RV8 pre-serp pulley's
Discussion
Has anyone changed the front pulley/belt arrangement on a pre-serp engine to a poly V one ala serp engines without having to change the front cover as well 
. Pictures would be great!
My pre-serp belts really struggle to stay on at max chat, particularly on changing up at peak power, the belt gets thrown off more often than not L. I have even gone to the extreme of using a crow bar on the alternator body to get the last bit of tension on the belt
. I’ve had enough of spending as much time looking at the voltage meter as out of the windscreen when pressing on 
.
What’s needed, is it a matter of just changing over the pulley’s or does there need to be an idler too .
My engine is fully balanced so I am a little worried that the crank pulley change may affect this is some way.
I have what I think are suitable pulley’s that I got from V8D a few years ago but never got around to getting them fitted, however they are not the same diameter as the ones coming off, which again worries me as it will affect the water pump speed as well as the alternator.
Any comments gratefully received, particularly from Rob at V8D
. Even better if someones does it or has had it done costs would be good too
. Pictures would be great! My pre-serp belts really struggle to stay on at max chat, particularly on changing up at peak power, the belt gets thrown off more often than not L. I have even gone to the extreme of using a crow bar on the alternator body to get the last bit of tension on the belt
. I’ve had enough of spending as much time looking at the voltage meter as out of the windscreen when pressing on . What’s needed
, is it a matter of just changing over the pulley’s or does there need to be an idler too . My engine is fully balanced so I am a little worried that the crank pulley change may affect this is some way
. I have what I think are suitable pulley’s that I got from V8D a few years ago but never got around to getting them fitted, however they are not the same diameter as the ones coming off, which again worries me as it will affect the water pump speed as well as the alternator.
Any comments gratefully received, particularly from Rob at V8D
. Even better if someones does it or has had it done costs would be good too HarryW said:Havent got a clue how to answer the crux of your questio Harry,but the serps do have a tensioner pulley,so i would expect the front cover needs changing?
What’s needed
Sorry i cant be any real help,just though i'd give you something to think about.
GreenV8S said:
You probably have the wrong width belt Harry, or the pulleys are misaligned.
Yes thought that myself more than once, but the belt is the right one and the pulley's seem to be aligned, but I will check them again.
Not sure if I'm running at the limit of the pre-serp belt capabilities tbh, last tuned up found a bit more on both maps and puts it around the 280 mark, which whilst not unheard of, it is pretty unusual for a pre-serp.
I hope rob has a look at the thread and comes up with answer, as I'm sure V8D would have come across this before, besides the pulleys I have come from V8D but no idler with them
. Engine power output is irrelevent (and yours is by no means the most powerful V8 still running a pre-serpentine front end ) surely RPM is the only thing that matters. Mine doesn't often go the far side of 6k revs but it has been there a few times over 170 k miles with various engines and never had any problems with the belt - except one occasion where the belt failed and I fitted the spare helpfully provided by the previous owner, which looked spot on but turned out to be subtly wrong and jumped off every few miles, fine when I fitted the correct belt. All I can suggest is you recheck the alignment and also check that the belt is engaging in all the pulleys properly and also not bottoming on any of them.
) surely RPM is the only thing that matters. Mine doesn't often go the far side of 6k revs but it has been there a few times over 170 k miles with various engines and never had any problems with the belt - except one occasion where the belt failed and I fitted the spare helpfully provided by the previous owner, which looked spot on but turned out to be subtly wrong and jumped off every few miles, fine when I fitted the correct belt. All I can suggest is you recheck the alignment and also check that the belt is engaging in all the pulleys properly and also not bottoming on any of them.
v8 racing said:
Hmm i do recall me mentioning to you back at bruntingthorpe a couple of years ago why dont you convert to a poly vee arangement after it throw a belt then!!! there is need to fit the serp pulleys we do the pulleys that replace yours!
Yes its done it two or three times over tha lst few years, always managed to catch it. It been doing it to often now, can;'t be power related as Peter says but it has coincided with the lastest tune up. If i list what I have in the way of pulleys perhaps you could tell me what I missing as I can't work it out, it can't be that difficult
. I did get them off Ray a few years ago, strangely enough straight after Brunters
.v8 racing said:
Sorry harry i thought you were still on the old v belt system? if you are on poly vee now and it still chucking belts there is obviously a big problem!, just check the water pump bearings havent collapsed or the front pulley nut hasnt come lose? power is regardless it is rpm related
no no no I have the poly vee stuff but have never fitted it
, just the stuff I have is 4 pulleys which are differnt to the sizes to the three that will come off and I'm confused , check my first post. A picture/sketch would be great .Harry
I think Rob has hit the nail on the head here - one on the pulleys is probably damaged in some way .. whether it be because of a collapsed bearing or badly mounted on a shaft.
Maybe even a mount has not the proper support that it needs..
I think taking the belt off and checking each pulley for tightness and side to side movement is what is needed.
I think Rob has hit the nail on the head here - one on the pulleys is probably damaged in some way .. whether it be because of a collapsed bearing or badly mounted on a shaft.
Maybe even a mount has not the proper support that it needs..
I think taking the belt off and checking each pulley for tightness and side to side movement is what is needed.
I'll measure them tomorrow and post sizes, perhaps you could tell me what one goes where . I take it the crank pulley one is OK and won't affect the balance. I seem to recall mine was one of those rare beasties, a properly balanced one from day one by Dom at TVR Power, as it was used a Cam developement bench mule engine before finding it's way into my car.
>> Edited by HarryW on Thursday 2nd March 00:40
. I take it the crank pulley one is OK and won't affect the balance. I seem to recall mine was one of those rare beasties, a properly balanced one from day one by Dom at TVR Power, as it was used a Cam developement bench mule engine before finding it's way into my car. >> Edited by HarryW on Thursday 2nd March 00:40
Had another look today, the pulleys I have will not fit 
. The altenator one needs the centre opening out a little and is quite a bit bigger dia than the exisitng one. I have two diameters ones for the water pump, one very similar to the exisitng the other bigger. The bigger one is, I assume, to help prevent the cavitation. However, the three bolt holes have far too small a pcd to fit to the pump pulley seat. Basically I'll give them a miss .
Back to the exisiting arrangement, I've run my eye back over them and it would appear that the water pump pulley is inset by a few mm from the crank one. I have added some washers behind it to bring it out a bit, hopefully this should sort it. The alt can be adjusted to any position and is not a concern.
Question was the few mm's inset on the water pump pulley enough to throw it, I'll give it a try out tomorrow anyway.
. The altenator one needs the centre opening out a little and is quite a bit bigger dia than the exisitng one. I have two diameters ones for the water pump, one very similar to the exisitng the other bigger. The bigger one is, I assume, to help prevent the cavitation. However, the three bolt holes have far too small a pcd to fit to the pump pulley seat. Basically I'll give them a miss . Back to the exisiting arrangement, I've run my eye back over them and it would appear that the water pump pulley is inset by a few mm from the crank one. I have added some washers behind it to bring it out a bit, hopefully this should sort it
. The alt can be adjusted to any position and is not a concern. Question was the few mm's inset on the water pump pulley enough to throw it
, I'll give it a try out tomorrow anyway. 
. Also noted that it flames very nicely at around 4K5 rpm on the overun jhbarford said:
Try Adrian Venn (Exactly TVR Ltd - tel/fax 024 7659 6883 or mobile 0795 695 6042) he has developed a mod to keep the drive belt in place. I am having it fitted to my 4 ltr Chimaera engine.
Any idea what the mod is? I don't see why there'd be any problem unless the wrong belt is fitted or the pulleys are misaligned, so I'm intrigued to know if there is a mod which can fix these faults.
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