Early vs late model block

No difference in the block itself, and the crank is also the same, however there are differences in the rods, pistons, heads, and timing cover.
 
What r the differences in the early and late heads? I was not aware changes were made in head design over the years. Which years would b considered "best"?

Adam
 
Not all of the above is accurate information.

The blocks are slightly different. 1) Not all 94/5 blocks are drilled for a crank sensor mount. 2) The tabs for the main bearings are in different spots and the only aftermarket bearings available are for the early block. Bearings have to be modified to fit a late model block. Those are the only differences.

On the heads the valve cover rails are wider on the 94/5 heads so that the newer design gaskets will seal. If you use 94/5 valve covers on 89-93 heads, they will leak. The other difference on the 94/5 heads is the heat treating. The 94/5's had extra heat treating so that the material is harder, but this also makes the 94/5 heads more prone to cracking. There were some very slight cooling passage revisions internally on the 94/5 heads, but nothing of significance. So the 89-9 heads are less likely to be cracked if they have been abused/overheated. Few things worse than spending a whole lot of money porting a set of 94/5 heads only to find out after you put them on that they have cracks, or develop them shortly after they've been installed.
 
Thanks guys! I have a spare motor in my garage out of a 90 I was thinking about using for my base build and didn't know if there were major things that would stop me from eventually using it in my 94.
 
You must log in or register to reply here.
Back
Top