The Stovebolt Site Forums The Parking Lot Big Bolts 1968 C60 Bus motor size?

I just got a 1968 Chevy C60 full-length schoolbus, and the previous owner swears it's powered by a 305? Could this be true? Is it the GMC 305 V-6, or a smallblock V-8? I assumed it was a V-8 and didn't even count wires under the hood, and now it's in storage so I can't find out for myself for a few days.

Truck that old could have almost anything swapped into it. I'd think that a Chevy 305 V-8 would be an easier swap, so could that be what's in it?

Curiosity got me, so I drove to my storage area at midnight and popped the hood - it's defintely a smallblock V-8, but the displacement answer eludes me. The motor code under the VIN on the firewall is "DD". It wouldn't surprise me if the motor was swapped in, but 305 still doesn't make sense - it's too small for a full-size bus. Also, it looks old enough to be original, with painted orange valve covers that read "chevrolet" in magneto font that looks 60s-ish, so I dont' know what to make of it.

The 305 v6 is a GMC motor so if your bus has the v6 then I wouldn't think it would be original - unless Chevy schoolbuses were an exception to the rule.

I've personally seen the 305 v6 in an old full-sized logging truck, so I don't think it's totally irrational that it wouldn't be used in a 60 passenger schoolbus. The bus might be seriously slow when loaded down with students but it would eventually get them to school.

I would think that the 327 (smallblock) or 366 (big block) v8 would be the standard gas engine for a bus of that vintage. Plenty of power and torque to get a loaded bus moving easily.

-ftyler

that was my thought, that a 327 or 366 would make more sense. It's definitely a smallblock, and the seller adamant that it's a 305, so I guess it must have been swapped in. If that's the case.

Chevrolet script valve covers? I'm not sure what you mean by magneto font, but I have a set of Chevrolet script valve covers that came off an early 283 or maybe even 265.

Instead of the bolt holes being straight across from each other, the top two are closer together than the lower two. If yours are the same it means you have some very early heads, which would not be original on a 305 or on any other small block made after... I'm not sure exactly when, but late '50s or early '60s.

I'm thinking those were not used any longer when the 327 came out in 1962, but my memory is vague on some of these details, and they could have stopped even earlier, like maybe 1958 when side mounting became standard.

You may need to check all the casting numbers to figure out exactly what this thing is...

It could be a 307.

Haha, the mystery unfolds. This bus is such a mutant - an earlier owner had the frame chopped behind the axle and welded back on at an angle toward the ground, creating an incline in the back of the bus body. The rear doors of the bus have been replaced with a wood and aluminun ramp that folds down to the ground - I think you all know where this is going - the bus is now a car transporter. It even has an electric winch mounted in the floor to pull disabled cars into the vehicle. As such, it would only be appropriate that power come from a mutant small block of dubious origin. A mechanic I know is doubting that the 305 had been introduced until around 1970, and that the block was usually light blue. My block is faded and rusted orange, and the valve covers are orange as well. Anyone else with insight, please add your two cents. I appreciate all the input so far.

I'm still leaning toward the 307. Get the numbers from the block & do a search. That's one way to find out for sure.

where would the numbers be located? I checked under the valve cover on the passenger side head on somebody's advice, and found nothing there

It would be stamped on the block deck. Passenger side front. Probably behind the alternator.

Actually around '70 the 307 would have been common. The 305 came a few years later. I have a '78 305.

The serial number should be on the top surface of the block just in front of the passenger side head. While you're looking for that, check for a machined surface on the front of the head. A rectangle with a triangle on top of it means a power pak head.

Double bumps mean fuely heads and were once considered desirable. If there are accessory mount holes on the forward surfaces of the heads it means the heads are later. No holes means early heads.

I was out there tonight with a flashlight. couldnt find any numbers (grimy block, darkness), but the rectangle with the triangle on top is present, which I guess means powerpak heads. Were they specific to a particular motor, such as the 307?

The 307 was a low end economy motor and the power pak heads were the performance option heads used on early 283s. I've seen power pak heads on other motors, so their presence is only telling you what the heads are, not the motor.

There's a machined pad on the block, just ahead of the passenger-side cylinder head. There should be a number stamped on it, followed by a 2 or 3 letter code. The letters will tell the story, displacement, and year of manufacture, and usually what vehicle the engine originally came in. A diamond shape on top of a rectangle on the ends of the heads denotes a 58-CC high-compression head with relatively small valves, used on high-performance 265 engines in 56 and 57, and 283 engines from 57 through about 1965. With bigger valves, 1.94" intakes, and 1.6" exhausts, they will breathe pretty well, and make 11:1 compression on a 350 with flat-top pistons. I do that on "claimer" engines at the race track pretty often.
Jerry

All great info, thanks folks. At this point all I can do is try to find those numbers, which I haven't succeeded in doing due to poor light when I've had the chance to get out there, and the possibility that they've been scratched off. What Hotrod Lincoln said about the high compression heads makes some sense, because the engine has headers and true dual exhausts - maybe he did put a 305 in but tried to hot it up a bit to yank the weight of a bus around.

update: no luck on identifying the engine, but a set of points and 10 gallons of fresh gas have the mystery V-8 up and running. now if I only knew what the hell it was...

PS - I'm new to old ignition systems - how does one set the points? The bus is running well, but we didn't adjust anything, and someone told me incorrectly set points can burn out quickly

OK, does the distributor cap have a small metal "window" in it, with a sliding cover? If so, there's an adjusting screw that's accessible by sliding the cover up. You'll see a 1/8" Allen screw behind the cover. With the engine idling, turn the screw clockwise slowly until the engine misses or stalls, then turn it back counterclockwise exactly 1/2 turn. The "dwell" will be set to 30 degrees, exactly where it needs to be. Don't worry about point gap, the dwell setting is more accurate. Once the dewll is set, then the ignition timing can be adjusted. One degree of dwell change makes a 2 degree timing change, so adjust the dwell first.
Jerry