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 
Rough Idle and Part Throttle Roughness
Posted by: alphasud ()
Date: August 11, 2019 02:49PM

I recently got my car on the road. Bought the 140 engine from another owner who rebuilt it a number of years ago. I know it has new pistons and barrels,and a valve job. I went through all the carburetors cleaned, set up the linkage, and balanced. I don’t have another 140 to benchmark but there are 2 issues that I wanted to ask the community since I’m new to the Corvair world.
The first issue was at light throttle the engine starts breaking up. Came to the conclusion that this was too much advance and disconnecting the vacuum advance the engine runs much better but still has a little of the roughness at part throttle. Accelerate from that condition and it feels great. No issues with misfire under hard acceleration. With my timing light I confirmed I have 18 degrees of mechanical advance and about the same with the vacuum advance. That makes my total advance all in at 2000 at 54 degrees. Seems strong to me. Have it set at 18 before at idle.
The second issue is if the previous owner cracked the case open and replaced the factory cam with something more aggressive or maybe has the cam advanced a tooth that would explain my lopey idle and only having 10” of vacuum at idle. I’m at 3000 feet so I’m already going to see a few inches less than you would have at sea level. Car runs out pretty good till about 5K and then it starts to fall off. Again I don’t know how good a properly tuned 140 should feel like. Any input would be appreciated. I guess a compression test or putting a degree wheel on the crank and measuring When I’m at .050 would be another way.

David North Idaho
1965 Corsa Turbo converted to 140
1971 Super Beetle with 2.5L Subaru engine
2004 F350 work truck
2004 Cayenne Turbo

Options: ReplyQuote
Re: Rough Idle and Part Throttle Roughness
Posted by: MattNall ()
Date: August 11, 2019 03:10PM

That's way too much... at 2000!

That was at a standstill? Under load you wouldn't have the VA...


You only want 32 to 36 total...


I'd leave the VA plugged... Back the initial down to 14 btdc and test drive

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: Rough Idle and Part Throttle Roughness
Posted by: alphasud ()
Date: August 11, 2019 05:45PM

Right that’s at a standstill. The VA falls off on accel. I will have to look at the shop manual. I thought I saw a advance curve to check what I have against the desired advance curve.

David North Idaho
1965 Corsa Turbo converted to 140
1971 Super Beetle with 2.5L Subaru engine
2004 F350 work truck
2004 Cayenne Turbo

Options: ReplyQuote
Re: Rough Idle and Part Throttle Roughness
Posted by: cnicol ()
Date: August 11, 2019 06:01PM

Do you have the VA connected to the vertical carburetor port? That's "ported" vacuum so you should have zero advance at idle. It should only show vacuum at cruise.

The way I read the book, the VA should only advance about 6 degrees, so you might have the wrong VA too.

Have you confirmed that you have an 1110330 distributor? That one is the one for a 140 and advance should be "all in" (18 degrees M + 18 degrees I) at 2800 RPM.

If you want to check the distributor, I have a distributor machine.

Craig N. Coeur d'Alene ID.
66 Black Monza 4dr, 4.2L V8 49k
61 Seamist Jade Rampside 140 PG
60 Monza coupe (sold, sniff sniff)
66 Sprint Corsa convt - First car! Re-purchased 43 years later
2+2 gnatsuM 5691

+17 Tons of parts

Options: ReplyQuote
Re: Rough Idle and Part Throttle Roughness
Posted by: cnicol ()
Date: August 11, 2019 06:12PM

FYI, the 140 VA should have "248" stamped on the advance arm.

Craig N. Coeur d'Alene ID.
66 Black Monza 4dr, 4.2L V8 49k
61 Seamist Jade Rampside 140 PG
60 Monza coupe (sold, sniff sniff)
66 Sprint Corsa convt - First car! Re-purchased 43 years later
2+2 gnatsuM 5691

+17 Tons of parts

Options: ReplyQuote
Re: Rough Idle and Part Throttle Roughness
Posted by: alphasud ()
Date: August 11, 2019 06:51PM

I will confirm and get back on that.

David North Idaho
1965 Corsa Turbo converted to 140
1971 Super Beetle with 2.5L Subaru engine
2004 F350 work truck
2004 Cayenne Turbo

Options: ReplyQuote
Re: Rough Idle and Part Throttle Roughness
Posted by: 66vairman ()
Date: August 12, 2019 08:49AM

The 1110330 Specs. at 2K engine RPM.

18BTDC + 9 TO 13 deg. MECHANICAL ADVANCE + 20 TO 25 VACUUM ADVANCE = 47 TO 56 ADVANCE. So your 54 is in spec., BUT that's at 2K RPM running the engine up with no drive load and vacuum at 15".

Options: ReplyQuote
Re: Rough Idle and Part Throttle Roughness
Posted by: alphasud ()
Date: August 12, 2019 01:00PM

Craig,
I confirmed I do have the 330 distributor it I ha e a 410 VA unit. I think I should pull the unit and maybe run it on your machine. He said he rebuilt it but I would feel better to confirm. Could be my timing light but today I see 21 degrees mechanical.

David North Idaho
1965 Corsa Turbo converted to 140
1971 Super Beetle with 2.5L Subaru engine
2004 F350 work truck
2004 Cayenne Turbo

Options: ReplyQuote
Re: Rough Idle and Part Throttle Roughness
Posted by: MattNall ()
Date: August 12, 2019 01:42PM

Alpha.... today 50 years later who knows..

Infamous Banger engine has a 330 case....but Turbo guts! I rectified that fast!

110 heads

Now it's 11 BTDC static / idle, 20 total at 2000 and 30 total at 3000

VA was adjusted per FAQ's here.. to not start to pull in until 11 in. hGa

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.