Temp problem.

[HTX86chevy]

I did a 305 to 350 swap a few months back. I threw brand new parts all the way around to avoid having anything fail prematurely. I put a brand new radiator, matched it to my old one. Threw in a brand new temp sensor, the one on my 305 was too small to be reused. I got a new 195degree thermostat and radiator hoses.
My temp gauge is going all the way up to 260 degrees while idling or drivingo for 10 mins. its about 50* outside today and I cranked her up and let her sit for 15 mins and she reached 260 on temp gauge. This is also the second temp gauge I have installed thinking that the 1st gauge was the problem.
any ideas?

[ont_guy_38]

Is it really overheating? If the new sensor is smaller it's possible that it isn't the correct one. Even though it fits, the ohms might be different and therefore not register correct.

[HTX86chevy]

It doesn't seem to be overheating. Just reading the temp pretty high. The new sensor is actually larger than the old one. O'rielly only had two to choose from and I have the only one that fit. The old temp sensor that was on my 305 was too thin to fit on the new 350
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[ont_guy_38]

Sounds like that's the possible problem to me. Just get an adapter and use your old one.

[Swed-Chevy]

My gauge shows just above 100 when hot,but i suspect that the engine is an
350 and not a 305.The temp sensor has a large thread on my car to.

Have all the 305 engines the smaller thread temp sensor ?

[king-918]

If feasible boil some water using a thermometer and test both sensors
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[king-918]

Of ohm them both
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[cmyc5575]

Is this you d/d or weekend toy? How many miles are on the 350?

[HTX86chevy]

its my DD and only about 1500 miles on the new 350

[cmyc5575]

Originally Posted by HTX86chevy

its my DD and only about 1500 miles on the new 350

Ok, well i would start with the sensor to like stated above and see where that gets you. I would imagine that they arent that expensive.

[bigd65]

My 82 is doing the exact same thing. It will go all the way to 260, slowly. But if you open the hood, you can lay your hand on the valve covers and radiator and such.

Mine is not the original ANYTHNG. it use to be a diesel and the PO cut everything. I find all the wires and hooked them up. Had to get another cluster (thanks JONBOY) so I don't know what that cam out of. All the other gauges are fine, just the temp increases all the way to max and it's not over heating. I wonder if the sender is a IDIOT LIGHT SENDER.
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[motornut]

my 78 had a stock 305,now it's 350
the cluster was idiots(in block),I changed to gauges/tach
and used the one in the box with adapter

[bk2life]

buy a cheap 20 dollar mechanical temp gauge, screw it in and run your motor to see what your temp really is. but 260? your motor would be boiling the paint. obvisuouly the wrong sending unit.