14 Interference (Parts 2 and 3)

Since I believe that the worst thing that you can do to a vehicle is to not drive it regularly, I try to drive the hot rod to work at least once a week.

On one of these trips, I heard a loud snap, then the engine started to backfire through the carburetor under load. By removing one plug wire at a time, I was able to determine that the problem was in number three cylinder. When I removed the valve cover, I found that the exhaust rocker arm on #3 was broken in half.

 I bought three rocker arms (two of Egge Machine # 44000, the type that broke, and one #44001).  One was hand filed for clearance as mentioned in Chapter 9, installed on the right rocker shaft, and reinstalled on the engine. (Nailhead Buick cylinders are numbered  1, 3, 5, 7 on the right bank and 2,4,6,8 on the left.)
 

Less than 1,000 miles later, the #3 exhaust rocker arm broke again.

Less than 500 miles later, the #3 exhaust rocker arm broke a third time.

Thinking that the problem was that the rocker was hitting the edge of the (larger diameter) Kenne-Bell valve spring retainer, I decided to keep the Kenne-Bell cam, but install a stock head on the right bank until I was able to determine how to fix the problem.

 I found a stock 425 head with rocker assembly at Wheatbelt Antique Auto, a Buick specialist in Carrier, OK. When it arrived, the UPS driver was the first and only delivery person to acknowledge the sign in the empty planter along side of the front porch which read "Please place deliveries here". I had to reach down two feet into the clay pot and lift the heavy sucker out of there. After that ordeal, installing it on the right side of the engine was relatively easy. For nearly three years, there have been no further problems with the right bank valve train.

Recently the engine developed a miss and an intermittent tick on the left side. Because I don't know all of the peculiarities of Nailhead Buick engines, I decided to find  someone who had experience building them to see if we could find a permanent fix.  Most of the builders I talked to had never worked on a Nailhead.

Ryan at Ryan's Rod Service said he had some experience with Nailheads, and he knew an expert to go to if he ran into trouble.   
                  

I asked him to degree the cam at 113°ATDC ± 1° per the cam card and check out the miss problem . (The cam was originally installed straight up at 118°ATDC, 5° retarded from where it should have been.)

This engine was built following  the 1997 series of articles in Street Rodder written by Doc  Frohmader. There was an error in Part 6 (June 1997) describing advancing the cam to the 2A marks. However, the particular and peculiar crankshaft gear that we both used is marked in camshaft degrees, not crankshaft degrees. The cam should be advanced to the 4A marks. On page 60 of the magazine, the photo caption on the left hand photo is correct.

A minor problem cropped up when reinstalling the timing cover. The original rope  front crankshaft seal and stamped  steel retaining ring  had been removed and replaced with a more modern nitrile lip type seal sourced  from Carmen Faso at  J&C's Parts in North Tonawanda, NY. Carmen is not on the internet. TA Performance in Scottsdale, AZ  lists a neoprene seal part number TA 1514 but that number does not cross to any other manufacturer. The source article did not mention an application. A little digging on http://www.v8buick.com  revealed that a National 474272 seal, an SKF 19786 seal or a Chicago Rawhide 19786 seal will work. I still don't know the application. Getting this solved took way more time than it should have.

After correcting the cam to crank timing, Ryan removed the left valve cover and discovered a broken rocker arm on number two intake valve. According to his sources, Nailheads with non-stock cams break rocker arms because of incorrect valve train geometry. That makes sense because of the complexity of the valve train. However, they said that the rockers will break when the pushrods are too short, which is counterintuitive.

Ryan installed one of the filed  rocker arms from  the modified head  I had removed from the right side. The pushrod was reused. If another rocker arm breaks, the plan is to order Smith Brothers adjustable pushrods and install them with the adjustment end near the lifter (upside down) for easier adjustment. The intake manifold and valley cover will need to be removed to adjust them, but it should only have to be done once.