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Fan belt won't stay on at high rpm #1224667 04/30/12 07:36 AM 04/30/12 07:36 AM
Joined: Mar 2010 Posts: 984 Tennessee H Hemi ragtop OP super stock
Hemi ragtop OP super stock H Joined: Mar 2010 Posts: 984 Tennessee	I am finally driving, and enjoying my HEMI convertable. With approximately 200 miles on the car, I began to add power a little at a time to see how the car would react to 635 HP on street tires. Holding it in low gear with modest wheel spin until approx 4K and shifting to 2d etc. The problem is, it throws the fan belt. The pullys and brackets are all repro HEMI and everything lines up perfectly. The belt is a repro without the i.d. notches ie: modern fan belts. Does anyone have a suggestion? 7185551-100_0329-Copy(2).jpg (124 downloads)

Re: Fan belt won't stay on at high rpm [Re: Hemi ragtop] #1224668 04/30/12 07:41 AM 04/30/12 07:41 AM
Joined: May 2009 Posts: 409 Lexington NC twinscrew698 mopar
twinscrew698 mopar Joined: May 2009 Posts: 409 Lexington NC	I don`t have a Hemi,but i had the same problem with my 400! What i did was take a straight edge to the crank pulley and the pulleys to make sure they was lined up even tho they looked like it the power steering pump was off just a little so i shimmed up the pump with washers behind the brackets and it cured my problem! Just an idea that might help ya!

Re: Fan belt won't stay on at high rpm [Re: Hemi ragtop] #1224669 04/30/12 08:16 AM 04/30/12 08:16 AM
Joined: Jun 2003 Posts: 21,487 It's a dry heat gtx6970 Too Many Posts
gtx6970 Too Many Posts Joined: Jun 2003 Posts: 21,487 It's a dry heat	Quote: The belt is a repro without the i.d. notches ie: modern fan belts. Does anyone have a suggestion? Put a quality belt on it will probably cure the problem

Re: Fan belt won't stay on at high rpm [Re: twinscrew698] #1224670 04/30/12 09:37 AM 04/30/12 09:37 AM
Joined: Sep 2004 Posts: 22,873 Chicken coop dustergirl340 Chicken Little
dustergirl340 Chicken Little Joined: Sep 2004 Posts: 22,873 Chicken coop	Quote: I don`t have a Hemi,but i had the same problem with my 400! What i did was take a straight edge to the crank pulley and the pulleys to make sure they was lined up even tho they looked like it the power steering pump was off just a little so i shimmed up the pump with washers behind the brackets and it cured my problem! Just an idea that might help ya! I had the same thing, Duster kept tossing the belt right at the finish line at the track. Turned out things were just a little off.

Re: Fan belt won't stay on at high rpm [Re: Hemi ragtop] #1224671 04/30/12 11:02 AM 04/30/12 11:02 AM
Joined: Oct 2003 Posts: 4,013 South Park, Pa. 68LAR master
68LAR master Joined: Oct 2003 Posts: 4,013 South Park, Pa.	Quote: The pullys and brackets are all repro HEMI and everything lines up perfectly. The belt is a repro without the i.d. notches ie: modern fan belts. Does anyone have a suggestion? I agree with the suggestion to check everything with a straight edge again. A little miss alignment and it will toss. Also, a trick from back in the day.... loosen the belt tension up a bit. If it's too tight, it will stretch on the low tension side of a pulley and come off. 4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight

Re: Fan belt won't stay on at high rpm [Re: 68LAR] #1224672 04/30/12 11:14 AM 04/30/12 11:14 AM
Joined: Apr 2012 Posts: 18,880 - R RSNOMO Moparts Torchbearer
RSNOMO Moparts Torchbearer R Joined: Apr 2012 Posts: 18,880 -	I took the 'old school' approach... Ran a piece of string;gave me more reference points to take a measurement... Ended-up having to shim the alternator pulley... I like about a quarter-inch play in the belt tension... A new belt is gonna 'stretch'... Might have to re-check the tension...

Re: Fan belt won't stay on at high rpm [Re: Hemi ragtop] #1224673 04/30/12 12:06 PM 04/30/12 12:06 PM
Joined: Mar 2008 Posts: 5,746 Ontario, Canada Dodgem master
Dodgem master Joined: Mar 2008 Posts: 5,746 Ontario, Canada	Well once it throws a belt it must be thrown away they take a little twist and keep throwing. Check alignment Then Tighten belt warm right up no high revs then re tighten belt they stretch first time warmed up. then make sure not does not loosen again.

Re: Fan belt won't stay on at high rpm [Re: Dodgem] #1224674 04/30/12 06:05 PM 04/30/12 06:05 PM
Joined: Mar 2010 Posts: 984 Tennessee H Hemi ragtop OP super stock
Hemi ragtop OP super stock H Joined: Mar 2010 Posts: 984 Tennessee	Thanks for all the help from everyoe. The concensus seems to be, #1 re check alignment, then belt tension AFTER warm up drive and start with a new belt. I will try the above, so far, that is the only "issue". I don't feel to bad having had the car COMPLETELY apart and back together LOL.

Re: Fan belt won't stay on at high rpm [Re: Dodgem] #1224675 04/30/12 07:56 PM 04/30/12 07:56 PM
Joined: Jan 2003 Posts: 27,421 Balt. Md 3 383man Too Many Posts
383man Too Many Posts 3 Joined: Jan 2003 Posts: 27,421 Balt. Md	Quote: Well once it throws a belt it must be thrown away they take a little twist and keep throwing. Check alignment Then Tighten belt warm right up no high revs then re tighten belt they stretch first time warmed up. then make sure not does not loosen again. That is correct as I found out years ago once a belt is thrown it will keep coming off even if you fix a problem. I would definetly try a new good brand belt. Ron

Re: Fan belt won't stay on at high rpm [Re: Hemi ragtop] #1224676 04/30/12 09:51 PM 04/30/12 09:51 PM
Joined: Feb 2010 Posts: 404 IL us I ink mopar
ink mopar I Joined: Feb 2010 Posts: 404 IL us	I also had same problem with may 440-6 pack and it also was the pulleys not perfectly true only after 100-110 mph it would smoke the belt.

Re: Fan belt won't stay on at high rpm [Re: 383man] #1224677 04/30/12 11:30 PM 04/30/12 11:30 PM
Joined: Aug 2003 Posts: 43,286 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,286 Bend,OR USA	Quote: Quote: Well once it throws a belt it must be thrown away they take a little twist and keep throwing. Check alignment Then Tighten belt warm right up no high revs then re tighten belt they stretch first time warmed up. then make sure not does not loosen again. That is correct as I found out years ago once a belt is thrown it will keep coming off even if you fix a problem. I would definetly try a new good brand belt. Ron Once it comes off it will continue to come off at that RPM, even if you fix the original problem that caused it Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: Fan belt won't stay on at high rpm [Re: Hemi ragtop] #1224678 04/30/12 11:33 PM 04/30/12 11:33 PM
Joined: Jan 2003 Posts: 12,861 Gloucester,VA STOP MOVING HERE RangerDan440 I Live Here
RangerDan440 I Live Here Joined: Jan 2003 Posts: 12,861 Gloucester,VA STOP MOVING HERE	actually I think I can see the problem-youre using a dual groove pulley alternator designed for an AC car when you should be using a single groove-the dual groove pulleys are aligned differently. 68 Valiant 408 69 Charger 318 69 Cougar 351W 70 Torino GT 351C 71 Country Squire 351W 71 Road Runner 440+6 71 Satellite sedan 318 73 Duster 318 73 Challenger 383 77 Grand Prix 455 83 Malibu 9C1 383 84 Delta 88 403 87 Grand National 96 Ram 360 09 Crown Vic 10 Challenger R/T M6 15 Challenger Hellcat M6

Re: Fan belt won't stay on at high rpm [Re: RangerDan440] #1224679 05/01/12 12:59 PM 05/01/12 12:59 PM
Joined: Nov 2003 Posts: 1,029 Southeast Virginia 68jim super stock
68jim super stock Joined: Nov 2003 Posts: 1,029 Southeast Virginia	Factory Hemi will use a dual pulley on the alternator. I'm not sure though if the one he is using (A/C??) will have the same offset to match up with the repro pulleys. Jim 7187616-DCP02701.JPG (92 downloads)

Re: Fan belt won't stay on at high rpm [Re: gtx6970] #1224680 05/01/12 01:22 PM 05/01/12 01:22 PM
Joined: May 2005 Posts: 6,446 NJ-USA H HPMike master
HPMike master H Joined: May 2005 Posts: 6,446 NJ-USA	Quote: Quote: The belt is a repro without the i.d. notches ie: modern fan belts. Does anyone have a suggestion? Put a quality belt on it will probably cure the problem The repop belt is the problem...Junk... MB

Re: Fan belt won't stay on at high rpm [Re: Hemi ragtop] #1224681 05/01/12 02:29 PM 05/01/12 02:29 PM
Joined: Mar 2003 Posts: 4,848 Memphis HemiRick master
HemiRick master Joined: Mar 2003 Posts: 4,848 Memphis	Where are the cords in the belt? Cheap belts have them in the middle, good belts have them towards the top or fat side of the belt. Finding good belts these days is a chore, 40 yrs ago all belts where made with the cords on the fat side. Last edited by HemiRick; 05/01/12 02:31 PM. Take care, Rick 68 Coronet R/T 440 & 68 Charger 528 Hemi,and 5 Challengers! 6 cyl, 318, 360, 383, 451

Re: Fan belt won't stay on at high rpm [Re: Hemi ragtop] #1224682 05/01/12 07:51 PM 05/01/12 07:51 PM
Joined: Apr 2010 Posts: 4,154 bethlehem pa M mikemee1331 master
mikemee1331 master M Joined: Apr 2010 Posts: 4,154 bethlehem pa	could also be the pulley itself is a little untrue.

Re: Fan belt won't stay on at high rpm [Re: Hemi ragtop] #1224683 05/01/12 08:10 PM 05/01/12 08:10 PM
Joined: May 2008 Posts: 5,399 Aurora, Colorado 451Mopar master
451Mopar master Joined: May 2008 Posts: 5,399 Aurora, Colorado	My 505 I just built, I am working on pulley alignment. I used an aftermarket aluminum water pump and housing, and crank dampner (also crank) and the crank pulley is slightly closer to the block than the fan pulley. I just got the power steering pump so I could see if the problem is the pump or housing. I had used the dampner before on a different engine so it should be OK, unless the crank has the timing chain sprocket closer to the block than the stock crank (or the sprocket is thinner?)

Re: Fan belt won't stay on at high rpm [Re: HPMike] #1224684 05/02/12 01:31 AM 05/02/12 01:31 AM
Joined: Sep 2004 Posts: 408 Manhattan, IL SixPackRT mopar
SixPackRT mopar Joined: Sep 2004 Posts: 408 Manhattan, IL	Quote: Quote: Quote: The belt is a repro without the i.d. notches ie: modern fan belts. Does anyone have a suggestion? Put a quality belt on it will probably cure the problem The repop belt is the problem...Junk... MB https://board.moparts.org/ubbthreads/show...&PHPSESSID= Maybe read here to. Seems to be a common issue with repo belts. Scott 70 Coronet RT 440+6 64 Dodge 330 - Future Hemi Clone 17 Challenger Hellcat - Green Go Driver 86 Buick T-Type Turbo V-6

Re: Fan belt won't stay on at high rpm [Re: 451Mopar] #1224685 05/02/12 07:18 AM 05/02/12 07:18 AM
Joined: Mar 2010 Posts: 984 Tennessee H Hemi ragtop OP super stock
Hemi ragtop OP super stock H Joined: Mar 2010 Posts: 984 Tennessee	The Dampner, pullys and brackets are all Hemi. I have looked at the line up and it seems perfect. I DID us the "Q" belt as it was not cogged. based on the post, that was a mistake. I am going to change the belt and see if that helps. The car is NOT a trailer queen, in fact, I don't even own a trailer! If the car goes anywhere, it gets driven!

Re: Fan belt won't stay on at high rpm [Re: HemiRick] #1224686 05/02/12 07:22 AM 05/02/12 07:22 AM
Joined: Mar 2010 Posts: 984 Tennessee H Hemi ragtop OP super stock
Hemi ragtop OP super stock H Joined: Mar 2010 Posts: 984 Tennessee	Quote: Where are the cords in the belt? Cheap belts have them in the middle, good belts have them towards the top or fat side of the belt. Finding good belts these days is a chore, 40 yrs ago all belts where made with the cords on the fat side. The belt is a Quanta. It is beginning to look like that is the culprit.

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