I'm looking at a block that has 55mm roller cam bearings. How special are these cams? Is there anything I need to know about installation, base circle, use? How easy is it to get cams? Where would I look for some good used 55mm cams?

Seems like they are $7-800 from Comp Cams, but they don't always have the 55mm cores in stock.

We keep a couple blank cores on the shelf to grind into hemi or wedge as we need them. Hard to get.
Todd

Is there something I should do to the block to put in a better/more popular style cam bearing?

Not much to do at this point. It is kinda like unboring a hole. Todd

the 55 millimeter stuff is becoming more and more popular... what's nice about having the 55 roller cam tunnel... you can also run a 60mm Babbitt in the same hole.. I have been running mine for some time with great results... I would not be afraid of it one bit

I AGREE with White Dart. I prefer the flat bearing. Just my opinion and the bearings are not priced bad at all. Todd

I'm guessing that the bigger bearings allow for a larger diameter lobe and keep a decent size base on the shaft. Doesn't bother me, 55 or 60, as long as I can get a cam that will work well with my combo.

They use the same core. 55mm roller and 60mm flat. You need something pretty nasty to use one but they for sure work. Todd

I'm a vote for the 55mm roller bearing now. They won't turn in the cam tunnel and blow your investment up. Also, try turning a motor with a wrench with a 55mm babbit bearing and then turn one over with a roller bearing. There's no comparison.

I'm guessing this is a SB Mopar R3 block. Ford seems to have good prices on the roller cam bearings. I bought a SS Hemi block that was bored to Ø2.500" which seemed like a strange size. It turns out that is a Ford bearing size for a Ø2.125" journal size. That is just over Ø54mm. Here is the Ø55mm roller bearings.

http://www.jegs.com/i/Ford-Performance/397/M-6261-D351/10002/-1

The Ø2.125" journal seems to be popular for the Hemi roller cams. These are the bearings I bought for my block. My engine builder likes the roller bearings as more oil is available for the main bearings.

http://www.jegs.com/i/Ford-Performance/397/M-6261-A460/10002/-1

BB..........

Indy Max RB

Might make sure the rear bearing can got to 55 Roller on that block...Seems like the way the oiling works there isn't enough room to bore the cam tunnel that big on the back.

My KB Alum 426 has 54mm, #1-4 & #5 standard

I have an Indy block,KB, and older mega block with all 5 cam bearings 55mm roller,the oiling is not a problem

My Hemi block has the standard rear (#5) cam bearing. The Ø2.125" roller bearings in 1-4.

I have built several Indy Maxx and Mopar(World Products) blocks with all 5 and no issues to report. I have not seen a block like you have Mr 340. Interesting. Is it a World block or an earlier Mopar block?

I'm sure it started out with standard cam bearings. I bought the block from Dan Zrust, he got it from Jim DeFrank. Supposedly Joe Allread machined it many years ago. The decks have been cut down to 10.400", big cam bores, bored to Ø4.310". Waiting on heads from Bob at Modern Cylinder Head and a big pile of cash to fall from the sky to move the project forward. It's one of the older MP Hemi blocks, Cummins style.

2.125 is a 54mm bearing. or 2.1259