Did the old 283 dual point Corvettes overheat?

[Tom H.]

This should be right up Duke's alley. I understand that the early V8 Corvettes with dual point distributors had no vacuum cans but did not overheat. Why?

[Michael H.]

Re: Did the old 283 dual point Corvettes overheat?

This should be right up Duke's alley. I understand that the early V8 Corvettes with dual point distributors had no vacuum cans but did not overheat. Why?

This oughta be good.

[John H.]

Re: Did the old 283 dual point Corvettes overheat?

None of my 57's (with original 891 dual-point distributors) ever showed any overheating tendencies, but all had re-cored radiators and correct fans, spacers, and shrouds.

A neighbor's '58 overheated regularly (original radiator), and when I finally convinced him to have the radiator re-cored, it never overheated again.

40-year-old radiators don't reject heat very well.

[Duke W.]

Re: Did the old 283 dual point Corvettes overheat?

Virtually all cars of that era had more tendency to overheat than modern cars due to lower pressure cooling systems (and alcohol based antifreeze), which yields lower boiling temperature than later 15 psi systems with ethylene glycol antifreeze.

If anyone cares to run a test I will be willing to place a substantial wager on a 283/230 running cooler in very hot weather/low speed traffic than a 283/245 as long as both had relatively new radiators to eliminate the effect of radiator aging/deposit buildup on the results.

AFAIK they both had the same radiator and fan.

Why don't you run your own experiment, Tom? Assuming you have a model with a full time vacuum advance engine, disconnect and plug the signal line, reset/optimize the idle speed mixture, go drive in low speed traffic/hot weather and record the temperature readings.

Anyone else can run the same experiment, and the archives are full of stories about ported vacuum advance engines (like L-72/71) running much cooler after being converted to full time vacuum advance.

The reason engines run cooler with full time vacuum advance lies in a basic understanding of combustion and themodynamics, and I've explained it a number of times.

The explanation and supporting data are in the archives.

Duke

[Clem Z.]

Re: Did the old 283 dual point Corvettes overheat?

None of my 57's (with original 891 dual-point distributors) ever showed any overheating tendencies, but all had re-cored radiators and correct fans, spacers, and shrouds.

A neighbor's '58 overheated regularly (original radiator), and when I finally convinced him to have the radiator re-cored, it never overheated again.

40-year-old radiators don't reject heat very well.

the fins loose contact with the tubes on old rads and that is why they can't transfer the heat. that is why "roding"out the tubes don't work

[Dick W.]

Re: Did the old 283 dual point Corvettes overheat?

I had 283's way back when, and I never had any problems with heating.

[Michael H.]

Re: Did the old 283 dual point Corvettes overheat?

I had 283's way back when, and I never had any problems with heating.

I may have mentioned this before but.... I haven't had an operating vacuum advance on my 66 L72/425 HP 66 for almost 25 years, and it stlll doesn't over heat. Same radiator, same fan clutch and with or without a thermostat. (no change)

There's a small steel ball stuffed in the vacuum adv hose at the distributor so there's absolutely no vac adv., ever.

I must be doing something wrong.

[Jim T.]

Re: Did the old 283 dual point Corvettes overheat?

Michael if you drove the car much in a conservative manner before the steel ball prevented vacuum to the vacuum advance unit, is there any loss of gas mileage in preventing the vacuum advance unit to function?

[Clem Z.]

Re: Did the old 283 dual point Corvettes overheat?

I may have mentioned this before but.... I haven't had an operating vacuum advance on my 66 L72/425 HP 66 for almost 25 years, and it stlll doesn't over heat. Same radiator, same fan clutch and with or without a thermostat. (no change)

There's a small steel ball stuffed in the vacuum adv hose at the distributor so there's absolutely no vac adv., ever.

I must be doing something wrong.

i converted my vacuum advances to a threaded rod so i could change the timing without a timing light. i knew how many turns of the nut on the threaded rod moved the timing so many degrees. worked great for impromptu to drag races picked up at the local curb service.

[Tom B.]

Re: Did the old 283 dual point Corvettes overheat?

Back when I drove my '59 as a daily driver it was just a 10 year old used Corvette 270 horse. It never overheated even putting around town on the local cruise loop. As far as I know the radiator has never had any service other than drain and refill with ethylene glycol antifreeze.

Tom

[Bill M.]

Re: Did the old 283 dual point Corvettes overheat?

I ran my '59 283 with no vacuum advance (914) and no shroud for many years ('63-'70) and never had a boil-over problem, even in stop-and-go traffic in downtown Chicago.

I read that Ferrari ran their 50s cars without a fan, so I thought I'd try that. One trip through stop-and-go traffic in Detroit ('76) proved that wouldn't work! I just barely made it without a boil-over.

[Michael H.]

Re: Did the old 283 dual point Corvettes overheat?

Michael if you drove the car much in a conservative manner before the steel ball prevented vacuum to the vacuum advance unit, is there any loss of gas mileage in preventing the vacuum advance unit to function?

Jim,

Yes, there would definitely be a slight reduction in fuel mileage if the vac adv unit were inoperative. Fuel mileage was one of the reasons why the system was designed//used in the first place.
The problem, though, was that in the 50's and 60's, engineering was working with an entirely different gasoline and the timing requirements/limits @ RPM/load were a LOT different than with todays 93 octane fuel. (and for the last 25 years)

Too much timing will eventually cause some serious engine damage. The extra fuel mileage isn't worth the risk.
Someone once refered to pinging/detonation as the "death rattle" for engines but I don't remember who it was. (Jennings..Yunick?) Who ever it was, was dead on accurate. Betcha Clem will absolutely agree too.

Yer playing with fire if you allow an engine to bang away, especially a big block. (Hanson said that)

[Duke W.]

Re: Did the old 283 dual point Corvettes overheat?

Jim,

The problem, though, was that in the 50's and 60's, engineering was working with an entirely different gasoline and the timing requirements/limits @ RPM/load were a LOT different than with todays 93 octane fuel. (and for the last 25 years)

I have yet to hear of a case where adding a proper vacuum advance to a non-vacuum advance engine or switching from ported to full time with a proper VAC causes detonation. Detonation is almost always a WOT issue.

93 PON is equivalent to 97-98 RON, which is nearly the equal of the 98-100 RON of the sixties. I've discussed the various octane rating methods and how to convert one from another many times.

Duke

[Stuart F.]

Re: Did the old 283 dual point Corvettes overheat?

The early model Chevy Distributors with vacuum advances were prone to having advance plate tipping which would throw the timing way out of whack. The dual point distributors with a fixed plate were a blessing. My very first V8 from the junk yard in 1956 had a vacuum advance distributor and after going through all the work to install it in my 50 Chevy Coupe, first time out I mashed the throttle and it ran up to 3500 rpm on my S-W Tach and started sputtering like crazy. I had no such prior experience and it took me a while to figure it out by disconnecting the vacuum advance and plugging it. That was a bad experience that I didn't recover from until I bought my 63 Vette new some 7 years later and learned to live with them until today.

Stu Fox

[Tom H.]

Re: Did the old 283 dual point Corvettes overheat?

Duke- I am thoroughly acquainted with most of your excellent research. I've already done the vacuum blocked experiment in my ill informed youth- boy that temp gauge rises quickly. What I'm interested in finding out is: were there any special engineering considerations given to the cooling system on these early V8's to control operating temps given that they didn't have permanent antifreeze, clutched fans etc.??