I am fairly new to the Buick family of engines even though I have had my Suncoupe for 22 years. I bought it from a junkyard in 2000 and haven't done much to it until recently. I am in the process of getting it ready for bodywork and paint. The engine that is in it is from, I believe, a 71 model year Skylark. It is a 2 barrel 350 and it is seized solid. I was able to find a running 68 350 locally and got it. As I have been doing some research it seems that the early 350's are better than the later ones. At least that is the impression that I am getting. I am curious as to what the differences are in the 350 engines over the years and why some are saying that the early ones are better.
In 1971 GM lowered the compression on all their engines to 8.5 to 1 to run on unleaded regular fuel. Depending on which 350 model your ‘’68 motor is compression ranged from 9.0 to 10. The 68 motor also probably had richer Fueling and a more aggressive timing curve. So, the 68 350 is likely to feel a bit more peppy than the 71 motor.
The 68 I believe had oiling that was different than the later motors, you will have to change it to pushrod oiling. My 71 ran good with a 2bbl carb and with 4 bbl and headers with duals when I got there.
There arent many differences that couldnt be changed to improve reliability or performance. Most notable are the connecting rods. In 1973 Buick went to a cap screw rod verses the nut and bolt. The cap screw is suppose to be stronger, it certainly looks beefier than the nut and bolt rod. In 1970, Buick went from sending oil thru the rocker shaft to sending oil thru hollow pushrods to oil rockers, oiling thru the pushrods is a better set up. To change over you need the proper lifters, and pushrods, and then tap and plug the oil passage in the deck of the block, which is no big deal. You change compression by changing pistons, deeper dish equates to lower compression, shallow is higher compression. No big performance gains in heads from year to year, just changes in emisions passages and water passages.
