I have a '68 1200c pickup with the original 266 engine. According to my information my truck came with up to a 345. How hard would it be to put in a 392? I am assuming that the engine mounts will be different and I doubt that the 392 bolts up to the same 4 speed transmission my 266 has on it. I prefer a 392 but since the 345 was a factory option for my model maybe that is a better choice. Does anyone know what engines bolt onto my transmission? Hard to find much technical data for this so I appreciate advice.
266 to 392 swap
- Thread starter Gdalton
- Start date
1975IH200
Active member
Engine mounts are the same, so no problem.
Transmission mounts to the bell housing, not to the engine.
Bell housing for 266-304-345-392 are the same for the 4-speed transmission, so no problem for you there.
Difference will be when you try to hook up the down pipes to the exhaust manifolds.
345 + 392 are taller engines, so you May need some new exhaust down pipes.
Easy swap!!!!!
Transmission mounts to the bell housing, not to the engine.
Bell housing for 266-304-345-392 are the same for the 4-speed transmission, so no problem for you there.
Difference will be when you try to hook up the down pipes to the exhaust manifolds.
345 + 392 are taller engines, so you May need some new exhaust down pipes.
Easy swap!!!!!
FDChappie
Well-known member
Well, the 392 is a couple of hundred more pounds more than a 266 so your front end might sit a bit lower and or bottom out easily. So you might need to add a leaf to the spring pack. Still an easy-peazy swap. My 1210 tett'e went from a 345 to a 392 a couple of years ago and that 392 really moves that truck around easily. You'll enjoy the bump in power. Also that 266 redlines up around 4200 rpm's and the 392 redlines @ 3200 rpm's so make sure you'll have tall enough gears to get you up to speed.
Scoutboy74
Moderator
As stated in on page 61, section e of cts 2130-k, the recommended maximum (sustained) engine speed for a 304 is 3900 rpms. Peak horsepower for this engine occurs at 4400 rpms. The 266 had been discontinued by the time this table was created, but characteristics of the 266 and 304 are quite similar. There is no recommended maximum speed figure listed for the 392, but there is a governed speed of 3800 rpms stated. Peak horsepower is reached at 4000 rpms. 3200 rpms, while near the upper end of the spectrum for any stock sv8 engine, is still well within the designed continuous operating speed range. The 392 in my Scout has seen brief bursts above 4k with no ill effects. The valves will often begin to float before you reach 4500 rpms, which serves as somewhat of a built in rev-limiter. It isn't fail safe of course. They certainly can be over-revved. The overall point of all this is to say that one shouldn't have any fear of occasionally pushing a healthy sv8 up around 4k. They can handle it.