One side hot.. one side cold

[mjhsandiego]

I am new to Corvairs, so forgive me in advance.. please. I am trying to get my 140 engine to run reliably. I got the carbs rebuilt and the engine starts right up. However, on the driver's side, the exhaust is cold, while the exhaust is warm on the passenger side. Nothing changes, even as the engine gets to temp. Please provider some expert troubleshooting advice.

Thanks!

Mike

[cvair4life]

Mike - All I know is it's a multi-flavored issue.. I really don't know how to solve it but I'm in the same boat a bit. Has a good deal to do with air flow balance through the carbs and spark heat, etc etc. I'm going to follow your thread and hope the experienced folk on here help both of us out.

[miniman82]

If a bank is not running, it points to a common problem for all the cylinders on that side. The idle jet could be plugged up or linkage adjustments bad for that side, or that side may not be getting fuel. I find it hard to believe a spark problem would manifest on only a bank, so make sure you're getting fuel.

[Mountain Pilot]

First off it does sound like lack of fuel on the cold side.

But we need more information.

Just where are you judging the Hot verse Cold ? The exhaust pipe where it comes out of the sheet metal, valve cover or ???

Does it idle smooth ?

How does it run at road speed ( 35mph - 60 mph ? )

Mileage on engine, since carbs rebuilt etc,

More information you can give the better the feedback...

[mjhsandiego]

Here is a bit more information. I am 99% sure the cylinders are getting fuel. I say this because the carbs were just installed after being rebuilt by Wolf Enterprises,, so I feel confident there are no blockages anywhere. I installed clear plastic fuel filters and I can see they are full of gas and I can also see gas entering the carb throat. The car is not road worthy as there is a problem with the brakes.

As far as judging the temp, I judged the temp by feeling the exhaust gases at the exhaust tip. I covered the end of the cold side and listened for obvious leaks but heard none. I also touched the sheetmetal of the fan shroud from the top of the engine and one side was warm, while the other was cold.

I am happy to get more details with your direction. I am a novice mechanic.

I also think I detect a smell of unburnt fuel from the cold side exhaust.

Thanks.

[Mountain Pilot]

Lets test the exhaust just as it comes off the manifold. Start it up for about 30 seconds, shut it off and get under both the left and right sides and see if the exhaust pipes where bolted onto the manifolds are warm and both about the same temperature. They should be.

Also since the engine starts up ok and idles smooth I would assume both of the banks are running.

When the engine is cold are both of the Air Doors at the lower back of the engine closed? Also the driver side usually opens first which may be the reason why the driver side is cooler...

[terribleted]

A Corvair engine running on one cylinder bank (right or left) will often idle smoothly. Every time I have had this issue (one side hot and one side cold...and I have seen it a number of times) it has been because of a carb problem on the cold side. Often a piece of junk blocking the effected sides carb internally (blocked main well jet or idle passages), or a float or bad carb adjustment issue. Just because the carbs are new Wolf units does not mean they are not the problem. Something may have been damaged in shipping or the rebuilder may have made a mistake somewhere. I would remove the cold sides carb, open it up, re-clean (ensure all passages are open), and recheck all adjustments per the shop manual.

Before above tho I would check the fuel flow at the fuel lines to the carbs (simply because it would be annoying to go through a carb when the fuel line is blocked, and this can be done with little effort). Remove positive wire from the coil (position it where it can not spark to anything...sparks and possible spilled gas are not a good combination), remove the line at the connection to the carb (do one at a time,,,the primary carbs are the concern at this point), position a suitable bottle or other container over the end on the disconnected line to catch the spurting fuel, and have a helper crank the motor over. Fuel should spurt similarly at all carbs. Before you reconnect the lines, remove the large fitting where the line connects and remove and check the fuel stone filter for blockage. Everything looks good?? Proceed to inside the cold side carb.

[mjhsandiego]

Here is what I verified today.
1. All carbs are getting fuel. I can see the fuel inject into the carb throat when I move the linkage.
2. Per a user's suggestion (Mountain Pilot), after a 30 second engine run, the passenger side manifold is warm, while the drive side is cold to the touch. This car came to me with no air doors. I need to replace them.

Car started right up. I am going to post a video in YouTube for you to witness the startup. On the first crank, I had not pumped the accelerator at all. After 2 pumps, it started right up. Here is the videohttp://youtu.be/VaBUfk9pLxQ

Just out of curiosity, I removed all 3 driver side wires, and the car did start and run, although a bit rougher.

Thanks for the pointers!

Next steps?

Mike

[terribleted]

Just because the accelerator pumps squirt gas when you move the throttle does not mean you have full fuel flow to the carbs, but it does mean you should likely idle ok...you have some flow. Compression ok on the left side?? I still think you may have a defective left carb but before spending shipping money or re-rebuilding it yourself, check the compression. Low compression not much fire low heat...also make sure the secondary carbs are closed (just noticed from your sig that the car is a 140 yes? ) at idle over rich from seepage thru a secondary could cause one side to be cold from flooding and the resulting weaker firing and fuel vaporization in the intake. You said you smelled gas from that side hmmm (could also be a stuck primary float (open) or problem in the primary carb same issue). I would in fact disconnect the secondarys and wire or rubber band them closed for further trouble shooting...less variables that way.

I have had freshly rebuilt carbs do what your describing and it has always been trash in the carb, blocked idle passages, or severly maladjusted carb (internal). Hmmm thinking of this are you sure both carbs have approximately the same idle mixture setting 2-3 turns out maybe? They should be about the same. Have the carbs been synchronized? All these little things could impact a situation like your describing. Check and fix all the externals. No difference? Get the carb fixed.

[UNSAFE]

[quote I am 99% sure the cylinders are getting fuel. I say this because the carbs were just installed after being rebuilt by Wolf Enterprises,, so I feel confident there are no blockages anywhere][/quote]

Feeling 99% confident just because someone else did the rebuild is not a good way to approach mechanical problems .

From my experience the "carbs rebuilt by Wolf" are likelythe problem and finding aluminum shavings in the bowl could be expected.

As was mentioned getting a squirt of gas when you push the pedal has nothing to do with the one side not firing.

The problem is the carb ! - it has an obstruction or it is way out of adjustment.

A simple test would be to slowly dribble a small amount of gas down the bad carb while it's running and see if the rpms increase.

Or swap the carbs from left to right and see if the problem follows the carb.

It is not an ignition problem if it's only one side of the engine not running.

Check out my Corvair tune-up videos on Youtube under 1unsafe1 to find out how to adjust and balance the carbs, They must be balanced or one side will run colder than the other.

[UNSAFE]

I watched the video but it doesn't show anything .

It does sound like the idle speed is very high and it's likely running partly on the high speed circuit instead of the idle circuit on the side that's working.

Also check to be sure that the secondary carbs are closing all the way at idle . It not the engine will suck air thru it and the primary carb won't be getting enough air flow to" suck'" the fuel in at idle.

[terribleted]

[quote I am 99% sure the cylinders are getting fuel. I say this because the carbs were just installed after being rebuilt by Wolf Enterprises,, so I feel confident there are no blockages anywhere]

From my experience the "carbs rebuilt by Wolf" are likelythe problem and finding aluminum shavings in the bowl could be expected.

The problem is the carb ! - it has an obstruction or it is way out of adjustment.

[/quote]

I was hesitant to call out Wolf directly but I too have had problems in the past with Wolf carbs. Trash inside, badly mal-adjusted, mismatched sets (carb bodies different), etc. One set caused exactly this problem.

[cvair4life]

I was hesitant to call out Wolf directly but I too have had problems in the past with Wolf carbs. Trash inside, badly mal-adjusted, mismatched sets (carb bodies different), etc. One set caused exactly this problem.

Ted since you bring up the mis-matched set thing.. that's a question I've always had... How do you tell if the carbs are matched or not? Does that really matter?

[terribleted]

The carbs I had were obviously mismatched. The base on one looked like most late model carbs the other was an oddball emissions carb of some kind. The bottom of the casting was alot different in shape (open on one side all the way to the round opening in the center bottom, instead of fully cast the shape of the carb base gasket). That carb also had an additional opening internally that was plugged (some kind of emmissions oriented air passage I was told). Different jets in a set I have seen that as well. Totally different adjustments carb to carb as well.

Yes matched does matter. There were many different changes to the basic Vair carbs over the years. A matching set adjusted the same way will make the engine perform in a balanced fashion instead of working against itself. Jets on each pair should be the same size. The carbs should be physically the same. Do they both have idle vents on the bottom or not? Do they both have idle enrichment circuit (an extra hole under the venturi cluster with a brass drop in) or not? Are the venturi clusters the same (a number of variations of these...different arm angles and openings) or not? All passages shape of bases and tops, ports, jets, needles, floats (spring assist or not), needle valve and seat assembly, power valve and spring, etc. should be identical for best engine function. All adjustments should be the same. Any differences and imbalanced flow is expected and engine performance is hindered. I personally like the 65 and later power enrichment circuit carbs for almost all primary carb applications (not 60 models of course).