Ok, I think my only question that I have is concerning the lifter bores. I've done some searches on this, and I've read that the lifter bores need to be ground down so the top of the lifter sticks out far enough so the reatainers can fit over them. But what I can't figure out is why? The top of my flat tappets sit flush with the top of the lifter bores when in the closed position. Now Comp lists their "High Energy" push rods for 55-Up SBC at 7.794 inches. And lists the OE Hydraulic roller cams at 7.195 inches. Now if the roller lifter's pushrods at .600" shorter, that has to mean that they're .600" longer then flat tappets right? So if they're .600" longer, that should mean that they would stick out .600" above the lifter bore right? And over a half inch should be enough to fit the retainers. If my thinking is wrong, someone please let me know. Oh by the way, I have kind of an off the wall motor, It's a 92 with a two peice rear main, so maybe it's possible that it got the lifter bores machined for rollers but just didn't get the valley rail machined. So maybe this is what is making the lifter bores look like they will work without maching.

Tom

 

Oh by the way, I'm looking to install OEM lifters and not Retros.

 

The tops of the lifter bores isn't the problem, the area on the wall of the lifter valley is.

Here's a couple of pics I have that should expain it...

This pic is of a block that has NOT been machined for clearance

 

Here's one from GM that HAS been clearanced.

Also notice the lack of bungs for the retainer "spider" to bolt to on the block aren't there. Good luck getting the "spider" to stay somewhere.

One more thing...

You say you have a block that was cast in '92, but is a 2 pc. rear main seal???

Either it's a replacement engine (AKA "GoodWrench" block), or it has an adapter to fit a 2 pc crank into a 1 pc block.

 

..

 

and, just in case you had the thought that I had at one point - no, you can't drill and tap that central 'spine' there - it's an oil galley.

I've thought about something working off the underside of the intake manifold. Seen the lifter valley baffles they make? They've got two braces that fit against the bottom of the intake.
Problem is that the pre-made ones all say they only work with flat-tappet cams. I suppose roller tappets stick up too high, but the concept is a start...

 

Why not just get the retrofit cam and hydrulic roller lifter kit for pre 1987 small block chevy?

 

Twice the price. But anway, like Blueyes said, when I went out to size up the situation, I realized that it was an oil galley. But couldn't you still drill and tap it and either put in a stud or even a bolt with some thread sealer?

Tom

 

That oil passage is the one that carries pressurized oil to the main bearings, rod bearings, and cam bearings. Do you want to risk a leak there? I didn't think you would, I wouldn't either.

If the block doesn't have the provisions for the factory's goofy roller "system", it will probably cost you more in machine work to "retrofit" it, than it would to either just get the right block for it in the first place, or to simply use the sensible original roller design. Don't forget, you'll have to have it machined for that retainer plate at the front of the cam, too.