Funny engine in a '69

[Martin McDonough]

Hi all: Just looked at a '69 coupe basket case which the owner has had for about 5 years. A friend of his had it for 15 years prior to that. It is supposed to be a 427/400. The apparently original engine has been recently rebuilt and is on a stand. Swears his friend never used the car. Serial number (020xx) matches the chassis. Looks real, broach marks are faintly visible. Here's the catch - block casting # is 3916321 and the ID code is 'IM', which is '68 model year stuff. Additionally the 'M' is definately an overstrike. It looks like the original code was ground off. Owner says it had a solid lifter cam, and he changed it to hydraulic. 'IM' is an L36 hydraulic lifter block with 3x2 and 4-speed. The only scenario I could come up with was the factory needed a 427/400 block in '69, took a leftover '68 L36, put 3x2's on it and put it in the car. Is there any history of this sort of thing. He's asking 7k and it is tempting.
Marty McDonough NCRS 2781

[Norris W.]

Re: Funny engine in a '69

I have a 69 400 horse car with THE original motor, but I can't remember the code or even how early the car is without checking tomorrow. I wouldn't think the casting number is impossible, although unlikely unless the car is very early. As far as the solid lifter camshaft, I'm unsure from your post if the previous owner feels it was original, but if so it would've obviously been in a 4 bolt block and not installed in a 400 horse car. There's no question that there were some "I" codes used in 69. The first design L88 is one example. I just don't know where the line was drawn as far as holdovers. Overstamps in conjunction with casting numbers generally used in 68 would certainly require some more investigation if originality is your priority.

[John H.]

Re: Funny engine in a '69

Martin -

Maybe someone else has better references, but the Spec Guide shows the 621 block used for "'68 Early" applications, and the new Colvin Corvette book shows the 621 block being replaced by the 439 block about January '68, which was a long time before '69 production began. My other references show no usage for the 621 block in any Chevy product after mid-'68.

[Martin McDonough]

Re: Funny engine in a '69

John, this is what I thought. But it looks so real. Maybe Terry McManmon or someone will have some thoughts.

[Joe L.]

Re: Funny engine in a '69

Martin-----

The "IM" suffix code was used for 1968 with L-68. So, even if they had been able to do so, there would have been no need for St. Louis to make up an L-68 from an L-36; the "IM" code would indicate an L-68 to begin with. Basically, an L-68 is simply an L-36 core engine with an oval port, 3X2 manifold and carbs in place of the oval port, single 4BC manifold and carb used on the L-36. However, these installations were done at the engine plant.

As far as whether this engine is original to the car, I have some doubts about it. Although the 1969 car in question is an early build-car, the GM #3916321 block casting was used for EARLY 1968. I really doubt that such an engine would have been left "lying around" for installation in an early 1969 Corvette. I don't know how to explain the fact that the engine stamp pad has the car's VIN derivative on it. That part would seem consistent with an original engine and, if it were a re-stamp, that would not be consistent with the ground-off and restamped "M" character of the suffix code. If one was going to go through the trouble of re-stamping a VIN-derivative to match a particular car, then why not stamp a perfect and APPROPRIATE suffix code?

Here's a possibility, though: the engine may have been a 1968 engine returned to Tonawanda from St. Louis. The engine may have needed repair or rework. It could have languished at Tonawanda for several months awaiting "off-line" repair. Originally, it may have been another configuration (and suffix code), but it was reworked into an L-68. Consequently, the last character of the suffix code was ground off with a die grinder (a common practice at the engine and vehicle assembly plants) and restamped to coincide with the engine's new configuration. By the time it got back to St. Louis, it may have been very late in the 1968 model year or, even, very early in the 1969 model year. St. Louis wasn't going to throw it away, so it was installed in this car.

One thing you might do is to perform a "quick and dirty" check to see if this car was an original big block car. Look to see if it's equipped with a rear stabilizer bar and cap-type stub axles (as opposed to the u-bolt type used for small blocks). If the car doesn't have these components, then you know that it was an original small block car and the engine's VIN-derivative stamping is not original or authentic. If it does seem to be an original big block car and considering the state of the engine pad stamping, then I'd say that this car is a factory anomoly. They were, by far, the exception and not the rule, but they did happen. The problem will be documenting it to the satisfaction of judges, if it's your plan to restore the car for entry in NCRS, NCCB, or other judged events. The scenario that I presented above is just a THEORY of how the circumstances could be consistent with an original engine. THEORIES may not be satisfactory in judged events.

[David H.]

Re: Funny engine in a '69

Martin; This may sound dumn but make sure you are looking at a 69 and not a 68 corvette, one time a guy swore up and down he had a 66 but there were no vents on the sail panels, and the 68 and 69 look alot alike save for door handles, interior, and serial #s. Just a thought. David

[Martin McDonough]

Re: Funny engine in a '69

Thanks David - It's a '69. I have had 1 for 20 odd years now, and even in my advanced age I remembered the things you mentioned. The VIN plate is a '69 plate also

[Terry M.]

Re: Funny engine in a '69 *TL*

About all I can say is "Never say never." This one sure taxes the limits though. Joe Lucia summed it up nicely below. Even if it is real, it is a square peg in a round hole and would be a hard sell at NCRS or NCCB.
Any chance you can get a good photo of the pad to email to me? There is no substitute for seeing the goodies.
Terry

[G B.]

I saw one in 1996

In late 1996 I drove to Cincinnati to buy a '69 427 from a drag racer. He had a vintage racer Willys coupe. In it was a '69 (390 hp) 427 block. He also had a disassembled spare 427 that he wanted to sell. He was going to switch the Willys to a Hemi.

I bought the 390 hp engine but passed on the spare block. The reason I didn't buy the disassembled engine was that it had a 1968 casting number. However, I remember that the front pad had a factory overstamped '69 Corvette application suffix, as well as a '69 Corvette VIN derivative. Both blocks were as real as could be; the racer wasn't into Corvettes at all.

I listed the VIN's from both blocks in a 1997(?) Driveline ad hoping to reunite the blocks with their original Corvette bodies. I didn't get any calls though. I later sold the 390 hp block that I had bought. I don't know what became of the other engine.

[Martin McDonough]

Re: Funny engine in a '69

Terry - I may be able to get a pic. I didn't have my camera with me at the time, and the owner got a little annoyed with me. Have to be next week, going out of town for the weekend.