hi, i swapped out a 302 for a 351w in my f100 1979,and the gauge shows she's overheating but not boiling over, maybe not the right gauge or are they all the same?thanks

 

Whenever there is question about the gauge, I like to install a mechanical gauge. A $15 Sunpro from Autozone would do it. Put it in place of the factory sender.

As far as sending units go, I believe all dent era sending units are calibrated the same. If you have a later engine it could be different.

The mechanical gauge give confidence that your setup is OK or help in further trouble shooting.

 

i do have a mechanical gauge in it, but i have a 197 thermostat, would it help if i put a 190 in her?

 

Yes it would help.

 

It would help if you could describe the overheating a little. How hot? How fast does it overheat? Is it worse at a stop? How about running steady down the highway?

That would give some clues where to look for the problem.

FWIW I think up to 210 is fine, 220 getting warm and 230 hot. It usually won't boil with antifreeze and pressure cap until it gets to 250+.

 

Between 180-210 seems to be average operating temps. Like already suggested, more information on your symptoms would help with diagnosis. A 7 degree difference in your thermostat really isn't going to make any difference except in maybe a race application.

 

Agreed. Keep the hot stat in it. Especially with winter coming up. You'll be thankful to have it.


$15-20 buys a laser IR thermometer. Invaluable for looking at actual temperatures.

Get one and see what's actually happening.

 

thanks everyone, well,she is normal at the start up but rises slowly, then i go for a spin she rises again slowly ,the needle way passes the danger mark, but did not overflow, and i do have a laser thermometer,i will try that, thanks

 

How's the condition of your water pump? Worn impellers might not be pushing enough coolant. Do you have a fan shroud on your radiator? No shroud (or even a damaged one) will cause over heating, because then, rather than pulling air through the radiator, its pulling air in from around the radiator.

Also, I don't know if this is a concern or not but, are you still using the 302 radiator? It might be a little under sized? I don't know if they are different, just a thought.

 

So after engine swap, she is hot. Does that mean over 230F?

Measuring coolant temp directly with an aftermarket mechanical gauge is best and that sounds like the setup you have.

Often after the cooling system is opened up air gets in and needs to burp out. You have probably already re-checked coolant level after cooling down but worth mentioning just in case.

Does it heat up in stop an go traffic? Or running steady down the highway or both.

If it heats up running steady at speed, that usually means the radiator is plugged up or too small. Or the water pump is fubar as mentioned above. A plugged radiator is much more common.

Heating up in stop and go often means the fan or shroud is not adequate. Can you post pics of the fan/shroud setup?

 

i have a new rad in it, they told me thats the right rad, it is a 351w small block, its a ford gauge, where it came from i don't know i got it of eBay.

 

also i have a new distributer with dual vacuum lines, known me i might have the vacuum lines wrongly will take pics next week,'ll get back to you guys thanks

 

If the timing is retarded, it will slowly get hot....
Check that out. Should be running somewhere between 8-12 degrees BTC.

 

"its a ford gauge, where it came from i don't know i got it of eBay."

Is the gauge mechanical or electric? If electric, the sending unit you have may not be compatible.

 

Also make sure radiator hoses aren't collapsing. And radiator cap should be checked also.