Hey, Who Took The Drain Plugs?

[Joe C.]

When did Chevrolet discontinue the use of block drains. There are none on my '85.
Joe

[Joe L.]

Re: Hey, Who Took The Drain Plugs?

Joe-----

I think that you need to look closer. As far as I know, all small blocks have the block drains. My 1992 LT1 has them. What may be confusing you, though, is the fact that for certain engines, they're not just a "plugged" orifice as they were in days of old. Chevrolet finally used them as the mounting points for the engine knock sensors. I believe that the knock sensors for your engine are installed in the block drain fittings. So, in order to drain the block, you have to remove the knock sensors. Be careful when removing and re-installing---they're easily damaged and thus rendered useless. If you damage one, then you buy a new one. In your case, it's GM #10456287 and they GM list for $55.35/each.

[Joe C.]

Re: Hey, Who Took The Drain Plugs?

Joe:

Nooooooooooooo, I wouldn't touch them with a ten foot pole, unless they were inoperative. Chevy probably used the taps to insert some input sensors, possibly knock sensor(s). I simply flushed the engine with fresh water until it ran clear, then aded the required volume of e-glycol to make a 50-50 coolant mix.

Joe

[Wayne M.]

If you add antifreeze w/o draining block ...

it's difficult to know when you have an OVERALL 50-50 water-antifreeze mix.

For instance, my C2_327 drained a total of 12.5 litres (3.30 US gal.), of which 5.0 litres was in the block (2.75 drained from RH plug removal, then another 2.25 from the LH plug removal).

So, you'd have to add around 70% antifreeze to the rad, if the block initially contained only water, to achieve the 50-50 desired mix.

[Joe C.]

Re: If you add antifreeze w/o draining block ...

Wayne:

The service manual shows capacity of 1985 Corvette cooling system to be 14 quarts. I flushed the system with fresh water, including the overflow tank, and kept tasting the runoff until it no longer tasted sweet (just kidding). When the runoff ran clear, I drained the radiator, shut the petcock, and added 7 quarts of straight antifreeze. Whatever didn't fit in the rad., I added to the overflow tank.

When I drained the block of my 1965, I got about 3 quarts out of each side..........about 6 quarts total in the block.

I found something new and disturbing when I bought the antifreeze last week. They now sell it premixed @ 50/50. Be careful to know what you are buying. The packaging is very close between the premixed and the full strength, so READ THE LABEL CAREFULLY. I looked very hard, and found two gallons of the full strength stuff, which I bought.

Joe

[Jim T.]

Re: If you add antifreeze w/o draining block ...

Joe like Joe Lucia mentioned a knock sensor is in place of your block drain on the passenger side. It is easy to remove and replace, not that delicate. On the drivers side you should have a drain plug if you do not have the optional cooling system. With the optional cooling system it is very easy to drain the block, just remove the coolant hose from the block nipple. Our 85's only have one knock sensor. Duke Williams convinced me to change over to Dex-Cool about 5 years ago in my 85. Now I have to decide to change to the newer Zerex type he has mentioned or stick with the Dex-Cool.

[Joe C.]

Re: If you add antifreeze w/o draining block ...

Jim:

Thanks for the response. My 1985 has Z51, which requires heavy duty cooling. I didn't want to fool around with any plumbing or electrics, so I opted to flush the old fashioned way, until the H2O ran clear. The cooling system is now refilled with fresh 50/50 to my satisfaction.
I very much enjoy driving my '85 with 700R4. It is a blast to drive, quasi-modern, and a torque beast. I gather that you enjoy yours as much as I do mine.

Joe

[Jim T.]

Re: If you add antifreeze w/o draining block ...

Joe I do enjoy driving the 85. Enjoy it more since I put in a switch that disables the lock up of the torque converter for driving around town. Driving speeds under 30 with torque converter lockup it was annoying, before I installed the switch I would sometimes drive in 2nd. It was something to come off the interstate without using the brakes and then accelerate lightly, the 700R4 would not shift down, torque converter locked, and the car running 900 rpms. There is supposed to be a factory prom that corrects this but I just installed the switch. It only connects to the brake pedal switch.

[Joe C.]

Re: If you add antifreeze w/o draining block ...

Jim:

When my car was less than 1 year old, the engine began a severe "hunting" problem, where the RPM's would begin to oscillate with larger and larger amplitude, until it would eventually stall. A TSB was freshly available, indicating the problem, and a new PROM (Programmable Read Only Memory) chip was installed. Not only did it cure the problem, but the operating characteristics of the car were noticeably changed. The idle was smoother and more stable, the engine produced more power (mixture settings and advance map was likely set for better driveability), the occasional lean misfire was gone, the trans shift points were raised, the converter lockup was raised to 41 MPH.
Once the car was delivered, GM satisfied the CAFE (Corporate Average Fuel Economy) standard, and so a Service PROM (programmed for more power)could legally be installed. Curiously, I never noticed a fuel economy deficit. If there was any, it must have been miniscule.

Joe