Thread: 1990 350 Cam Question-Roller?

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As far as I know, Chevrolet began installing roller cams in 1987, mostly in car applications. They weren't as quick to install them in trucks and vans, as I've been made aware of those vehicles having flat tappet cams installed in them even up into the mid 90's. Some blocks were released using flat tappet cams with the spider bosses un-drilled and un-tapped. I'm not sure if any of them used flat tappet cams with spot-faced lifter bores.
http://image.hotrod.com/f/10025959+w...ock_engine.jpg

Personally, I wouldn't assume anything to do with these motors without actually seeing what the innards look like by, like Glenn said, looking down the pushrod hole with a very strong light, or removing the intake manifold. The differences include the middle oil galley being drilled and tapped in 3 positions on the oil galley rail in the middle of the block to secure the sheet metal spider that holds the dogbones, the dogbones themselves and the tappet bores being spot-faced on the top to allow the dogbones to lay flat and in a 90 degree relationship to the centerline of the tappet.

Be aware that cam lift is limited due to the fact that lifter rotation is eliminated by the use of the dogbones. Many aftermarket cams are ground on a reduced base circle so that an increased valve lift can be ground into the cam profile. If this reduced base circle allows the tappet to drop down too far in its bore, then the tappet could drop completely out of the dogbone, twist the tappet roller on the cam lobe and the ballgame is over. As a rule of thumb, limit valve lift to 0.535" with the factory roller setup and inspect the dogbone/tappet relationship closely on your trial mockup.

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