58 GMC 1/2ton truck with GMC302 engine; mild build with 3/4cam, 9:1 compression, Clifford Intake& matching Headers, HEI ignition; stock radiator Thinking a electric puller fan would cool the truck better than stock fan? Thanks 4 input
Frees up some horsepower if you need it. I would use it with a temperature activated switch. Not knowing how you plumbed your engine, but your 302 cylinder head should have two 1/2" pipe plugs on the top near the rear. Many use the rear one for their temp gauge but that's wrong on a 302. There was a 90* fitting and it lead up to the thermostat housing on the left side where there should be another 90* fitting and a line between them. The next one farther forward is used for the temp gauge. The line I mentioned keeps the rear cylinders cooler and helps wth the total engine cooling. Most folks never see a 302 in its natural engine compartment in a large truck. On my avatar you can see a AN -8 line coming off that fitting, It goes to the water tank in the back a long with an AN line from the original thermostat housing. I use an electric pump on this engine. I use a 14" pull thru fan on my 40 Chevrolet. There is also not much room with the longer engine and I've seen electric fans which do not have the motor in the center and you my need that type. Good Luck.
If you have the room, I'd go with a steel six blade engine driven fan. If you decide to go with an electric, the only one to use is a Spal. They don't use them on Ferraris for nothing. Gary
Go to the junk yard and get one from a mid 90's Ford Taurus. They'll suck the chrome off the bumper of the car in front of you! Google it and see.
I'll second Gmans vote for Spal. I run a 14" Spal pusher on my 32 coupe and it is excellent. If you are short on room for a puller type due to the length of the 302 then you could use the pusher . Spal come in 3 versions, low, medium and high output and the length of the unit is governed by the output. Check outtheir website.
That's exactly where I have mine. The next one going towards the front has a inverted square plug in it; that neither a 3/8 or 1/2" ratchet fits. Like this- https://www.amazon.com/Spal-3010204...=UTF8&qid=1492903469&sr=1-6&keywords=spal+fan Shroud needed?
This is the HAMB. Put a heavy duty mechanical fan on it. If that doesn't work, then (and only then) start considering street rod parts.
Fix the plumbing first, right now with your gauge feeding from the last plug is sensing the hottest spot on the cylinder head. Think about it; there's only one hole in the water pump to the block( not like the Chev 6, it has 2) and has to get all the water to the rear of the block, up to the head, and back to the front. You need this stock line water return line on these larger GMC's; I've been running these since 1961 and racing them since 1975. If your cylinder head was ever cut it may not have its brass water flow deflectors which aimed the water from the block to the exhaust valve water jacket area. If these are missing you need to get this hottest water away from the rear of the head. Why do you think there were so many cracked GMC heads. GMC engineers were a hell of a lot smarter than we hot rodders when it comes to building these engines to pull 2-1/2 ton truck, trash trucks, etc. we just put them in lighter vehicles and got away with a lot. Good Luck.
full fan shroud for whatever fan that you decide on - install new mechanical temp gauge - replace thermostat & coolant if has not been done in recent past
If you go with an electric fan surplus center has fans that are supposed to be used on Ferrari cars, dont know if they are Spal. 16 inch puller, 2469 cfm, 12vdc, $150.00
Ok I ended up drilling& tapping that rear hole. going to run a line from it to the side of the thermostat housing. Temp sender in center of head now.Still am going with a puller fan tho
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