OK... AMC V8 Service Replacement Block

[Karvin]

I only know a bit about these blocks... trying to find out some more info.

Short story: I went to look at a 77 Cherokee Chief, I was told it was a "stock" motor only because the current owner doesn't know the details. The engine was replaced with a factory service block in the early 90's... not a crate motor, not a re-manufactured motor, but a service replacement block.

After about an hour of fiddling around with bad connections at the starter solenoid it fired right up. This engine has the best throttle response I have ever heard, so I did some looking online and found the small mention about service replacement blocks used in Javelin's for Stock and TransAm racing.

What else do you guys know about these engines?

Links to reputable websites?

[joe]

A factory replacement block will not have the 360 CID cast into it at the motor mount areas. It won't have zip there just plain cast finish.

[Karvin]

Right, I am aware now that I am an hour and a half south of the vehicle to check the displacement casting by the motor mount.

I also know that there were pre-built warranty blocks in the various V8 flavors... I am kind of wondering if there is some performance difference that should be expected, or more likely: if it just depends on how that particular service replacement block was put together. Overall it is far more powerful than other FSJ's with 360's I have test driven... far more than I would expect from even a mildly built 360. I have never driven a 401, however with the larger pistons etc I would expect a slower throttle response. By throttle response I mean throttling up and throttling down, very crisp and powerful on the way up and back to idle quickly. By the lope of the motor it is fairly apparent that there is at least a cam hiding in there... RV or more aggressive.

I find myself wishing I would have ensured the SD card in the camera were empty when I went up and put a deposit on it. I will upload a pic of it that was sent to me by the seller... you never know, somebody might recognize it.

[Karvin]

Stock blocks are painted Teal? Warranty and Service Replacement blocks are red? Pretty sure this one was painted black... it was a long day though and a long drive with the Toyo MT's humming for quite some time.

[Ghinmi]

A service replacement block is basically just a 401 block that hasn't been bored out to 401 size. Dealers could use it for 360 or 401 applications with a little machine work. They're desirable for VERY high performance applications because they are a 401 with the bore of a 360, so very thick walls and the beefy 401 main webbing. Once they have been bored to 401 size they are just another 401 block. The service replacement block has no performance advantage over a normal 360. The only application where it has an advantage is an extreme all-out race engine where every bit of cylinder wall strength counts. That being said, I wouldn't worry about what it actually is. If it runs good that's all that matters. Nice Cherokee by the way!

[Carnuck]

Actually, they are a 401 with 304 bore. (so sez my AMC rep.)

[Ghinmi]

Nope, the service replacement blocks came with a 4.08 (360) bore. I forgot to add that they can also be decked to be correct for a 343 or a '68-'69 390.

[SC/397]

Not to burst anyone's bubble but I bought a 360 service block a few years ago and that is exactly what it is. It is a 360 block with the 360 embossment on the side of it. Absolutely nothing special other the little aluminum tag wired to it with no numbers on it what so ever.

[Karvin]

There were indeed service replacement blocks in all the amc flavors, however there were also some that were not setup as direct replacements for pre-bored sizes.

I am not claiming to have anything special, and in fact I pretty much doubt that it is some ghost factory race block. What I do know is that it out-performs the other AMC 360's I HAVE driven, and has better throttle response as well... to include a nicely built SBC 400.

The block is painted black, not teal or red, and while I was looking at the rig I did not check for the displacement stamp like I should have. I will be buying this rig and have already put a deposit on it, should be parked at my house next weekend.

Maybe it is simply a nicely built 360, but at this point I just don't know.

[mrtazwrench]

Originally Posted by SC/397

Not to burst anyone's bubble but I bought a 360 service block a few years ago and that is exactly what it is. It is a 360 block with the 360 embossment on the side of it. Absolutely nothing special other the little aluminum tag wired to it with no numbers on it what so ever.

Not sure if it's the same, but I'm pulling the engine in what's left of my Dad's 78 J20, it had a new short block from the dealer at one point in it's life, still have the OE one on the shop floor, it too is stamped 360.

[jeepsr4ever]

There were a couple flavors of replacement blocks. Not all were thick webb'ed no name blocks with small bores. Some were just 360 or 5.9 embossed blocks...some were 304 as well. The old rumors about the stellar factory service block are true but they certainly werent a replacement for all blocks 72-91.

[mdill]

What he said, the Trans-Am block was sold with a factory replacement part # and could be ordered, but I don't think many if any were sold into as stock replacement/warrenty blocks, pretty sure the Trans-Am block was sold as a bare block, with machining assembly needed to build an engine. (not a good way to make money for a dealer vs. slapping a assembled factory long block (all non Trans-Am casting as far as I have heard) service replacement in the hole. )

Originally Posted by jeepsr4ever

There were a couple flavors of replacement blocks. Not all were thick webb'ed no name blocks with small bores. Some were just 360 or 5.9 embossed blocks...some were 304 as well. The old rumors about the stellar factory service block are true but they certainly werent a replacement for all blocks 72-91.

[Ghinmi]

My kingdom for a "no displacement cast" thick web block that can be bored 4.125. Well, I don't have a kingdom but I'd trade a virgin 401 core for one.

[twisted frame]

Did the seller know anything about the carb and cam in the engine? Great throttle response sounds like the carb is set up right with a snappy cam, pointing to your mention of how it was built.

[SC/397]

Wanna see something cool.... This a official "AMC Race Block"!! it is the last one that Wally Booth had.



Check out how thick the webbing is on that bad boy compared to a stock 401..