Tearing into the drivetrain has always been a favorite part of any rejuvenation project of ours. Many questions about your Chevelle will be answered once the drivetrain has been extracted, dissected, and audited. Of course, there's always a possibility that just as many questions might be raised as well. But, if you followed our advice from the last segment, you've already researched your Chevelle thoroughly, and know just what you're looking for to help authenticate it.
1. After draining and removing the radiator, we unbolted the front bumper as its frame attachments. Don't forget to unplug the parking lights connections, like we did.
2. Begin unbolting the front end with two bolts located on the front and top of the firewall, then remove two more at athe bottom, rear of the fender. Presoaking the with penetrating oil makes their removal much easier. Finally, remove the bolt located abouve each door hinge. Make note of the body shim stack-up and respective locations if you plan on reusing your original sheetmetal.
3. A single 5/16-headed bolt secures the front wiring harness to the bulkhead connector located behind and below the power brake booster. Once it's disconnected, you can remove the entire front end as a unit.
Matching numbers seems to be one of the most overworked and misunderstood terms in our hobby today. But what does "matching numbers" mean, anyway? To some, it may mean that the last six digits stamped on the block (and maybe even the transmission) match the last six digits of the car's Vehicle Identification Number (VIN). To others it may mean that although the engine is not the original, one from a similar application of the same year model has been installed, and all the correct casting numbers for the application are present.
Maybe we're a little too hard core, but to us, matching numbers means having the original block and transmission, with all the correct VIN and engine code stampings. It also means that the correct casting numbers for all major components are present, as are the proper date codes.
4. Our engine was disassembled and lying in the trunk when we bought the Chevelle. A dropped valve in #1 cylider will require a sleeve to repair, and some touchup in the combustion chamber. The block will clean up at .030 over, and the crank will go 10-10.
Date codes.....Now that's a sticky issue. Casting numbers, list numbers, ID numbers, they're all pretty much set in stone. But date codes have been the subject of more than one intense conversation amongst Chevelle enthusiasts. How long prior to the assembly date of the car should major components be dated? How close should casting dates be to the assembly date of the engine?
It seems most of the Chevelle cognoscente agree that dates should generally fall from two weeks to two months prior to the assembly date of the vehicle. There are exceptions. Plenty of them. For instance, we've seen a Chevelle with the original engine and an assembly date for it a full three months prior to the assembly date of the car. While some-what unusaual, such dating is not unheard of. Under no circumstance, however, should the casting or assembly dates fall susequent to the assembly date of the car.
5. Our block stamping indicates a September (09) twelfth (12) assembly date, with the CKO verifying the engine's 375hp status. Our block's casting number, 3869854, came with both 2- and4-bolt maincaps; it was used on 350 and 375hp versions of the 396. A casting date of H 30 9 translates to August 30, 1969.Vehicle Identification Numbers (VINs), too, have been known to stir up controversy on occasion.The most commonly discussed error seems to be VIN sequence numbers that are only one digit off, one way or the other. We've witnessed this phenomenom on "original-engined" cars, also, and can only attribute it to the fact that the numbers were hand stamped by humans, and as such, were subject to an occasional error. On other occasions, the VIN sequence has been known to be missing from one major component, even though it may be present on another (something we've experienced first-hand).
We have yet to see an example of a major component missing both the VIN and the assembly date (and codes, if applicable); at the very least the plant / assembly data seems to be always present.
6. Four-bolt main caps are shown here, along with the L78's steel crank. The wide parting line of a steel crank is noticeably different from the thin one found on cast cranks.
7. The L78 engine used "291" cylinder head castings as shown here. The words "HI_PERF" are also partially visible in this photo, and indicate rectangular-port heads. A casting date of 1 12 9 and 1 10 9 indicates September 10th and 12th, 1969, the same date as the engine was assembled. Since the block assembly and head casting dates are too close together, we suspect that it may have had some dealer head work done under warranty.
Our Chevelle's drivetrain teardown yielded some pleasant surprises. Virtually all the components were correct and original for the car, with the exception of the distributor, the starter, and a suspiciously early date on the water pump (it has the correct casting#, though). Also, the heads appear to have been swapped out at a fairly early date in the Chevelle's existence, and the VIN is missing from the normal location on the front, passenger side of the block. A close inspection failed to turn up any trace of the VIN above the oil filter location as well. It is, however, clearly visible on the side of the tranmission case. Go figure...
Finally, while we chose to remove the entire front end of our Chevelle, that decision was based more on the fact that the car was going to be fully disassembled anyway, than on our need to gain easy access to the engine compartment. Nevertheless, we'll share our tips for removing the front sheetmetal in one piece. We'll also show you casting number and date locations, as well as how to decipher them. So what are you waiting for? Let's get on with our drive-"training!"
8. This little "hump" on the end of a big-block head generally denotes the rectangular-port, high-performance variety. It's a lot easier than pulling the valve cover to confirm your suspicions.
9. Our Holley carb carries the correct list number, part number, and suffix. The 903 date code breaks down like this: 9=year, 1969; 0=10th month, October; 3=week of month, third. Likewise, the intake sported all the right 3963569 casting number and date.
10. We were really surprised to find the original altenator still in place. It, too, sports a pretty early date: 9=1969; F=June; 17= date. Note the deep groove pulley is still intact, and the low 37 amp rating is correct for non-optioned, high-horse Chevelles.
11. Our exhaust manifolds checked out, too. The casting numbers are the same for all big-block '70 SS applications, while our J 27 9 casting date breaks down to October 27, 1969.
12. Both the VIN and the assembly information were stamped on our transmission main case on the passenger side. It appears that two attempts were made to stamp the VIN into the trans case (maybe since it got two, the engine got none!), while the assembly data can be translated to: P = type, Muncie; 0 = year model, 1970; K = month, November; 25 = date, 25th; B = trans type, M-21 close ratio.
13. Finally, we checked out the main case (3925660) and tailshaft housing (3857584) casting numbers, and found them to be correct, too. The main case casting number is quite faint and not nearly as prominent as other "660" cases we've seen before. The bellhousing also bore the proper 3899621 casting number, and a 2nd week of September date code.
Electronic pages by AL
