All - I'm heading Wednesday to look at a barn find of a 1970 W30 442 Convertible that i've already been able to view the car window sticker. Based on that alone, it's legit and I realize what I'm going to see. I'm a huge vette nut and know this is like a 68-69 L88 in the vette world. But, in the vette world, I know what to look for and where to look for originality/matched #'s, etc.. So, I don't have a clue where to look on the car what what turns on, turns off the collector or enthusiast. So I'm looking for help - if you can give me the Top 5 things I need to confirm, i would appreciate it. Now, for the record and to fit in - I did drive a bad *** 1969 Cutlass "S" in High School and wish i had never gotten rid of it(see pics). But, maybe this is where the W30 is bringing me back in - any assistance is greatly appreciated! JIM

 

Window stickers can be faked now, so be careful. Is the car an automatic or 4 speed?

Oh yea, Welcome to the sight. You'll get a lot of help here.

 

M40 -TH400 -trying to figure out this reply thing lol

 

I'll throw a few ID characteristics your way.

First, the lone letter in the VIN should be an M and the assembly plant on the trim/cowl tag should be LAN (Lansing MI). All W-30 optioned cars were built at the Lansing assembly plant.

With an automatic transmission, if the decal on the oil fill tube is still there and it is original to the car, it should read TT. As well, the number stamped into the oil fill tube is the engine unit number. The first number on the tube should be a zero, indicating that it is a 1970 model.

The casting number on the block, visible between the intake manifold and the timing cover, should read 396021 F. Later blocks had the same number but the F had a small "a" after it.

There is a VIN derivative stamped into the block just below #1 cylinder (forward most driver side). It's on a raised pad that will be hard to see if it is covered in oily dirt. It's a shortened version of the full VIN and just like the VIN derivatives on Corvettes (I used to have a '71). You can tell if the engine is original to the car by matching the VIN derivative with the VIN. The same is true for the transmission - the VIN derivative will be stamped into the casing on the driver side.

The ID tag on the passenger side of the THM 400 will have an OW code.

The intake manifold should be aluminum with a casting number of 406115 and have either "OLDSMOBILE W-455" (early W-30 production) or "OLDS W-455" (later W-30 production) cast into it.

The cylinder heads should have a large "F" cast into them, clearly visible at the forward end of the driver side head just by looking down onto the head. The casting number on the heads should be 404438, and visible externally just below the valve cover in the middle (between front and back) of the head.

The correct carburetor for the 1970 W-30 with M40 is the 7040258 Rochester quadrajet.

The correct distributor for a 1970 W-30 with M40 is 1111979.

The differential should be anti-spin (i.e., posi-trac), with (W-27) or without an aluminum rear axle carrier. With W-27, the rear axle codes would be SV (3.23), SX (3.42), or SZ (3.91). Without W-27, the rear axle codes would be TM (3.42) or TO (3.91). The rear axle code is usually located on the passenger side axle tube, forward and upside down. It could be hard to see if the axle tube is dirty/rusty.

I'm sure there are other things to look for and others will chime in as well. I'm not overly familiar with the W-30 cars but I know what you are going to see is pretty rare. According to my book, there were only 264 W-30 convertibles made in the 1970 model year!

Randy C.

'68 4-4-2 convertible (best in class, 2011 OCA Nationals)
'69 4-4-2 convertible (nice driver)