SBC 350 with overheating issues

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glades cat
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Re: SBC 350 with overheating issues

Post by glades cat » Thu Nov 05, 2015 4:14 pm

Hey Bruce, glad you got up there alright. How was the trip?
Check the fuel pump and make sure it is supplying sufficiently. The cold and lack of use may have hardened the diaphragm. No float adjustment will compensate for a pump deficiency.
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Hardtail
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Re: SBC 350 with overheating issues

Post by Hardtail » Thu Nov 05, 2015 7:53 pm

glades cat wrote:Hey Bruce, glad you got up there alright. How was the trip?
Check the fuel pump and make sure it is supplying sufficiently. The cold and lack of use may have hardened the diaphragm. No float adjustment will compensate for a pump deficiency.
Hi Rick,
We had a great trip left Miami at noon on Monday and arrived in central Minnesota by 6:30 PM on Tuesday, drove straight through just stopping for fuel and food.
I ordered a new carburetor 750 double pumper Holley, should be here on Friday sometime,
Took my AC boat out today and crossed the swamp just fine, saw 5 deer so far today 1 nice buck 2 does and 2 fawns , so looks good for Saturday, opening day.
Anyway the carburetor on there seems to be flooding with fuel for some reason.

Hardtail
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Re: SBC 350 with overheating issues

Post by Hardtail » Thu Nov 05, 2015 8:02 pm

SthrnStyle3 wrote:May need to clean or rebuild the carb. Especially if you thought you had bad gas, it could be gummed up. Sounds like a fuel issue to me, imo.
Yes
I'll find out tomorrow when I get that new carb on, also I ran at high idle for 15 minutes and got to 140 degrees so I went to town today and got a thermostat 180 degrees, and going to put that in as well, now that I know how to purge the cooling system, never noticed that little valve before, so when I opened it and poured antifreeze in I could hear it gurgle through the motor and then come out that valve, took about a gallon.
Thanks all for the help. I'll let you know how the new carb works out tomorrow.

terrible ted
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Re: SBC 350 with overheating issues

Post by terrible ted » Fri Nov 06, 2015 7:53 pm

where you have the petcock I put a small hose fitting and plumed it to the x tank. Never had to worry about burping the system again.

Hardtail
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Re: SBC 350 with overheating issues

Post by Hardtail » Fri Nov 13, 2015 10:49 pm

I put in fresh high test fuel, purged the coolant, cranked up the engine let it idle until temp gauge got to 120 degrees,(has no thermostat just a washer) run the RPM's up to 4500 RPM's for about 30 seconds then the engine backfired and almost shut down, so next I went and got a new thermostat, drilled 3 1/8" holes in it installed it then purged the system again then run it up again, still the same, it would backfire and try to quit, this time I noticed the temperature gauge would fall dramatically as soon as I got the RPM's up above 3000 RPM's, the outside air temp was around 40 degrees, it would run fine all below 3000 RPM's.
Next I ordered a new carburetor, 750 Holley double pumper, put it on and it fired right up after a few seconds, I ran it up to full throttle and again same it would just shut down to an idle, temp gauge would fall very quickly as soon as I raised the RPM's
SO next I went and got another thermostat, put it in without drilling holes in it, now the engine would rev up to just under 5000 RPM's and didn't try shutting down this time, but the temp gauge still drops 25 to 30 degrees, and stayed running
Any ideas, Question,,, Could the coolant be causing the engine to cool to much, and cause the engine to just shut down?

Davie GSO480
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Re: SBC 350 with overheating issues

Post by Davie GSO480 » Sat Nov 14, 2015 7:31 am

Poping backfire usually indicated a lean condition. Airboat motors need more fuel due to constant load. If its an "out of box" carb., id go up 4 jet sizes and read plugs.
As well, pull and check your spark plugs, run the coldest plug you can run, a hot plug will also cause backfire. Total timing should be like 34 deg. No vacume advance. Should be totaly advanced by 2500 as well.
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