Z-11 vs BBC
- Thread starter jim_ss409
- Start date
Pat....it would be obvious to me that the single four was for NASCAR. I heard somewhere, and I can't remember where, that 4 were made.
I knew I had one once so looked up the customer's log because I always list part numbers and casting dates on stuff like this. The intake I had was 0-217053 and was dated 5-53-62. That customer also bought a water pump....0-217949 & #3837691 dated 1-16-63. He also got an NOS Z-11 front backing plate, used original Z-11 rear backing plate and an NOS Z-11 balancer. And a Z-11 crankshaft. 2 months later he bought 3 sets of Z-11 rods and 3 weeks after that....pair of Z-11 heads and a Z-11 oil pan. I was probably out of Z-11 parts at that time!!!!! 14 years before that I sold him a pair of NOS Z-11 aluminum rear outer bumper braces.
Wished I could have kept everything....................
I knew I had one once so looked up the customer's log because I always list part numbers and casting dates on stuff like this. The intake I had was 0-217053 and was dated 5-53-62. That customer also bought a water pump....0-217949 & #3837691 dated 1-16-63. He also got an NOS Z-11 front backing plate, used original Z-11 rear backing plate and an NOS Z-11 balancer. And a Z-11 crankshaft. 2 months later he bought 3 sets of Z-11 rods and 3 weeks after that....pair of Z-11 heads and a Z-11 oil pan. I was probably out of Z-11 parts at that time!!!!! 14 years before that I sold him a pair of NOS Z-11 aluminum rear outer bumper braces.
Wished I could have kept everything....................
61 Bubble
Well Known Member
YES I know the felling sometimes. BUT not to the extent of this
TERRYVPWCSDC
New Member
Did any 1963 Z-11 427 Impala's end running in Nascar or other racing venue
There had to be at least 500 of that model produced to be legal back then or as many as one car for every make's dealership in the nation had to be sold to the general public to allow it to be raced.
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Well Robert, to tell you the truth, I usually just spread a little BS, but sometimes I have to do a internet search.
I remembered part of it but wanted to know for sure.
I remembered part of it but wanted to know for sure.
That wasn't the case yet in 1963,the 500 rule didn't come out until 65 amid the cammer ban and resulting Hemi argument both the 63 mystery motor and the 64 426 Hemi neither remotely came close to meeting the 500 rule.
Didn’t Mario Rossi build a 366” hemi to beat the ban requirements? I don’t recall the driver but it was the only one out there
Robert
The smaller cubic inch hemi's were later also and were to avoid a weight penalty,the hemi argument was double sided 1 the hemi heads and 2 the Mopar B body they were running it in was smaller and lighter than the full size C-body,Rossi may have been the first to run reduced displacement,but hardly the only,lots of 396" hemis were running for a while,Kellog started gaining their fame making destroker cranks for Hemis some with Mopar part numbers.The Hemi head required a higher weight per cubic inch per the rules than wedge heads.Even in late 66 when some Ford and Chevy teams started switching over to mid sized Fairlane and Chevelle bodies some ran 396" engines on short tracks for the weight breaks,Ford also had some Nascar parts listed for use building 396" engines.By late 67 the mid size cars were predominant and some rules were starting to be relaxed.During the 65-66-67 racing seasons France was furiously rewriting the rule books to the point that the ink wasn't dry on the old ones before a new one came out.There was even a short period where multi carb setups were again allowed on wedge head engines.I think the B-body Mopar wheelbase and track width wouldn't handle the weight they would have had to carry with a full size Hemi,otherwise you'd think they would have just carried the extra weight on the big tracks to use the big engine.
Back to the BBC vs. Z11 discussion,the reasons I had heard for the development of the mystery motor,was more around the perception that the quality of airflow into the cylinders of W engines at the stratospheric rpm's of the superspeedways was starting to become a liability and that the engineers felt they could do better with the conventional chamber with the multi angle valve placement that became the porcupine headed mystery motor and later mark 4,while the W design seemed to do fine for short blasts at the dragstrip on the superspeedways extended high rpms they seemed to believe that power would start to fall off,in those days when drafting was beginning to become the norm on the superspeedways,the pull out and pass maneuver just didn't seem to be there for the W and for whatever reason the engineers felt that was due to the head design.While I've never seen or heard of any specific cause for it,the fact that the mystery motor didn't seem to have any trouble with that tactic would seem to imply that they were on to something.Once the superiority of the mystery motor on the speedways was shown it was inevitable that Chevrolet would continue with a design that would be successful in all forms of racing versus build 2 different designs.
The air flow on the mystery head was way superior to any BBC GM ever made. They were foolish not to run with it.
It wasn't until Dart came out with one of their big heads that anyone had a better head.
I don’t know what the numbers were but I thought I remembered reading that the Z11 head flowed just as well as the mark big block Chevy ......... there were all kinds of articles written stating that the W motor didn’t respond to cam changes and compression changes like the typical small block or like the mark motors would
The Z-11 heads did flow well and would have been comparable to the mystery motor , but the square cornered intake was a big drawback to its horsepower potential, great for breaking up fuel droplets but terrible for flow. The mystery motor had smooth rounded corners for much better flow. The other area of power loss of the W design was the large crevice volume , or area between piston and cylinder wall above the top ring. This is still the biggest area of loss today with these engines. A very high compression dome makes this crevice volume , which traps spent combustion gasses and prevents that area from filling with a fresh air-fuel charge on the next intake stroke, even worse .
One of the main reasons for the two different "Rat" and "Porcupine" heads was that the "Poky" heads were meant to be used on a specific side[l.side on l.side ,right on right side only.Smokey was upset with Chev. for changing it,but it was a cost saving measure.Darned "Bean Counters"!
Greg Reimer
Well Known Member
At Super Chevy Sunday in the fall of 1983, the last one for Orange County International Raceway, and the day I got my '63 to run an 11.91, the Chevy Performance trailer had some displays, one of which contained an original Daytona Mystery Engine, and it was conspicuous in that it had large round exhaust ports. Definitely different than the later 396. That was probably only one of many unseen differences that added up to a big difference.
