Hey Gang I have a 1958 392 hemi with a Edelbrock EC6 high rise 6x2 intake manifold. I have 6 Holley 94's and I'm having a hell of a time with it. First off my whole entire passenger side is running lean. I mean it starts to turn the pipes red. While the drivers side is perfectly fine. At first I thought it was the carb but with some research I found to have a major vacuum leak on my drivers intake manifold near cylinder 1. I'm totally amazed that a vacuum leak will suck all my gas off my passenger side primary carb and send it to the side with the leak leaning my left bank. My issue is I've replaced the gasket twice and its still there. Also the EC6 intake doesnt use water ports so the ones in the head gets blocked off. Problem is it starts to ruin the gasket very quickly. I'm just not sure how to seal it properly?
You could try taking off the carbs and the gaskets set the manifold on the head with a bolt at each end and just snug them up, take a feeler gage and check the clearance around the manifold to see just what is flat and what part is not. That type of check will give a starting point, does the manifold have a balance tube from side to side Have to used a ' Uni-Syn ' to set the carbs, it takes a bit of time to get them all adjusted Have you re-set the throttle blades in each carb and set the idle set screw using a feeler gage on each carb then hook up you linkage so they will idle down My friend fired up his new sprint car and the Hilborn had a loose arm on one side and turned the chrome ex pipe blue, he just knew that he had everything tight but sometimes things just have a way of changing in the middle of the night!! Good luck, G Don
The '55 331 & up intakes are dry so that shouldn't be causing a problem. If something is happening to the gaskets you have poor quality gaskets or some other thing is messing them up. If the intake is square maybe your head is warped a bit on the sealing surface. If that is square & no gouges or other problems, maybe try 2 quality gaskets sealed together with copper coat might seal it up, unless it's actually a carb problem. Did you confirm vacuum leak with spray around the seal surface? Could it be a carb base to manifold leak?
If you know where the leak is and only on the outside I would be tempted to run a bead of weather strip adhesive on the joint and see how it works. Gary
With the motor idling spray some wd40 with squirt bottle, not spray pack/rattle can around the suspect area. The engine will change song when the oil hits the vacuume leak. If the block has been decked or a lot off the heads to up compression. the angle can change or sealing surfaces can miss match. Really lean or hard starting is more than likely in the carbs butter flies Good luck with it
...Random thoughts... If you found the leak then why can't you seal the leak? You say: manifold is perfectly straight and smooth :/ What about the head? Was the intake rail cut to compensate for decking? Have you bolted up the intake minus the gasket and checked for gaps? (turn the shops down and lay a trouble light in the valley) Does the gasket come off clean enough for a visual of the suspect area? Have you been using a sealer on the gasket? Please correct me if I am mistaken, but, isn't your manifold a 2-piece deal ? so either side should seal without issues if the head and manifold are, in fact, flat. .
I don't know about your motor, but are you sure the bolts aren't too long keeping you from clamping it all the way down? I've seen that problem on valve covers. I've also seen blind holes that had enough rust in the bottom to keep correct length bolts from working proper as well.
I would think isolating the leak with just your primarys on the rest blocked off and go from there. Unless you know its a manifold to head surface problem. I would think you could get it to idle good enoff and sync in the rest of the carbs as you go. I'm no expert at this but I work on rail cars all day and know the frustration of leaks !!! Good luck, love the truck. Riley
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