Something went wrong.... BOOM

[ratio411]

Not true -- there were a lot more changes than that to get to a certain smog standard. I know, I had one. I wish I still had the shop manuals so I could scan and show you the specs. They were different; pistons, cam duration and (I think) lift, distributor timing and an awful exhaust system. Timing gears would make no difference, the gears and chain were installed so that the cam was straight up anyway.

You are right about the pistons... brain fart.
They changed pistons to lower compression because it was cheaper than changing head castings.
The cams, at least early on, were the same. The timing gears were machined and dots placed so that when they were installed "straight up" the cam timing was changed. Usually heavily retarded. I am sure they got around to changing the grind eventually. However the 351m/400 spent most of it's existence with a retarded 351c cam... I guess it worked well enough. I have no real interest in knowing if it was true for the SBF as well or not...
My main point was that the engine in question would not be using stock parts no matter the year (hopefully).
I got sidetracked in details. Sorry.
Dave

 

[VictorII]

You are right about the pistons... brain fart.
They changed pistons to lower compression because it was cheaper than changing head castings.
The cams, at least early on, were the same. The timing gears were machined and dots placed so that when they were installed "straight up" the cam timing was changed. Usually heavily retarded. I am sure they got around to changing the grind eventually. However the 351m/400 spent most of it's existence with a retarded 351c cam... I guess it worked well enough. I have no real interest in knowing if it was true for the SBF as well or not...
My main point was that the engine in question would not be using stock parts no matter the year (hopefully).
I got sidetracked in details. Sorry.
Dave

No worries. I built a '74 block with performance parts, and flat top pistons and home ported '68 heads to get the compression back. It screams, even with 155,000 miles. It didn't when stock. That together with what I learned from the '72 and '73 I had told me what I needed to do get to the 300HP/300 ft/lb mark. And I did. We all have brain farts, Dave. I have some major ones, mostly around the female gender. Cars I understand.....