I built a 312 years back.  The motor was a stock D code out of a 57 Retractable.  When I had the block hot tanked the machinist installed new cam bearings.  I was told Isky was the cam to use.  I called Isky and they connected me with the old man himself.   I told him what I had and he sent me a cam.  The cam was very tight in the bearings.  I could turn it with a wrench, but not something that I wanted in my engine.  As I recall I had to work over the bearings with emery cloth to get the cam to fit correctly.  I have been told this is common with Y Blocks.  You may have to align bore the cam bearings.  Talk to your machinist.  Not all machinists are knowledgeable on these old engines.  Modern parts don't always fit.

As a side note.  I don't know what cam old man Isky sent me, but it was killer.  The motor ran pop up pistons, three twos on an Edelbrock manifold and headers.  It blew the cogs off the cluster gear right out of the box. 

Just measured cam journals at exactly 1.926, so it must be the cam bearings that are the issue. I have ordered some more bearings, hopefully this will solve the issue. Thanks everyone 😀

Hi, I had the same problem (still have),  the old cam was worn and fit the bearings, however the new one would not even start, I am going to remove the cam bearings and try another set, my cam is a Howards ground on a CWC blank, I think the bearings may have been oversize and I did not read the box. 

Hi Ted. I bought stock bearings from Mummert. I didn't check the size. I installed them and the old stock camshaft slid in easily so I think the bearings must be stock. I cant measure the cam journals right now as the cam is at my workplace, we did measure it yesterday but I can't remember what it measured.

I’ve dealt with a lot of Isky cams and never had one that wouldn’t fit the stock cam bearings.
 
By the book the cam bearing journals are expected to be 1.926 ±.0005”.  I checked a new Isky Y camshaft I had sitting here and it falls to the low side of that spec (1.9255”) so no problem there.  I do keep cam bearings in stock that are 0.010” undersize (oversize depending upon your perspective) which requires the cam journals to be turned down.  Those undersized cam bearings are clearly marked with a special suffix on the part number though.  Is there a chance you are dealing with a set of 0.010” undersize cam bearings?  What are the journal diameters on the new Isky camshaft you have?

Lorena, Texas (South of Waco)

Thanks all. Seems a little strange. I will contact Isky and see what the score is. It's a bit awkward dealing with the USA from here in the UK,, but I'll try and get through to somebody 😀. I could turn the cam down but I really shouldn't need to.

Did you try contacting Isky about it?



Lawrenceville, GA

Line bore the bearings to make it fit? Seem to recall that this was standard procedure back in the day? Definitely had to do some minor fitting on the bearings on my 312 when I rebuilt it in 1968 and installed new cam bearings and a Crane cam.

I'm lucky to be local, but call Isky in Gardena Ca. and tell them what you have. I know they make larger diameter journals and bearings for blocks that have spun them. They have always been ez to work with and if the cam is new they may just exchange it. If not redoing the journal surface is not that big of a deal. Good luck

56 Vic, B'Ville 200 MPH Club Member, So Cal.

I put an E4 in mine three years ago with no problem, can't imagine why yours is .010 larger?