I have timing chain concerns . My 1997 F250 HD 7.5 (460) AutoTrans , has 197,000 . Some time ago I began to lose fuel economy . When I got the truck it had 60,000 and would get over 13.2 MPG loaded pretty heavy I use this truck as my service truck and has a utility bed ,tools and material all the time . Any way long story getting short NOW . Ok I changed plugs and cap, rotor , Wires not really what old and still look to be ok , did the have a look in the dark for sparks test . But still can't get my MPG back above 11.7 MPG . So I starting thinking timing chain . So Now to the point and Question . How much slack in the Chain is "OK" . My Cillton book tells me 1/2in deflection is allowed , BUT I do want to tear it down just to have a look . And the truck runs V fine other wise . So I did the old turn the crank one way then back other way until the rotor moves ! As best I can tell I have about 3 deg ,No more than 4 deg slack . What would you true mechanics tell me about that ? And second question are the OME gears in this 1997 460 steel or nylon ? If they are nylon I will tear it down tomorrow . I have had a chian "slip" before tore that engine UP ! I depend on this truck a LOT so if you can or would give good advice I will be very thankful .

 

You know, if you're getting 11.7 mpg loaded, don't complain. That's par for the course for a 7.5L gasser. Mine has 168K and that's about what I get, empty or loaded on the freeway.

As stupid as it sounds, tires make a big difference with mileage. 235/85R16 highway tread, aired up to full tooth loss pressures will give the best mileage. 315/70R16 mud and snow tread tires, aired down for best ride will get you some really poor mileage.

Your method of testing timing chain slack will show several degrees of 'slack' and that's the nature of the beast. If you really must know how much slack you have and go ahead and tear it down, just resign yourself to replacing the timing set. If you're already there, why put it back together with an old timing set? Replace the front main seal and oil pan gasket while you're at it.

 

Well raystankewitz , I don't like working on the truck . The whole point is to try and determine if I must . steel gears with a little slop i could live with , It is high milage . Nylon gears yes I will bite the bullet before it bites me . Thanks for taking the time to answer .

 

After doing a bit more searching, I'm pretty positive the timing gears are both all-metal, not steel/nylon composite as the older sets were. Also, the timing set from the factory on the EFI motors are a double roller set, not the Hy-Vo chain.

I know these 460's really don't know how to die if treated properly but I'm going to freshen the engine in my war wagon next year. It's hard for me to wrap my head around the mileage these newer motors will crank out. When I was a kid, back in the last century, a car with 100K on it was toast. As an example, I had a '71 Ranchero with a 351C-4V that was shot at 70K. Heck, with today's technology, 70K is barely broke in.

 

I just replaced the timing set in my 95 E350 Bus with the 460. It has 140K with original timing set. There was alot of slop in the chain(over 1/2" for sure), with the new set, hardly any slop.

I replaced mine as I had to take off the timing cover to remove a snapped off water pump bolt. I replaced it so I won't be doing that job twice! With a 2nd A/C compressor in the way(for rear AC unit), it is not fun at all.

 

My 92 460 is over 270K on original chain. Some wear? I'm sure there is, but engine has never been opened up, no leaks and no noticeable consumption between 5K oil changes. I'm leavin it alone.

 

I've always said about 8 degrees measured at the timing marks. New double roller usually have 2-3 degrees and I have seen sbc with 24 degrees of slop and still running.

 

...And adding 1 qt oil every 1000 miles was considered normal...even desirable. "At least it's getting enough oil on the cylinder walls and valve guides". I worked at a Ford dealership in '76, and for new vehicle warranty purposes, oil consumption had to exceed 1 qt/400 miles. Before tearing down/replacing however, the engine was run at fast idle (1500-2000 rpm) and borax was sprinkled down the carb, along with squirts of ATF...5-10 minutes. This cut the glaze on the cylinder walls/rings. The tech then took it out and drove the hell out of it, came back and changed oil/filter. The customer was told to bring it back in 1000 miles for another oil/filter change...gratis. I don't think the customer knew what this "Ford Authorized Procedure" entailed, or what the "Special Additive" was...but in most cases, it did decrease oil consumption...and saved Ford some $. Incidentally, the engines involved were 351M/400's...not a stellar engine by any stretch. I don't recall seeing it done to FE's, 385 series, Windsors or 6's. Out of curiosity, I'd like to know how long these engines lasted. After 12K miles Ford could not have cared less.

 

So Eddiec1564 , You spoke of replacing the original timing set . A key part of my question was/is the timing gears , are they steel or a nylon tooth ? It may well be a dumb question ,But ! I would like to avoid tearing this motor down unnecessarily . Meaning if they are steel gears I won't worry as much . I have never seen a timing set in a engine newer than 1976 . And the only Ford I have seen was a 1968 390 and I lost that motor because of nylon timing gears . So please pass this info to me .

 

Some 460s had nylon timing gear.

 

The timing set I got was both steel sprockets and double row chain, not gears like the 300 I6 has.

The original 95 460 was also steel and double row chain. I got mine from Advance Auto Parts for around $53.00