Very Silly Question on Vacuum...
Thread Starter
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 99
From: Ontario
Very Silly Question on Vacuum...
And this may demonstrate the power of wishful thinking. I have had moderate pinging problems on hard acceleration; particularly from 60 to ???mph on the highway. Timing is bang on spec at 12BTDC.
Yesterday was a round-to-it day, one of those being to fix a vacuum leak at the heater control module on the shift console. I could not get defrost activated. That is now fixed. A bonus was that I found out that the gauge bezel was not connected to the console! Remnants of the stereo shop installation of my Pioneer unit three years ago I would imagine.
Early this morning was drive time; city and a brief jaunt on the highway. Acceleration from 60mph to ??? is very brisk :) with little if any pinging. I tried a 10 to 50mph run with the same result. The motor sings!!
So the silly question is: [B]Can a vacuum leak in the heater control system affect the vacuum advance at the distributor?[B]
[Modified by paul79, 9:53 AM 9/8/2002]
[Modified by paul79, 9:53 AM 9/8/2002]
Yesterday was a round-to-it day, one of those being to fix a vacuum leak at the heater control module on the shift console. I could not get defrost activated. That is now fixed. A bonus was that I found out that the gauge bezel was not connected to the console! Remnants of the stereo shop installation of my Pioneer unit three years ago I would imagine.
Early this morning was drive time; city and a brief jaunt on the highway. Acceleration from 60mph to ??? is very brisk :) with little if any pinging. I tried a 10 to 50mph run with the same result. The motor sings!!
So the silly question is: [B]Can a vacuum leak in the heater control system affect the vacuum advance at the distributor?[B]
[Modified by paul79, 9:53 AM 9/8/2002]
[Modified by paul79, 9:53 AM 9/8/2002]
Drifting
Joined: Jul 1999
Posts: 1,542
Likes: 43
From: Plano TX
Re: Very Silly Question on Vacuum... (paul79)
Paul,
A small vacuum leak can cause pinging if your car is on the edge because this could cause a lean condition. However, to verify this fact, was the air temp the same and was the humidity the same. Lower temps and higher humidity will also reduce pinging.
You Canadian guys (cars) seem to run more advanced timing than we do in the states. MY 1980 L82 is 8 BTDC per factory spec. I think most if not all in the states are 8 BTDC.
I also want to let you know that when I put the ZZ4 engine in mine 2 years ago I also began to have pinging at part throttle (cruise). The ZZ4 has slightly higher compression and also does not have heat passages in the heads for EGR (EGR reduces pinging). I had to find a vacuum advance unit with less advance. This solved the problem, so you may consider this if it comes back. Your local parts house should be able to look up the advance for the stock unit, then look up a unit with maybe 2 degrees less advance.
Not sure if this is any help.
Dave
A small vacuum leak can cause pinging if your car is on the edge because this could cause a lean condition. However, to verify this fact, was the air temp the same and was the humidity the same. Lower temps and higher humidity will also reduce pinging.
You Canadian guys (cars) seem to run more advanced timing than we do in the states. MY 1980 L82 is 8 BTDC per factory spec. I think most if not all in the states are 8 BTDC.
I also want to let you know that when I put the ZZ4 engine in mine 2 years ago I also began to have pinging at part throttle (cruise). The ZZ4 has slightly higher compression and also does not have heat passages in the heads for EGR (EGR reduces pinging). I had to find a vacuum advance unit with less advance. This solved the problem, so you may consider this if it comes back. Your local parts house should be able to look up the advance for the stock unit, then look up a unit with maybe 2 degrees less advance.
Not sure if this is any help.
Dave
Drifting
Joined: Jul 1999
Posts: 1,542
Likes: 43
From: Plano TX
Re: Very Silly Question on Vacuum... (paul79)
Paul,
I forgot to ask: Do you know if the Whisky A go-go is still up the 400 (I think it was an exit just north of the ETR tollway)? I used to visit Toronto a lot a few years ago. Very entertaining club LOL
Dave
I forgot to ask: Do you know if the Whisky A go-go is still up the 400 (I think it was an exit just north of the ETR tollway)? I used to visit Toronto a lot a few years ago. Very entertaining club LOL
Dave
Thread Starter
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 99
From: Ontario
Re: Very Silly Question on Vacuum... (DaveL82)
The temp difference was significant. Most of the summer was 85-90F. This morning was about 70F. The sticker under the hood (and the factory manual) says 12 BTDC but I can pull it back to 8 BTDC to see what happens. I use the same gas consistently. I also have a new AC Delco vacuum advance in the basement (pic) and may pop it on. The one on the car is almost 24 years old. I did not know you could order vacuum advances with different ratings!! I have heard of adjustable units....
[Modified by paul79, 10:46 AM 9/8/2002]
[Modified by paul79, 10:46 AM 9/8/2002]
Race Director
Joined: Apr 2002
Posts: 11,485
Likes: 1
From: Far side of the Moon
CI 4-5-6-7-8 Veteran
St. Jude '03-'04-'05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15-16-'17
Re: Very Silly Question on Vacuum... (paul79)
My 73 says 12 BTDC also (350 with TH-400 tranny). Purrs like a kitten.
A vacuum leak will cause all kinds of problems. Leans out the mixture and delays the vacuum advance to name a couple.
Sounds like yours is runnin fine now. :cheers:
A vacuum leak will cause all kinds of problems. Leans out the mixture and delays the vacuum advance to name a couple.
Sounds like yours is runnin fine now. :cheers:
Le Mans Master
Joined: Sep 2000
Posts: 5,635
Likes: 4
From: Orlando Floriduh
Re: Very Silly Question on Vacuum... (gb4622)
Yesterday's specs. usually don't work with today's gas. You just have to find what timing specs work for you with the gas you are using. Never ever use regular except in your lawn mower. :rolleyes:
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