The block is not required to match the head, and vice-versa. Some '80-ish engines had 7/16" head bolts, but the rest have 1/2" and are compatible AFAIK. You could have a '71 head on a '78 block, for example. I believe up through mid-74, the 258 head was like the earlier Rambler 199/232 six, and had a rocker shaft. Later heads used bridged rockers. Likely there are some casting numbers online somewhere. Maybe here - https://forums.off-road.com/threads/jee ... ory.76020/ If the casting number is not visible, it probably can be seen under the valve cover. It will be somewhere in the raw casting surface of the head.backroader wrote: ↑Thu Feb 29, 2024 7:22 pm The point for my purposes is I don't know the origin of the engine in my truck. I pulled it out of a 1971 Wagoneer that I had bought for parts, but the engine wasn't original to that vehicle, since the block numbers show it was built in 1978. ...
I recall you can use a head with 1/2" holes with 7/16" bolts if you put spacers in the bolt holes. HESCO sells spacers IIRC, or a friendly machinist could easily make them.backroader wrote: ↑Fri Mar 01, 2024 12:54 pm...
I don't want to re-use the head on the 1981 engine that came out of the truck even though it is in okay condition for several reasons. It uses 7/16" head bolts rather than 1/2". ...
IIRC the heads meant for the plastic cover always had these blind holes that looked like they should have bolts. Not meant as bolt holes AFAIK.... It has the plastic valve cover. The holes are there for a bolt-on style cover, but not tapped for threads. ...
Yeah, I never checked to make sure they even matched the older style, but I'm positive I don't want any more of those plastic valve covers...tgreese wrote: ↑Wed Mar 06, 2024 12:05 pmI recall you can use a head with 1/2" holes with 7/16" bolts if you put spacers in the bolt holes. HESCO sells spacers IIRC, or a friendly machinist could easily make them.backroader wrote: ↑Fri Mar 01, 2024 12:54 pm...
I don't want to re-use the head on the 1981 engine that came out of the truck even though it is in okay condition for several reasons. It uses 7/16" head bolts rather than 1/2". ...IIRC the heads meant for the plastic cover always had these blind holes that looked like they should have bolts. Not meant as bolt holes AFAIK.
Yes, It would require drilling out the holes in the 1981 head to 1/2".
... It has the plastic valve cover. The holes are there for a bolt-on style cover, but not tapped for threads. ...
Yes. Power is torque times RPM. They change with each other.backroader wrote: ↑Wed Mar 06, 2024 12:59 pmThey show torque at 1800 rpms as 240#, which is considerably higher than any of the later models. Would the ratings change also affect the torque output?