Underdrive pulleys?

mudslayer · Jun 8, 2018

So for a couple yrs now I've been fighting overheating issues, mild built 350 on propane, griffin aluminum radiator and a Taurus fan. Runs about 190 or so if I'm cruising at normal speeds and flat, as soon as I'm on inclines the temp starts climbing and climbing. On the trails I have to shut down to cool it off to where it's become a major inconvenience. I've tried everything from different fans,water wetter, etc, to still having this pain in my ass. We'll I've never really thought into pulleys much but when I bought this rig it did/does have an aftermarket crank pulley on it which now I think is an underdrive pulley. I went and took measurements and the crank pulley is smaller, has anyone delt with this or know more about it. Why would you want this on a crawler??

hlb3 · Jun 8, 2018

What diameter is it? If it is drastically smaller, it can definitely effect cooling, if it is only slightly smaller (like an 1"), it probably isn't causing many issues.

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mudslayer · Jun 8, 2018

hlb3 said:
What diameter is it? If it is drastically smaller, it can definitely effect cooling, if it is only slightly smaller (like an 1"), it probably isn't causing many issues.

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Looks like there's about 1.25-1.50 difference. I can't figure out what else it could be.

crash2 · Jun 9, 2018

Its very possible. Even 1" can have a drastic chance in circumference. I can see going smaller on something like an alt but for the crank that seems ass backwards for a wheeler,

mudslayer · Jun 9, 2018

crash said:
Its very possible. Even 1" can have a drastic chance in circumference. I can see going smaller on something like an alt but for the crank that seems ass backwards for a wheeler,

My thoughts exactly, already ordered new pulley from summit.

POR · Jun 12, 2018

Is your fans fully shrouded? What size radiator? hows oil pressure? Has it had this priblem since you bought it?

mudslayer · Jun 12, 2018

POR said:
Is your fans fully shrouded? What size radiator? hows oil pressure? Has it had this priblem since you bought it?

It had a small black magic electric fan when I bought it, and it was on gas not propane. Had the griffin aluminum radiator already, which seems to be pretty good sized. I've since switched to propane and have tried a couple other fans, I'm running a Taurus fan now which covers about 80-90% or so. Oil pressure is a little low around 30 psi. Yes, Its always had temp issues. Crank pully is about 1-1/4 smaller than w/p pulley.

zukkev · Jun 12, 2018

What's the measurement of the pulley on it now?

boardbysled · Jun 12, 2018

I'm no expert, but don't you need to adjust the timing on a propane motor to keep it from getting hot?

POR · Jun 12, 2018

mudslayer said:
It had a small black magic electric fan when I bought it, and it was on gas not propane. Had the griffin aluminum radiator already, which seems to be pretty good sized. I've since switched to propane and have tried a couple other fans, I'm running a Taurus fan now which covers about 80-90% or so. Oil pressure is a little low around 30 psi. Yes, Its always had temp issues. Crank pully is about 1-1/4 smaller than w/p pulley.

I'd get the shroud and fans that goes with that Griffin radiator, if the pulley doesn't work. Wouldn't that pulley cause low volts as well or a lagish steer pump? Your thinking it's not turning the pump enough revolutions?

mudslayer · Jun 13, 2018

POR said:
I'd get the shroud and fans that goes with that Griffin radiator, if the pulley doesn't work. Wouldn't that pulley cause low volts as well or a lagish steer pump? Your thinking it's not turning the pump enough revolutions?

I've had a small issue with steering also in 4 low, not to bad, but if I gave it some skinny pedal it would turn. I run 2wd low most the time just to help steer and avoid that. The Taurus fan covers way more than rigs I've had with smaller fans? I'm not running a high pony rig, headers and a small cam- intake. I'm just tired of it. Almost everyone in our group has built 401's and run all day in 80+ with no issues.

POR · Jun 13, 2018

mudslayer said:
I've had a small issue with steering also in 4 low, not to bad, but if I gave it some skinny pedal it would turn. I run 2wd low most the time just to help steer and avoid that. The Taurus fan covers way more than rigs I've had with smaller fans? I'm not running a high pony rig, headers and a small cam- intake. I'm just tired of it. Almost everyone in our group has built 401's and run all day in 80+ with no issues.

If the fan doesn't have a shroud it can't efficiently pull air through the radiator.. maybe your fan is in the high mileage side and isn't pulling the cfm it's supposed to.. that just happened to a buddy of mine's buggy. In my old jeep I had to run a pusher fan with a mechanical fan to push enough air to keep sbc cool. My other thought is.. maybe it's been dunked and has had mud in it and it's not internally cooling well cuz of bad oiling... I've also done that to a sbc. I'd also wrap the headers with heat tape to reduce underhood temps.. if of course new pulley doesn't fix issue. I'm kinda thinking it's not going to..

mudslayer · Jun 13, 2018

The fan has the factory shroud, which covers 80% or more of radiator. It's possible the fan is slow, it does turn kinda rough and is loud, but moves alot of air still. I guess the oil pressure could be part of it, I do tend to bury it in muck most trips. I'm gonna pull the pan and do the pump just because. I've had it apart down to the block and most everything looks good.