4G64 differences?!

[sefipoly]

Ok I have a 93 MM. the engine is getting tired (264k) and i just picked up a 91, 6 bolt engine to rebuild and put in the 93. other than the obvious 6/7 bolt cranks, what other diffs are there? I do see different part # for the main and rod bearings, and oil pump. how different are they, size/ width? which is better? Thanks for putting up with my ignorance.

kevin

[pennyman1]

Didn't know there was a difference, but the 6 bolt motors are the stronger ones, whether its the 4g63 or 4g64. That being said, they are both good motors, just 6 bolt is better. There may be minor differences with the emissions stuff, but nothing insurmountable

[camoit]

If you find out any differences please put the information in the Wiki. We need good hard facts in there.

[sefipoly]

This truck for me is my daily driver, with that said, that is why I bought a second engine. It will probably be 3-4 months before I am ready to install and dont know if i will get a chance to compare both engines, side by side. The millage on the truck I took the motor from had over 240k, so when i pulled it apart yesterday i expected to see a lot of wear. i was surprised when i could see the cross hatching in the cyl walls and no lip, the inside was fairly clean, no sludge. the bearing with the most wear was the thrust bearing. I did have a lot of carbon build up in the valves and piston tops. will b measuring parts this week to get my parts list together. Definitely not something i expected from a pull-a-part motor.

[MainstreaM]

What is a 6-bolt engine?
What is a 7-bolt engine?
A 6-bolt engine is one that has a 6-bolt flywheel - that is, there are 6 bolts holding the flywheel to the crankshaft. A 7-bolt motor has 7 bolts there.

Along with the flywheel change, there are many other internal changes between the two engines. The crankshafts are different sizes, as are the rods and crankshaft seals. 6-bolt motors have 'big' rods, while 7-bolt engines have 'small' rods. The journal and bearing widths different, although the bearing diameters are the same.

There may also be other changes between the two engines, and the parts are not interchangeable.

taken from:
http://members.shaw.ca/costall/1000Q/answers-terms.htm#Whatsa7boltengine

In my experience, this holds true in the SOHC motors.

[sefipoly]

Thank you MainstreaM, thats the info i was looking for!!! I also bookmarked that page for future reference.

Kevin