advice on band throwing at high rpm... PLEASE!

[Geneman]

HI peeps... good afternoon sunday . thought problem for today

background: 77 tub backdated to a 74 RSR ish...915 race box (put a 88 3.0 converted to 3.4 ish motor, twin plug, NA, MDSs . etc. had exact 3.2 shroud, fan housing, fan pulleys and belt from the 88.. never had a problem befor....

at svra indy it started throwing fan belts . like once a lap . friggin nightmare. with agiing nascars sporting 800 hp bearing down on you....

so i aligned everything as best i could. stock 3.2 pulley on top all with proper spacers ., housing looks fine , , brand new high volt valerio . ( not reman) . spins fine , mounts fine, no obviuos warpage in housing, the bottom pulley is one from DZUG when theye were making those gold blingy ones
the alter seemds to spin true at least by finger turning rpm.

i have tried multiple new belts. properlly tightened, and the fan housing is secured

i bought one of thos aftermarket clamps housnig with two bolts... i thinking itss by rothssport. maybe pms

the alter. does not seem to bind, but i cannot tell if it does at high rpm, puts out plenty of juice, pulleys alihgned . using the wood level method.

everything tight... ..

any thoughts?

as a backup . i have purchased an aluminum fan housing, supposedly RSR qusality, with the smaller fan, and also purchased the whole clewett serpentine belt setup ( which can go on either fan/houising setup.

i am concerned about swappingthe complete fan unit ans assembly to the clewett alt, pulley sysem with knowing what the problem really is.


btw not to drag this out ... bot it clear there is adifferent type/size of alt that fits i n the 3.0-3.2 bstiock housing and thesmaller "RSR" housing. see photo below.. which alt do i buy?

tsee pics of the aligned . alt that came with rsr unit on bottom



any thouhts? btw i havebeen racingfor 5 years, sometimes with help of Dawe boys and knightrace so i think i know my way a bit around these cars... this one si stumping me.... kevin fire up your brain,
btw .

seems to happen on the downshift during the blip.
_

[manbridge 74]

Is the top of the belt flush with the top edge of both pulleys?

[spuggy]

Originally Posted by Geneman

btw not to drag this out ... bot it clear there is adifferent type/size of alt that fits i n the 3.0-3.2 bstiock housing and thesmaller "RSR" housing. see photo below.. which alt do i buy?

From Ayle's post in this thread: Alternator Sizing




FWIW, my thinking is that the issue has to be either tension or misalignment. The Clewett serpentine belt system is even less tolerant of pulley misalignment than the factory setup, so would probably show it up real quick if that's it...

I like the Clewett setup. My factory belt would shriek momentarily rev-matching from higher RPM even adjusted as tight as anyone was comfortable with - not a peep since.

Might be worth pointing out the Classic Retrofit alternator is designed to fit early car fan housings (the strongest), but with one/both of the spacers will fit any. Because race car, and the CR is actually lighter than the 90A units.

[blue911rsr]

I had a problem like that at road Atlanta turns out my torsion bar tube
was cracked and made engine move around a lot tossing the belt of about
Six times till I figured it out
check your chassis out
Good luck

[Geneman]

holy crapo!! the torsion tube. something never would hsave thoughtof. thanks to all.. will get back with answers THANK YOU

[3rd_gear_Ted]

DAYCO PORSCHE fan belts, highly recommended

[Geneman]

thanks t3degenerated,,, anther thing to check... i was alos wondering if the motor anf trans mounts could be, it... i am riunning the stomski yellow mounts . pretty much the softest ones. (i also have the red and black ones) .the motor makes about it 370 hp . . thanks to wiilliam kinghtrace... no obvious vibrations in chassis transmitted to the frame or cockpit....

[Geneman]

manbridge . good point . on the top, adjustabe pulley on the fan it is well below the top of metal.

but on the bottom crank piulley, THE gold one from DZUG . most of the belts i have tried are very close if not even at the very top... all of the ones i have fitted are like this . .... the belts do not fit well down into that bottom pulley... you think thats it?.... THANK YOU

[manbridge 74]

Find a well fitting belt to current lower pulley or vice versa. Needs to be as close to flush as possible. I doubt your engine mounts are the cause.