holley list#8004

In the reverse idle setup which you probably have if the carb is less than about 25 years old, the mixture is enriched by turning the screws CW. CCW leans the mixture. The case you describe would indicate the engine is wanting more fuel at idle for some reason. This may be because the secondaries or primaries are open too much at idle causing loss of vacuum signel at the idle fuel ports. This can easily happen if you have modified the engine especially with a performance cam. I suggest you make sure the carb is clean, the correct metering block and bowl gaskets are installed and, the float level is correct. Check the adjustment of the secondary idle screw. When you remove the car, make sure you check the position of the primary throttle plates. If you are having to adjust the idle speed screw (not mixture) to the point that you are startingto expose the transfer slots in the primary throttle bore, then you may have to drill the primary throttle plates to allow them to close more at idle. This procedure is common in performance engines and is described along with picturesi in many performance publications including the older Holley literature. You may want to check the link below for some basic tuning tips.

Lugnut

Lugnut:

Sorry to change the subject but...

I found an old post from 2003 where you were helping a person with a pitting of their cylinder wall in their resulting from cavitation.

I understand why it occurs and how to prevent it in the future, but once it is there how can one repair it?

I've seen references to having the cylinder 'sleeved' but are there other alternatives?

Your advice would be greatly appriciated. thanks.

lugnut wrote:

On 11 May 2006 12:07:19 -0700, "kraftamle" wrote:

Snip

If the cylinder walls are excessively pitted from cavitation, there are a couple of solutions possible depending on the design of the specific engine. Diesel engines are most commonly built with wet liners in medium and heavy duty applications. The only repair of which I am aware for an engine with wet liners is replacement of the liners during overhaul which may be required if a liner has failed. An engine that does not have liners can in many cases be bored and repaired with a liner that is pressed and, possibly, welded into the block by a machine shop. This is not the most desireable repair but, in the case of a block that is no longer available, it may be the only choice. Keep in mind that a normal overhaul in engines with wet liners usually includes replacement of the "cylinder kit" which includes piston, rings and liner. You can, of course buy individual parts as needed for most engines. I don't know of any manufacturer that recommends or even provides oversize pistons and rings for an overbored wet liner. The bottom line is that a wet liner that is excessively pitted needs to be replaced. There is no way of "seeing" how deep or large the pits are below the surface. Liner replacement may require that a machine shop press the old liners out and the new ones back into the block. Others simply use seals around the bottom of the liner and are capped with the cylinder head. The ones that use seal can also have cavitation pitting of the block which may require machining of the block in the seal surface area and installation of a repair sleeve. This is determined by the engine design. You did not say which engine you are dealing with but, the Ford/Navistar which was being being discussed at the time, IIRC, should have new liners readily available. The block will have to be evaluated at teardown with respect to the liner sealing surfaces. Also, keep in mind that it is rare to see a Diesel torn down after several hundred K miles with absolutely no pitting. It is the accelerated pitting that results in early failure that you should seek to prevent with proper coolant treatment.

Hope some of this helps Regards Lugnut