Okay, my suspicions are confirmed. The motor in my '72 is not original. The number on the pad below the driver side head is 33M405642. Does not match VIN of car. I'm assuming this engine is '73 or newer, since it DOES have EGR . Is there any way to determine the actual year by the above number? I'm thinking a '73, since my parts book lists "M" as power plant code for '73 350 4bbl. Is that what the "M" in this number refers to? Also the block number above the timing cover is 395558 follwed by a larger size "2". Haven't got the number off the head yet. I'm also suspecting that the tranny was swapped as well. Need to get numbers there also. Also the valve covers say "OLDSMOBILE" in block letters. Have not seen this on any other '72s.

Chumley

 

Chumley,

The 33M number indicates it is a Oldsmobile (3), 73 motor (3) and the car it came from was assembled in Lansing. The last numbers are the plant sequence code.

C.J.

 

I've been told the valve covers with the name Oldsmobile pressed into the metal were only used in 1973 and maybe 1974. Sure the valve covers could have been changed but this agree's with what C.J. keyed out from your engine number. Those valve covers are in demand, so if you ever decide to change them don't throw them in the scrap metal pile! John

 

I thought that's probably how the numbers decoded. I'm not familiar with VIN code syntax after '72, but I guess it's pretty much the same as for '72. I had no idea about the valve covers. What I really want is a '72 motor in there. Can I swap heads and intake for a '72 with no problems? Is the rotating assembly for '73 much different from '72? Also what about engine wiring harness? I wanted to replace it with a '72(with HEI conversion) but want everything compatible. Right now there are wires cut and missing to accomodate the '73 when it was installed. Too many questions, I know, but I'm anxious to make a plan and pursue it. Thanks for all your help....Chumley

 

It's all the same as far as heads and intake go, but it'll still be low compression. Not sure how low, but I know they killed performance in '73.

If you are near San Antonio, I will have a peppy street/strip '71 350 for sale soon. And there's a 72 motor in the for sale section.

C.J.

 

I thought in '73 they made the heads with smaller valves, but larger combustion chamber, hence lower compression. Actually, the car cruises fine with enough power. I'm not looking to hop it up, just want it to run smoothe when I go to sell it. I'm in CA., so no can do on the engine you have. There are sources out here, I'm just trying to save $$$$.
Chumley

 

There really should not be much to a wiring harness for the 73 engine since there is no computer involved. It should be almost identical to the 72. From what I understand, the 73 actually had flat top pistons and the compression was lowered by using large combustion chambers in the heads. The 72 had dished pistons to lower the compression. Use some 72 heads (#7a) and it should work fine with probably a 9.5 CR. When you hook up the HEI, make sure you have a full 12 volts to it.

 

You guys are right about the heads. 79cc versus 64 cc for the 68-72 heads! From what I've read, they indeed use the pre-70 flat tops.

So...with some good heads, intake and rejetted carburetor, you should be able to pump up that engine quite nicely.

C.J.

 

Have the number 8 heads ( that is what should be on the 73 ) rebuilt with a good valve job and mill them .030 . The # 8 heads used the larger 1.625 exhaust valves and had hardened valve seats for use with unleaded fuel. Use the .028 head gasket from Corteco and you should have a street friendly compression. Just my .02 worth.

 

I KNEW Dan would have a solution!

C.J.

 

Thanks for all the info, guys. I think I'll just keep the engine as is since it runs pretty decent(except at idle, need to look at carb issues). It already has HEI, somewhere I read that this was factory ignition for '73. Was it in the "tech" section on this site? What would the chamber volume be after milling .030? I need to run a compression test to see if rebuild is warranted.

Chumley