65 impala SS 327 4 Spd - Impala Tech
Engine General Engine Discussion.

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post #1 of 16 (permalink) Old 04-22-2020, 06:49 PM Thread Starter
 
 
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65 impala SS 327 4 Spd

Looking to get some opinions, so I bought the car a few months ago and I noticed it would choke up when accelerating so I took it to a shop and figured I’d do a new carburetor. Driving the car home from the shop my impalas temp gage started marking not to much more from the cold side after driving it for about 20mins. Before this the temp gage would heat up to normal. I pulled out thermostat and tested it, worked as it was supposed to. Next was the temp sensor I replaced that and now my temp gage is reading overheating. I also replaced the fan clutch and put a new thermostat in and still over heats. Any thoughts?
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post #2 of 16 (permalink) Old 04-22-2020, 08:00 PM
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Was the drive home from the shop through town and in stop-and-go traffic or sustained highway? Need to understand how much air-flow should have been going through the radiator.

I am not sure I understand this sentence: "Driving the car home from the shop my impalas temp gage started marking not to much more from the cold side after driving it for about 20mins."
It sounds like the needle barely moved above Cold, but you said it was overheating? I'm confused.


It's possible your temp gauge is malfunctioning, it's also possible that your new carb is making your run really Lean which can make things run a bit hotter.

I have one of those cheap Harbor Freight infra-red temperature checkers. Pretty damn handy for situations like yours!

HOW A NOVICE REBUILDS A 66 IMPALA CONVERTIBLE:
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post #3 of 16 (permalink) Old 04-22-2020, 09:10 PM Thread Starter
 
 
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The drive home was indeed through town as for that sentence i was saying that during the whole drive the temp Gage never reached proper temp it stayed cold the entire way home.

I thought the same thing so I switched to bigger jets and that didn't help either. I started thinking water pump or clogged radiator.
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post #4 of 16 (permalink) Old 04-22-2020, 09:12 PM
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It is also possible that your "new carburetor" is a rebuilt Rochester Quadrajet with the wrong jets and rods for a stock 275 horse 327 in it so that it is running leaner, which causes it to run hotter (such as using a 305 carb as a core). Another thing I would check is the ignition timing as I will bet your mechanic wanted to impress you with her new mileage by retarding the ignition timing causing it to run hot.

Big Dave
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post #5 of 16 (permalink) Old 04-22-2020, 09:35 PM Thread Starter
 
 
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Thats exactly what my thought was, so I had him come to my house and re time it. Whats weird is I put the old temp sensor back today and it marked cold again and the new one marks hot.
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post #6 of 16 (permalink) Old 04-23-2020, 12:23 AM
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I have run into problems with the temp sensors not being calibrated correctly for the gauges in our old cars. The companies seem to make one to cover years and years of different models and while it may have the correct resistance for certain gauges, the ones I've found don't seem to register correctly in mid 60's GM products. A few years back I tested about 7 different senders (some old originals, some new aftermarket replacement sending units) in the same boiling pot of water and the resistance shown by each individual sending unit varied an awful lot.
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post #7 of 16 (permalink) Old 04-23-2020, 09:12 AM
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Where is your timing?

KNOW that the is timing right before futzing with anything else.

Here's some useful info:

https://www.chevelles.com/forums/374...ion-101-a.html

Pete
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post #8 of 16 (permalink) Old 04-23-2020, 10:36 AM
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Quote:
Originally Posted by Big Dave View Post
It is also possible that your "new carburetor" is a rebuilt Rochester Quadrajet with the wrong jets and rods for a stock 275 horse 327 in it so that it is running leaner, which causes it to run hotter (such as using a 305 carb as a core). Another thing I would check is the ignition timing as I will bet your mechanic wanted to impress you with her new mileage by retarding the ignition timing causing it to run hot.

Big Dave

65s didn't get Quadrajets. Also, the engine is either a 250 or 300hp. 250 got the Rochester 4Jet, 300 got an AFB.

Two doors, four doors, wagons, and ragtops.
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post #9 of 16 (permalink) Old 04-23-2020, 10:52 AM
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Quote:
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65s didn't get Quadrajets. Also, the engine is either a 250 or 300hp. 250 got the Rochester 4Jet, 300 got an AFB.
You are correct. SBC didn't get the new for 1965 Rochester QuadraJet introduced OCT '65 with the new 396 BBC Mark IV engine and the TH400 Automatic until 1966.. 1965 was the last time the Rochester 4G was used by GM.

Makes the carb even more suspect as few know how to tune the 4G carb (though there are no rods just jets).

Big Dave
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post #10 of 16 (permalink) Old 04-24-2020, 12:52 AM
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Quote:
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1965 was the last time the Rochester 4G was used by GM.


Big Dave
Yes, true for Impala and Chevelle. For some odd reason if you ordered a 66 Nova 283/220hp (4 barrel) you got a Rochester 4 jet, not a Quadrajet.
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post #11 of 16 (permalink) Old 04-24-2020, 10:04 AM
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Sounds like you're on the right track. Trust nothing until verified with other pieces. Test in multiple ways, Rule out the bad bits.


The sensor is in the side of the head right? Thats where mine is and I get a good consistent 190 out of that on my very old analog gauge setup.

HOW A NOVICE REBUILDS A 66 IMPALA CONVERTIBLE:
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post #12 of 16 (permalink) Old 04-24-2020, 11:29 AM
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The electric gauge in these cars measures volts not temperature. It has an alloy of metal inside that changes resistance with heat. It is usually fairly accurate (no where near as accurate as a mechanical Mercury filled bulb is, but it is better than an idiot light).

However have you ever heard mention of grounding issues on these old cars? If you have a bad ground; say some one painted the head and got a plastic insulator called paint on the threads, or there are no grounding straps connecting the dash and the engine that should be attached to the firewall and the bell housing, or you have a bad terminal that is all corroded on your battery, don't expect anything to work correctly or consistently.

Big Dave
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post #13 of 16 (permalink) Old 04-24-2020, 12:53 PM
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This is very true. I had grounding issues moving the battery to the trunk in spite of having clean metal and grounds directly to the frame. The steel in the body/frame is just not as electrically conductive as you might imagine. Once I ran a separate ground wire to a front bulkhead terminal the problems went away.

Quote:
Originally Posted by Big Dave View Post
The electric gauge in these cars measures volts not temperature. It has an alloy of metal inside that changes resistance with heat. It is usually fairly accurate (no where near as accurate as a mechanical Mercury filled bulb is, but it is better than an idiot light).

However have you ever heard mention of grounding issues on these old cars? If you have a bad ground; say some one painted the head and got a plastic insulator called paint on the threads, or there are no grounding straps connecting the dash and the engine that should be attached to the firewall and the bell housing, or you have a bad terminal that is all corroded on your battery, don't expect anything to work correctly or consistently.

Big Dave

1969 Imapala convertible build thread here:
https://www.pro-touring.com/threads/...ghlight=impala
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post #14 of 16 (permalink) Old 04-29-2020, 10:18 PM
 
 
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Big Dave,
That is very interesting. I have a 65 SS and all the gauges work except Engine temp. It seems to work until it gets warm and then if I use the turn signal or the brakes, the needle pegs to full hot, like the circuit is open. Your idea of running a ground strap from the engine to the firewall may be a good fix. Do you happen to know where I should run the strap to?
Thanks!
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post #15 of 16 (permalink) Old 04-29-2020, 11:49 PM
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There should be a bulkhead stud on the fire wall. One end goes there. other end goes under the bare steel bolt holding on your free of paint aluminum bell housing that doesn't have insulating plastic paint between the block and the face of the beel housing.

People who own old cars lve to paint everything with shinny plastic paint. the factory painted the motors from ten feet away with what looked like a fire hose. it sprayed all over the fully assembled engine (no paint between parts and all over things that most mask off. Factory was building a new car every 12 minutes and had no time to build a white glove concours correct car. Paint burnt off exhaust manifolds. Few had aluminum manifolds for the intake, and paint on plugs would be gone by there first change. Different mind set from people who want a chalk mark correct restoration. Just look at pictures of the motors being received from Flint or Tonawanda. They come off the train orange top to bottom with only a black starter and an aluminum alternator below a black air cleaner.

Fact is they missed as much as they painted as you can look under the exhaust manifolds and see bare cast iron.

https://www.ecklers.com/full-size-ch...SABEgKAWPD_BwE

Any way enough ranting about originality. The other bare grounding straps go from the fire wall to the dash, and from the engine to the frame.

Big Dave
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post #16 of 16 (permalink) Old 05-06-2020, 09:32 PM
 
 
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Thanks Dave. That is very helpful. I think this will solve my problem.
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