low compression - running rich

I just bought a new-to-me 1970 beetle with a 1600SP engine from the original owner. It has always been a sea level car until I bought it. I live at a 7000 foot elevation.

The car has seemed to run ok when the weather was 50 degrees or higher but the plugs showed that it was running rich. Now that the temperature has fallen to below freezing, it seems to be running very rich to the point that it is fowling Bosch W8AC plugs. The compression is low ranging from 58 - 70 psi which would equate to 72 - 86 psi if taken at sea level.

I know the engine is getting tired but I don't want to rebuild it right now. I am currently looking out my window and it looks as though I am in the Sahara Desert during a sand storm but instead of sand, it is snow.

My question is would a hotter plug help? Do I have to rejet my Solex 30-PICT-3 carburetor? So far, I haven't taken it out of the city to actually use the main jet yet. I am using 85 octane gas because I felt it runs hotter than higher octane. Is my assumption correct?

Thanks in advance - Bob

Reply to
Robert
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owner. It has always been a sea level car until I bought it. I live at a 7000 foot elevation.

plugs showed that it was running rich. Now that the temperature has fallen to below freezing, it seems to be running very rich to the point that it is fowling Bosch W8AC plugs. The compression is low ranging from 58 - 70 psi which would equate to 72 - 86 psi if taken at sea level.

I am currently looking out my window and it looks as though I am in the Sahara Desert during a sand storm but instead of sand, it is snow.

30-PICT-3 carburetor? So far, I haven't taken it out of the city to actually use the main jet yet. I am using 85 octane gas because I felt it runs hotter than higher octane. Is my assumption correct?

Low compression in all cyls. Hmmmmmmmmmm. Have you checked the valve clearance yet? First step.

If the clearance is correct, the engine may be close to sucking in a valve head and then you won't be able to rebuild it...ever.

If you're sure it's running rich, check that the float needle valve closes tightly and that it's screwed in tightly.

One fix you can play around with is to add washers under the needle valve. That will lower the fuel level in the bowl and reduce mixture. (Shouldn't be necessary, but there you have it.) Or, change main jet size.

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Speedy Jim

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Reply to
Speedy Jim

Thanks for your reply. I did adjust the valves and only a couple were at

0.004" and the rest were at 0.006" so I made them all 0.006". I guess I can just hope that it doesn't suck a valve. The engine was rebuilt in 1981 and seems to run well other than fouling the plugs. The plugs become jet black.

I will change out the needle valve tomorrow with a known good one.

The web page you gave me is good so I will follow those instructions as well.

Incidentally, my rear bearing replacement job went well, thanks for your advise. - Bob

Reply to
Robert

I have a H30/31 carb on a 1600DP with a pretty free flowing exhaust setup and mild cam. It's on my buggy. I run at 4-6000' and it's running quite nice on a 50idle and 125 main, 125air. You might even get by with a 50 idle and

120 main, which by the way, is what these H30/31's usually come jetted with. These are the modern replacement for the carb you have and I believe that is ballpark jetting for a1500SP.

RT

Reply to
Raymond Lowe

Engines will run rich at higher altitudes, due to the lower density air. So, you could try fitting a smaller main jet and see what happens, as a result. However, the low compression suggests that you may have more serious problems to consider first.

7000 foot elevation.

The car has seemed to run ok when the weather was 50 degrees or higher but the plugs showed that it was running rich. Now that the temperature has fallen to below freezing, it seems to be running very rich to the point that it is fowling Bosch W8AC plugs. The compression is low ranging from 58 - 70 psi which would equate to 72 - 86 psi if taken at sea level.

I know the engine is getting tired but I don't want to rebuild it right now. I am currently looking out my window and it looks as though I am in the Sahara Desert during a sand storm but instead of sand, it is snow.

My question is would a hotter plug help? Do I have to rejet my Solex

30-PICT-3 carburetor? So far, I haven't taken it out of the city to actually use the main jet yet. I am using 85 octane gas because I felt it runs hotter than higher octane. Is my assumption correct?

Thanks in advance - Bob

Reply to
Peter

Reply to
Robert

Reply to
Robert

It runs richer as the temp drops cause the choke is on which amplifies any other problem area and if you let it idle to warm up, you can wash the cylinders which fouls plugs and puts gas in the oil and lowers compression and causes wear problems. Adjust your choke, check the operation, warm air tube etc. Just my opinion of course. Been there, done that.

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Reply to
Dennis Wik

I took the heads of and noticed that the heat riser was blocked, #3 exhaust valve was much lighter in color than all the rest and #2 spark plug hole was almost completely stripped out. I ordered rebuilt heads and will put it back together with a good intake manifold next week. thanks for everybody's advise. - Bob

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Reply to
Robert

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