Fuel Leakage

I have a '74 Chrysler New Yorker that originally came with a 440 engine. Of course this is a heavy machine, so one of the first things I did many years ago was build a .030-inch over 440 with SpeedPro 10.5:1compression pistons, a Mopar Magnum "Resto" cam, a set of mildly reworked 906 cylinder heads with oversized 2.14/1.81 inch valves and hardened exhaust seats. I put on a Holley Street Dominator intake manifold and a Holley 750 vacuum secondary carburetor. I ran the engine on the dyno after it was built, using a set of 1-7/8-inch headers, and was happy with 417 horsepower. I know that I could do a lot better with today's parts, but I just put it in my spare bedroom where it would be warm and dry. That's where it sat for about ten years.

I eventually put the engine in my New Yorker, and last month was ready to fire it up after the long sleep. The problem was that the carburetor gushed fuel all over my detailed engine like a waterfall. I knew the floats were set right when we last ran this engine, but when I went to take off the bowls and metering blocks, they were stuck to the gaskets. When I finally pried everything apart, I found the cork gaskets had shrunk to about half their normal size. I can easily rebuild this carb again, but I don't want that to happen again. Is this normal for Holley carbs after sitting a long time, or can you recommend a kit that is better?

Felix Cline - Via moparmuscle.com

Felix, back in the day, there were many aftermarket sources of rebuild kits for those Holley 4160 carbs. Unfortunately, often times, the materials used left a lot to be desired, and the experience you had was not uncommon when using a generic carb kit. The problems were exasperated by running the carb and then letting it dry out after a long period of inactivity. I well remember those cheapie carb kits with cork gaskets that would shrink after a month or two on the shelf. The new gaskets from Holley are designed for minimal shrinkage while in storage, and feature an anti-stick coating. In my experience these red or blue gaskets have proven excellent. I have several dyno carbs that sit for long periods between uses, and can tell you that those old problems are a thing of the past. Order a genuine Holley rebuild kit and your 750 will be better than new.


Aluminum or Iron

I am building a 360 for my '79 Aspen Wagon, and I am thinking about using a pair of Edelbrock cylinder heads instead of rebuilding the factory cast iron heads. The concern I have is whether there are any problems or issues regarding reliability and longevity of factory versus aluminum heads in a daily driver? What problems might I encounter? I like the idea of getting more power out of the engine with the cylinder heads, but am worried about getting left on the side of the road with a problem. My dad says the aluminum heads will blow the head gaskets. What do you think?

Craig Jordan - Via moparmuscle.com

Craig, aftermarket aluminum heads have been around for decades now, and they are proven by countless enthusiasts to be very reliable. The best steps to take to ensure longevity is to run clean coolant and change it every year to prevent corrosion. A good quality set of aftermarket heads such as the Edelbrock castings you are considering should last like an iron head.


Bothersome Blow-By

I have a Duster had a six cylinder, that I replaced with a 360. I also replaced the automatic transmission with a four speed. I found a 1973 cast 360 block, and had it rebuilt. The build included a set of flat-top forged pistons, .030 inch oversize, a mild Comp hydraulic cam, and an Edelbrock Performer RPM intake manifold with an Edelbrock 750 Carb. The heads are the factory 360 iron castings, with all new stainless steel valves and 2.02-inch intake valves and 1.60-inch exhaust valves. The heads are fully rebuilt with new guides and a good valve job. I am using the stock exhaust manifolds. I had a local machine shop handle all of the machine work and assembly of the engine.

The problems started once the engine was installed and fired-up. Everything seemed to be going fine, and the engine had good oil pressure and sounded fine. The thing I noticed is a significant amount of blow-by through the air cleaner breather with the PCV valve unplugged. I expected to see a little blow-by until the rings seat, but I now have approximately 1,000 miles on the engine with no improvement. The engine does not seem to be burning oil. With the PCV attached, it seems fine, but I would expect a new engine to show virtually zero blow-by. I went back to the machinist for an explanation and was told that he assembled the engine with chrome moly rings, and that it would take several thousand miles for the rings to break-in and seat. One of my buddies suggested running an abrasive powdered household cleanser down the carb to help seat the rings.

Mark Monroe - Via email

Mark, crankcase blow-by showing up in a running engine is caused by combustion gasses getting past the piston rings in the cylinders. A freshly rebuilt engine should show little if any blow-by if everything is correct, and unfortunately there are many possible causes of poor piston ring-seal, and none of these are easily addressed. Potential pit falls include the sizing of the cylinder and parts, the quality and finish of the cylinder walls after honing, and the dimensional accuracy of the parts and clearances. All of these factors should have been checked and accounted for during the rebuild process.

It is true that the piston ring type will affect the break-in period, and further, it will influence the appropriate cylinder wall hone finish. You indicate that the engine was built with chromemoly rings, and there is some confusion here. Chromemoly is a common term used for a type of alloy steel, but piston rings are typically iron, and are commonly available with a molybdenum facing to reduce wear and actually improve seating and sealing. Chrome faced rings are also available, but are not very commonly used. Chrome rings feature outstanding durability, though the break-in process is prolonged. The ring type is a major factor for the machine shop to determine the cylinder wall finish when honing the block.

To diagnose your engine problem, I suggest using a cylinder leak-down tester and checking for excessive leakage past the piston rings. A leak-down tester utilizes compressed air plumbed into the cylinder and a set of gauges to determine the percentage of cylinder leakage. If you find excessive leakage, there is little that can be done except getting back inside the engine and starting over. I would not recommend running any abrasive through the engine. There is no way that such a procedure will result in a proper cylinder wall finish.


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