66 427/425 Rear Bearing

[Walter R.]

I had posted earlier about lifter failure on new rebuild. It was understood from advice received that the 1966 block should have a groove on the rear cam journal, which it didn't, and the rear bearing should have 3 holes to get correct oiling to top end. My block has a 73 casting date, as a new short block was installed by the dealer in 1973. Would the block require the groove and 3 hole bearing or is there any way to tell if it should? I am doing this again and truly do want to get this right.

[John H.]

Re: 66 427/425 Rear Bearing

Walter -

Only the '65-'66 big-blocks required the groove in the rear cam journal and the 3-hole grooved rear cam bearing. The design was revised for '67 by adding a machined groove in the O.D. of the rear cam bearing bore and a one-hole non-grooved rear cam bearing, with no groove in the rear cam journal. A 1973 block will have the '67-up features, and will not require a groove in the rear cam journal.

[Walter R.]

Re: 66 427/425 Rear Bearing

This engine was rebuilt and wiped out several lifters and cam within 1 hour. This is second time in 8 months that this has occured. The cam installed did not have a groove on the rear journal and the rear bearing had one hole. I know from all posts that it should not require a groove on the rear cam journal. That is the only thing that has changed with these two rebuilds. The cam taken out before the first rebuild did have a groove on the rear journal and engine did not have an oiling problem. My oil pressure has been great after both rebuilds.

[John H.]

Re: 66 427/425 Rear Bearing

This engine was rebuilt and wiped out several lifters and cam within 1 hour. This is second time in 8 months that this has occured. The cam installed did not have a groove on the rear journal and the rear bearing had one hole. I know from all posts that it should not require a groove on the rear cam journal. That is the only thing that has changed with these two rebuilds. The cam taken out before the first rebuild did have a groove on the rear journal and engine did not have an oiling problem. My oil pressure has been great after both rebuilds.

Walter -

Does the rear cam bearing bore in the block have an oil groove machined in it? If it doesn't, and the one-hole rear cam bearing is used, you'll have great oil pressure, but the lifter galleries won't get any oil.

[Joe R.]

Re: 66 427/425 Rear Bearing

Walter,

There is an easy way to tell if the top end of your engine is getting plenty of oil. Before firing it up, remove the valve covers and intake manifold. Turn it over by hand with a socket wrench on the harmonic balancer. You should see the lifters, rocker arms, valve springs, etc getting flooded with oil. If not, time to figure out why not before proceeding. I saw this technique on a DVD recommended here called "How to Build Your Chevy Engines like a Pro."

Good luck!
Joe