Help with carbs

[John Wurner]

I have a 58 normal Cabrio.
The car was previously in Denver (mile high), now in Oregon (400ft high).
Do I need to re-jet the carbs or adjust them?
Car has the normal Zenith carbs. Car runs OK here once she warms up, as is.
I read a story in the registry mag about cars running too lean at lower elevations and dont want to do damage.
Thanks, John

[Wes Bender]

If the previous owner jetted the carbs for 5000 ft, you should put the stock jets back in it for your elevation near sea level. Just adjusting wouldn't be sufficient.

[John Wurner]

Thank you, Wes
I will call Carb rescue Monday and have them provide the jets.
I am a total novice on carbs.
John

[Wes Bender]

If you can, check the numbers on the main jets that are in the carbs now. The PO may not have changed them. If you don't have the factory service manual that indicates which are the standard jets for your carbs, 356 Carburetor Rescue will know. I'll bet they will ask what size jets are in there now.

[David Jones]

John, you need to check the jet sizes before doing anything unless you know they were changed for a higher elevation. Back when the cars were new carbs were jetted from the factory for very general use and even fluctuations in barometric pressure can affect jetting but unless you are racing the difference in daily driving is barely noticeable. As you go higher in altitude there is a tendency for the car to run richer and if it was rejected for high altitude there is a chance it could be running leaner as you descend towards sea level so you are right to consider doing what you are doing but there is a possibility you have stock jets in already..

[John Wurner]

Large jets are 230, small 120 looking in to the top with the air cleaners off.
I have a second set of carbs with the same size jets, so these may be the originals.

[David Jones]

John, the main jets are under the cover on the side of the carb, and when you remove it there is an "O" ring in the cover which after many years has gone the way of all flesh so it will probably have to be replaced. The 230 number is the air jet which is correct. The main jet underneath the cover should be a 115 for a 58 1600 normal.
Here is the carb rescue web page to refer to.
http://www.356carburetorrescue.com/carburetorspecs.html
http://www.356carburetorrescue.com/images/32ndix.jpg
The main jets are item 67 in the exploded view.
Here is a link to the Der white manual showing jet positions.
http://derwhites356literature.com/New35 ... etors.html

[Ron LaDow]

I would not trust what the stampings claim to be the jet size.
For most of them, you can push a bamboo skewer in and measure the resulting 'shoulder'. The jet size is the hole diameter in mm.
This is you don't have a jet measuring set.

[John Wurner]

Thank you, David, they are indeed 115.

[Jim Alton]

I actually asked Matt Blast of Eurometrics about high-altitude jetting for Porsche carburetors (I was curious because I owned a Series III Land Rover for 11 years and there are high-altitude jet kits for them).

His answer was that Porsche carbs handle altitude pretty well and rarely need re-jetting. Somebody competing in the Pike's Peak Hillclimb might re-jet, but not most mortals.

The carburetor specs from the "Little Spec Book"

Ron LaDow is quite right--if somebody did re-jet your carburetors it might have been done by altering the existing jets. If you're concerned enough to check, you should actually check the jet sizes.

[David Jones]

If you look at the spare set of carbs and they have the same jet sizes and they look to be the same as the ones n the running carbs then there is a very good chance you do not need to do anything at all. You could take your jets to a local motorcycle repair shop and it is likely they can measure the jets for you.
Another way to do it is to buy a set of micro drill bits and use the shank of these to measure the jet orifice. They are cheap from Harbor freight or a welding shop.

[Craig Richter]

My brother-in-law's 356 used to travel a lot between the SoCal flat lands (sea level more or less) to Lake Arrowhead (5,000' more or less). The idle speed would drop several hundred RPM's at the lake, and very occasionally die when idling. No stop lights back then so not really a big problem. But if we knew we would be up there for awhile, some gentle twisting on the throttle stop screws got the idle RPM back up. First gas stop down the hill (gas cheaper down there) and set things back. Only took a few seconds when checking the oil; no need for any synchronizing equipment.
The lack of power was noticeable (less oxygen makes some black smoke from being too rich), but not enough to bother changing main jets at Arrowhead. If you live at 7-8000' and stay there, go down to 1.10 main jets. You'll be happy.

[John Wurner]

Thanks all.
I now know what to do.
John

[Tim Berardelli]

John,

In addition, check injection "squirt"-if the carbs have been set up for high altitude use this has been reduced.