big block cooling

1966 corvette with modified big block cooling the car will not cool even on open road has 180 degree thermostat kb high dome pistons, comp cam 268 hollley 870 cfl msd ingnition  

what temp is it running at...     what percentage of coolant do you have in it... or measured amount with a 5 buck tester from prestone or other brand...

have you tried a 192/195 thermostat...    

have you verified that the radiator cap is holding pressure?????  

are you running full sized pulleys or under drive pulleys...

is the block filled ????   some people use a type of block filling concrete to reinforce the blocks..  leaving only an inch or two  of coolant at the top...  if not filled...  how clean are the block cooling passages around the cylinder walls...  

when  the motor was assembled????    was additional sealer used to seal the head gaskets... something like hylomar...  it really seals the head gaskets well...  prevents tiny leaks...


got an extra threaded hole in the intake manifold coolant crossover.. something you can put a pressure gauge in... just for testing.. make sure that there is pressure behind the thermostat...


do you have a bypass circuit..????    

you do understand.. that the water pump circulates water into both sides of the block.. up the back of the block and into the heads.. forward through the heads and  and into the coolant crossover in the intake..    if there is no bypass circuit that allows circulation through the block, heads, and passing the thermostat until the heat builds up enough to open it..

this bypass circuit maintains as close to a even coolant temp as possible...    inside the block



now.. what kind of cooling fan do you have????/  rigid..  flex.. clutch?????  there are different CFM ratings...

do you have a fan shroud...   is there room for one??????

when you rev the motor .. will the airflow through the radiator hold a shop rag to the front of the radiator??????
is the fan the right fan.. not for a reverse rotation water pump ???   blowing forward???  


what about ram air through the radiator????    any way to block off any exits... that let air flow out and around the radiator.. instead of through the core????

got an oxygen sensor port in the headers??? something you can screw an oxygen sensor into and hook up air fuel ratio meter.. or a wide band version along with the wide band display??   lean fuel mixtures will cause it to overheat..

what sort of fuel system...     mechanical fuel pump?????    can you do a cranking fuel volume test??? into a plastic container...   have somebody crank the engine while you watch the fuel pump pulses into the container...   they should all be even full pulses...   not reducing in volume as you crank it..  a pint in 10 seconds...    i have found cars with crushed fuel lines..  clogged fuel lines.. that pressure tested the fuel pump just fine.. but failed the free flow volume test...
after the third pump ... the pulse was getting smaller.. by the sixth.. it was almost none..   the line was so restricted.. i could pull a vacuum with a brake bleeder hand pump...  it would take 15 seconds to drop to 0...  

i used a universal speedo cable to open it with  3 friends and a variable speed power drill to clean out the fuel line until a replacement could be ordered..  

so many things it could be...

there is a spring in the lower hose right.. so it does not flatten out at rpms from the suction of the pump???? the upper hose many need one also...

describe your problem better.. so we don't have to guess... it takes a lot of time typing out educated guesses...without a lot of description...

wayne..