Corvair DiagramCorvair Photo
Corvair Center
home forum corvairs calendar links Corvair Podcast
California Corvairs
Clarks Corvair
Clarks Corvair
“CORSA"



Chevy Corvair License Plate
Chevy Corvair Chrome Wheel
Corvair Center Forum :  Corvair Center Phorum The fastest message board... ever.
Corvair Center 
tuning with Vacuum gauge
Posted by: spesce ()
Date: June 26, 2020 05:12PM

Okay I have the carbs synched, the timing set and idle down to 600. That took a while....It is running fairly well, but am interested in getting the idle down to 500 as you all have recommended. I believe I need to tune the air fuel mixture more accurately.

The manual says to hook a vacuum gauge to each carb by removing the choke thingy hose and hooking two calibrated gauges or to hook a line connecting each and teeing to a gauge and then just squeezing each side to use a single gauge. The gauge that I have is erratic and is not steady. What is the issue, my gauge or another tuning of the engine?

The manual also says to connect to the balancing tube between the carbs to have 14-18 pounds. While this vacuum gauge reading is much more steady than at each carb, it is still erratic by about 10 psi high to low and very fast. NOT Steady

What should be my next move?

Electronic ignition, completely warmed up engine. The engine is a 1962-1964 HPE engine. I also confirmed that I have 12 volts at the coil for the electronic ignition......This has been my similar tuning experience for 5 years and this is my third engine. While I am a shade tree mechanic, it should be easier or I can say I am ignorant.

Any pro's in the (I hate to say?) in the Seattle area? More on the eastside? that would be interested in helping?

Options: ReplyQuote
Re: tuning with Vacuum gauge
Posted by: AZ Troy ()
Date: June 26, 2020 05:44PM

I have seen Valve adjustment cause an erratic reading. (or a non sealing valve)

a leak down test may help.

Troy G. / Scottsdale Arizona

'65 140 Corsa Coupe
'66 180 Corsa Coupe - Crown Converted in the '60's

Options: ReplyQuote
Re: tuning with Vacuum gauge
Posted by: gwrench ()
Date: June 26, 2020 05:52PM

You could try pinching the hose to the vacuum gauge with a vise grip. Don't pinch it closed, just close it down some.

A motorcycle tune some years ago needed that trick.

Dale
Loveland, Colorado

1965 Monza 140 barn find

Options: ReplyQuote
Re: tuning with Vacuum gauge
Posted by: MattNall ()
Date: June 26, 2020 05:52PM

Personally I don't use vacuum to "tune", let alone set idle speed, due to the Corvair's intake manifold layout.

Low idle and erratic readings go in hand!

Flat / horizontal engines are very TIMING sensitive vs rpm! Especially at idle speeds!!

As per my Instructions in our FAQ's..adjust idle MIXTURES to get the smoothest idle.

[youtu.be]

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

Options: ReplyQuote
Re: tuning with Vacuum gauge
Posted by: corventure Dave ()
Date: June 30, 2020 11:26AM

Your vacuum gauge needs a small port where you connect the hose. Pinching the hose as suggested by Dale will work.
I put a brake line tube that I brazed up and put into the vacuum gauge port and drilled out with a 1/16 in size drill. This stabilizes the gauge.

With automatic's in drive and at idle, balancing the carburetors is more critical, in order to have a smooth standstill at traffic lights and stop signs.

Corventure Dave

Options: ReplyQuote
Re: tuning with Vacuum gauge
Posted by: spesce ()
Date: July 01, 2020 09:12PM

I have been offline for the last few days. Thank you for your suggestions. I think the last three engines I have had in this rig, the vacuum gauge always erratic. I will try the necking down of the flow to the gauge.

"Personally I don't use vacuum to "tune", let alone set idle speed, due to the Corvair's intake manifold layout.

Low idle and erratic readings go in hand!

Flat / horizontal engines are very TIMING sensitive vs rpm! Especially at idle speeds!!

As per my Instructions in our FAQ's..adjust idle MIXTURES to get the smoothest idle."

I will go to that as well and let you know results. I am getting there, but this very fine tuning (to me) I need all the help I can get.

Options: ReplyQuote
Re: tuning with Vacuum gauge
Posted by: MattNall ()
Date: July 01, 2020 09:49PM

Get a Magnehelic 15-0-15 gauge and hook to verticle ports of carbs.

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

Options: ReplyQuote


Sorry, only registered users may post in this forum.
This forum powered by Phorum.