|Differences - Engine
A while back, I was looking on eBay for a replacement engine for my Jeep and I came across a 304 International
Harvester Engine that I thought I might be able to use. I was unsure if the AMC and IH engines were similar
enough to do the swap so I posted a few questions to the forums to see what people would say. I also did a
lot of research on the forums and I found that this was not really covered in the past.
There were a lot of questions surrounding the 360 differences between
AMC and Mopar, but not the 304 differences. What I found out was a ton
of information on how the AMC 304 differs from that of the IH 304.
Basically the swap would not work, but I wanted to know more, so I
continued to investigate. Here are some captions from what I found.
1) AMC and International 304's are totally different engines. The
International is a heavy truck engine sharing the same block at there
345 and 392. I believe the AMC is a much lighter and more compact
2) Looks like a totally different engine. The dizzy is not in the
same location. Water pump inlet & outlet are different. If you need to
rob any parts from your current AMC 304 I don't think they will fit.
3) Bell housing bolt pattern is different, too. Main thing is that
you're not going to find adapter kits to drop an IH block into a Jeep
4) It's a completely different engine (as are the Mopar 360/AMC
360). The only thing they share is the same displacement. Power to
weight ratio is much poorer with the IHC. They didn't have the budget
for the sophisticated engineering to lighten them up (and didn't really
need to, so much, considering the applications they were put to.) IH
engines are very heavy as well. They are goofy enough that to set the
timing, your pickup goes on the #8 cylinder instead of #1.
5) The engines are totally unrelated; nothing interchanges except
perhaps the 2 bbl carburetor. They are incredibly heavy but due to
their industrial nature are very solid and pretty hard to hurt. There
is no timing chain, all gears, when tuned they get pretty good mileage
considering the weight of the vehicles. If I had a scout I'd be happy
with keeping the IH motor but I wouldn't swap on in.
So with that research done, I set out to find a 304 motor from AMC that
I could use. I knew that it was produced between the years of 71-81 and
some were better then others. From research done on jeeptech.com, you
can see when it went south.
"The AMC 304 uses a cast iron block and heads with overhead valves and
hydraulic lifters. The AMC 304 was introduced in Jeep vehicles in 1971
in J-series pickups and Wagoneers and in 1972 in the CJ vehicles. Early
304s performed well, so well that frame changes were made to the CJs in
'73 to prevent cracks."
It goes onto say that emissions killed the 304 engine's performance in
the following years. "The last two years of the 304 in the CJ were in
'80-'81. The horsepower and torque specifications of the last version of
the 304 narrowly beat the 258 use at this time. The 258 used between '80
and '81 was putting out 110 HP @ 3500 and 195 ft/lbs @ 2000."
I finished up the research by reading about possible modifications to
the 304 block.
1) 360 heads will not fit a 304 without modification the valve will
hit the block.
If you do this mod (which is a bolt on) you'll have to have valve
reliefs cut into your block. (Not a big deal). You'll have larger valves
for more horsepower in the whole power band.
2) Do not get confused, International 304 engines and Jeep 304
engines are two completely different engines. This goes for the Dodge
360 and Jeep 360. "Different". The only thing that's interchangeable is
the gas and oil.
3) AMC dogleg heads were introduced in what I think is 1970. I had original
had 73 in here, someone said their stock 72 had them and then I also heard
that it could go back as far as 1970. Not sure exactly, but somewhere in
that time. They are flow rated higher than any other stock head except the
HEMI. Also have big valves stock. No need to upgrade.