WHYDTYTT: What Have You Done To Your Truck Today?

[Nothing Special]

.... Bill - How much interaction is there between AFR and ignition timing? IOW, you mentioned spark knock due to being too lean, but you can get there with timing as well. So is it better to be a bit more rich so you can have more advance? Or?....

What I remember from my brief time working in an engine test lab and then an engine design group at GM (a long time ago, when I actually owned my '85 F-250!) is "MBT-LBT", which stood for "Maximum (spark advance for) Best Torque - Leanest (mixture for) Best Torque". Advance the spark until torque dropped, then back it out a bit to get the torque back. Then lean out the mixture until torque dropped, then richen it just enough to get the torque back. For what that's worth.

[ArdWrknTrk]

.... Bill - How much interaction is there between AFR and ignition timing? IOW, you mentioned spark knock due to being too lean, but you can get there with timing as well. So is it better to be a bit more rich so you can have more advance? Or?....

What I remember from my brief time working in an engine test lab and then an engine design group at GM (a long time ago, when I actually owned my '85 F-250!) is "MBT-LBT", which stood for "Maximum (spark advance for) Best Torque - Leanest (mixture for) Best Torque". Advance the spark until torque dropped, then back it out a bit to get the torque back. Then lean out the mixture until torque dropped, then richen it just enough to get the torque back. For what that's worth.

So this is essentially tuning for BMEP.

If it works on the dyno, numbers don't lie.

But Gary has a given package -as far as cam timing and distributor curve go- and Scott has spent years getting his tunes down.

I imagine he has to start with fuel, at the power ratio, dial in as much initial as he can, and lean the carb out until it starts falling off or knocking.

Gary, just be sure to leave yourself some headroom.

I find ive gotten some sub-optimal fuel probably 3-4 times a year.

You know right away when you can hear it 2 blocks from the filling station.

Your engine is too nice (and too costly) to have broken rings or melted pistons if you're out in the middle of nowhere.

Though your plans to trail ride and overland all seem to involve places with more altitude, I'd imagine crossing Death Valley is not the place you want to find out you cut things a little too close.

If you recall I had to dump a gallon of toluene in each of my tanks last year.

 

[Gary Lewis]

What I remember from my brief time working in an engine test lab and then an engine design group at GM (a long time ago, when I actually owned my '85 F-250!) is "MBT-LBT", which stood for "Maximum (spark advance for) Best Torque - Leanest (mixture for) Best Torque". Advance the spark until torque dropped, then back it out a bit to get the torque back. Then lean out the mixture until torque dropped, then richen it just enough to get the torque back. For what that's worth.

That's the kind of info I was looking for.

But that was a generic question, and not anything I am going to use on Big Blue - at least right now. For BB I'll run the Eddy as set and certainly the ignition as Scotty dialed it in.

 

[Nothing Special]

What I remember from my brief time working in an engine test lab and then an engine design group at GM (a long time ago, when I actually owned my '85 F-250!) is "MBT-LBT", which stood for "Maximum (spark advance for) Best Torque - Leanest (mixture for) Best Torque". Advance the spark until torque dropped, then back it out a bit to get the torque back. Then lean out the mixture until torque dropped, then richen it just enough to get the torque back. For what that's worth.

That's the kind of info I was looking for.

But that was a generic question, and not anything I am going to use on Big Blue - at least right now. For BB I'll run the Eddy as set and certainly the ignition as Scotty dialed it in.

As I said, that's what I remember from 35 years ago. But what Jim hinted at is true as well. When you're looking at dyno readouts and changing spark and fuel with the bump of a toggle switch it's easy to dial it in. And the engines we were working on (the 2.0L normally aspirated and 2.0L turbo engines for the Pontiac Sunbird) had knock sensors and would pull out spark if they did start to knock, so we had the luxury of being able to get aggressive without much worry about what would happen with a tank of bad fuel.

So as I also said, "for what that's worth"

[FuzzFace2]

Dave, some of the YFAs have a small round plug in the air filter flange, it is for the final mixture tweak during bench flow testing. With it removed a small skinny Phillips head screw driver can access the screw on the metering rod hanger, counterclockwise for lean, clockwise for rich. If you can find something to cover the hole then you can drive it, adjust it and drive it some more. I would start with 1/2 turn CCW and go in 1/2 turn increments until it feels sluggish or spark knocks at light throttle, then go back 1/4 turn and recheck.

Thanks for the information hope I get lucky and have the opening as I don't remember when I rebuilt the carb as part of my rebuild.

Dave ----

[ArdWrknTrk]

As I said, that's what I remember from 35 years ago. But what Jim hinted at is true as well. When you're looking at dyno readouts and changing spark and fuel with the bump of a toggle switch it's easy to dial it in. And the engines we were working on (the 2.0L normally aspirated and 2.0L turbo engines for the Pontiac Sunbird) had knock sensors and would pull out spark if they did start to knock, so we had the luxury of being able to get aggressive without much worry about what would happen with a tank of bad fuel.

So as I also said, "for what that's worth"

I'm glad to see you say you were tuning for torque.

It is torque that turns the tires.

As -usually- torque peaks well before 5252 rpm (at least in these engines)

While spinning the engine faster can pump more AF mixture through, and therefore at the horsepower peak torque has fallen off.

[JG2020]

I'm glad to see you say you were tuning for torque.

It is torque that turns the tires.

As -usually- torque peaks well before 5252 rpm (at least in these engines)

While spinning the engine faster can pump more AF mixture through, and therefore at the horsepower peak torque has fallen off.

Today I scored a very decent brown vinyl bench seat for $50 at a local junkyard!

I also replaced all the window rubber on the passenger door. 36 year old dried rubber does not like to be removed. It's just like a new door now. No rattles and rolls smooth. Driver side door is next.

Also added new LMC door handles to replace the wooden ones someone installed at some point.

 

[Frank Wyatt]

Today I scored a very decent brown vinyl bench seat for $50 at a local junkyard!

I also replaced all the window rubber on the passenger door. 36 year old dried rubber does not like to be removed. It's just like a new door now. No rattles and rolls smooth. Driver side door is next.

Also added new LMC door handles to replace the wooden ones someone installed at some point.

Nice find, and those arm rests look good.

[JG2020]

Nice find, and those arm rests look good.

Thanks! Not too bad a job on the window rubber but not that fun either.

Too bad someone painted the door panels and dash a diff color than stock but that's a project for another time.

[Frank Wyatt]

Thanks! Not too bad a job on the window rubber but not that fun either.

Too bad someone painted the door panels and dash a diff color than stock but that's a project for another time.

I need to do my window runs on my truck as well as they rattle a lot. I'll get to them some time. Plenty of other things to do yet. Again, nice job.