ig109

To start off with this isnt your typical truck.. It is in my modded El Camino.. I have a healthy 350 and a t5 5 speed manual transmission swap.. I have an issue to which i cannot see the better solution..

When i built this engine i swapped to an S-10 4.3 front accessory drive.. Serpentine belt, reverse water pump.. the whole deal.. Well i am still running a clutch fan and i run this thing really hard when i drive it and i spin it up to around 6500.. When it gets to around 6500, where i shift, it starts to vibrate just slightly and then the water pump falls off.. It works the bolts out with the vibration and the pump physically comes away from the block.. I have cleaned the threads, and put locktite on the bolts, to no avail.. I thought the fan may have been out of balance.. But no, i am on the third one..

I am debating on the solution..

1. intstall the Mallory HEI rev limiting control module..

2. install an underdrive crank pulley to slow the pump down..

3. Install Efans, which i hate ( i like mechanical things, me and wiring arent friends)

I am trying to keep the project on the cheap but i am not sure what to do.. the march underdrive pulleys should slow down the fan/pump quite a bit.. Any advice?

budhayes3

iTrader: (19)

I'd probably go for the efans, and get some good locking washers for the water pump bolts

TurboGibbs

iTrader: (6)

Going to a flex fan may solve your problems (and free up some hp). That factory fan may be getting getting into a harmonic frequency at those rpms and going nuts.

Also may check the shaft on the pump and make sure it isn't warped. Have you tried another pump?

EVILGMC

iTrader: (47)

locking nuts with studs perhaps...

ig109

I thought about using a flex fan.. But im not sure that ive ever seen a reverse rotation flex fan.. the studs and lock nuts and washers were going to be employeed reguardless what i decide to do.. I think im going to do a combination of all.. I will keep the clutch fan.. order a set of underdrive pulleys to slow it all down (80 bucks) and then replace the bolts and things with studs and locknuts and lock washers.. Shouldnt have that issue anymore..

Wishing i would have stayed with the damn vbelts..

Thanks

hirdlej

iTrader: (31)

Wow the water pump blows the bolts right out of the block huh??

ig109

Yeah, i know what you are thinking.. Im full of **** but i assure you, i have been installing the bolts with blue locktite too.. When you feel the harmonics, then shift then feel the harmonics then shift the bolts are already loose the first time, second time they are nearly out, by the time you get stopped 3 of them are gone and water pump is just sitting there, coolant pissing out.. And i am torqueing the fasteners properly as well as using locking washers.. to no avail.. Im not fighting the bolts coming out. Im fighting the root cause.. An NVH issue..

Like i said.. It acts as though the 4.3 fan assembly isnt balanced to run at that high of an engine speed.. The pulley for the fan is way smaller than the crank pulley too so it turns faster.. So the engine turning 6500 could be like 9000 on the water pump.. Which is cookin.. So the pulleys i ordered are a 25% underdrive making 6500 engine RPM seem more like 4900.. Which in turn slows down everything else.. It comes with an Alternator pulley to keep it charging though..

Should work out.. Waiting for parts to get here tomorrow then we shall see..

00ChevyScott

iTrader: (10)

I've heard of the SBCs having a problem with pulling water pumps out sometimes.

TurboGibbs

iTrader: (6)

Maybe the underdrives will do the trick. If not, the flex fan would be a good shot. I used to have on my carbed 383 in my 95 1500 reverse rotation.

http://www.summitracing.com/search/?...ex%20fan&dds=1

ig109

Turbogibbs: Thanks for the info and the link.. Had no idea they made reverse rotation fans.. Will give that a shot if this doesnt do the trick..

Thanks again