The Stupid Engine Questions Thread

[PlayingWithTBI]

That's a 7/16 NF bolt IIRC.

 

[PlayingWithTBI]

I guess I need to clarify - this is for the harmonic balancer right?

 

[CNewport]

I guess I need to clarify - this is for the harmonic balancer right?

Yes it is. I’m a noobie to all of these bolt terms and whatnot. Mind filling me in? UNF, UNC, NF, etc. what do these acronyms mean?

 

[CNewport]

Something else I was wondering. Going from a 4.3 to a 5.7 TBI, what computer peice do I have to change out, is it the PROM? Also can I use the wiring harness from the V6 considering the harness doesn’t have any connections specific to the number of cylinders?

 

[PlayingWithTBI]

Yes it is. I’m a noobie to all of these bolt terms and whatnot. Mind filling me in? UNF, UNC, NF, etc. what do these acronyms mean?

UNF = Unified Fine thread, a lot of people call it NF or National Fine - same thing
UNC = Unified Coarse thread or National Coarse. Your bolt should be 7/16 - 20 (the regular disclaimer applies)

Here's some other threads to help confuse the issue. Oh yeah, don't forget NPT - pipe thread, NHT - hose thread, ACME thread (square), and probably the least popular Buttress thread, flat on one side and tapered on the other, (look at the cap on your tube of toothpaste) - fun stuff huh?

You must be registered for see images attach

 

[evilunclegrimace]

UNF = Unified Fine thread, a lot of people call it NF or National Fine - same thing
UNC = Unified Coarse thread or National Coarse. Your bolt should be 7/16 - 20 (the regular disclaimer applies)

Here's some other threads to help confuse the issue. Oh yeah, don't forget NPT - pipe thread, NHT - hose thread, ACME thread (square), and probably the least popular Buttress thread, flat on one side and tapered on the other, (look at the cap on your tube of toothpaste) - fun stuff huh?

You must be registered for see images attach

You forgot Straight pipe thread

 

[PlayingWithTBI]

You forgot Straight pipe thread

Yeah - electrical conduit thread.

 

[Frogprince]

Just a question regarding my Burb. Took it off-road this weekend and it was the first time I ever tried to wheel it.

Is it normal for the 7.4l to basically cruise in drive without much throttle at around 30mph? Was on some flats in 4x4 high and could just let off the gas and it would just want to roll at those speeds.

Idle is normal, engine RPM was around 2k during this. Not a big deal just not used to a truck with this large of an engine.

 

[bigfutz]

@Frogprince 2k doesn’t sound like what I would call normal idle, but I’m no expert esp. on the diesels.

 

[DerekTheGreat]

Just a question regarding my Burb. Took it off-road this weekend and it was the first time I ever tried to wheel it.

Is it normal for the 7.4l to basically cruise in drive without much throttle at around 30mph? Was on some flats in 4x4 high and could just let off the gas and it would just want to roll at those speeds.

Idle is normal, engine RPM was around 2k during this. Not a big deal just not used to a truck with this large of an engine.

Is the engine cold when it does this? Until the engine warms up and the ECM commands it to run at base idle that is normal, to an extent. I had a 7.4 and currently a 5.7, both manual transmissions. When I pull away in the morning and get into 4th gear, either one would want to cruise right at 1,700 rpm. Idle strategy is different than cruise strategy for the IAC. I saw IAC counts increase once wheel speed was something other than 0, IAC counts would decrease when the vehicle stopped moving. The IAC is what controls your idle.

If your vehicle is doing this when warm, you've got other issues. Also, if the computer sensed a "stall condition" (likely with wheeling) it will increase the idle a good bit as well, until it has a chance to be at 0 mph and wind itself back down.