In January 1972, my Buddy and I were prepping our 63 340hp Vette to return it to use out of storage. We were in the basement garage of his Mothers Restaurant with the door open and outdoor temp around 0 degrees. We had adjusted the valves from their collapsed sate, pumped out the Wynn's Friction Proofing, and put in a new set of plugs. We cranked and cranked the engine over until "Wamm!" We had a glorious crankcase explosion which blew the valve covers off. Now, I have told that story over and over through the years to explain to everyone why I have replacement valve covers on the engine. And they say; uh huh, oh ya, that's an interesting story. And to this date I believed it was caused by a stuck PCV Valve. Now, after 36 years, I just received my copy of the new 63-64 NCRS Technical Information Manual and Judging Guide, and low and behold, on Page 216, there is a copy of an Interorganization Letter which describes our situation as if someone from Chevrolet was standing there looking over our shoulder. The letter was written on February 12, 1963 - can anyone tell me how it is possible that no one ever knew about this that I ever talked with at Dealers, the Zone Office, or Chevrolet, or at every car show I've been to with my car in 36 years? I don't think I will attempt the Flame Arrestor mod they describe after all these years. I hasn't happened again and I live in Florida now so it is never that cold.
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Re: Never Too Late Chevrolet/NCRS
Most people didn't understand crankcase ventilation systems or the need for a flame arrestor to protect the crankcase vapors from a carburetor backfire back in those days, and most folks still don't understand it today. There's lots of information in the archives if you search under "PCV" or "crankcase ventilation". -
Re: Never Too Late Chevrolet/NCRS
"We had adjusted the valves from their collapsed state."
Being as how the 340 HP engine has mechanical lifters, this statement makes no sense.
If you lashed them as if they were hydraulic lifters, the engine would be more likely to backfire through the carburetor during cranking than actually start because the valves will never completely close.
I don't have the new JG, so I am not familiar with the letter. Can you type in the text?
DukeComment
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Re: Never Too Late Chevrolet/NCRS
I completly agree. Thing is, the Sevice letter was dated in February 1963 and we didn't take delivery of the car until August 1963. You'd think the flame arrestor fix would have made it to the production line after 5+ months, or at least some one at zone or a dealer would have a bell go off in their head in response to my inquires.
All I can say now is; Thank you NCRS and all the fellows responsible for the content of the new manual. My life is now complete!Comment
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Re: Never Too Late Chevrolet/NCRS
In the petrochemical industry, integral gas engine-compressors have been used for decades. I doubt a new design has been made since the fifties, and most I saw were built back in the forties. Crankcase explosion were rare, but if one did occur, and an employee happened by at the wrong time, there would be a fatality.
On the crankcase side opposite the compressor cylinders, the crankcases of these engines had bolted doors of heavy steel plate between all the main bearings...to change a main (or rod) bearing was a job because everything about these engines was heavy duty and just plain HEAVY. I tried to lift one of the doors once...I could kind of rotate it a little, but one single man wasn't going to lift one. A crankcase explosion would blow those heavy doors, fastened by multitudes of 1/2-5/8" bolts, across the compressor house...anything living that stood in the way was going to die.
In the mid-seventies, a safety edict came down from the government or the company (Exxon) that all engine-compressors would be retrofitted with blast prevention doors. I never saw how they operated, but each door had a compressed accordion cylinder with a round cover covering an opening in the center of the door. Those "blast preventers" didn't seem like enough to tame that kind of energy.
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Re: Never Too Late Chevrolet/NCRS
Duke;
Back in the Day, we used to prep our engines for storage by filling the cylinders with Wynn's Friction Proofing, then back off all the valve lashes so as to close off each cylinder (yes, they are mechanical). Don't ask me why we did that. Probably a method we picked up reading an old Corvette magazine, I don't know. The letter reads as follows, Dated February 12, 1963:
"Subject: Engine Crankcase Backfire - All 1963 Corvettes Except Fuel Injection - A. I. 63-10
An accidental carburetor backfire during severe cold-weather starts, may result in a flame traveling down the air cleaner to crankcase vent fresh air supply tube, igniting the fumes in the crankcase. In extreme cases, the resulting explosion may damage the oil pan and rocker covers.
A final production correction has not been determined at this time; however, installation of a flame arrestor screen to the inside of the air cleaner (as illustrated on the attached sheet) will prevent reoccurance of this condition.
Signed by; H. A. Bangsberg,
Technical Service Department"
Page 2 describes the modification instruction and an illustration.Comment
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Re: Never Too Late Chevrolet/NCRS
I worked for Electromotive Division GMC for over 22 years and it was common equipment on Marine applications to replace the Handhole covers in some crankcase positions (access covers in the crankcase and air box) with explosion proof covers which were like a relief valve (spring loaded cover). Guess when you're out to sea, it's not fun having a crankcase explosion as you could go down with the ship! Better to be able to limp the engine back to port.Comment
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Re: Never Too Late Chevrolet/NCRS
Thanks, I was not previously aware of this. In the first several years of operation my 340 HP frequently backfired through the carburetor at 4500 plus revs when the ignition broke up due to the sloppily assembled distributor. I solved the problem by adding a TI off the "12-mile L-88", but finally reinstalled my "blueprinted" single point distributor circa 1975 after the TI failed the second time. I fixed it and eventually sold it to David Burroughs to install on the car from whence it had come.
Maybe I was lucky that I never had a crankcase explosion.
My car was built in mid-March and the air cleaner housing has no screen on the fresh air inlet.
Does anyone have such a screen on a '63 that appears to be either added in the field or factory installed?
DukeComment
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Re: Never Too Late Chevrolet/NCRS
Well, you probably have a point there. However, the path to the problem most likely was the open crankcase vent. The content of the Wynn's Friction Proofing probably added to the volitility and therfore the severity of the explosion. Both valve covers tore out of their mounting screws taking the choke tube and clean air hose with them on the RH side. The ceiling was low in the garage and the covers ricoheted all over the place. We had to duck, needless to say. It was a very memorable occasion. When I tell people that it is the original engine and it's never been apart, they look at the parting line in my replacement covers and say; "ya, right". That's why I have had to explain this so often and now I have a copy of the letter to prove it.Comment
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Re: Never Too Late Chevrolet/NCRS
Your story isn't the first one I've heard about this and I've seen the results of a few of these explosions in the past.
The service repair recommendation still left a clear path to the air cleaner for fumes but the screen that was suggested by engineering for 63, and later added as part of the 64 and later build, was there to keep the oil from entering the air cleaner base. It worked, kinda.Comment
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Re: Never Too Late Chevrolet/NCRS
The 63 had a number of issues that were later addressed in 64 and beyond. The nice chrome fuel line (between filter and carb) helpd conduct a lot of the heat from the water manifold to the carb and contributes to the "Stinky fuel fumes" I talked about in one of my previous threads. Proof of this is the use of a hose in place of the chrome steel line in 64 365 HP. Also, would you believe, all the chrome on the inside of my air filter housing base peeled off (down to the copper). Most of it I peeled off by hand when I saw a curled up end as I sure didn't want my engine internals to deal with it. Chrome is hard! I hope I got most of it, but probably won't know for sure until I pull it down some day. It has lasted though for 45 years and almost 45,000 miles, so guess I got most of it.Comment
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Re: Never Too Late Chevrolet/NCRS
The July 1999 Vol 27 # 12 issue of Vette Vues ran a copy of the 1963 Engine Crank Case Back Fires letter in their Factory Facts colum. My old copies are well buried in storage. Maybe someone else can post it here.Larry
2002 Z51 Convertible
1969 L46 ConvertibleComment
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Re: Never Too Late Chevrolet/NCRS
Michael;
We're in Orlando now since July 2004. Spend some of our Saturday nights at Old Town, and havn't missed a winter meet there since about 2003. Live just east of the airport at Lake Nona area. Both of my twin sons fly out of there for JetBlue and have our only Grand Kids. That's why we moved. One son has a 78 P.C. which he got Top Flight (ed) this past January here.
Lawrence;
I'm sure I have that issue boxed up in my garage too. Havn't unboxed everything since our move, but intend to to complete my library.Comment
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