Overheating G10 HELP!

HELP, new to this but dont know where to turn! Have a 1966 g10 I converted to 4 wheel drive an put a 350 gm v8 in it. The engine is a brand new long block from jegs everything on the motor is new intake, water pump, 160 thermostat, radiator hoses, monster 4 core aluminium radiator with a 6 bladed fan an a electric fan on the other side of the radiator. I have no air pockets in it filled it by doing a vacuum on it also shows I have no leaks. not a blown head-gasket thought the first motor had that problem since it was slightly used so bought a new still running hot. I have ran the van with no exhaust to make sure there was no blockage. I have a smaller style pulley so it spins the water pump faster have been through 3 water pumps since I thought it was those I know the water is circulating. The timing is correct on the motor. I have even went as far as extending the motor box so it scoops air in from the front grille. PLEASE HELP don't know what else it could be anyone else do v8 conversions

I'm not a V8 expert, but, its my opinion that an electric fan in front of the radiator actually blocks air flow, many others have said the same.  A 160 stat sounds good, but it may be opening and closing too fast, the coolant needs time in the radiator to cool down, try a 180 or higher, its opposite of what you might think.  Same for the faster pump, the coolant needs time in the radiator to cool, not buzz through.... New motors need break in time? and may run hotter? experts? Also, most V8 installs in a 1st gen need a ram air tunnel like the 2ns gens have, everyone I've seen here has done that mod for a V8.

lets see some pictures of your cooling set up

M1D

Welcome to VV. I'm assuming it's overheating because it's blowing past the radiator cap. Check to make sure you have correct pressure rating for the cap. If the pressure rating is too low it'll cause the cap to open too soon and relieve pressure in the system. Do you have the fan shroud installed? If not install one. I would also move the electric fan away from the front of the radiator. You can leave it in front, just not bolted flush with the radiator (if it is). The thermostat at 160F seems low for a V8, but all that does is ensure your engine reaches temp before opening (it should only open once).

Welcome to VV. Both M1D and I have successfully done v8 conversions.

Please post pics of your cooling system so we can see what you are missing.

Understand -this - the thermostat is too cold! allows flow of coolant too quickly & is always open - that alone will add to overheating! Now - next is this- get rid of that small Pulley!! allows same -too fast of the coolant flow!! now - have a fan - NEAR>> the radiator? Like within 1 "?? Shroud?? likely NOT! that is a must today on these radiators-shrouds! Clutch fan?? Remember gm designed these to cool in the hottest conditions! When =NEW! I have aftermarket radiators on all my early vans & cars. yet -always use a shroud too. Learned that lesson many times! The radiator companys do make them yet -i usually build my own. Now all that being said - the aftermarket fans - usually dont push/pulll enough air!! Look in the archives here & get a lincoln or tarus fan - a/c type from a late model car!! cheap & do they ever move air!! These are 3 wire fans & have a low & high speed in them -need the relay on those too!! Now also take some pix of your install & post here - front back (fan side) and top & bottom too. that will aid everyone ! What size radiator do you have 2 / 3 / 4 core & crossflow or downflow type?? consider also putting a electric fan/ blower in the rear of the doghouse area too. pulls heat out!!

on your electric  fan, is the one on the front of the radiator pushing air to the
rear of the vehicle?
I have discovered that when water moves to fast through the radiator it will not
take the heat out of the water/coolant and will also cause an overheating problem,
if you think this is a problem with your set up just pinch off upper hose about 1/2 way
closed and see if you overheating problem improves

Runs hot on the road @ 60 mph? gets hot idling? Just plain gets hot n matter what ? and what are you calling hot?

Question: If the water pump spins too fast could that cause cavitation, making a pressure drop in the pump and the fluid in there boils which inhibits proper flow through the motor?

Helsing is right, once the thermostat is open, it's open, end of story.

I'm with Digz here, when are we overheating? Improper timing could be a major culprit too!

Kakster, in theory yes, however that pump would have to be spinning very fast to be able to do that. I could start doing experiments to figure out when, however that's outside of the scope.

we used to have a member in our local van club who had a 68/108 4x4,
he installed a flow cooler water pump on his 350 and it ran hotter, installed
the original one and problem went byby. my first early could do 45 mph all day
long in 95 plus degree days and stay cool but when you pushed it up to 65 it would
run hotter, the only thing that changed was it was moving water through the radiator
a little faster than it was a 45, installing an overdrive trans will do the same thing as
traveling slower down the highway, just harder to accomplish