The Stupid Engine Questions Thread

[Aloicious]

I'm not familiar with hgs units of vacuum...is it in inches of mercury (i.e. gauge reading or absolute?), also, what's your altitude?

I dont know of any generally accepted measurements of acceptable dizzy play, but a little bit is normal, I'd say 1/8" is normalish, 3/16 might be a bit high, do you have any indications of a knife-edged distributor gear like a p0300?


GMCYukondriver - I'm not familiar with PAC, where did you see that acronym?

 

[heavychevy98]

I looked for PAC and plasma arc cutter/cutting is the only thing i found thats even remotely related to this forum. May be something i missed tho. Unless your renting a car? Then its insurance for personal accidents and cargo.

 

[Aloicious]

I looked for PAC and plasma arc cutter/cutting is the only thing i found thats even remotely related to this forum. May be something i missed tho. Unless your renting a car? Then its insurance for personal accidents and cargo.

heh
or Political Action Committee, or the PAC-12 college sports conference, or of course, PAC-MAN and his feminist couterpart, Ms. Pac-man

 

[Hezsus]

I'm not familiar with hgs units of vacuum...is it in inches of mercury (i.e. gauge reading or absolute?), also, what's your altitude?

I dont know of any generally accepted measurements of acceptable dizzy play, but a little bit is normal, I'd say 1/8" is normalish, 3/16 might be a bit high, do you have any indications of a knife-edged distributor gear like a p0300?


GMCYukondriver - I'm not familiar with PAC, where did you see that acronym?

no p0300 but you can feel the miss/stumble at idle, and see it on a tech 2, it pings with low rpm and high load as well

1072' from sea level and hgs is units of mercury (inches) it reads 17 on the guage, not sure what the absolute would work out to, I get 28-17 but I dont think that right

 

[SAATR]

Does anyone know what PAC stands for?

Are you talking about PAC Racing Springs? The guys that make the PAC 1218 springs that are popular on LS engines?

 

[SAATR]

no p0300 but you can feel the miss/stumble at idle, and see it on a tech 2, it pings with low rpm and high load as well

1072' from sea level and hgs is units of mercury (inches) it reads 17 on the guage, not sure what the absolute would work out to, I get 28-17 but I dont think that right

You need a barometer to work out absolute pressure, but assuming that your local barometric pressure at the time of your vacuum reading was 28inHg, then absolute would indeed be 28inHg - 17inHg, or 11inHg absolute pressure.

 

[Aloicious]

at your altitude, the atmospheric pressure should be roughly 28.9inHg, so your absolute inHg that you're pulling sould be 11.9inHg or 40.3 kPa (sorry kPa is the unit I'm used to working with, so it helps me to do that conversion)...which seems a tiny bit high, but really probably nothing to worry about, there also may be other factors attributing to the reading too, like where the reading was taken at, etc.... I am used to seeing 30-35kPa at ~4500' elevation through the MAP sensor.

if you're feeling a issue that you think may be due to the dist gear, you can always pull it at check, especially if you have access to a tech2 (it sounds like you might), you should be able to set the distributor offset with the tech2 when you re-install.

 

[gmcyukondriver]

Sorry, I forgot I asked that question in here. It's on the instructions for the whipple. It says they are for a 93-95 5.7l TBI system without PAC system.

Also, I had a question for Aloicious. I called the guy that had this kit before me. He said he had it on a stock 95 tahoe with 120k. I asked him if he ran colder plugs and/or higher octane and he said no. I was surprised. I know elevation has an effect on that. What do you think? I'm at 87 ft above sea level, so not too high. It would be nice to not have to switch from 87, but I won't hesitate to go to 91 if it's not safe. I'll be running 3 psi. and I'm planning on running one range colder plugs.

 

[Hezsus]

at your altitude, the atmospheric pressure should be roughly 28.9inHg, so your absolute inHg that you're pulling sould be 11.9inHg or 40.3 kPa (sorry kPa is the unit I'm used to working with, so it helps me to do that conversion)...which seems a tiny bit high, but really probably nothing to worry about, there also may be other factors attributing to the reading too, like where the reading was taken at, etc.... I am used to seeing 30-35kPa at ~4500' elevation through the MAP sensor.

if you're feeling a issue that you think may be due to the dist gear, you can always pull it at check, especially if you have access to a tech2 (it sounds like you might), you should be able to set the distributor offset with the tech2 when you re-install.

Thanks for that on the vaccume, I never thought it was a problem but I figured i'd double check.
I dont have a tech 2 or compatible (local dealer noticed it when i got a crank relearn for my tune) I have scanxl software and torque for android and I dont think I can check the timing with them,
my fuel trims (long) are always around -12 to -14 at idle and dont hit a positive # till about 2k
I also get the occasional 'gas cap' code (forget the number) but just clear it and continue

Is there any harm in pulling the dist to check and putting it back in or would I still need the tech2 to get it 100%?

 

[Aloicious]

Hezsus, you'd need some kind of scanner that can read the CMPRET PID (cam offset retard) to get the cam position 100%, its REALLY sensitive, you might be able to mark and reinstall the distributor and get it close enough to not throw a code, which is fine, but for it to be 100% you'd definitely need a scanner, a shop or dealer should be able to check it for you if you wanted, but I don't know what they'd charge, its really easy, but they might have to charge an hour's rate or something even though it's only like a 15 minute job...

-12 to -14 trims are pretty rich. though with the poppets and only a mail order tune there may not be much you can do about it...the gas cap code might be due to the cap not sealing well enough, the gasket in the cap does wear out after a while...

gmcyukondriver, 3psi isn't much, even at sea level (87 ft is pretty much sea level)...you might be alright with 87, but it's hard to say, I'm not up on my TBI PCM ability, do you have a way of logging or live scanning to see if you're getting any knock spark retard? I always ran 91 octane in mine when I was supercharged, but I also had advanced spark maps, and ran around 6 psi over atmosphere (which ended up being closer to 4psi above sea level pressure), among other mods...I ran NGK TR6 plugs gapped at .045 (vortec stock gap is .060), but stock ones might be fine...I typically recommend at least 91 octane for boosted applications, but if you're getting adequate fuel and are able to monior the knock amount, you can give 87 a try and see how it responds...