Hey Guys, I'm in need of some help. My grandfather (lawman) and I built a 38 Chevy bobber truck. The engine is a 350 Chevy bored to a 355ci. Single 4 barrel Holley. The engine only has about 300 miles on it and everything around it is brand new. I am running a 67 mustang v8 radiator with a flex fan. I have had the truck for some years now we never had any issues with it running hot. Even at a car show, stop and go traffic it never got higher than 190. Probably just a quince dense but I used to have an edelbrock carb and it started to give me issues and then all this started. I changed the manifold and carb to a Holley. As I start driving the temperature starts to climb I watch it hit 160 and the tstat opens I see the gauge hang there for a min. The temperature continues to slowly climb as long as I stay rolling at 35-55 it gets to about 195-200 as soon as I stop or pull back in the drive way it boils over and by the time I open the garage keeping it running its at 230. This happens after about 15 min of driving and if I get on the express way running 3,000 rpm temperature hangs at about 210. I have tried everything I know of. I do not have a grille. I tried adding an electric fan on the front pushing and a flex fan pulling because iv never ran a fan shroud, didn't make a difference. I changed the thermostat to a brand new 160 degree didn't make a difference. Checked and adjusted the timing, no change. Took the water pump off and back plate off to inspect the impeller everything is still brand new. Flushed the radiator thinking its clogged, no difference flushed the engine in case of a clog with the tstat out and water would flow through one hose and out the other as fast as the garden hose could fill the engine and the radiator. Flushed both out twice and left the thermostat out. Removed flex fan and only ran electric fan, no difference. Still no change temperature climbs after 10 min of driving as as soon as I stop its over 212. I have no fenders or fan shroud and just need some input before making a fan shroud which I really don't won't to do because of looks but any input would be greatly appreciated and thanks in advance.
If I'm reading your information correctly. Everything was fine until you changed the intake manifold? Maybe that in the cause.
So, if you ran the truck for several years and never had a heating problem, but now you do, something has changed, right? If it was airflow, it would've heated up before, right? So I don't think it's an airflow issue. The change seems to coincide with a change in intake manifold & carb, though I'm not sure from your post if you changed the intake first and then it started to over heat; or if it started the over heat problem before you changed the intake. Maybe you can clarify that, but if the heating condition started after the intake swap, then perhaps there is a restriction in the coolant passages of the intake manifold that are slowing the circulation of the coolant through the engine. Another thing that can occur is a blown head gasket that allows exhaust gases to enter the coolant, causing the coolant to over heat. There are kits you can get to test a sample of the coolant to see if exhaust gases are present. http://www.amazon.com/gp/product/B000NPDL76/ref=s9_dcacsd_bhz_bw_c_x_1
Swapped out the carb and intake? Maybe some crap fell into a water passage and is clogging the system?
I had the same thing happen to me on 3 different motors in the T. Switched everything still heating. Ran duel gauges to see each bank. Passenger side always got hot and then all got hot. I was told knock on the thermostat till it stayed open about 1/4" and try it. Amazing it worked and stays about 165-180 all times. Never thought of it and it cost me 2 motors. Apparently there was trapped air. Sent from my SM-T310 using H.A.M.B. mobile app
I had a similar issue and my timing was waaaaay the fuck off. I'd start there seeing as you'd have pulled the dist to swap the intake
problem because you put a Holley on a Chevy (just kidding) - so, how does motor run - smooth at idle & acceleration? trapped air can be eliminated by running a heater hose from outlet on intake manifold to inlet on water pump - thermostats comes in different styles - get a robertshaw fast flow, do not run without thermostat - what mix of coolant? - for the overall protection of motor running a fixed fan with shroud will help air flow because of extra air flow turbulence from having no fenders/hood - as least a electric fan with shroud behind radiator - take electric fan off front because of blocking air flow
In the first place, the thermostat ONLY delays circulation until coolant temp reaches a certain temp. A hotter or colder one should not change final temp. You said temp is fine going down the road. I think unlikely an engine problem. 1946caddy made a good suggestion. What pressure cap are you running? I bet a dollar to a donut the radiator is partially plugged. Flushing will not help. Have it rodded out. Also a possibility the radiator is a tad small. I am not familiar with a '67 mustang v8, but the radiator was sized for it. Your 350 may be putting out more HP, therefore more heat. You said the truck has been driven for several years without overheating? Same engine? Only 300 miles on engine?
Odd that the problem started with an intake and carburetor replacement. First off flex fans are worthless. Replace it with a steel fan. Pusher fans restrict airflow. Other then that your problem to me appears to be radiator related. Gary
Had a customer put so much silicon gasket sealer on his intake gaskets, he blocked the front water passage of the intake manifold. I would rather run a solid fan rather than a flex fan, look out for the vee belt bottoming in the various fan/alternator/crank pulleys, definitely plan on replacing the radiator with a NEW thick core from one of the vendors, obviously change the thermostat to a known good one. A little under an inch for fan to radiator clearance, and the man is right about feeling to see "cold spots" to prove to your self your radiator is toast. I have also seen water pumps blocked from too much silicon gasket maker..
Looks like the alternator is swung out to the very end of its adjustment range. Are you sure the belt is properly tensioned and not slipping? As mentioned, make sure belt is not bottomed out in the pulley grooves, and maybe try one an inch or two shorter.
OK you had a problem with the edelbrock and pulled it and the intake and swapped to a Holley.... Is there a fuel filter anywhere in the fuel system? Trash in the fuel system can plug up a main jet partially and cause a lean condition. Which would then possibly do the same with a Holley once it got plugged. Also you say you checked the timing but did you check that the advance moves freely. I had a distributor that was fine when checking timing at idle but once the advance kicked in it would not return and stayed advanced all the time until the distributor stopped spinning. Then it would pop back. Sounds either fuel or timing related to me.
Maybe it was in the engine from the beginning! After checking radiator and coolant for contaminants, you will know. That size radiator will work for a 350. I cool a BBC with one. A quick test w/heat gun across the top of radiator tubes while running will spot cooler tubes that are not flowing warmer water. I recently had the center tubes quit flowing and temp just kept going up. Best solution was a new auction site aluminum rad for a Mustang.
Thanks for the reply's just to answer a couple questions it started overheating before the carb started to give me problems the timing and the advance has all be checked and set correct. The belt is set properly the tension is good. The lower rad hose does have a spring in it. I on,y used a small head of silicone on the front and back of the intake. I will have to check and make sure there is not an air pocket. I was leaning towards a clogged radiator I have it drained currently i will go ahead and swap it out since it has a lifetime warranty from advanced auto (which is a hassle) if not i will test it with a heat gun. I will take the electric fan off the front. Thanks again this is great info.
check your plug wires too , the 5-7 firing order can cause problems and its often missed . , and a drilled thermostat is a must if you do not run a heater .
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