As for other differences, the oiling system is the most significant. In the ZL1 they moved the main oil galley up from the pan rail to adjacent the camshaft tunnel. This design was supposedly created by none other than Bill "Grumpy" Jenkins. It gave priority oiling to the mains, and it worked out so well that GM incorporated the design into the Gen V-and-later big-blocks. Another thing we found is that they installed a stainless steel shim between the stock chain-drive cam sprocket and the thrust face of the aluminum block. Otherwise, the aluminum gear riding against the aluminum block would cause disastrous galling. Remember, they ran nylon camshaft gears in these engines from the factory!
Unless you were running a class where weight was doubly important, there wasn't much difference between the two engines. It cost you about $3,000 in '69 to option up from the $1,000 L88 to the ZL1 and save 150 pounds. Most of the good features were found in the slightly heavier L88.
OptisplatQ My '95 Z28 has a misfire. I used an ignition tester and found out all the plugs are getting fire except the No. 7 cylinder. The car has 129,000 miles on it and runs fine if you look beyond the stumble at idle and while accelerating. I'm guessing it's the OptiSpark, but I don't want to change it. I'd rather switch to the Delteq setup, but I don't know if I have a healthy optical sensor. I'd really hate to buy the Delteq kit and still have to buy a new OptiSpark. Could it be the cap and rotor?Michael MillwoodVia e-mail
A I was bitten by the OptiSpark bug with my LT4-equipped '65 El Camino, when I didn't install the manifold vacuum to the OptiSpark distributor. A thunderstorm ensued and left a growth of corrosion that killed several cylinders. Is your problem the OptiSpark? Did you check the No. 7 plug wire to see if it was open?
The Delteq Opti-Direct Solution you refer to is a really nice upgrade from the standard OptiSpark system. It utilizes Cadillac Northstar coil packs to give you a true coilover plug system. Not only does this get you away from the OptiSpark cap and rotor, but you gain spark energy by increased dwell time to saturate the coils. You didn't state if you were having any OptiSpark trouble codes. With the engine running fine on all the other cylinders we would agree with you that it should be your cap and rotor, and the Delteq system would take care of the problem. The kit comes complete with Delphi coil packs and modules, custom-length 8mm plug wires, mounting brackets and hardware, plug-and-play wiring harnesses, and complete conversion instructions.
Oval UpQ I have a Mark V block that was a propane-running 427 tall-deck. I have had the block sonic-tested and it came out clean as a whistle. I've had it bored 0.040 inch and plan to stroke it to 4.25 inches, with 6.535-inch H-beam rods and Keith Black Hypereutectic pistons. I'm thinking about running Edelbrock 454-O aluminum heads and want to use a dual-plane manifold that will fit on big oval-port heads. Is there anybody out there making a dual-plane manifold for a tall-deck that fits on the big oval-port heads without running spacers? Could you tell me anything about tall-decks, things to look for and remember when building one? I've done a lot of research on this thing, but any recommendations would be appreciated.Ryan SchepisVia e-mail
A As you know, the real luxury of building a tall-deck is being able to stroke it and keep a decent rod length. Also, with the stroker and the long-rod piston, interference isn't an issue. Everything about a tall-deck is relatively the same as a short-deck. The main difference is that the heads are going to be 0.400 taller in relation to pushrod length and header fitment. Let's go hunting for a manifold.