Symptom the pulley belt is slipping?

[olchakla]

Running a 2.80 pulley with 740 belt and don't have the idler added to my setup.

Boost would hit up to 14 lbs, then at higher rpm, it would drop down to 11 lbs. Belt is tight when you pull on it by hand.

Is this a sympton that the belt is slipping and time to replace or normal for the Eaton?

 

[Poisonous Mods]

Strange enought my boost never falls back down from 13psi with a 2.80upper & Idlers.

My 3.00 did show a bit of sign of slipping with Belt Dust & also the Dyno Sheet showed it as well.

So i had 2 ways of finding out if it slipped or not. Belt Dust & Dyno Charts.

 

[CobraBob]

Originally posted by Poisonous Mods
Strange enought my boost never falls back down from 13psi with a 2.80upper & Idlers.

My 3.00 did show a bit of sign of slipping with Belt Dust & also the Dyno Sheet showed it as well.

So i had 2 ways of finding out if it slipped or not. Belt Dust & Dyno Charts.

Same here. I'm pulling 14 psi with my 2.90" and idlers with no sign of any boost drop right to redline.

If you're dropping boost from 6,000 rpms or less you could very well have some belt slip. A dyno pull should confirm it. Belt dust isn't always obvious.

 

[Poisonous Mods]

Bob is right.
Belt Dust isnt always a 100% way. Had Belt Dust under the hood but not so much as it did with the new belt.

 

[olchakla]

Dyno pull did show a drop but I figured it was due to the high heat and humidity. Time to change it out and see how it goes.

 

[trey193]

Which 74 are you using a gates or gatorback?? I use the Gatorback 74 with my 2.80 and never see it go back near 11 on my stock guage, it seems to just peg it out and stay there, I really need a good guage!!!!

 

[FAST 03']

just orderd 2.80pulley and going to need new boost gauge any perfered gauges.

 

[wicked03snake]

now this is weird. on my 2.8 pulley and 74 belt and no idlers in cool air i saw 13 or 14. now ive put on 2 100mm and 1 90 mm idlers and no auxillery and used factory belt on 2.8 and the boost hits maybe 13 or 14 in and drops to 11 or 12 in second gear. in third it pegs at 13 or 14 and stays there. both tries were on the street and pulled all the way to about 6700 rpms. im just suprised that im still seein that much boost since i have a o/r x-pipe and flowmaster 40 series on stock cat back pipes

 

[Poisonous Mods]

Damn i wont even see 14psi on a good day :bash:
Running Gates 740 & my dyno sheet was a pretty good flat line

Strange how our cars act differently to almost similur mods.


Any Boost Gauge is good FAST 03. Its all Mechanical so take ur pic.

:thumbsup:

 

[wicked03snake]

i dont think im really seein 14, but with just the stock gauge its hard to tell. does 10psi start at the first of the fat line or end? i need to get a good boost gauge so i can really tell

 

[coleman]

olchakla, my boost dropped off from 15 to 11s when i had my 2.80" upper.

first, cheapest, replace that belt & see if you have the same signature.
second, more expensive, get an additional upper idler that causes the belt to wrap around the s/c pulley more.
and/or, get a bigger lower pulley so you can run a larger upper to obtain the same boost level overall & also get more belt wrap.

now it's quite likely that the more a belt slips, the more likely it is to slip from then on. i'm guessing here, but that makes sense.

i was fed up with the boost dropping off so i went with a KB which can be your fourth option too... :lol1:

 

[olchakla]

Originally posted by FAST 03'
just orderd 2.80pulley and going to need new boost gauge any perfered gauges.

I seen an 03 Cobra Nox car that had a Ford Performance boost gauge mounted on the pillar. It is lighted and gives good display while driving. I would like to have a shift light installed next to it. For me that would be the ideal location to have my shift light.

I didn't notice a problem until I was doing Dyno pulls and the numbers were down some from what they were before. The Dyno tech had said the belt was slipping and causing the boost to drop from 14 to 11 at the 6000 rpm range.

The current readings were similiar to what Coleman was getting when he had the 2.80 pulley and similiar mods, said it was typical for the Eaton and promted him to go the KB route.

I guess the only solution is to replace the belt and then go back to that same shop and pull a few more runs for comparison to see if there is a difference.

 

[trey193]

I know the boost will drop some but 4lb seems to much, def. get rid of the stock belt and put a gatorback on it, like I said I still have the stock guage it just pegs out and stays there but I have seen it fall back just a tad on a 3rd gear pull to redline but not back where 11 would be I dont think, its not close to that big hash mark that indicates 10lbs!

 

[mosconiac]

It is a well-known rule of thumb among Mechanical Engineers that if a serpentine belt slips once, the damage is done. From that point on, it's power transmission capability is reduced to roughly 85%.

That is, if you have evidence that your belt has slipped, it will slip again.

It would be a big mistake to discover you have belt slippage, buy an expensive idler package, and not replace the belt. You may not totally solve the problem, because the belt has already been compromised.