Joe Lynch

I put a new mechanical water temp gauge on the 67 big block today and drove it around some. Normal temp appears to be 200F with 80F ambient, normal street driving. I can't remember what this car ran normally 25 years ago with the same engine and dirtier radiator, but I don't remember it being that high. Is it normal for the big blocks to run 200-210 F with the stock radiator even if everything is in good condition?

Haven't tried any water wetter or anything like that yet.

Joe Lynch
Midland, TX

LT1driver

Most people with big blocks seem to running hot these days. Nobody seems to be able to fix the problem without a new radiator, usually made of aluminum. However, things to check: gauge inaccurate-check against known gage or IR gun, maybe sender is wrong for gauge, may have been replace. New senders from most everyone seem to read high. I remember my 67 435 many years ago in Arkansas never going over 190, even in the summer, same for my 70 454 I had back then. :seeya

poortom

My 66 427 all still original stays about 180-190..even in hot weather....it's be consistant since 1972...only changed thermostat :chevy :chevy Poortom

Kid_Again

Joe...i think you should start with the basics and assume that your temp gauge is incorrect (either too high OR low) because of a likely electrical mismatch between the new temp senders and the gauge...even if you have the original sender, calibrate your setup at idle with an IR gun or the good old fashioned way of a thermometer in the radiator.....

...in my experience (2 big blocks), the cost of a new aluminum radiator is not warranted if you can recore the existing brass radiator...that fix alone should work wonders, cost less than half of a new aluminum radiator (ignore the manufacturer's marketing ploys).....flush your system very well, including pulling the block drain plugs and consider going to water/pump additive/water wetter and a direct drive fan and you will be in hog heaven, running well, well below 200 deg all the time...also consider adding real lead to your gas during the hottest months as this will increase combustion efficiency, increasing performance and decrease the combustion temperature....with these fixes, and the AC on, i run about 180 on a 80+deg ambient day with the 390hp

396 RAT

Yes, (200-210 seems about normal listening to the board)

Agree, the direct drive fan seems to do the trick
if the rest of you cooling system is in good cond,
and your still running hot. My car got a factory replacement
alum rad. in 72 and a direct drive using stock fan at the same time.
It still runs 180-200. (But it does not get into the 100's
here either)
I wonder if some of these BB's with cooling problems
have been bored out too any times?
Not saying your car has, just as time goes on
it seems more and more are overheating?
(some will say they always have, and in part my be true)
I keep hearing about how everyone thinks all BB's
over heat and don't handle well?
Just for the record, mine does not over heat,
and corners like its on rails- just squares 'em off.
Ditch the fan clutch & see what happens.
:cheers:


[Modified by 396 RAT, 9:46 AM 9/6/2001]

andy60

Becool (sp) make a great fan setup for the Vettes. Saw them at Carlisle. I installed one of their radiators in my 63 car and was happy.

Joe Lynch

Thanks for all the replies. I bought a new sending unit and a new thermostat, pulled the old ones, and tested them all at one time.
What I found was that the old thermostat opened at 205F but not fully, the new one opens fully by 190F, and the new sending unit will make the gauge read too high, since the resistance versus temperature curve was off by 10%. So in the new thermostat and the old sending unit and I will check what happens later this weekend.
http://www.lx.net/jlynch/vetthermo.jpg
Will report back later.
This is fun.
Joe

StrayDog

JOE...my 66 big block runs 185/190 area.......Suggest the use of 1967 427 with air conditioning radiater seal,its made of molded rubber & fits on top of radiater ,it clips on ,only takes a few minutes to put it on , prevents air from going between top of radiater & hood forces all air through radiater..........only costs 25 bucks or so,,worked for me.


[Modified by StrayDog, 6:31 PM 9/7/2001]

Joe Lynch

Stray Dog--That's a great tip, I'll try it. Thanks. I think we are in pretty good shape now. Got to drive the car some today in the heat of the middele of the day and it stayed under an indicated 200 or so, and I know the gauge is 5-10 degrees high.
Joe

Elmer

Joe, I live in Dallas and have a 396/424HP 1965 Vette. My car has a temp gauge from a 67 which is a 250 degree gauge, with 210 as the middle temperature. I do not have AC on the car. My car runs 210 if I don't drive it hard, and higher if I do. Can you tell me any and everything you have done since I haven't been able to get mine under control. Thx...Elmer in Dallas

Joe Lynch

Elmer--I'll do what I can. I went through the original 427/450hp engine in this car in 1969, we went 0.060 over with 11.0:1 TRW pistongs and a Crane flat tappet cam, 4.11 gears, Hooker 2-1/8" side mount headers. Stock 66 250F gauge stayed pretty much below 210 best I can remember. Parked the car on 1977 after putting 40,000 miles on the rebuild with no problems, even with a full drive non-viscous drive fan.

Pulled the engine after 23 years in storage and had to go to 0.070" over to clean up the corrosion from the storage time. Went back in with 10.0:1 JE custom pistons, stock heads, Comp Cams hydraulic roller. Also rebuilt the original radiator, went back to viscous drive 5 blade fan. Replaced thermostat .
Engine ran warm when first run in the car, but had been fine on a dyno. Bought a #10207381 thermostat and a #12334869 sending unit. Checked against other parts and found the differences in the thermostat and the sending unit described above. Haven't checked the part number for the sending unit again yet. This is a one owner car so I am sure the original gauge and sending unit were still in the car.

My recommendation is to install a mechanical gauge in place of the electrical sending unit to see where you really are first. You can tie wrap the gauge to the coowling just in front of the windshield wiper and the capillary tube will fit with the hood closed. I used some weatherstripping to prevent any scratches. When I did this, the mechanical gauge read 200 under the same conditions the stock gauge read 210, so I knew the stock gauge was off some, but that I still had a problem. In my case, the prblem was the thermostat, which was just plain opening too late. You can check the current one and a new one on the stove easily just like I did and make sure of the parts before you change them.

that said, this car never ran at a thermostatically controlled 180 in the summer, I don't think, but it never ran over 210 either. I am calling it good for now.

Elmer

Joe, thanks. Is it a pretty simple matter to find a mechanical guage at a local parts store ? Thx Elmer