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Tune-up help please
Posted by: Peeeot ()
Date: May 09, 2019 08:08AM

I have followed the shop manual’s guidelines for tuneup, but am not satisfied with the results and am hoping ya’ll can help get me closer.

Ignition-wise, I have the dwell at 32 and initial timing at 16 BTDC. Plugs are new NGK B6HS gapped to 0.031”.

I went through the carburetors to verify clean, clear passages, correct float level and drop, replaced accelerator pump cups, and set them up exactly as the manual says: 0.003 feeler gauge plus 1.5 turns for idle screw and 1.5 turns for mixture screw. From there, I had to open the mixture screws up to about 2.5 turns for best idle. Mechanical synchronization was executed per manual.

Manifold vacuum at the cross tube port is about 13” at idle. The needle is not rock steady but wiggles a little. I checked the vacuum at each carburetor through the choke pull off port and the needle was vibrating between 10-12” on the pass side carb and 11-13” on the driver side carb. Idle speed is about 750 and quality gets worse if I slow it down any more.

There is a noisy lifter on the driver side. It seems to quiet up almost entirely if I drive the car some.

Other than the low vacuum, my other problem is stalling. It will idle steady for a while, then it might start slowing down a bit then quit. Once started, it might quit before I can get out and walk to the back. If I rev it above idle after starting, it will generallly stay running for a few minutes at least before eventually stalling again.

So, questions:

1. Is a bouncing vacuum needle at the carb ports normal?
2. Why might vacuum be so low?
3. What is the probable culprit for the stalling?

Thanks in advance!



Edited 1 time(s). Last edit at 05/09/2019 08:09AM by Peeeot.

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Re: Tune-up help please
Posted by: MattNall ()
Date: May 09, 2019 08:29AM

1 & 2 are normal at low idle.... 550-650 rpm

Forgot... no sigline to remind us!

PG??

Pertronix II

Known problem!

Otherwise find a UniSyn and balance airflow "dynamically"

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

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Re: Tune-up help please
Posted by: Peeeot ()
Date: May 09, 2019 08:34AM

Sorry, it’s a 4-speed manual with points ignition.

1963 convertible - 102hp - 4-spd - 3.27 posi - central NC

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Re: Tune-up help please
Posted by: Timothy Shortle ()
Date: May 09, 2019 09:30AM

What results are you not satisfied with? How about the fuel filters in the carbs as well as the rubber fuel hoses? Are you getting proper vacuum and centrifugal advances from the ignition system?

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Re: Tune-up help please
Posted by: joelsplace ()
Date: May 09, 2019 10:11AM

Do a compression test to make sure the engine is in good shape.
Check to make sure fuel isn't dripping from the clusters in the carb throats at idle. You may have a high fuel level from either float issues or high fuel pressure or both. What is your float level?

Joel
Northlake, TX
5 Ultravans, Lost count at 100 Corvairs...

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Re: Tune-up help please
Posted by: Peeeot ()
Date: May 09, 2019 01:43PM

I am not satisfied with the idle quality and stability, mainly.

Both advance mechanisms of the distributor are fully functional. I didn’t specifically check the fuel filters, but there don’t seem to be any problems at higher speeds.

I did a compression test before I bough the car and got these numbers:
1 150
2 166
3 157
4 152
5 165
6 140

They may have shifted a little since valve adjustment (cold) but not by much I wouldn’t think.

I have seen the occasional drip from the Venturi cluster while idling. Pretty sure I set the floats to 1-1/8” per popular opinion on this forum. The floats looked about parallel with the air horn. They are the early-style float.

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Re: Tune-up help please
Posted by: joelsplace ()
Date: May 09, 2019 04:18PM

Since you adjusted the valves you should check the compression again. I can't remember how many times that is the issue. Very common problem.
Since you are getting drips you should check your fuel pressure. Maybe move the float level to 1-3/16".

Joel
Northlake, TX
5 Ultravans, Lost count at 100 Corvairs...

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Re: Tune-up help please
Posted by: 7004doorL ()
Date: May 09, 2019 04:53PM

16 Degrees BTDC Initial Advance? I thought that was too high for a Manual Transmission?

Has the vacuum advance been checked out using a timing light?

Mike
1960 4 Door
PG

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Re: Tune-up help please
Posted by: Peeeot ()
Date: May 09, 2019 05:58PM

Since my earlier post,I spent some more time with the corvair this afternoon. I double checked the carburetors and there was no drip from the Venturi clusters at all this time.

One thing I found was that manifold vacuum and idle quality both improved if I advanced timing farther. I went as high as 20 degrees initial at 750 rpm, which increased manifold vacuum to about 15” Hg. I did not observe any ill effects of this increase— no harder to start, no spark knock under normal driving (didn’t try flogging it yet). So I will leave it there for now.

I did not observe the frequent stalling from this morning, but after idling long enough the car did eventually cut out. This time when I started it it stayed running. I test drove around and the engine cut out several times when I let off the throttle and slowed near a stop. It always started again but made traffic lights unnerving.

I will redo the compression test soon and also see if I can adjust the tick out of that noisy lifter.

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Re: Tune-up help please
Posted by: Vin ()
Date: May 09, 2019 06:55PM

When I first read your post I thought ah, you need to do a cold valve adjustment first before anything else. But then later you said you did one. But you mention this ticking valve. I say double check you got the valve adjustment right. It isn't difficult but if you dont have some experience with it or really know what to look for and be certain of the sequence you can mess it up.


Vin
Dayton, OH
1965 Corvair Monza Convertible (4 speed)

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Re: Tune-up help please
Posted by: Carburetor ()
Date: May 10, 2019 09:11AM

Peeeot Wrote:
-------------------------------------------------------
> I have seen the occasional drip from the Venturi cluster while idling. Pretty sure I set the floats to 1-1/8” per popular opinion on this forum. The floats looked about parallel with the air horn. They are the early-style float.


Per Bob Helt's book (page 89 - opened right here in front of me) the float level for early carbs ('60-'63) is 1-13/64" though he also recommends a float setting of 1-1/4" or 1-17/64" to prevent fuel dribbling from the cluster at idle. The float setting for the late carbs is 1-1/16" with a recommendation of 1-1/8" to prevent fuel dribbling - mine are set at 1-1/8".

I can testify firsthand that the fuel dribbling from the venturi cluster at idle can come and go, and that ANY dribble will severely affect idle quality.

Jim C.
Chesterfield, MI

1966 Monza convertible (140 / PG)
2017 Chevrolet Trax (daily driver)
2017 Chevrolet Volt (wife's ride)


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Re: Tune-up help please
Posted by: Peeeot ()
Date: May 10, 2019 09:26PM

My engine is a ‘63, but the carbs are 64 or 65: they have the vent valve at the base and the extra enrichment needle. I read something somewhere saying there were two kinds of floats and the later models used a shorter float with an assist spring which was why later models used a higher float setting. Am I making that up? At any rate mine don’t have the assist spring or the spot for it. Is 1-13/64” still the spec I need to use?

I took another test drive and everything was great engine-wise till I got home and it stalled when I pulled in the driveway. I think you’re right and intermittent Venturi cluster drip is what’s causing the stall.

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Re: Tune-up help please
Posted by: Carburetor ()
Date: May 12, 2019 06:07PM

According to Bob Helt's book (if you don't have it, you really need to get a copy), the vapor vent valve was added in '64 and the power enrichment system (PES) was added in '65 (I'm assuming that is the enrichment needle you mentioned).

My understanding is that the float level matches the float, not the year of the carb. In other words, an early (larger) float would use the 1-13/64" spec and a later (smaller) float would use the 1-1/8" spec.

However, on page 10, Mr. Helt states that the smaller floats were used to raise the fuel level in the bowl about 1/8" to speed up the transition from off-idle to the main circuit and increase the range of fuel level variation in the bowl. The assist spring was added to maintain float stability on bumpy roads. If it was my car, I would replace the floats with later floats and the assist spring so the carb internals match how the engineers designed it to work.

Just my $0.02...

Jim C.
Chesterfield, MI

1966 Monza convertible (140 / PG)
2017 Chevrolet Trax (daily driver)
2017 Chevrolet Volt (wife's ride)


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Re: Tune-up help please
Posted by: Peeeot ()
Date: May 14, 2019 10:27AM

I adjusted my float levels. Previous level was not 1-1/8”; it was more like 1-5/32”. The sheet that came with my rebuild kit specified 1-7/32” up to 62 then 1-3/16” for 63 for some reason. I seem to recall trying to split the difference between these specs.

Anyway I set it to between 1-7/32” and 1-1/4”. Thurs morning’s road test indicated no trouble at all and possibly the best overall running at at any RPM. I didn’t have time to get it good and hot though so I’m not sure yet whether the stalling has been cured. I’m feeling optimistic though!

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Re: Tune-up help please
Posted by: Peeeot ()
Date: May 14, 2019 06:17PM

My optimism was misplaced. Idle quality remains marginal with manifold vacuum hovering around 13”. Mixture adjustment can make it worse but not better. Stalling still occurs. It stalled while I was watching the carburetor throats and there was no fuel drip visible at all. Used my engine analyzer to check the points and dwell; both were good.

I don’t suppose it’s possible for timing marks to be off on a solid-pulley 145 ci?

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Re: Tune-up help please
Posted by: MattNall ()
Date: May 14, 2019 07:17PM

Very unlikely..


you are setting timing with the VA's hose off and plugged?

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

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Re: Tune-up help please
Posted by: Peeeot ()
Date: May 14, 2019 07:46PM

Yes sir.

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Re: Tune-up help please
Posted by: MattNall ()
Date: May 14, 2019 08:26PM

And what RPM is it idling at HOT? Have tried resetting both carbs the same amount....say 1 turn CW when hot and see what happens?

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

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Re: Tune-up help please
Posted by: krfjkm ()
Date: May 14, 2019 08:35PM

What part of N.C. are you in?

KRFJKM
Charlotte NC
1965 Corvair Corsa
1966 Corvair Corsa (60 over with an Isky 280)

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Re: Tune-up help please
Posted by: Peeeot ()
Date: May 15, 2019 05:49AM

Matt, it’s idling about 700 rpm hot.

Krfjkm, I sent you a PM.

This morning I indexed my distributor so I could advance initial timing farther to see if it would help. Best idle was around 24 degrees initial, but maximum vacuum was still around 13”. Re-checked carb balance via vacuum reading at the choke pull-off lines. At idle both carbs showed a needle bouncing between about 9 and 12; at 1200 rpm both carbs showed 13-14.

At this point I feel all ignition and tuning-related avenues have been exhausted, so the next step is the compression test I’ve been avoiding spinning smiley sticking its tongue out and pending those results possibly valve re-adjustment.

1963 convertible - 102hp - 4-spd - 3.27 posi - central NC



Edited 2 time(s). Last edit at 05/15/2019 05:51AM by Peeeot.

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