Engine Overhaul


The inside of the motor looked really clean. The cam showed some wear but nothing unusual. All the plugs looked good and consistent with each other. All the valves and chambers look consistent and relatively clean.


Although there was a little carbon buildup in the pistons, you could still see the machining marks on them. The ridge above the pistons was visible but no more than .002".


Since I had to pull the heads to replce the freeze plugs anyway, I completely removed the factory exhaust manifolds. The manifold heat control valve on the passenger side had been rattling for the past 2 years and driving me nuts.


Since pulling the manifolds was no simple task I had been tolerating it. Now with the manifold off I was able to completely remove the valve and plug the shaft holes with bolts.



Bad news. As you can see above this head is cracked. Actually, both heads were cracked in the same area. The exhaust valves on the central cylinders are rather close together, causing excessive heat in this area. I picked up two other sets of heads, all of which were also cracked in the very same area. My original set was of the 975 casting ('75 400-440). The two replacements were of the 902 casting ('74 400-440). My third replacement set, a 346 casting ('71-72 383-400-440), was ok.

I replaced the old cam with a new Ultradyne cam. It is a little milder than the Purple shaft .509 I had. It has less duration, especially on the intake, but it ramps up quicker. I decided to get a cam that was better matched to my engine configuration. It's another hydraulic with a split duration of 288/296 (231/239 @.050) and lift of .485/.507. Lobe separation is 108. Tim there at Ultradyne was really helpful at helping me select a good grind for my application.


Here you can see the cleaned block. It wanted to rust quickly after taking it down to bare metal.


With the block clean and free of rust, I painted it the original Chrysler blue. Time for the new core plugs, cam shaft, and timing gear. Also time to retorque the main cap and rod bolts.


I got my heads back today. I had them shaved .020" to bump the compression just a bit.


I also had the flashing in the bowls cleaned up a bit as you can see above but no fancy porting job.


Here's the Six Pack setup on the motor. It's a pretty massive thing. The intake is aluminum, made especially for Chrysler by Edelbrock. The carburetors are Holley's and just like the intake, are all reissues of what was originally supplied on the Six Pack cars.


The center carb flows 350 CFM while the front and rear flow 500 each for a total of 1350. The outer barbs are opened by vacuum as evidenced by the large vacuum diaphrams visible.


Here's a rear view.


I painted the exhaust manifolds with Eastwood's high temperature paint. To prepare them for painting I sand blasted them to bare metal. Just before painting I baked them for about an hour at the lowest setting to drive off any moisture. The paint was applied with a dabbing motion rather than by stroking to avoid brush marks. It went on easily and dried fast.


Just about ready to drop in the car. Don't forget the oil pan.


John stayed out late to help me drop the motor in the car.


I definitely needed a shower.


Here's the finished product. I broke in the motor with a 150 mile cruise and it ran great. I'm still getting used to all the extra bottom end power. Maybe that's why I only got 8 miles to the gallon.

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