cwb442

Hi

Wanting to switch to a hydraulic roller cam and just wondering what modifications are required? I have c heads ported and bigger valves with Comp Cam roller tip rockers. Other than that stock. I know it would require different springs and pushrods , but do I need full roller rockers, larger rocker studs, langer diameter pushrods, etc.

Thank you

Fred Kiehl

Just the roller cam and lifters. The push rods should be the same, and the valve springs may be sufficient as well. Roller rockers are a choice. Unless you are getting a hotter cam, most of the parts will be good to go. I would get new pushrods to allow them to wear in on the new lifters.

My442

I don't agree with the information above.

First, you need to be sure the cam gear that drives the distributor is compatible with your existing distributor gear. If not, then that has to be changed.

Second, the valve spring pressures on a roller cam are different and higher than a regular cam. You will have to change them as well.

Third, the roller lifters could be taller than the hydraulic lifters, so the push rods probably won'r fit.

Are you planning on using the 5/16" rocker studs? The spring pressure may be too great, and you will have to upgrade to 7/16".

You will also need a cam thrust bearing to control the cam "walk".

Be sure to cover all the bases or you will have an expensive mistake.

cutlassefi

x2. First post from Fred was waaaay wrong

cwb442

My rocker studs say max of 350# spring pressure and I'm guessing a roller is going to be well into 400's pressure. Ok so check cam/crank thrust, dist gear (pending cam core material), drill and tap for bigger rocker studs, and new pushrods pending cam? Sound about right? Two questions I have. When changing pushrods, length is different, but is there a recommended thickness with higher spring pressures and is the rocker pushrod pocket going to determine the thickness? Also other than Harland sharp what is a good rocker arm to use, or will these roller tips work fine? Thank you

GOSFAST

Hi "cw", couple items, when setting up/checking the cam end-play make absolutely certain you have the water pump bolted in position.

If you plan to use the OEM "tin" intake gasket you'll need to "window" it to clear the roller lifters (photo below). Also fabricated a heat-shield below the intake heat-crossover as a precaution due to the gasket mod.

We fabricated a cam button using the factory cam bolt and a "nylon" button.

We've done numerous Olds and Pontiac builds with Comp's "-9" retro-hydraulic roller cams (these are based on steel blanks) and the OEM distributor gears and so far not a single gear failure?

The last Olds (1972/9.7:1 C.R./pump-gas) came off the dyno with over 400 HP @ 5200 and over 480# Torque @ 3800. It was a 100% stock-appearing build, Q-jet to factory exh manifolds. Floated wrist pins and H-beam rods, stock crank.

Heads got guide plates and Sharp rockers, all fit under the OEM v/covers! Springs were set up at 140# closed and 340# open with .480" lift. We also "pin" the rope rear main seal through the lower cap also just as a precaution!

Thanks, Gary in N.Y.

P.S. Wishing all here a Merry Christmas and a Happy New Year.

oldsmobiledave

This post deserves it's own thread with additional details in the engine build section.

oddball

The roller tips will probably be fine for the higher spring pressure, but call Comp to see what the cutoff is.

Pushrod size is more limited by the guide plates (easy to replace!) and clearance through the head. I'd recommend going with a 3/8" quality one piece pushrod due to the spring pressures. You can get them with 5/16" ends if needed. And, yes, bigger pushrod ends may not agree with stock-swap rockers, like the roller tip units. You may just have to mock up to see if you have any clearance issues with the pushrod holes, but I think clearance issues are fairly uncommon on Olds.

No one mentioned a thrust washer to go between the block and the flange on the cam. I've heard some say they're critical to prevent wear on the block, others say the block is just fine and it's a marketing gimmick.

My Hardland Sharps fit under stock valve covers *with* the 3/8" thick gaskets, but I'm also using the shorty polylocks. With just normal gaskets you get some tapping. Some have had to cut speed holes in the oil baffle to clear the poly locks.