DeltaT

iTrader: (5)

I have a Vortech 8-rib 3.12" pulley on my V-2 SQ S-trim on a 383. Everything's running great - I get about 7.5 lbs. of boost after the FMIC and throttle. Power is strong until maybe 6400rpm.

When I put on my slightly smaller pulley, an ASP 2.95", I get a lot more rubber dust and less boost - on the datalogs you can see the boost actually dropping as you spin the motor tighter. I have checked the pulley's dimensions (like offset and stuff), and everything checks out like the Vortech pulley. But I get a lot more slip. Now I'm believing that the pulley surface maybe has a different finish. Both pullies are black anodized.

I am running a 7" ASP crank pulley.

I could strip, partially or fully, the black anodizing off just the rib portion. I would used a bead blaster after I masked off the other parts of the pulley.

Questions:

- Is the slip due to surface issues? I really cranked it down in tightness, so I could barely twist the belt 90 degrees.

- Will the pulley wear a lot faster with a partial or full strip?

- Has anyone tried different surfaces to reduce slip? Is that what the Renegade pullies are?

- Anything else I am not thinking of, or other suggestions?

Thanks,

Jim

2001WS6Vert

Maybe use a spring loaded tensioner to absorb slack when the load gets high. I know my tensioner moves a lot when you rev it.

Fire67

iTrader: (3)

Stripping the surface will definitely make the pulley wear faster.
What kind of boost are you running? It may be time to step up to a 12-rib pulley to increase surface area... As the only surface issue I can see causing slip is a lack of sufficient contact area.
Im not sure about the "Renegade" pulleys, but there is a company that adds cuts across the ribs to increase grip...
I'll try to find the link and post it up.

Pro Stock John

iTrader: (34)

Try adding more belt tension first. I've made anywhere from 18-21psi depending on weather and other factors. My belt is tight like a banjo string. Maybe take a shot of your belt setup for us.

DeltaT

iTrader: (5)

Thanks for all the inputs.

Here's a couple shots of the belt setup I built:



AND:



I am already running quite a bit of belt tension and am nervous about adding more. Pro Stock John, can you twist your belt 90 degrees?

The idea of a spring-loaded tensioner is good and I could add one right before the blower.

I am only getting about 7.5lbs of boost after the FMIC and throttle, but this is a very good breathing 383 with ported E-Tec 200 heads, a 230/236 112LSA CC Xtreme Street Roller Cam, net lift .575/.583, full LT 1 3/4" headers to true 3" dual exhaust, ported Holley Commander 950 intake, huge Bell FMIC with 34 downtubes and a core of 23"W X 6"H X 4.5"D. 3" tubing throughout.

I didn't expect too much more from a V-2 SQ S-trim. I have heard rumors of a V-2 SQ E-trim. Anyone ever seen one? Also there's a Vette guy who says he has a V-2 SQ T-trim which could be interesting if it's true.

Any feedback or suggestions appreciated. This ls1tech.com forum is one of the best around for FI questions.

Jim

My Site: http://home.mindspring.com/~jim_fisk/id1.html

Pro Stock John

iTrader: (34)

If I can twist my belt 90 degree it's slipping. So no I cannot.

2001WS6Vert

Another suggestion might be to try a Gates belt. I think there was a poll here once and it was prefered over the Gatorback.

GTOLarry

Long story short I had similar issues. I assumed it was a tension or traction issue with the belt. Tried Gates and Poly-V, seemed like they would just stretch. I kept belt very tight, 90 degrees max twist. Seemed like there was nothing I could do to keep it from stretching and slipping. I would tighten it and it would be good for a very short time then slipping again. Eventually I found the problem, bad bearing in the blower. It was dragging and normal belt tension was no longer enough to turn the blower at speed. The bearing eventually had a complete failure and had to cut the belt to get the car home. I was running the same blower you are and Vortech rebuilt it for me under warranty. Now I have the belt on with far less tension, 90 + degrees and no slipping ever now. So.... it may not be a belt issue. Looking at your picture I also notice that your wrap around the crank pulley seems a lot less than mine (could be an issue). With the smaller pulley you need even more belt traction to turn things because you are driving the blower faster.

DeltaT

iTrader: (5)

Thanks for the replies, I appreciate them.

Jim

95 TA - The Beast

iTrader: (2)

Hey there, I just took a look at your setup and site, pretty much the ultimate 'sleeper', huh?

VERY nice job on everything, very well thought out...

But, in regards to your belt-issues, I beleive your biggest problem is there is not enough crank pulley surface area for the belt to 'bite' on. As you increase boost you also increase the impeller speed, which means there is more resistance. You should have at least 45-50% pulley to belt contact area to maximize the amount of grip of the belt. Based on your pictures, I would say you are lucky to get 25-30% pulley to belt contact...

Now I cannot tell, but is it possible to remove the upper right pulley and allow the belt to loop around the crank pulley a lot more? (I beleive the waterpump bolts might just be in the way too much to do this? It might be more advantageous, if possible, to change the routing by removing that uper right pulley and re-arranging the tensioner so that it forces the belt out of the way of the waterpump if that is the case?)

Also, one thing to look into is I believe I read somewhere that it is much better to have the tensioner on the 'tension side of the belt vs the 'slack side' the way you have it. In other words having it on the side that sees more 'tension', ie between the crank pulley and the blower pulley in the direction of belt travel (so in your setup the lower left quadrant), even tho on your setup it loos to be almost impossible to accomplish that with any sort of rigidity, so you may have to use the routing you have...

DeltaT

iTrader: (5)

95 TA - The Beast - Thanks!

I actually was running the belt routing you suggest, and it worked mostly fine until I really started cranking up the tightness of the belt. Then it pulls the tensioner at an angle it wasn't designed for, and actually twists the tensioner mount, then the belt slips over a rib and the belt gets destroyed on one rib. Another $28 down the drain. I need to re-think the tensioner device and mount.

I would agree with you about belt wrap on the crank but the rubber dust is all up near the blower, and it's a 7" crank pulley.

I haven't tried that routing since I put the new engine crossbrace in - it is possible that a little tensioner rework is all that's needed now.

I do have the option of making a new 3rd plane plate like you can see under the blower pulley. Then I could put a static tensioner on that side and maybe convert to a spring-loaded one where the current one is, and run the shorter routing.

Still tweaking for the 'perfect setup', but it's running like a raped ape!

Jim