how many miles does a F4 survive ?

Of course maintence makes a lot of difference but what kind of distance in miles does the F4 engine make before a rebuild is needed ?

The one i bought shows 43,000 on the clock . Motor was removed to install a V8 . Im putting the F4 back in it , prevous owner claimed it ran ok but who knows . Should have it fired up tomorrow and ill know for sure if its any good .

 

The one that I blew up in my '59 must have had at least 150,000 miles on it. It blew up because I was a dumb kid and insisted on over revving it all the time....

 

43,000 isn't much, even for an old F134. As you said, how it was cared for will make more of a difference. Personally I would at least drop the pan and pull the valve cover off so I could inspect it a bit. My grandfather owned my 1955 CJ5 with a F134 since 1959. It had about 500,000 miles on it when I got it. The first engine was swapped out for a new F143 sometime around 1970. The second engine was rebuilt twice that I know of. By the time I got it (three years ago) it was shot.

 

My experience with F heads in FC 150 work vehicles was a new bore/ring job someplace between 60 and 75k. Never had one make 100k although that may depend on one's tolerance for a following blue smoke cloud.

 

Recall that the 134 is an old, old, old design, being derived from the Willys 77 engine of 1933. Engines in that era did not last as long as modern engines. Today, people drive a lot more than they did through the 50s (modern highways as we know them didn't arrive until the 50s) so engine longevity was judged on very different terms from today.

So, I would think that 100K miles before the first overhaul on a F134 would be doing pretty good. Expecting 50K after an overhaul (as opposed to a complete rebuild) would not be unreasonable.

That said, don't guess - measure. Look at the oil pressure, measure the compression, do a leak-down test if you own a compressor. If the engine is tired, it will show up in the compression and the oil pressure.

If it were mine, I'd take the opportunity to freshen it up with new rings and rod bearings, and maybe a new oil pump. Maybe grind the valves. Plus whatever items typically need service on a F134. But it's not essential if the engine measures well. Also depends on how many miles you plan to put on the vehicle - if you plan on more than a few thousand miles per year, some preemptive service might be worthwhile.

 

I got a full 80,000 miles out of my last rebuilt F-134.
Only maintainance involved was normal oil / filter changes and distributor maintainance with ZERO other repairs during those 8 years.
Eventually a rod bearing started knocking down at the crankpin journal because I did not size the rod bores.

I run em relatively hard. My sustained cruise speed is 63 MPH @ 3000 rpm.
Excellent engines with exceptional torque, just not a lot of cubic inches.

 

:iagree: 100% depends on the driver as well as the service record, if you just put around around 45mph and dont rev the crap out of it its no telling how many miles you can get out of one. the m38a1 engine i rebuilt had around 50k on it and the cylinders & pistons were fine but the crank needed turned and i went ahead and had a complete valve job done (new seats for todays unleaded gas & new valve guides, valves.

 

I have knowledge of older motors but not this motor persey . Just do to the time frame it was built i wouldnt expect more then 100,000 with out having a real oil burner . It will see very few miles with me . 2 or 3 K a year at most .

 

Id check compression and leak down. If its not bad run it. Thats just me