Thread: Engine Surging in slow traffick

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Just thought i should ask,,,how long have you had this problem with surging??

This has been going on for the past couple years. The 18 years before that I have not had the problem.

In answer to other questions:

I have a Holley 80273S carburetor. That is a carb that is designed with the vacuum hookup to provide the manifold referencing. So, as DennyW says, the vacuum port is already there.

However, if I understand DennyW's replyl correctly, he is saying to put the vacuum to an adapter below teh carb, but above the blower. That is inaccurate. The power valve needs to know what the vacuum is at the manifold. That is what determines how it works. That is what is meant by 'manifold referenced power valve'.

Instructions on that are here on the Holley site.

With regard to which power valve, I have had multiple conversations with Holley tech on this. They say to take idle vacuum and divide by 2. So, my 9.5" vacuum gives me a 45 power valve. I have tried lower and higher. I seem to constantly be over rich, no matter what I try. It doesn't seem too bad right now on richness, but a little rich. I do have the 45 in it now.

Earlier posts indicated that possibly my surging was a 'minor vapor lock'. And, given that I had a hard vapor lock (no fuel getting to engine at all) last weekend, that lends credence to that theory in my mind.

One thing I have changed (don't remember exactly when): I hooked my electic radiator fan that is on the front of the radiator to a temp unit that is supposed to turn it on. Problem is, the radiator has the place for that at the bottom, instead at the top. So it comes on rather late. I seem to have problems when my engine gets to 200, which isn't all that hot. Although it gets quite hot under my hood. (I do have a fan on the front of the engine as well. I had hoped to pull the electric one off the front, but now, I need to get it going all the time I guess.)

So, my immediate problem is "How do I best cure vapor lock?"