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View Full Version : Putting 9 blade composite fan on stock clutch


JFerg65
03-02-2009, 17:37
O.K. On to the next project as the snow begins to melt. I have a 96 late year Burb. It has the HO water pump on it. The fan clutch seems to have the 4 bolt pattern. Can I simply purchase the duramax 9 blade composite and bolt her up to what I currently have or will I need to upgrade the fan clutch as well. Haven't gotten a clear answer from searching prior threads. I hope to someday get the Kennedy clutch but will have to wait as spare coin comes available. I don't plan on doing any heavy towing at this point anyhow.

Any thoughts or suggestions??
More Power
03-02-2009, 23:54
Technically, the correct 6.5 fan-clutch that fits the Duramax fan didn't arrive till the 1997 model year. However, there were some intermixing of cooling system parts in the late 1996 model year. You may have the right fan-clutch.... :)

Jim
JFerg65
03-03-2009, 04:37
Thanks Jim

I may just go ahead and order it, then if I do't have the correct fan clutch... oh well I will just have to get the Kennedy one sooner :)

What do I need to look for to see whether I've got one (clutch) that will work or not?
DennisG01
03-03-2009, 09:17
Maybe a friendly Dealer can give you the specs on the hole pattern of the Dmax fan. Or try calling John Kennedy. By the way, if memory serves, I think John acutally recommends using the steel fan.
DaveBr
03-03-2009, 17:40
J.K. did recomend the steel 9 blade fan when I purchased my upgrades. If I remember correctly you have to trim your shroud with the 21" composite & your OK with the 20" steel. If you call him he will tell you if it will fit a standard clutch fan.
JFerg65
03-03-2009, 17:44
Thanks, I'll give him a call. I know I can get the fan about 10 -15 bucks cheaper elsewhere, but his advice is worth more than the 10 -15 bucks I might save. I guess I would rather support the advertisers here anyhow.
More Power
03-03-2009, 18:01
Most people who installed the 21" composite fan didn't have to trim the shroud. I suppose it all depends on the condition of your motor mounts. If the fan fits in the opening and doesn't hit with th engine off, try a mild power brake to rock the engine. If there's interference, it'll begin buzzing. If you're easy on the pedal, it shouldn't hurt anything, but then you'll know whether you have to trim the shroud.

The engine will torque toward the passenger side during a mild powerbrake.

Jim
JFerg65
03-03-2009, 18:20
Thanks for the advice. Do you happen to know why JK recommends the Steel fan over the composite? I would think the Composite would be somewhat more balanced and less noisy overall. I know it has to be significantly lighter but from what I've read it doesn't make that much of a difference.
Artworks
03-04-2009, 05:59
When I had my accident last year, the body shop replaced my fan with a factory composit / plastic on my stock clutch, larger and more blades, was change up from GM .
Kennedy
03-04-2009, 07:51
Thanks for the advice. Do you happen to know why JK recommends the Steel fan over the composite? I would think the Composite would be somewhat more balanced and less noisy overall. I know it has to be significantly lighter but from what I've read it doesn't make that much of a difference.


Performance curves were pretty close between the steel and composite blades. There was a slight advantage to the composite blade when static psi was low and slight advantage to the steel blade when static psi was high. Basically, the steel blade has the advantage when there is work to be done.

IMHO the blade debate isn't worth getting involved in, as it's the CLUTCH that is the key...

15992650 blade on my clutch is what I recommend.