[andrewcanada]

I've got this '77 long wheelbase dump truck, GMC 6500 that had a 366 when new (as indicated on build slip). Now it has a GM Goodwrench with a tag on the drivers side of the block, with serial # 123 39197. Or maybe that was the model or series #. OOps, it was cold yesterday (10f) How can one identify one BB from the other? It also has a square bore Holley, 5 speed Clark, 2 speed axle

 

[wfd44]

12339197 is a GM part number not a serial number. I searched a couple of GM and dealer sites and it is a Goodwrench replacement 366.

Hope this helps:shades

 

[andrewcanada]

Oh well, I was hoping it was a 427/390. Thanks for the effort. Is there any difference from a 396/402. Except for the bigger water pump and intake, could one use it like a passenger BB? Or are there bolt placement differences ( or something) on the "truck" blocks in general?

 

[Alan]

The truck blocks are something like .4" higher from crank centerline to top of the cylinder bores (deck height). I think that is to accomodate a third compression ring. That moves the heads further apart so that manifolds for regular big blocks won't fit.

As far as I know, the truck blocks were only in 366 and 427 versions. The 427 is a pretty good powerplant but I've heard that the 366 isn't much more than a 350 for power.

 

[andrewcanada]

Simple enough, I could just measure accross the intake. I think I read that the 454 was never available in the medium trucks. That explains that. Thanks...

 

[wfd44]

The 366 will run about the same HP as a 350 but with more torque (due to a longer stroke). All 366's are "tall deck" truck blocks and cosequently use a wider intake manifold. 427's were built in both short and tall deck versions. I am not sure if there is a difference in the number of compression rings or not (but it sound reasonable). The deck of the block is thicker (read more stable) and therefore should reatain head gaskets better.

Later in the previous generation of GM mediums the 427 was replaced with the 454. I am not sure if the 454 for mediums is a tall deck motor but I would assume it to be so.

 

[Alan]

I've never seen 454 flags on any medium GM truck, all I've seen is 427 and (I think ) 366 although I can't specificly remember if they marked those or not. While the 427 was made in both short and tall blocks I don't think the short block was ever used in anything beyond the 30/35 series.

 

[wfd44]

Alan, you are correct. Tall deck big blocks were exclusively used in medium duty (and larger) trucks. All 366's are tall deck. 427's were never available in a light truck but were certainly famous in Corvettes, Impalas and special order muscle cars of the mid-late '60's. Therefore 427's were built in both tall and short deck versions. 396's and 402's were only built for passenger car an light truck and only in short deck hight. 454's were for the longest time also passenger and light truck only but were offered as in mediums (presumably with the taller deck) around the 1999-2002 era bfore the change over to the new style which uses the 8100. The only GM mediums I recall seeing with external identification of the engine were 67-72's with the 366 or 427. These had the faxe louvers in the side of the hood with the engine designation set inside the louver. Kind of a muscle car identifier for big trucks.

 

[Alan]

Early to mid-60s there was a 409 offered in medium (60 & 70 series) trucks. I have no idea if that differed from the car engine or not.

The Schwann's Ice Cream folsk are running a whole fleet of propane powered 366s that are probably in the 98-02/3 age range.

There's a guy a few miles from here running a 6 yd dump on a C60 chassis in the 68-72 body style. That has the louvers you're talking about with the 427 badge on it. The drivers side louver was functional, there's an air duct leading to the carb with a big foam seal to match up to the louvered opening.

I just dug out my 1970 GM truck shop manual and got he following specs.

350, 4 bbl, 255 hp, 355 ft lbs torque, available only in 10-20-30 series

350. 2 bbl, 215 ho, 335 ft lbs torque, available in the 40 and 50 series

366, 4 bbl, 235 hp, 345 ft lbs torque, available in the 60 series

427, 4bbl, 260 hp, 405 ft lbs torque, available in the 60 series

There was a 400 used in the 10-30 series, 310 hp and 400 torque, and three diesels, a 3-53N in PT30 (probably a bread van style) which made a whopping 82 hp and 193 lbs torque, a 4-53n in the CD50, making 130 hp and 278 torque and a V-6, DH478 with 165 and 337 for output.

My 1971 C5500 came with the 350, 2 bbl version which I swapped to an Edelbrock Performer intake and 600 Holley. That makes a very driveable powerplant for a truck grossing 20-22K. Transmission is an SM465 with a two speed rear having (if I remember right) 6.62 & 8.85 high and low ranges respectively.

 

[The Boss]

I've got a Chevy 396 block dated 1972 for sale if anyone is interested.

 

[andrewcanada]

Oh Baby, you guys are great!

That's the kind of help I needed. I've got tons of manuals and magazines from the late '40's through '80's, and I quess I could have looked up those specs. in one of my GM manuals. But it's easier and more comfortable to sit in my warm house than reminice in the barn. Way back in 1978 I was living in Montreal and had a 1967 Pontiac 2+2 convertible. It was of course a Canadian built model, so it had a 283 powerglide. Instead of stealing a missing hubcap off of another similar car, my best friend bought it, and we cruised the summer of 1978 away. That was until he blew the 283, and we found a 409 dumped in a 1957 Chev 2 door wagon. No, it wasn't a Nomad. Well, it's a long, long, long, long story, but we eventually got that 409 running in his 2+2. Remember that we lived in the rust belt, so both of these cars were very rusty. As of 5 or so years ago, he still had the 2+2, but the very expensively rebuilt 409 had long blown up, and a 327 was in its place. I barely looked at my 2+2 until last year, when I got fed up moving it from garage to rented garage. After 25 years, I sold it for under $1000. It still had the original 283 with a TH350 I had installed in a freezing garage, 3.36 12 bolt Chev. posi. But long gone was the Edelbrock 6 pack I had installed the first summer my father gave it to me as an 18th birthday present. But I still have the '66 Skylark GS conv. that kind'a replaced it. But that's another long, long, long, story. And then there's the '66 Toronado..... www.caddyedge.com/CadForums/index.php?showtopic=1796 Scroll down to DON'T DRIVE MY CADDY! And I've got tons of clear pictures..... I'll post them one day....... Andrew:canada

 

[Z71]

Is there any difference from a 396/402

Only different is CID, no HP increase. The 396 was overbored to make it a 402 just because they could.

Prior to 1970 it was a GM corporate policy that no A-Body car (Chevelle, GTO etc) was to have an engine larger than 400 cid as a regular production option (RPO). Those engines above 400 cid were reserved for the big cars and Corvette. Thus the 396 was born in 1965 to stay under the 400 cid limit.

The 427 Yenko and Camaro were dealer inspired COPO cars and not RPO cars. COPO was the term refereed to as Central Office Production Order that had to be authorized by the Fleet and Special Order Dept. These COPO had to be specially priced and programmed for parts content.

But in late 1969 model GM because of what its competitors were doing dropped the 400 limit and the SS 454 Chevelle as well as the 402. The 396 was raised to 402 but because of the name recognition of the 396, then continued to market it as the SS 396 when in fact the engine was a 402. So any 396 made from 1970 on is really a 402.