Mystery Motor

busterrm

solid fixture here in the forum
Hey Grumpy, Do you remember when I asked you about the Chevy Big Block Mystery Motor? The guy I told you about confirmed it was actually a MK II 427. He asked me tell you to thanks for the info!
He spent some money doing it! He had to have some custom parts made to get it done! The pistons, rods and crank were all usable. The bores were still in good shape, a good hone and a set of .002 oversized rings, mains/rod journals were ground .010 on the crank. Pistons were cleaned and checked fir flaws. I don’t remember what roller cam he used, but he had to have one of the cam journals machined for oil flow. I want to say it was the rear journal. He called Brodix and had to have the heads custom made because the bolt pattern was different on the MK II! They had to retool and change the casting to allow for new bolt pattern. But he had them use the basics of their 294 cfm 113 cc Race Rite rectangular port head. He ended up paying 600 dollars extra a head, so they ended up costing him about 3200 bux for the 2 heads. He said the cam duration is 246I/254E , lift in the mid 600, don’t remember the LSA or LCA! He used 1.65 rockers! The intake is a single plane with 850 double pumper Holley carb! He built his own headers and exhaust! He is retired, so he has plenty of time. It’s in a 68 Camaro with a T56 manual tyranny and 373 rear gear!
We went for a ride and he scared the shit outta me!
 

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
Im glad I could help a bit and thank you for getting back with that info!
 

busterrm

solid fixture here in the forum
It is not really street friendly, below 2500 rpms it’s not much, but once you hit 3000 rpms it’s like a bullet. It’s as if you hit a button for Nitrous Oxide! It pulls real hard up to about 7200 - 7300! It literally scared the pee outta me! When he shut it down, I told him to pull over cuz I was about too pee my pants!
 

busterrm

solid fixture here in the forum
Im glad I could help a bit and thank you for getting back with that info!
I think what really helped most was the fact that the bolt pattern on the MK II block for the heads is not like the MK IV blocks. He said that stopped him from buying the wrong heads, he would have had to buy a second set of heads! That would have been about a 2000 dollar mistake! He said he had to use a set if rockers from another engine make to get the 1.65 ratio for the MK II ratio. I’m not sure what aftermarket brand he used! He had a list of things that were custom made also! All together he has well over 20K in just the engine bay, the tranny was already there from the former BBC in the car previously! I wish I had known I was going to see it already done, didn’t have my phone, so I don’t have any pics!
 
Top