1990 350 Cam Question-Roller?

[Mr Blue]

Just a quick question please. Does a 350 small block 1990 Chevy Suburban with center bolt valve covers have a roller cam?

I am hearing conflicting reports with most people saying that roller cams were installed in 96 and up Suburbans. Thanks for the help.
Don Jr.

[rspears]

I'd send member glennsexton a PM if you need something quick. He's a wealth of SBC info.

[glennsexton]

Hey Don:

I think 1996 the Vortec was the first truck motor that used a roller cam so if it's the original engine, probably not; however, the 350 blocks back as far as 88/89 were drilled and ready for rollers. Only sure way is to check - pull a valve cover and use a good light to look down the pushrod hole. You'll recognize a roller. Even if it's not a roller, the hard work has been done by GM in terms of lifter bosses and tapping the oil galley so you could use factory roller lifters, spider, etc. without a lot of additional machine work.

Worse case - Howards makes a real good aftermarket kit that has everything you need to install roller in a non-roller block. they tie lifters together with a bar that prevents rotation and provide the proper length pushrods (I still always check them - you don't want to find out the hard way they're too long - just trust me here!), cam button and retrofit springs, seals and locks. I like to replace the front cover (regardless) with one set up for roller cams to make sure the cam stays put. If they walk even a tiny bit you can toast the cam in a New York minute.


Best,
Glenn

[techinspector1]

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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[Mr Blue]

rspears, glennsexton and techinspector,
Thank you for the information! I had thought all along that my Suburban had a roller cam. Another wrinkle on the brain :-) Thanks again!