I thought I'd put this in the Z-11 section because that was the final, and most powerful version of the W motor.
It seems to be an accepted fact that the BBC was a much better design than the W motor but I've often wondered just how much better it really was.
The 427 ci Z-11 was rated at 430 hp but most sources state that it actually made somewhere between 475 and 500 hp. That's in the ballpark of engines like the ZL1 and LS6, they were also underrated at 430 &450 hp But I gather their actual output was in the 500 hp range or maybe a little more.
The Z-11 did have two 4 barrel carbs but it was really hampered by a terrible intake manifold with harsh 90 degree bends. The BBC's on the other hand had very nice intake manifolds. I think the ZL1 had an 850 cfm Holley carb and the LS6 had a 780 Holley.
Here's a picture of a rare single quad Z-11 intake...
Here's a L88/Zl1 intake. It has nice sweeping bends...
I'm no expert but I think a better manifold like this might have pulled the Z-11's horsepower up about 20 horsepower or more.
Another well accepted fact is that the BBC had a much better combustion chamber. Well if that's true why did they often need as much as 42 degrees of ignition timing where a W motor seldom needs more than 36 degrees?
I know some of the modern BBC heads out there have much improved combustion chambers but the factory stuff just wasn't that great. I could also add that the W motor is also less detonation prone.
Check out the size of the dome needed on this ZL1 piston, this doesn't make for good flame travel.
Another legitimate knock on the W motor is that the pistons are heavy but if you look at the BBC piston above you can see it's no lightweight either.
It's also true that the W motor's pistons get more and more lopsided when you start to raise the compression but there was an easy fix for that, much easier than designing an entire new engine.
Take a look at the pistons in this 348 engine cross section picture. They aren't lopsided at all, they're gabled like a roof.
The pistons only get really lopsided when you try to raise the compression ratio.
Here's an extreme example of a high compression piston.
The original design of the W motor didn't have a lopsided piston at all, it only got that way once they started pushing up the compression.
This may sound like blasphemy but when they changed over from the 348 to the 409 they probably should have changed the deck angle. Yes, it would have required changes to the machining process but it would have been a lot easier than building an entirely new engine.
I would concede that overall the BBC is probably an improvement over the W motor but I don't think the difference is nearly as big as most people think, especially if you compare the Z-11.
I'd love to hear some opinions on the whole BBC versus W Motor debate.
It seems to be an accepted fact that the BBC was a much better design than the W motor but I've often wondered just how much better it really was.
The 427 ci Z-11 was rated at 430 hp but most sources state that it actually made somewhere between 475 and 500 hp. That's in the ballpark of engines like the ZL1 and LS6, they were also underrated at 430 &450 hp But I gather their actual output was in the 500 hp range or maybe a little more.
The Z-11 did have two 4 barrel carbs but it was really hampered by a terrible intake manifold with harsh 90 degree bends. The BBC's on the other hand had very nice intake manifolds. I think the ZL1 had an 850 cfm Holley carb and the LS6 had a 780 Holley.
Here's a picture of a rare single quad Z-11 intake...
Here's a L88/Zl1 intake. It has nice sweeping bends...
I'm no expert but I think a better manifold like this might have pulled the Z-11's horsepower up about 20 horsepower or more.
Another well accepted fact is that the BBC had a much better combustion chamber. Well if that's true why did they often need as much as 42 degrees of ignition timing where a W motor seldom needs more than 36 degrees?
I know some of the modern BBC heads out there have much improved combustion chambers but the factory stuff just wasn't that great. I could also add that the W motor is also less detonation prone.
Check out the size of the dome needed on this ZL1 piston, this doesn't make for good flame travel.
Another legitimate knock on the W motor is that the pistons are heavy but if you look at the BBC piston above you can see it's no lightweight either.
It's also true that the W motor's pistons get more and more lopsided when you start to raise the compression but there was an easy fix for that, much easier than designing an entire new engine.
Take a look at the pistons in this 348 engine cross section picture. They aren't lopsided at all, they're gabled like a roof.
The pistons only get really lopsided when you try to raise the compression ratio.
Here's an extreme example of a high compression piston.
The original design of the W motor didn't have a lopsided piston at all, it only got that way once they started pushing up the compression.
This may sound like blasphemy but when they changed over from the 348 to the 409 they probably should have changed the deck angle. Yes, it would have required changes to the machining process but it would have been a lot easier than building an entirely new engine.
I would concede that overall the BBC is probably an improvement over the W motor but I don't think the difference is nearly as big as most people think, especially if you compare the Z-11.
I'd love to hear some opinions on the whole BBC versus W Motor debate.
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