This topic contains 449 replies, has 26 voices, and was last updated by 
VRSenator065 4 years, 7 months ago.
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VRSenator065
- Adelaide SA
- VR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project)
View build HERE
Posts: 5 777
^and that sort of info is why forums rock. Nice work. Great to see the car getting really sorted Pete.
Ah cool, thanks. Never seen that mod before.
probably didn’t help that I was thinking normal 6PK type pulley haha
I can not drill them all the way through, I wanted to do that, to drill them so they come out the lip on the front means the holes will be about 10mm from outer edge of pullie so would only be 8mm under the 50mm wide belt, the rear of pulley is even worse and holes would need to be about 5mm from edge, and where I’ve drilled them it’s solid alloy till the keyed shaft it slides onto so I had to pick a depth as just been random would mean the pulley would become unballenced
I didn’t actually measure, I simple set the drill press and just went for it might be more like 10mm actually as 5mm is pretty shallow and they do have a bit of depth
exactly right with it only been air been trapped, I was told to get the engine hot and then set it so the belt is not tensioned but it’s not flopping either
doin this I found on cold running it was hitting a harmonic frequencies and on down rev the belt would slap violently and I could feel this all through the car through the seats, steering wheel, even if you touched the windows or doors you could feel it, I could see it slapping with bonnet open and giving it a rev
I found loosing it just a tad more all vibrations at all times went away, so when it’s hot the belt is still a tad loose, I can slide across the pullie 5mm when it’s hot
drilling the the holes has made a huge difference, it is massively quiter, and now is just a blower whistle when revved, I could nearly get away with people not knowing its blowen while idling and that’s a big thing when it’s a v7ysi with a 50mm gilma drive
So if you tension it to the correct spec for the manufacturer of the belt it will be loud?
Don’t know if there is a correct tension spec for capas gilma set up, think the only rule is not tight and not to loose it can fly off
if there is little to no slack in the belt while hot then it will whistle, if you put a little tension on it then it will be louder, tiny bit of slack in the belt while hot and its quitter
gilmas are not Ment to be tight at all, Iv seen 8/71 blowers where the belt is really loose, like can push it about 50-60mm till the slack is taken out
myn I can push it maybe 30-40mm when cold till the slack is taken up and about 10-20mm when it’s hot
Hmm interesting, in industrial applications all the belts either V or timing belt (like gilmer) etc. have a spec given by the manufacturer of the belt for optimal performance. It’s often tighter than you would think. The spec is given in Hz normally, there are apps which use your smartphone mic but the best is an optical freq meter.
Wonder if anyone’s tried tensioning using this method. I would have thought with the belt flapping it would prematurely wear the pulleys then it will always be noisy. Of course assuming the pulleys were the correct profile to begin with.
sorry for the tangent, an interesting topic.
I like the tech talks, that’s why I’m on this forum
Yeah I’m not sure on specs, Iv never seen any and never been told any specs on tension and I 99% sure Scott from capa was who told me to not have it tight and check it while hot
having a 50mm wide belt if it’s tensioned up it puts huge load on the bearings and wears them out
my belt with the loose tension it is now does not flap, when it’s slightly tighter it does flap and can see it even when free revving it, with the belt been so wide when it flaps I know about it as I can feel it in the car as a vibration
would good old to know if anyone knows specs of tension of gilma belts
What’s the part number off the belt
VRSenator065
- Adelaide SA
- VR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project)
View build HERE
Posts: 5 777I like the tech talks, that’s why I’m on this forum
Agree 100%, learnt so much off others, lots of people willing to share knowledge.
Tech talk 101
Crank the sucker up and do a skid!!!!
Don’t know what the part number is
not a fan of posting illegal skids on public forums, maybe I can do a drive way skid
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This reply was modified 8 years, 11 months ago by
vs manta 218.
haha wicked skid! sounds tough as hell!
For that gates belt the min tension is 56lbs, that spec is for checking with a tension meter.
Where did you get that spec from ??
Not a chance In the world would I run a 2 inch wide gilma at 56lbs, that would total bearings real quickly and whine like all fuck and be under massive tension once hot
my Pullies are about 500mm apart, when it’s cold the longest part of belt can move about 35-40mm so 20mm from centre line up or down till it goes tight, when it’s hot this halves and only has about 15-20mm up and down total movement (slack)
even when I take all the slack out when it’s hot it still has 10mm movement due to the length between Pullies but that’s when it gets that slap up to it and vibrates and doesnt like it
its a big no no to run a 2 inch gilma belt under tension, I was told by capa if I run the belt with any tension it will distroy the bearings in my Crank brace in no time at all
check out a drag car next time you see one with a 8/71 fitted, I bet it’s belt has about 80mm slack in it, if you ever go to the v8supercars check out the arms 2 burnout cars that get around to them, there 2 inch wide belts have about 90-100mm slack in longest part of belt
Spec is from the gates technical book for that series belt. It’s interesting the trend in cars to run them so loose.
btw that is tension not force-displacement. So the force in the belt along its length, not the force to depress it. I’m sure then is more than 25kg force in the belt when it’s turning the blower
Yeah that’s the belt tension, but that is still fearly tight, like a normal v belt is about 120lbs or so isn’t it ?
Maybe it’s something to do with there application, I see they are mostly used for for machinery and stuff, maybe as a drive belt that is steady rpm and belt only does Like 1000-1800rpm that would be fine with big bearings to take the load but when on and off the throttle to 7000rpm so savagely and the little bearings used on the brace and blower pullie is where the problems starts
i know they will distroy a alternator bearing in no time if it’s tight
when i first got it and didnt have the brace I didnt know it was Ment to be so loose, even when just a little bit of tension was applied I could see it pull the blower around about 7mm or so and its held in place by a 10mm steel plate and to do the same with the old 8pk belt took heaps and heaps of tension
Interesting stuff
VRSenator065
- Adelaide SA
- VR Senator LSx454 1960 Kombi (project) 1921 Nash Hot Rod (future project)
View build HERE
Posts: 5 777Def interesting discussion, might be actually worth contacting Gates themselves via email? They have always been pretty much top of the tree for belts etc. Just might be interesting to hear what they have to say. (nice burn out btw!)
I’m actually not joking with running in the alternator, that seriously was the first time the tyres moved with that alternator hooked up lol, I literally started it up and checked volts, a small rev to 2500rpm then backed it out, washed it, warmed it up, run in the alternator and put it away lol
benk can you post a link to the belt tensions please
doesn’t really matter as its either to tight and whines, or just have the slack out of it and it vibrates and slightly looser where it works nicely so I know where I’m keeping it but I will send a email and ask the question
Sure thing, I’m away at the moment not back to my regular computer till 11th of Jan but you can google for the gates manual for the GT3 series of belt. Spec is in a table towards the back.
if you can’t find it I’ll post it when I’m back.
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