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377 stroker

 
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mrchevelle
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PostPosted: Sat May 20, 2006 9:28 am    Post subject: 377 stroker Reply with quote

hi
trying to help my son out here, he's running a 377 stroker in a 1970 chevy caprice,at 6500rpm, it's throwing the alternator/waterpump belt off.
he's using chrome pulley's now/its a show and a Go car.
As you know it's a high rpm motor/and he needs to find a pulley system that won't throw belt's.would appreciate any idea's or thoughts on this issue,
thanks
Randy

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af2
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1933 Willys Coupe

PostPosted: Sat May 20, 2006 9:47 am    Post subject: Reply with quote

Sounds like one of the pulleys is not in line. That RPM is not even close to what I have run and not thrown belts. Use a straight edge to check.
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The_Raven
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PostPosted: Sat May 20, 2006 10:10 am    Post subject: Reply with quote

af2 wrote:
Sounds like one of the pulleys is not in line. That RPM is not even close to what I have run and not thrown belts. Use a straight edge to check.


In addition to what af2 has suggested, also make sure that your accessories are mounted in a way that the brackets will NOT flex. At higher RPM, there is so much force pulling on the belt that brackets can bend and the accessory flex 'towards' the crank, or in the direction of the pulling force (usually the crank Wink). You will never see this with a straight edge, since the engine needs to be running AND at high RPM, and sometimes under load, which unless you're on a chassis dyno, you won't be able to stand there and watch the belt alignment under load. Laughing

You might also want to consider using deep V pulleys, and/or non-chrome pulleys, as the chomeing processusually makes the V narrower and will have the belt sitting 'higher' in that V closer to coming out, a little bracket flex, and it will ride the side of the V up, and off the pulley, spitting it.

Also no matter how tight you make that belt, due to harmonics and the firing of each cylinder, the belt will stretch just a bit with each firing of a cylinder, which allows for that ability to ride the side of the and off the pulley.

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Aerosmith
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PostPosted: Sat May 20, 2006 6:24 pm    Post subject: Reply with quote

I can totally feel his pain! I have been fighting this for 2-3 years now. All good ideas so far. I had a slight misalignment with my waterpump pulley being too far back. I tried putting flat washers behind the pulley on the studs but it's hard to find washers exactly the same thickness. Finally I found that Moroso has a set of 3 thicknesses of shims for this when I rebuilt my engine this spring. I didn't see them in their catalog or online but I stumbled onto them at My Jegs store. Today I was at the Pontiac Excitement nationals here at National Trails and Moroso had a matching kit on display for between the harmonic damper and the crank pulley.
I also bought a 25% underdrive pulley to try to fix it(yet untested) and now I suffer from borderline charging and cooling and frequent battery recharging. Finally, I think I have solved the problem with some homegrown fabrication...
I found that the alt belt throws first and most often (on passenger side mounted alts) due to the fact that the crank(where the drive comes from) is trying to push the belt to the alt. the alt builds more resistance as it spins faster and charges. Also that section of belt is the longest unsupported section of belt on the whole system(between 8-10" unsupported) so it flexes or builds slack on that section ALOT!
I went to tractor supply and bought a v belt idler pulley I assume intended for power equipment. It has a 3/8" bore on the hub and has a sealed bearing. I cut a plate out of 1/4" plate that mounts to the 2 water pump blots and to the hole in the lower alt bracket and made a slotted hole for the idler pulley so it's adjustable. I set it about 1/8-3/16" below the belt so that it is only used at high rpm/load where the belt flexes and does not cause drag and wear on the idler at normal cruise rpm's. The pulley was $9 and I spent about $7 on stainless bolts etc and the plate was free. Works perfect!
Sorry for writing a book.
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Big Dave
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PostPosted: Sun May 21, 2006 11:56 am    Post subject: Reply with quote

The other solution is to go with a serpentine accesory set up off a '87 up SBC. You can buy the whole set up new from GMPP for about $800 (with accesories) or get a used set up off of e-Bay (usually about $150).

Big Dave
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Aerosmith
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PostPosted: Sun May 21, 2006 12:32 pm    Post subject: Reply with quote

That's what some people do. Just remember if you go that route you have to get every piece and check for any differences between models. For instance serp waterpumps usually run backwards and f-bodies will have things mounted lower than trucks and possibly higher than corvettes. Another thing is a/c. If you don't have a/c you need a set off a non a/c car and vice versa. The best way to go the retro serp route without breaking the bank with an aftermarket set is to find a complete setup in a salvage yard and buy it all. But like Dave said..expect to have atleast a couple hundred in it.
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mrchevelle
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PostPosted: Sun May 21, 2006 7:03 pm    Post subject: Reply with quote

thanks for all the suggestion's/idea's everyone, really appreciate it/ I'll pass this one to him.and he can make the big descision
thanks

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