temperture reading difference

[gmhardwick66]

I know there are a few threads already on this subject but I could not find the answer there that I need. I am talking about the placement of the water temp sending unit or thermal coupling. The different reading between the driver side head versus the passenger side head. I had mine in drivers side head and moved it to the passenger side head to allow for putting a second sending unit for my dual electric fans. When I placed temp gauge in passenger side head the temp reading was at least 30 degrees hotter compared to the reading when gauge was in drivers side head. Everything was exactly the same except temp reading. I am not positive but I am hoping the difference was due to the fact as the water circulates through engine and heads it heats up so when it gets to the gauge port on drivers side head it has soaked up a bunch of heat causing the difference in temp reading between the to ports. Can someone please tell me if this is correct or do I have another problem all together.

[geezer#99]

It should be the same on either side. You could have a restriction in the side that shows hotter. A thermal temp gun might show where it is.

[RManson]

You mentioned installing the thermo switch for your fans in the head, I wouldn't do that. Does the coolant in the head ever cool down during normal operation? If not, the fans will always run. Might as well wire them to the switch.
On the flip side, if you mount the sender in the radiator near the outlet, the fans will only come on when the coolant inside the radiator reaches a particular temp. Stop and go traffic might trigger the fans to stay on but once you're on the highway and moving at a decent clip, the airflow will be sufficient to keep the radiator cool, thus negating the need for the fans. This is easier on the fans as well as the charging system in general.
Just my 2cents and the way I've got my '68 setup and it works very well.
Your head temp difference is slightly strange though. What motor are we talking about?

[gmhardwick66]

That is the crazy thing. the motor runs great and cools great. I have only one fan sending unit sender and its in the intake manifold right by thermostat. It is working ok. The temp gauge reads correctly along with fan operation with the fan sending unit. I am just curious to why I have such a difference in temp reading from one side to the other. I can see the cool water enters the front of the block and is closer to drivers side port so the reading would in effect be a cooler temp. But as water flow to the rear of block entering head on passenger side would in effect be a little warmer, but how much warmer is considered normal??? The engine is a fresh block with brand new aluminum heads, new intake. I have not checked my plugs as I wonder if running a cooler plug in cylinders on rear of engine.

[gmhardwick66]

Now I am worried. I did some more research and you were right as to flow from rear to front so I am going to get the temp gun to hopefully see the actual problem area. will keep you posted. I still don't understand why its running so good. I better find the problem before it does affect something other than the temp. I have put gauge coupling back in drivers side head and fan switch in manifold by thermostat. thanks guys.

[davepl]

It'll be fine wherever you put it. The closer to the thermostat the warmer your reading will be.

Remember, it can't be "hotter" in the heads, because that heat doesn't disappear between the heads and the upper rad hose. It's got to go somewhere. I suppose the coolant could pick up heat in the heads and lose it later along the way, heating up what comes after in the coolant path, but that'd balance out real quick.

Now if you were really hooped and had steam pockets in your heads and the sensor was in one of those you'd get a weird reading, but that's quite a stretch. On a car with gauges I've moved it from the head to the intake and don't recall much change, but never checked side to side.

Do you have a temp gun? Decent ones are cheap now and I use mine for so many different things it's hard to imagine not having one. That'd allow you quickly check external temps side to side and front to back, etc.

I hope that's just a covering over the fuel line and you don't have several feet of rubber hose. Your motor (and likely truck) are way too pretty to lose to fuel fire.

And while I'm picking on you for no apparent reason why not get the right upper rad hose? Have to imagine those universal ones cause a lot of drag and turbulence, and every thing else is so nice it sort of sticks out...

[geezer#99]

FWIW the coolant is drawn into the water pump and then is distributed evenly thru the block on both sides, up thru the heads and back to the thermo and to the rad.
The inlet to the pump can be on either side and not change the coolant path.
Could be the original builder of the motor had a problem with one core (freeze) plug and left it in the block.
X2 on the fuel hose. I've had the dubious pleasure of watching the fuel on the intake boiling just before the big fire.

[gmhardwick66]

To answer you both. First it is just some convulting cover over fuel line. It is for insulating at best. I will be upgrading it soon. As far as the upper radiator hose...these pictures are a little old. I will post a few newer this morning in a bit. And the truck had a running engine in it when I bought it. I had no cooling issue at all, BUT I didn't swap from head to head and compare difference in temp reading. Just as now with the same block but EVERYTHING wlse is brand new out of box. It to runs perfect and cool according to the reading in driver side head. Had I not swapped the sender to passenger side head, I never would have known that I had a problem. Is it possible that when I removed plug in passenger head that as coolant drained out during the install of sender that I have an air pocket in head? I am going to machine shop today that bored and honed block to ask him as to the block maybe being an issue.

[gmhardwick66]

The engine runs perfect. I only have about 100 miles on it and from your advice I pulled the spark plugs and I am running way rich. Could this cause my problem? I am running Autolite AR 3294 plugs gapped at .040. Should I jet down or maybe a hotter plug? I am running 38 degrees total timing. For what its worth...I have done a lot of carburetor work...swapping different carbs till I finally decided to buy a new one.

[geezer#99]

If it's running right and not overheating then you don't have a problem.
Worry about other things, like your over rich idle.
You say 38 degrees timing.
Questions?
What's initial timing?
Where's vac pot on dizzy hooked to?
What's your idle rpm?
Can you adjust your mixture screws in all the way and idle not change?

[gmhardwick66]

lol thanks geezer....I will never sleep again...lol I am at 12 degrees initial, idle mixture screws are adjusted to achieve highest possible idle. Dist not hooked up as I have a complete new MSD Pro Billet dist. not vacuum advance, it idles at about 900-1000rpm. But the carb does have changeable idle jets so do you think I need to go smaller on them and if so how much would you go down at a time? And by the way, thanks for the advice.

[geezer#99]

Leave the carb for now!
You gotta get your idle down. You're likely getting the mechanical timing starting to kick in.
Bump your timing up to 16 to 18. THen turn your idle down. You want it around 700 to 750 max.
That should make it idle leaner.
Or try this.
You want to cover the idle transfer slot up.
You might need to increase your idle with the secondary throttle screw in order to get your primary closed more.