Hot Rod Forum banner

1 - 7 of 7 Posts

·
Delta Alpha Tango Juliet
Joined
·
136 Posts
Discussion Starter · #1 ·
Do you guys know the difference between a retro-fit roller camshaft and a regular roller camshaft? If using a cam button, retro-fit roller lifters, and all other proper parts the pre-86 blocks need, could I use a standard roller camshaft? Or must it be retro-fit? Are they different sizes/lengths?
 

·
Registered
Joined
·
1,684 Posts
The factory "roller" cam blocks use a cam retention plate to hold the cam in place. The nose of the "original roller cams" or "retro" as some are called today is the same style / size as any hydraulic or solid lifter cam produced since 1955.

If your block is not a factory "roller" block, then you have to run the retro. Now keep in mind that you will need run a cam button to keep the cam from walking fore and aft in its bearings. Roller cams have no taper ground into the lobes that forces the cam to the rear of the block, like the flat tappet cams do. If you use the stock timing chain cover, you may have to stiffen it up some around the area where the button contacts the underneath side. You don't want the cover to flex.

You will need the correct lifters for the block you have when running a roller cam. You will also need shorter push rods and the rocker geometry needs to be spot on for it to live. If you plan on running a double-roller timing gear set, the front of the block may need to be clearanced around the top of the cam journal boss.
 

·
Registered
Joined
·
17,613 Posts
I used to cut a piece of 1/8" thickness cold rolled steel and tack weld it onto the back side of the timing cover for the cam button to ride on. Or you can use a cast aluminum cover that has the adjustment for the cam button built in, such as this one from Cloyes. Having the removable center piece will allow you to change cam phasing without dropping the oil pan. Drill the cam sprocket and use offset bushings on the cam drive pin.
http://www.summitracing.com/parts/clo-9-221
http://www.summitracing.com/parts/hrs-94505/overview/
 

·
Registered
Joined
·
14,168 Posts
Do you guys know the difference between a retro-fit roller camshaft and a regular roller camshaft? If using a cam button, retro-fit roller lifters, and all other proper parts the pre-86 blocks need, could I use a standard roller camshaft? Or must it be retro-fit? Are they different sizes/lengths?
The retro-fit roller cam requires a cam button on the front of a Chevy it will not accept the GM thrust plate. These use afthermarket lifters that are quite expensive as the non roller block doesn't support OEM style roller lifters which are taller and require a raised lifter bore; these are held in alignment with a thing called a dog bone which requires block clearancing and are held in place with a spider that attaches to the main oil galley casting resting on three rased bosses to which it is bolted. The bolts are positioned over the center three oil feeds to the cam and main bearings. I mention this as years ago it was popular to modify standard blocks to accommodate the spider by drilling and tapping into the oil passage, this takes care and modification to the oil circuts that exceeds the benefits as an error will cost main bearings in service.

The OEM roller camshaft uses a unique bolt pattern, it can be used with a cam button with modifications which also include the use of a modified thrust plate with the ears removed so it becomes just a thick spacer washer. This also requires the use of the OEM roller timing set which will also have to seat on the spacer.

There just is no escape from the cost of aftermarket roller lifters, the work around is as expensive or moreso than aftermarket lifters and the risks of component and work failure is high.

The OEM cam modified to use a cam button pushes you into some custom fabrication of making the thrust plate into a spacer washer and coming up with a means of holding the cam button in proler alignment to the shaft since the cam bolt securing plate of the flat tappet cams doesn't fit the bolt pattern of the roller cam.

You can run an aftermarket roller cam in a factory roller block if you treat it as if it were going into a non-roller block by using a cam button and flat tappet timing set.

Bogie
 

·
Registered
Joined
·
4,148 Posts
I once owned that exact cover and its a little too much for what I paid for it but I will give you a warning. If you use a cam bolt locking plate you will need to drill out the center hole bigger as the cam button on the timing cover will barely clear through it and if left alone it will sheer off the roller button.

I thought I had mine drilled out enough but not even close. When I went to do a cam swap and I took the cover off that is when I found out it completely sheered off and I was lucky I got to it when I did or could have had a major camshaft engine failure.
 
1 - 7 of 7 Posts
Top