Spitting off the belts?

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Valvebounce

Valvebounce

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I ran a 340/418 stroker at the drags yesterday.
First run it spat the power steering belt, and turned the water pump belt inside out.
We left the power steer belt off for the day. (After all, that power steer pump is stealing horsepower)
But next run it spat the water pump belt right off. (Fortunately it stayed on the engine, I left a supercharger belt on the start line once lol)
So we raced off to a parts shop to get a new belt.
Third run the belt stayed on fine.
fourth run it spat it again.
All the pulleys are factory ones. The alignment looks pretty good. It anything, there could be that one real thin shim missing from behind the water pump pulley.

Could that be enough to make it throw belts?
It's not a big ask to make new crank and alt pulleys from scratch for it. (Have a fitter and turner at the ready)
 
Yeah even a little mis-aligned and they'll swap over above mid-rpm. I spent a good day at with a couple different belts, and I added an idler pulley just for insurance.
 
Valvebounce said:
I ran a 340/418 stroker at the drags yesterday.
First run it spat the power steering belt, and turned the water pump belt inside out.
We left the power steer belt off for the day. (After all, that power steer pump is stealing horsepower)
But next run it spat the water pump belt right off. (Fortunately it stayed on the engine, I left a supercharger belt on the start line once lol)
So we raced off to a parts shop to get a new belt.
Third run the belt stayed on fine.
fourth run it spat it again.
All the pulleys are factory ones. The alignment looks pretty good. It anything, there could be that one real thin shim missing from behind the water pump pulley.

Could that be enough to make it throw belts?
It's not a big ask to make new crank and alt pulleys from scratch for it. (Have a fitter and turner at the ready)
Click to expand...

I went through the same BS with my 7000RPM 408. I have found, the factory bracketry, likes to flex and wobble too much for my liking (or for belts to stay on for that matter)

the power steering pulleys are thin, and easy to bend/warp. i threw them constantly at high RPM. (until i dumped PS altogether)

i do still run an alternator on the car. once the alternator gets to spinning, it puts out a load on the belt. if it's not perfectly aligned, it walks also, and usually throws.

We sell a small, milodon crank pulley, to slow the alternator belt down, and prevent throwing of the belt. It's the "cheaper" fix, than buying an entire serp setup. Sounds like you're a machinist. Dunno if i'd fire up the lathe for $70.lol

http://paceperformance.com/i-842271...ft-pulley-moroso-performance-64700-mopar.html
 
I found my problem to always be a junk autozone or advanced belt. Get a Gates belt. If that don't help check the pullies. You will usually find this happening when the belt bottoms out in the v of the pullyunder a hard pull. They will turn upside down the walk off..
Mine now stay on at over 8500 . stock 69 lower pully closer to crank and smaller diameter pully then a 70 and up style. A Hemi pully is the same with a deeper grove. Altenator is a GM race pully.

Fought my problem for awhile until I broke down and bought a good belt. I saw the recall at 9300 already and the belt stayed on. Once they turn around they are junk. They tear the cord on one side.

As I said if the belt sits on the bottom of the V take it back.
 
Also if you are running with power steering try and find a 340 pump pully. they are 3 spoke not solid. Less weight and easier for the belt to bring up to speed. The belt will lose some deflection with this pully.

I believe that is why chysler installed them on 340 cars. And no I don't have any my son threw them all out.

High performance fluid its thinner and no foam
 
Johnny Pace said:
I went through the same BS with my 7000RPM 408. I have found, the factory bracketry, likes to flex and wobble too much for my liking (or for belts to stay on for that matter)

the power steering pulleys are thin, and easy to bend/warp. i threw them constantly at high RPM. (until i dumped PS altogether)

i do still run an alternator on the car. once the alternator gets to spinning, it puts out a load on the belt. if it's not perfectly aligned, it walks also, and usually throws.

We sell a small, milodon crank pulley, to slow the alternator belt down, and prevent throwing of the belt. It's the "cheaper" fix, than buying an entire serp setup. Sounds like you're a machinist. Dunno if i'd fire up the lathe for $70.lol

http://paceperformance.com/i-842271...ft-pulley-moroso-performance-64700-mopar.html
Click to expand...

Thanks for your reply.
That pulley does look like a nice piece. How does the cooling sytem keep up witht he smaller pulley? The car is also used for towing sometimes. Although another two vehicle has recently been procured. (Due to it smashing a 68litre tank of gas in only 168kms while towing)
Plus we're in New Zealand. So that pulley would be nearer $150 our money by the time it's landed.

Car is still running a belt driven fan too. This must be placing quite a bit more load on the belt too. An electric fan is also on the to do list.
 
Valvebounce said:
Thanks for your reply.
That pulley does look like a nice piece. How does the cooling sytem keep up witht he smaller pulley? The car is also used for towing sometimes. Although another two vehicle has recently been procured. (Due to it smashing a 68litre tank of gas in only 168kms while towing)
Plus we're in New Zealand. So that pulley would be nearer $150 our money by the time it's landed.

Car is still running a belt driven fan too. This must be placing quite a bit more load on the belt too. An electric fan is also on the to do list.
Click to expand...

a smaller pulley will in fact underdrive the accessories by a percentage. i never ran a mechanical fan...so i can't say if it would affect much. the alternator only makes amps to a certain RPM, and it's obviously under 7k.lol

if you were putting a big electric fan on it, i wouldn't worry about it. if you want a mech fan, PS, WP, pick your evil...throwing belts...or less water pump rpm...your decision based on how hot it runs now.

i can ship USPS if it helps. Or if you want to make one, i applaud your machining capabilities. lol i'd never get those holes indexed properly. also idk how much a 6x6x6 block of aluminum runs over there...glad to help if i can.
 
I had trouble spitting belts years ago on my Barracuda; tracked it down to: alignment, over driving the alternator (6 inch crank pulley, 3 inch alternator pulley), down sized crank pulley, turned out that the alternator had bushings instead of bearings(lots of drag), replaced alternator with a better rebuild. Good to where I chip it at 7400rpm.
 
The belts are too wide for the pulls.

As the engine speed goes up, centrifugal force is trying to send the belts off. A narrower belt is deeper in the groove.

I never slow a water pump down.
 
i have experienced the same problem with an 8 blade water pump in the past , switched to a 6 blade and never had the problem again.
 
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