Hi,  I have a tech question for anyone in the know. I am building a 461 stroker based on a 400 block (68 YE code 400 block)into my 77 trans am. I am swapping out a numbers matching 400 (setting it aside) and building this one in it's place. From research I have done and the Pontiacs I own, I just noticed that my base 400 has a harmonic balancer, when I was always led to believe my engine should not. It is an original 400 (non w72) 4 speed car. I had read a while back all non w72 engines were the same as all other 77-79 400s, (all blocks with code number 500557)in that they were lightened internally, and externally via removal of the harmonic balancer. Further proof of this is a 77 (grand prix) 400 that I pulled from a junk yard years ago had only the hub of the balancer(to mount the pulleys), and a revised timing cover and timing tab corresponding to it. but yet both blocks have all the same block codes (both 500577) and same heads(6X-8), the only difference being the application. also, both were cast around the same time during late 76-early 77. Any info would be great.  

All 326-455 engines are internally balanced I had a 1976 350 with the small diameter balancer I was building for a costomer and changed it out with the larger diameter balancer with the rubber ring and there was no difference as far as vibrations only that the larger one will absorb the harmonics better.  

Thanks. I knew about pontiac engines being internally balanced, I guess the point of my original question was kind of vague...I had already purchased an SFI approved balancer for my 461 buildup, but my question was pertaining more to the timing cover usage,  and the fact my original 77 400 shouldn't have a balancer, but in fact it does. I have no documentation to specify that my car is equipped with the better engine option (W72) but it has most of the features of this engine, including the balancer, factory chromed valve covers (sort of a matte chrome), but block code numbers tell me otherwise. I guess my questions are do I have a W72, and will the timing cover work with a full sized harmonic balancer?  

Yes the timing cover will fit but the timing pointer might not.it is a bolt on timing pointer right.  

yes, I agree with Pontiacman8 (as usual).  

The issue is the timing pointer, which is a bolt on piece of sheet metal on 1977 and later (IIRC) as opposed to the earlier (and larger diameter) cover which has a built in timing sequence.  

Also the full harmonic balance is "better" than the small one.

Craig