I like big displacement engines and the torque they provide. I got to thinking about the increasing engine sizes and the troubles that came with them by doing so (I'm talking factory engines here folks). For example: the 392 Chrysler that grew from 331. In theory the 392 was great (and is), but the head cfm flow was a problem. Example 2: the SBC grew from 265 (although 262 was made later) to 400, but with that, it had siameased cylinders (some say heating problems) and the connecting rod ratio went all to hell. Don't get me wrong as there was nothing wrong with these engines, but it just points out that in thier factory form, they had their drawbacks. What other engine problems were there in the other makes - 303 Olds becoming 394, Buick 264 to 425, Cadillac 331 to 390 Etc....
Buick 401 nailhead I had was a monster! Well behaved, smooth, great driver until you got on the loud pedal, then all hell broke loose. 450 ft lbs @ 2800 rpm. Had a 428 Pontiac that was a absolute pleasure in a big old daily driver. Stomp on that a little too hard and it liked to bend cyl #8 push rods. Just got my 307 Chevy fired up. 283 bore and a 327 stroke. It really runs nice- sounds very healthy with 10.5:1 compression and a 262 cam. Had a 74 cubic inch Harley that went out to 93 cubic inches - fun bike to ride but couldn't keep it on the road for more than 2 weeks in a row. Something always screwing up or falling off. Took it back down to 88 and that was not as much fun but I worked on it a whole lot less so maybe it was more fun ? Have a 88 cubic inch harley that went out to 95. Much better bike at 95. No trouble at all. Unlike the 93 inch above. Have a 96 cubic inch Harley that went out to 103. Prefer the 95 but still not much trouble, the 95 has better manners. My hemi is a 354 that went out to 421 and a 671 blower. Can't wait to find out
I think you guys are missing what I'm asking. I'm not really asking about the performance increase. I want to know what the downfalls of the factory enlarging the engines internal sizes were. (rod ratios, short pistons that slapped, thin weak cylinders etc)
I realize that they are different internally in alot of ways, but the 400 shares the same block dimensions externally as the 265 that the SBC started as. I am speaking here of the 400 SBC.
I don't know the answer why, but for some reason stock 350's and 400 sbc's don't get near as good of mpg as the smaller motors. Even a 305 with Edelbrock intake, 600 cfm carb and an RV style cam out performs a stock 350. And the 305 is only .250 of an inch smaller per cylinder and same stroke as the 350.
Well, in your example there is not a lot of merit. The 392 went to a larger block (deck height) and heads with larger ports. Of course, they also used more or bigger carbs too.
When the Olds went from303 to 394 the deck height changed plus other changes so its not like they tried to cram a larger motor in the original package,when the size is increased there are more changes that are not easily seen.
You need to fill that bore with more fuel than a 305, 307, 283. Then in stock form the compression is so low that the engine doesn't make the most out of that fuel. In an abstract way of thinking, you are basically dragging 45 cubic inches of dead weight you have to feed. Drop the dead weight alone and up the mpg goes, quit feeding it along with lightenig the load and now it really goes up. That's stock form. Start changing things and that's all different.
I'm not sure if Pontiac is the only one But 326 to 455 is the same basic package, not really any problems. There's a bunch in there too. 326, 350, 389, 400, 421, 428, 455..the earlier Pontiacs are only slightly different but these are in identical packages. 331 & 354 are the same 392 is very different. New chevys the 4.8, 5.3, 5.7, 6.0 are identical. The 5.3 responds better than the others and its cheap to get up to stock 6.0 power levels and runs better than a 6.0.
Problems, problems. Burns up rear tires like crazy...lifts the front tires off the ground... I know what you're alluding to, BB. But there are ways of dealing with most of it. Besides...I'm too tired to ponder this. I wanna see some pretty pictures instead.
FE Ford. 352 went to 390 then 406 then 427 and 428. Also had 360 truck variant. Even the 427 SOHC was based on the same basic block.
following your logic the 455 Pontiac should be a piece of crap versus the 287 it started from. All pontiacs 55 to 79 (except smogger 301) share the exact same architecture. fortunately, most powertrain engineers seem to be cognizant that larger displacement needs a different airflow demand, bigger bores need the casting walls moved out, camshaft profiles need to be changed, etc. Very few problems are created by boring a cylinder a little larger.
It's not traditional, but I've always been a fan of the Ford 460. It started out as a 460. Lot's of room to grow.
Wasn't the 303 Olds always intended to be grown larger? I know they did some changes to the block, but I thought that Olds always inteded to push the limits with compression ratios and such, without having to completely redo the motor...wasn't the aim for 12:1 or higher comp ratios in the plans for that? I could be completely making stuff up here...
I guess nobody sees the troubles within ? At least haven't listed any yet. The factories have so much at there disposal, its rare for them to build things that don't at least last the warranty period. When they do, Its corrected in short order. The guys who push stuff beyond that experience the troubles.
The 429 and 460 were introduced at the same time. 460 in Lincolns, 429 in Fords and Mercs. Looking at the architecture, the 429 has a rather short stroke, long rods, and long pistons for the displacement. The bore/stroke and rod/stroke ratio's of the 460 are nearly the same as a 302. It's pretty much a 302 with Cleveland heads, scaled to 50% more volume.
In 1955 Pontiac started out with a 287 cu in V/8. It eventually grew to 455 cu in and some guys will bore those out to 468. The block never changed in deck height, cam tunnel height or bore centers so that's about as big as it's gonna go without seriously weakening the block. There have been problems with the block in the lifter bore areas but it's not because they made the engine bigger...it's just a weakness that could have been corrected starting with the old 287s and should have. With the old 287s bore centers, the 455s bore is about all the block can handle so Pontiac got it's cubic inches with a loooooooooong stroke. Means you can't rev the engine like a sbc because of piston speed at those rpms...it's gonna break rods, pistons and/or cranks but if kept at 5000 or less RPMs they'll absolutely boil the tires. 455 Buicks have a huge bore/semi-short stroke that have their torque up a little higher in the RPM band...keeps the piston speed down to a manageable level and they really crank! I love those old 455 Buicks and they tend to stay together better than the Olds/Pontiacs.
I've been hoping for some time that an "insider" from the car companies would educate us on the changes in foundry practices that allowed these big displacement changes. The Ford Y Block went from 239 cubic inches to 312 in a very short period of time. Even that didn't reduce engine weight enough so the developed the 221/260/289/302/351/400 family less than 8 years after the Y block was introduced. So what permitted those thinwall castings? Better metallurgy? Improved core making equipment? Chuck Schultz Winfield, Illinois
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