Engine Guru's

[g-71]

Quick question about engine temp. I have a 97 351, my engine temp has never exceded 175 degrees even in 100+ weather. I was on another site where they saying if your engine temp isn't running 190-210 then you are leaving some performance on the table. My question is should I change to a 190 thermostat ? After reading horror stories about cooling these 351's, I just assumed cooler was better ?
Thanks in advance, Mike

 

[B RON CO]

Hi, verify that your gauge is accurate before digging in. I use a laser temp thermometer on the thermostat housing and upper hose to check the temperature. The engine will be hotter after a drive then just sitting in the driveway. Good luck

 

[spap]

You would never notice a performance change from 175 to 190 degrees.
I rather stay on the side of keeping it a little cooler. If it isn't broke don't fix it. Just from experience
However thermostats are cheap. And it would be easy to do

 

[g-71]

Thanks for the reply. I haven't used a laser thermometer, but the dash gauge and the fi tech handheld both are fairly close to each other, usually runs right around 165 degrees.

 

[sykanr0ng]

Warmer would make the oil flow and lubricate better.
180° to 210°
Cool yes, cold no.

 

[DirtDonk]

And combustion can be cleaner at the higher temps as well. Especially good for EFI setups, but mostly for emissions I would think.
But the oil definitely appreciates it when the EFI is not putting in too much fuel because it thinks the engine is still cold.
I think by 175 the computer should be telling the TBI to go into normal mode, vs cold-start mode, but you can check with FiTech on that little point.

Paul

 

[g-71]

Thank you all for the replies. Paul you bring up a real good point, one of the settings points for the fi tech is 170, this truck seldom if ever reaches that temp. Am I not fully utilizing my Efi ?

 

[DirtDonk]

I would say that is quite correct. If it always thinks it's right below the transition from cold to normal operating temps, it's not necessarily going to self-tune properly for normal running.
And might even keep the enrichment map in play and you'd run unnecessarily rich.

That's my take on it anyway.

Paul

 

[g-71]

I replaced the 180 thermostat with a new 195, bronco still runs about 160. If I let it sit and idle temp gets about 186, bit as soon as I start driving drops back down. Did I buy a defective thermostat, or is this normal ? Any suggestions for getting the temp up ?
Thanks, Mike

 

[sanndmann3]

I think that temp is to cool... take a look at this link.
http://www.carnut.com/ramblin/cool3.html

running too cool might increase cylinder wear.

It does seem odd that it runs that cool. I would double check gauge and temp sender unit to make sure its accurate. what fan, water pump and radiator are you running?

 

[g-71]

Thanks for the reply. It's pretty much the 71 stock cooling system. I did put on a high flow water pump, and a 6 blade fan when I did the 351 swap. I removed the 6 blade fan and put the original factory 5 blade hoping it pull less air, but it didn't help. I haven't check it with a thermal laser yet but the fi tech handheld, and the dash gauge are fairly close to each other.

 

[broncnaz]

Many times thermostats wont close all the way might be more of a issue with highflow pumps and high flow tstats but Ive had the issue with standard pumps and both standard and hiflow tstats the temp would rarely get close to the thermostat rated opening point. When I tested the tstat I found it was opening at low temps so it never really closed or fully opened due to that. Swapped out for new one and the temp went up to its rated temp and work like it should. Many times new tstats will not work correctly.
Overall its probably not a big deal as at least its not overheating but in the winter you may find it running even cooler and pretty poor heater performance.

 

[DirtDonk]

Have you tried a quick test by blocking most of the air flow over the radiator with some cardboard or similar stuff? I would think that if it's overcooling due to an overly efficient radiator and fan setup, your temps would rise to normal at that point. Or maybe even a bit more if all things are otherwise normal.

But yeah, overall you did the right thing with the higher rated t-stat for the EFI setup. But yes too, to the fact that today even brand new made in the USA stuff can't be trusted.

I've heard of the high-flow pumps causing trouble for normal t-stats too, but never had that issue with mine. Everything worked as expected with my FlowKooler pumps using both regular and balanced-flow Robertshaw thermostats.

Good luck. Hate to think you have to take out the t-stat again just to check. But if you find that it's defective it could make life much easier down the road.

Paul