I've got a coolant leak from between the timing chain cover and block on my '97 F-250 CCSB 460. With 191K on the engine, fixing the leak seems like a good opportunity to replace the timing chain.

I've read about people putting a "straight up" timing set on 460s, advancing the cam about 4 deg (8 deg at the crank). What benefits are there in this? I've heard power. How about mileage? It's a 460 so I don't expect miracles, but picking up 0.5 - 1 mpg would sure be nice, but I really don't want to lose anything there.

Speaking of which, what do you lose with the cam advance? I'd guess it was done for emissions. Any other benefit to the retarded cam?

 

It's my understanding cams were retarded for emissions purposes, making new truck owners very unhappy at the time (1970s). There is a range on either side of maybe 6° or 8° advanced or retarded before pistons start hitting valves. Better low end torque is one reason for advanced.

 

All EFI 460 have straight up timing. The retarded timing set was only in smogger carb engines.

 

The intake closing event has the greatest effect on how power is made. The earlier the intake valve closes, the more torque the engine will make with a trade off of high rpm power because there isn't as much "time" for the inertia of the air in the intake to fill the cylinder with high piston speed and an early intake closing. Early closing intakes also increase cylinder pressure (compression).

Retarding cam timing does the opposite, a later closing intake bleeds off compression, sacrificing low rpm power and efficiency, but allows for better scavenging (air inertia) through the intake runners at higher rpm.

What you'd want for your truck is advanced, if anything. Advanced provides better off idle response and efficiency.

 

Don't do anything without a timing wheel. A friend bought a Competition Cams cam for his 302 and we all read 4deg retarded was the thing to do so he bought a adjustable timing set and put it in at 4 deg retarded. It detonated at idle. After a lot of headaches, we called Competition Cams and they said, "Yeah, 4 degrees is best, that's why we grind it into the cam." 4 deg on the cam + 4 deg on the timing set = 8 deg overall.

 

So my '97 would have straight up, but it sounds like advancing it a little more might still be a benefit. True?

I'm plenty happy with the low end torque I currently have (I'd actually be happy with a 351 and I have a 460). However, a mileage improvement would be well accepted! A lot of engine mods that improve torque also help mileage (if you keep your foot out of it), so I'm hoping this is an opportunity for some cheap gains there.

I'm sticking with the stock cam, so I'm not combining changes. And are you sure about 4 deg retarded being recommended and causing detonation? Everything I've heard would lean toward advanced cam timing giving performance improvements.

But it does bring up another question. If advancing cam timing (assuming sign_man just has it reversed) effectively increases compression, which can lead to detonation, I'd probably have to back off on my ignition timing slightly if I advance the cam (I already advanced it to the point I got detonation and then backed off 'til it went away). So if there are mileage improvements from an advanced cam, might they be offset by the mileage drop I'll see when I retard the ignition?.

 

If you want to advance the timing, turn the distributor till the engine pings, then turn it back a degree or 2

Like was stated above the EFI engines already have straight up timing

 

Yes, you will likely gain some responsiveness off idle by advancing the cam. You may also get a mpg bump. Without seeing the valve timing events of the cam, it's hard to tell the extent of improvement. If the intake valve already closes at or around bdc, there won't be much difference.

Brad, cam timing and ignition timing are different, although advancing ignition is a good idea also.

 

Any clue when a stock cam in a '97 460 closes the intake?

And yes, I've already advanced the ignition timing as much as I could without getting detonation. I'm at 14 deg BTDC. That's giving me right around 10 mpg for a year 'round average (more in the summer when MN puts less ethanol in the gas and it mostly gets highway miles, less on winter gas when it gets mostly commuter duty while my Bronco avoids the salt)

 

I don't know the factory specs, they really aren't easy to find, but it's likely that it closes a few degrees after bdc when measured at .050 lift. Worth a shot imo, it can't hurt if torque and mpg are what you are after.

 

Last I checked both the cam and crank gears have keyways and you cant just move the gears. Also moving a whole tooth on the chain would be too much

 

The old school Ford mechanics advanced the cam timing just to get it back to where it was, before the gubbmint got involved. I don't think you'd get much out of this.

 

I know it's not a matter of "adjusting" the cam timing like you can the ignition. But people talk about buying new timing chain and sprockets that will offset the cam timing from stock. Since my timing chain cover is coming off this seems like a good opportunity to replace a 190K chain. And if I'm doing that it seems like a good opportunity to replace it with a timing set that advances the cam (if that's a good idea, which it's seeming like it might be).

 

Correct, most aftermarket timing sets are adjustable.

 

EFI 460's are already straight up as mentioned above and I would definitely change the timing set with that many miles since you are going to be right there. I would get a double roller all steel gears if it was mine, no cast(exactly what I did on my 86) and I wouldn't advance the cam anymore. It made a big difference on carbed engines for low end torque but the straight up is good on EFI.