I know it's been asked before but I can't seem to track it down in 'Search'. How difficult is it to convert a late model (1-piece rear main seal) hyd flat tappet block to accept an '87+ hyd roller cam?

Comp Cams makes a retrofit kit with special lifters but the cam and lifters alone run $700 from Jeg's. No thanks! The GM Performance Parts homepage lists a roller lifter kit, #12371042, that includes new roller lifters, lifter guides, the retainer plate, and bolts for $200.86 (Jeff Kopp price). In the description for the kit it says that this is all you need to convert a late model hyd flat tappet block to accept a roller cam besides the pushrods. It doesn't mention anything about a cam thrust button but I assume you'd need one.

So...*drum roll* does this mean that all you need for this conversion is drill a few holes in the lifter valley for the roller lifter retainer plate and then buy all the OEM parts?

 

I've never had my stock rollers out so don't know how they differ from flat-tappet hydraylics. You might want to take a look at each to see if a "spider" in the valley is all you need to use stock rollers.

For sure you will need a cam button and maybe a new cover plate to take the pressure of the button.

I believe you will need different length push rods too. Comp Cams catalog lists different lengths for pre/post '86 SBCs.

I believe you would need new valve springs since a roller has more agressive ramps; new lower seals and upper O-rings would be a good idea too.

Lets see if anyone chimes in who has done this conversion.



[Modified by 65Z01, 2:49 PM 8/2/2002]

 

I've never read of anyone who has modified a non roller cam block to accept a late roller cam block camshaft, lifters, etc.

Since we fixed the Hubel telescope, I guess it CAN be done, but this would call for some serious measuring, drilling and tapping to get everything "right on", assuming, of course, that there is enough meat in the correct places to drill and tap.

The entire engine would have to be disassembled and thoroughly clearned afterwards to remove all the cast iron shavings.

Roller cam blocks, 87 and up, do not use a thrust bearing. The camshaft is retained by a plate bolted at the front of the camshaft, which would call for yet more drilling and tapping. Also, the roller cams used in roller cam blocks have a special "step" machined into the front cam journal because to the plate.

Talk about expensive and meticulous machine work!. You'd come off a lot cheaper just opting for a retro-fit roller setup.

In either case, changing from a flat tappet hydraulic to a roller cam setup is going to call for purchasing:

1. New camshaft - prices are about the same for late or retro-fit cams from the after-market, but GM cams will be cheaper by about $100 for the factory type

2. New lifters - retro-fit lifters are more expensive. Subtract the cost of the retrofit lifters from the cost of factory-type lifters to get the amount of the cost increase

3. New pushrods - probably about the same for either type cam setup

4. Valve springs - same cost

5. Thrust bearing and three piece Torrington bearing set for the Retro Vs cost of plate for the factory roller setup. Cost should be a wash.

6. Cost of disassembly/cleaning/reassembly, machine work and time/labor

The retro-fit option will come out a clear winner.

Just my thoughts

Jake

 

I believe all the 87-92 up gm small blocks (from trucks) will accept the factory roller rockers + they are 4 bolt main. Call GM and ask