"S" to "F" conversion

[poptopjr]

I have a new to me 97 K1500, 6.5TD, 3.73 gears. Motor and trans have almost 140k miles on them and I'm looking into the "S" to "F" conversion. What exactly needs to happen for this, how much power should I expect to gain, will I loose any mileage/gallon? Would I be better off with a performance ECM from somebody like Kennedy or Heath? This is my first diesel truck. Thanks in advance for any help.

Keith

[chickenhunterbob]

I'm in a little different boat, I replaced my intake manifolds with "F" intakes, but in a '94 only have to plug the vac hose to the EGR valve and as long as the solenoids are connected the PCM is happy.

I don't think that is the case with OBD2, 96 and newer, I think you would have a perpetual code.

The F and S intakes differ in that the S has a channel that runs between the middle two combustion chambers in each head, which allows exhaust gas to be drawn into the combustion chamber when commanded by the PCM. The F intake has no such channel, but the S intake can be blocked with a freeze plug, in the tower, or blocked at the manifold to head union with a set of F gaskets.

No power increase by switching manifolds, none whatsoever that I can tell, the only reason I did it, is (1) I got a manifold set relatively cheap, and (2) the accumulation of crud in the intake (I've removed and cleaned my old "S" twice), was becoming what I thought, excessive, engine is a high miler.

No fuel economy loss, or gain, the EGR does regulate the intake air temp for cleaner combustion when the engine is cold, but the difference in fuel mileage in my view is negligible.

The cheap way to avoid codes and to obtain a very slight power increase in an OBD-2 is to get a "F" PCM, they are relatively inexpensive, and maybe add 10 HP, or the alternative for more power is to get a PCM reflashed for more power and without the EGR, John Kennedy very well may be able to help you out there...

[poptopjr]

Thanks for the info chickenhunter. So I'm guessing that an intake (gets rid of the EGR), also get rid of the mass air flow sensor, and an "f" coded ECM and I'm in business. I guess I will start looking for a manifold and then decide if it is worth it.

Thanks again.
Keith

[chickenhunterbob]

The MAF is after '94, but as far as I know can be eliminated by using either a F PCM or reflash PCM (John Kennedy will be able to tell you for sure), I won't pretend that I know for sure though, as I said earlier, with mine being OBD-1, I'm in a different boat, in many ways, MAF being one...

But you don't need a new manifold set to get rid of the EGR, a frost plug to seal the middle "tower" on the lower intake will fix that, or a set of F intake gaskets, of the two, the frost plug is considerably less effort.

In either case they will block exhaust gas from entering the intake air charge, regardless of the PCM command, although I do think that you will get a code from OBD-2, the earlier versions (OBD-1) simply monitor applied vacuum, whereas the later (OBD-2) actually monitor EGR operation.

[JohnC]

A word of caution if you decide to use the freeze plug. Someone else did the same thing and reported that he later found the freeze plug had made its way through the turbine housing.

If you're sticking with the "S" manifold, cut all the webbing out of the top and replace the EGR valve with a metal plate.

[poptopjr]

I appreciate the input, all in all, it doesn't really seem worth the effort. I think when I am ready to jump I will contact Kennedy about an ECM. As long as they program S type computers as well I think I will just do that. How much more could an F type computer really get after both have been programmed? Thanks for the help.

Keith