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1.125 inch Bore Carburetors with 56 Jets
Posted by: Harry Moore ()
Date: September 05, 2020 05:57PM

I just picked up my Dad's carbs from Dave Kostich.
He took the 1965 carbs with Power Enrichment, vapor vent, non-staggared venturi's, and other mis-matched parts and built a set with early bases.

He used a lathe to make the base and the top half of the base perfectly flat, lathed the inside diameter to 1.125 inches, enlarged the holes in the venturi cluster and the accelerator pump discharge holes, and used a mixture of media to clean the carbs. He also put a 56 size jet in them.

These carbs are for a 1967 110hp, 4 speed, open diff, air conditioned monza coupe.


Harry Moore
66 Monza Sedan 140/PG
Southern California



Edited 1 time(s). Last edit at 09/05/2020 06:04PM by Harry Moore.

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: Harry Moore ()
Date: September 05, 2020 05:59PM

Here are a few more pictures.

With the media Dave uses, you can really see the different types of metal used on the bottom vs. the top. They come out slightly different in appearance because of this.

It is difficult to see in the pictures, but in person it is more apparent.


Harry Moore
66 Monza Sedan 140/PG
Southern California



Edited 2 time(s). Last edit at 09/05/2020 06:02PM by Harry Moore.

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: MattNall ()
Date: September 05, 2020 06:30PM

Put them on your driver and test /tune them.

MODERATOR
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..............................110-PG.................................................Webered-Turbo

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: vairmech ()
Date: September 06, 2020 05:22AM

If you cut the cluster arms off and use brass tube to insert in the cluster then make the ends come within 1/8" of the venturi you could then use a smaller jet, probably a #52.

You can also file on top of the cluster arm to make it more pointed and also thin it down a fair amount.

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: Timothy Shortle ()
Date: September 06, 2020 05:26PM

I think the metering jets used in A/C equipped cars were bigger than non A/C cars.

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: RobertC ()
Date: September 07, 2020 02:52AM

vairmech Wrote:
-------------------------------------------------------
> If you cut the cluster arms off and use brass tube to insert in the cluster then make the ends come within 1/8" of the venturi you could then use a smaller jet, probably a #52.
>

There is a bit of missing / misleading information in this thread.

First - modification to the 110 heads. I would assume at the least that the carb mount has been bored out to match the carbs.

Second - Thread states that 65 PEV carbs supplied, but early non PEV carbs (bottoms) returned?

If the current carbs have no PEV valve, then the.056 jets may be ok - might even be lean, actually.

An example: I converted my 140 to 4 primary carbs - decades ago - relocated jets; no PEV. Originally, put in .054 jets (against my mechanic's recommendation). I found that head temp read 50 degrees higher at freeway cruise (at night). I switched the jets to .055 and the head temp dropped to the previous normal at freeway cruise.

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: dryenko ()
Date: September 07, 2020 04:38AM

Agree.
Following to see what jets are eventually needed to make this particular engine run correctly.
My experience is they have to be much larger for that venturii bore size

Bob C aka Dryenko
Dobson, NC 27017

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: Harry Moore ()
Date: October 12, 2020 11:56PM

I put the carbs on the engine this weekend and it started right up. I quickly used a set of calipers to measure the inside of the carbs and then compared them to the carb mount hole in the head, the Bakelite insulator and the thin gaskets.

All the holes were bigger than the carb. So, no need to enlarge the head or cut gaskets! To my knowledge no other work has been don to the heads.

@vairmech - I asked Dave about this and he said there was no need to extend the venturi arms so they are closer to the venturi bore...I am taking his word on this since I have never ran carbs like this.

@RobertC - Yes I have all new carbs. I basically gave Dave my late carbs and he built me a new set using early bases to eliminate the PEV and vapor vents. I also had mis-matched venturi clusters in the carbs I gave him. He built me two matching carbs....that alone will help it run!!!

At this point, I need to finish the tune-up (Seth's wires should be here soon), then I have my Dwyer gauge to balance each carb at idle.



I don't have an exhaust analyzer or short/wide band 02 sensor to figure out the air to fuel ratio yet.....but I would like to. Anyone in the San Diego area have one I can barrow? I remember Ken Shiftner showing me this at a Coyote Corvair Club Meeting (this is why I have the Dwyer gauge!!)smiling smiley


Harry Moore
66 Monza Sedan 140/PG
Southern California

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: v8vair ()
Date: October 13, 2020 06:14AM

Why bore the carbs if your just gonna plug the hole by extending the clusters ,plugging up the hole you just enlarged ?
Obviously this is a performance upgrade which requires larger jets, the cost of doing business.
Enjoy your new carbs and if you have to spend a few bucks more in fuel, if they run good who cares .

1965 Crown V8 Racer
1964 Bill Thomas Monza Replica Racer
1964 Spyder Street Car
1979 Mazda RX7

Mike Levine

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: dryenko ()
Date: October 13, 2020 07:21AM

When boring the venturii .062" on each side, the tips should be still within 1/8" of the wall.
Extending them to the original clearance will maintain main jet response rate/ fuel flow curve.
As Yenko with the help of GM Rochester found to be needed.
Doing this could eliminate and flat spots in the engines acceleration under sudden changes in throttle position.
Using narrower tubing than the original cluster tips, keeps the venturii blockage about the same as the original configuration. [ IMHO ]
But probably all this is not critical on a 110 engine with the small valves and low airflow rate.
Especially with a stock cam and exhaust.
Assumed, since no info on these items were given.
It would be interesting to see a before and after dyno test to see if the carbs mods pictured have any measurable effect on actual rather than SOP perceptions of " power ".
Fuel economy , I suspect, will be poorer.
May not be a concern.
YOMV.
BC

Bob C aka Dryenko
Dobson, NC 27017



Edited 1 time(s). Last edit at 10/13/2020 07:27AM by dryenko.

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: azdave ()
Date: October 13, 2020 08:11AM

Harry Moore Wrote:
-------------------------------------------------------
> ...then I have my Dwyer gauge to balance each carb at idle.

You are better off balancing your carbs off-idle when the idle speed screws are not touching the arms. Any possible play or mismatch in your throttle linkage is hidden when the arms are up against those idle speed screws.

Set the RPM at about 1500 RPM using a temporary turnbuckle or coat hanger wire pulling on the cross-shaft arm and then compare the side-to-side balance. It is not always the same balance when you return to idle. Do you want the best carb balance at speed when the engine is under load or when sitting at a stop light?

With well-worn OEM parts there will be compromises. A Roger Parent throttle linkage system helps eliminate this at-idle/off-idle imbalance.

Dave W. / Gilbert Arizona
65 Corsa 140/4
66 Corsa 140/4
66 Corsa 140/4 w/factory A/C
66 Corsa 455 Toro V8
65 Monza Convertible 110/4
66 Monza Convertible 140/4 A/C
65 Monza 4DR 140/PG w/factory A/C
65 Monza 4DR EJ20T/5



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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: joelsplace ()
Date: October 13, 2020 08:33AM

I always do both. Why wouldn't you?

Joel
Northlake, TX
5 Ultravans, 113 Corvairs and counting...

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: azdave ()
Date: October 13, 2020 09:39AM

joelsplace Wrote:
-------------------------------------------------------
> I always do both. Why wouldn't you?

The point I was trying to make is that most people don't balance off-idle first (or at all) and that is more important with all the old linkages involved. Too many people set the balance while at idle and assume the carbs stay in sync after that.

Dave W. / Gilbert Arizona
65 Corsa 140/4
66 Corsa 140/4
66 Corsa 140/4 w/factory A/C
66 Corsa 455 Toro V8
65 Monza Convertible 110/4
66 Monza Convertible 140/4 A/C
65 Monza 4DR 140/PG w/factory A/C
65 Monza 4DR EJ20T/5



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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: American Mel ()
Date: October 13, 2020 08:33PM

azdave Wrote:
-------------------------------------------------------
> joelsplace Wrote:
> -------------------------------------------------------
> > I always do both. Why wouldn't you?
>
> The point I was trying to make is that most people don't balance off-idle first (or at all) and that is more important with all the old linkages involved. Too many people set the balance while at idle and assume the carbs stay in sync after that.


Okay, I will step up on behalf of everyone else who is in the same boat, but too shy to say anything.

Joel's question: Why wouldn'y you?
Maybe because they have NEVER heard anyone EVER mention it?

Dave's comments: ". . . . most people don't balance off-idle first (or at all) . . ."
And "Too many people set the balance while at idle and assume the carbs stay in sync after that."

Again, I have never done this, because I have never read, or heard of doing such a thing. Balancing carbs was something I had never done until owning a Corvair.
Remember, Multi-Carb engines, are not the common norm.
Since this has been brought up, please explain to this Inexperienced Naive Lowbrowed Philistine how you can set BOTH ? ? ?
It seems to me that after setting one, you will immediately upset THAT balance when you make an adjustment for the other ! ? ! ? ! ?
I would LOVE to learn how to do this additional step to fine tuning my fun little toy.

Maybe it would be a good idea to address this as a new Thread, rather than totally Hijack this one?

-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
WA. state, 1 mile south of the Canadian border,
I am not at the end of the world, but you can see it from here.
Have; '66 Monza Coupe - 140, 4-spd. Daily driver beater
'67 Monza Vert. - 140, 4-spd. Daily driver beater
'67 A/C Moredoor Monza
Have had; '61 Monza coupe, 80hp, PG
'62 Monza Wagon, 4spd.
'63 Spyder,
'65 Corsa
.
non-vair
'04 Dodge Cummins Quad Dually, approaching 400K
'03 Honda Del Sol
17'Terry



Edited 1 time(s). Last edit at 10/13/2020 08:43PM by American Mel.

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: joelsplace ()
Date: October 13, 2020 09:18PM

Adjust the mixture screws, set the idle speed and balance at idle using the stop screws. After that hold the throttle open some with the throttle rod (the one coming through the front shroud) and use the adjustable link to balance the carburetors after the linkage slop is taken out at 1500rpm or higher.
This is the only way to really have it run right and the 2 shouldn't bother each other unless something in the linkage is really worn out.
I just assumed everyone did something like this.

Joel
Northlake, TX
5 Ultravans, 113 Corvairs and counting...

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: RobertC ()
Date: October 13, 2020 10:33PM

joelsplace Wrote:
-------------------------------------------------------
> Adjust the mixture screws, set the idle speed and balance at idle using the stop screws. After that hold the throttle open some with the throttle rod (the one coming through the front shroud) and use the adjustable link to balance the carburetors after the linkage slop is taken out at 1500rpm or higher.
> This is the only way to really have it run right and the 2 shouldn't bother each other unless something in the linkage is really worn out.
> I just assumed everyone did something like this.

Think you guys are trying too hard.

If you change the adjustable link at 1500 rpm; you change the balance at idle.

Never had an issue , but, of course, I did not use worn out linkage pieces, either.

Good luck.

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: joelsplace ()
Date: October 13, 2020 11:23PM

"If you change the adjustable link at 1500 rpm; you change the balance at idle."
For that to hold true the linkage would have to have zero slop. Roger's isn't even that good.

Joel
Northlake, TX
5 Ultravans, 113 Corvairs and counting...

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: RobertC ()
Date: October 14, 2020 12:16AM

joelsplace Wrote:
-------------------------------------------------------
> "If you change the adjustable link at 1500 rpm; you change the balance at idle."
> For that to hold true the linkage would have to have zero slop. Roger's isn't even that good.

So, what are you really accomplishing?

Always adjusted balance at idle; never any indication that the carbs were out of balance at higher rpm.

Maybe you are more sensitive than I am?

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: azdave ()
Date: October 14, 2020 05:07AM

RobertC Wrote:
-------------------------------------------------------
> So, what are you really accomplishing?
>
> Always adjusted balance at idle; never any indication that the carbs were out of balance at higher rpm.
>
> Maybe you are more sensitive than I am?


Well it's not like that adjustment step could gain you 10 HP but why would you not want the left and right banks to be as balanced as they can reasonably be while the engine is under load? If you have all of your tools out doing a tune-up and balance at idle, why not set the balance off-idle wile you are at it? Do you drive around town at idle?

Here's the GM Jim Handy film that shows the recommended off-idle balance check.
[youtu.be]

Dave W. / Gilbert Arizona
65 Corsa 140/4
66 Corsa 140/4
66 Corsa 140/4 w/factory A/C
66 Corsa 455 Toro V8
65 Monza Convertible 110/4
66 Monza Convertible 140/4 A/C
65 Monza 4DR 140/PG w/factory A/C
65 Monza 4DR EJ20T/5






Edited 1 time(s). Last edit at 10/14/2020 05:09AM by azdave.

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Re: 1.125 inch Bore Carburetors with 56 Jets
Posted by: joelsplace ()
Date: October 14, 2020 08:57AM

I agree Dave. I want the carburetors balanced as close as possible in the most situations they will operate in.

Joel
Northlake, TX
5 Ultravans, 113 Corvairs and counting...

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