Re: [AMC-list] 360 build

[Frank Swygert <farna@xxxxxxxxxxx>]

Date: Mon, 17 Dec 2012 02:31:08 -0800 (PST)
From: Jack Dale<mercendarian@xxxxxxxxx>

(edited)
1) AMC HAD some 4-bolt main blocks, 360s for racing from group 19, but why not machine some up(--4-bolts) and tap & die holes to slap them on, if it's a two bolt?? ?I LIKE that they "fixed" the main bearing weakness, with the block-off piece in the left gallery).?? I had to drop thousands on a rebuild, because AMC shot themselves in the foot by NOT fixing that problem after hundreds, maybe thousands, of warranty replacement-engines.

2) WHY hasn't someone done an alloy block(-DESPERATELY NEEDED if you have any of their AMC-sixes because they were too heavy compared to other engines).? Once the Chevy small block appeared, even the Jimmies(292cu) were doomed, unless they had boost because the 235cu Chevy(--the "Blue-flame" base)?OUTWEIGHED the 265/283 V-8s?by more than 60lbs.? Without an alloy-inliner, the best thing for a sixer-jeep is a Buick 215cu V-8 @ 200lbs less(--they STILL put them in Rovers).? They(AMC) even SHOULD have gotten-back the odd-fire Buick V-6 and even-fired it like Buick later did for its Grand Nationals and others.

3) I LOVED the Pacer on intro(1975--though a mistake to shut-down the Javelin to make the Pacer, when Brampton could have expanded production), but knew it was a looming failure due to the heavy boat-anchor 6 they shoved in it.?? A V-6 would have made more sense, after the wankle was abandoned {--although obviously AMC management was "On drugs" to have even Thought of a wankle, because they'll put out a lot of horsepower if raced, but Mazda just dropped its RX-8, because, even 30 years later, wankles SUCK gas on a streeter.

=======================================

Jack you made some good points, but some of your opinions need some clarifying... those are what I'm commenting on.

1) AMC didn't make a four bolt main block. They did sell a four bolt main cap from an aftermarket supplier that could be installed. The 360 Service Replacement (SR) blocks were standard parts, I don't recall if they were Group 19, but I don't think so. It was done that way to circumvent homologation rules for Trans-Am and other types of racing. Since it was a standard part it didn't have to be used in a certain number of cars to qualify for racing use. It's a 401 casting number block and is identical to the 401 EXCEPT for the 360 bore (thick cylinder walls) and reportedly a thicker deck. It could be machined to replace any 66+ Gen2 or Gen3 AMC V-8. The webs are thick enough for a four bolt main with four bolts the same size. There are four bolt main caps made for the 360 block (or there used to be), but the two extra bolts are smaller -- 3/8" IIRC.

2) Pre 64 sixes (such as the old Chevys) are heavier than later ones because casting technology didn't allow a thin casting prior to 63-64. The older V-8s are heavy as well, even the first SBCs are heavier than later ones. There's not a lot of difference between a modern I-6 and V-8 because there's not a great deal more metal in a V-8. There's usually less than 100 pounds difference. The AMC six could have been a little lighter, but it wouldn't have been as tough. It doesn't really have to have seven mains, four would have been plenty for a typical street car. An alloy block would be nice, but it's not necessary, and would cost a lot more. Not so much now, but there are differences in an FE and AL block, so would have taken some time and cost for development. The I-6 engine is built using a different philosophy than V engines. It's a low speed torque motor, IMHO better for street cars and Jeeps, not so good for high performance. Grocery getters pay the bills!

AMC sold the V-6 simply because it wasn't "better" than the excellent AMC I-6 they were already producing. The only thing it had going for it was the short packaging. Again, performance wise it would have been better, grocery getter it's not. Packaging is why everyone has gone to the V-6 design -- short fore and aft and not so tall. It's hard to put a long tall engine under the hood of a sleek car. Not impossible -- move it back like AMC did in the Pacer or lean it over like Chrysler did, or both. But it's easier to stick a V-6 in. Back in the 70s packaging wasn't a problem for years to come, and AMC needed to recover some of the cost of buying Jeep, so they sold the V-6 back. Besides, they could have made their own V-6 from the V-8 and shared some parts, making it cheaper to produce than the Buick design.

3) The Pacer was only marginally better with the 304 V-8 than the six. The six wasn't as much of a handicap for the Pacer as most think, the heavy weight hurt it most. You could overcome the weight with a larger engine, but then gas mileage goes down even further. The Pacer hit about the same time as fuel shortages and skyrocketing fuel prices. It wasn't designed for great fuel efficiency, that wasn't too big a consideration until it came out at just the wrong time.

The Wankel engine isn't any more efficient than a piston engine of similar power. It never has been as far as a street car version is concerned. It does rev up quickly and can turn a lot more rpm due to the design, so race versions are a different story. They rev real high and put out more power than a cubic inch equivalent piston engine, but they suck gas due to the high rpm as well.

The big advantages of the Wankel are compact size and lighter weight than an equivalent power piston engine and fewer moving parts. Fewer moving parts = cheaper to build.

AMC had a license to build Wankels, but couldn't afford to tool up for the engine and a new car for it. GM agreed to sell AMC engines at least for a few years to make it more attractive for the GM production line -- more engines = less per engine cost.

GM also determined that the only way to really capitalize on the Wankel design was to build a car around it. No point in spending the money for the compact engine just to stick it in an engine bay made for a big V-8. AMC designed a car around the Wankel then had to make it use a conventional engine.
The Wankel isn't a clean engine though, and GM had trouble figuring out how to clean the exhaust up. Mazda figured it out, GM dropped it.

Mazda is dropping the rotary because it's just too different for most people for them to sell a lot of them. Nothing wrong with it, but people in general prefer something familiar. Even with today's more tech savvy consumer, Mazda would have a hard time selling cars if all were rotary. Most just don't like something that's way different than everything else, especially if they can't see a big difference in the end results.

--
Frank Swygert
Editor - American Motors Cars Magazine
www.amc-mag.com


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