideas for ya,
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 01-04-2010, 01:21 PM
302 Z28's Avatar  
Last photo:
Join Date: May 2003
Location: North Texas
Posts: 10,840
Wiki Edits: 0

Thanks: 1
Thanked 86 Times in 73 Posts
Are you using a standard grade bolt or are you using ay least a grade 5?

Vince
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 01-04-2010, 03:06 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
I'm willing to bet that if there's ANY appreciable deflection of the alternator when the belt is correctly tensioned, there's an even more pronounced harmonic that will really get things moving around at speed. I'd like to have a look at it in slo-mo. You could even hook up a timing light to 'freeze' the alternator- if it's moving around, you'll see it with the light.

I would also be looking at the run-out of that crank pulley. A combination of the two (alternator flex and crank pulley run-out) will certainly cause unwanted things to happen!

I'd be using a 7/16" stud in the head, and I'd also be looking for any way to get an extra rear brace (remember the OEM set-up?) on there to prevent the alternator/alt. bracket from deflecting.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 01-04-2010, 03:28 PM
Rickracer's Avatar
ASE Master Tech, Fabricator
 
Last wiki edit: Taurus 2-speed fan control wiring diagram Last photo:
Join Date: Jan 2010
Location: Kissimmee, Florida
Age: 55
Posts: 937
Wiki Edits: 8

Thanks: 0
Thanked 3 Times in 3 Posts
This may give you a bit of an idea. Years ago, all the Astro vans had this big steel horseshoe bracket for the serpentine belt setup. It was very common for the bottom two bolts on the driver's siide to come out or break off, and the bracket to crack right next to the P/S pump, which would make the belt flop around wildly. My fix was to repair/replace the bolts with some grade 8s, loctited in, weld up the crack, and weld a brace between the P/S pump part of the horseshoe and the middle of the bracket above the water pump. Never had one come back after that repair.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 01-04-2010, 03:29 PM
454headache's Avatar
Registered User
 
Last photo:
Join Date: Apr 2009
Location: Washington
Age: 34
Posts: 237
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I do not know what grade the bolt is. It's whatever March sent me with the bracket kit, I assume a standard stainless allen head bolt.

Can't post any pics or video as I'm away on business from the truck.

I really do not know of anyway that I could brace the alternator any better. I've looked at all the aftermarket set ups online, and none are any beefier than what I have on there right now.

The stock deal with the upper bracket that attached to the manifold fared no better. I even used a 7/16" stud at one point and still the same deflection issue. I was hoping that it was the culprit in fact, and that the March brackets billet would solve the issue, but they did not.

I have also tried going from a 40.5" belt to a 42" (along with using a longer upper billet bracket) out of just shear frustration. With a longer belt, the deflection is even worse.

What I do not understand is that in theory the belt is suppose to position itself on the crank and waterpump pulleys via the alternator pulley. As in, where the belt sits on the alternator is where it will move to orient itself on the other pulleys. Hence, why there is a flange on that pulley and not on the others. But instead it picks a nice spot on the waterpump and crank and then mashes itself right up against the front flange of the alternator pulley.

I really want to keep this gilmer drive for the sound and uniqueness, or go get a quality one from Black Mountain. After countless thrown belts, an overnight parking spot at the QFC waiting for a new belt to arrive in the mail, and this newest belt fraying after 10 minutes of running with tension so loose that I can move the belt off of the pulleys by hand...it just does not seem reliable and may go serpentine (standard pump rotatio) or v belt.

Last edited by 454headache; 01-04-2010 at 07:13 PM.
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 01-05-2010, 07:36 PM
Registered User
 
Join Date: Oct 2004
Location: Slidell, LA
Age: 65
Posts: 149
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by 454headache
What I do not understand is that in theory the belt is suppose to position itself on the crank and waterpump pulleys via the alternator pulley. As in, where the belt sits on the alternator is where it will move to orient itself on the other pulleys. Hence, why there is a flange on that pulley and not on the others. But instead it picks a nice spot on the waterpump and crank and then mashes itself right up against the front flange of the alternator pulley.
As discussed, the belt is trying to walk off the alternator pulley because the alternator shaft centerline is not being held parallel to the crank centerline. Because the alternator is deflecting, the forward end of the alternator shaft and crank centerlines are closer together than at any point rearward. A flat belt under tension wants to find slack, and thus works it's way forward against the pulley flange because of the closer centers.

Bob
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 01-05-2010, 07:53 PM
eloc431962's Avatar
Evil Wicked Mean And Nasty
 
Last wiki edit: Pilot bearing and bushings
Last journal entry: roof repair
Last photo:
Join Date: Nov 2008
Location: back in the garage.
Posts: 13,762
Wiki Edits: 37

Thanks: 50
Thanked 28 Times in 24 Posts
Quote:
Originally Posted by bobscogin
As discussed, the belt is trying to walk off the alternator pulley because the alternator shaft centerline is not being held parallel to the crank centerline. Because the alternator is deflecting, the forward end of the alternator shaft and crank centerlines are closer together than at any point rearward. A flat belt under tension wants to find slack, and thus works it's way forward against the pulley flange because of the closer centers.

Bob
I agree something is giving when you tighten it up/ It's out of line. I have hanging on my wall in my garage a for my SBC , A set of deep groove pulleys/ a set of stock pulleys/a cog belt system 2inch belt/a set of serpentine pulleys/ And i have a set of serpetine pulleys on my car now not any of the fancy stuff just a set of pulleys i rounded up and work really well. But none are going to work till you get all the weak points lined out and the pulleys straight. Do a search for the best pulley system we have discussed it here before.JMO

Cole
Reply With Quote Quick reply to this message

Recent Hotrodding Basics posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 2 (0 members and 2 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Throwing a belt biscuitville Engine 14 07-27-2008 08:25 AM
Gilmer belt question 1969NovaSS Engine 3 03-29-2006 10:35 AM
Gilmer belt question 1969NovaSS Engine 3 03-11-2006 09:36 PM
Squeeling Fan Belt - Out of true Pulley Billy Boy Engine 3 02-15-2005 06:51 PM
will i keep throwing my belt? uneedmorethen10s General Rodding Tech 4 02-03-2004 09:49 PM


All times are GMT -6. The time now is 01:26 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.