So I'm looking to install the GM 12370847 cam in my 383. I never really thought of this, but is there a lift limit on the factory roller lifters? I currently have a zz4 cam in there. The specs on the 847 cam are 234/242 and .539/.558. Of course thats .359/.372 at the cam...

Does anyone know if there is a manufacturer out there that makes solid roller step nose cams/factory type solid lifters for these factory roller blocks? I haven't seen anything like that.. yet.

 

Man,thats spinning that 383 really high,huh? Should sound nasty though.

Heres some lifters that look like they will work:
http://store.summitracing.com/partde...w=32&N=700+115

 

I don't believe lift affects the "lifters" that much, it will cause some bounce @ high lift, and require a rev kit tho, that's if your heads will handle the lift w/o the valve springs binding up or your retainers hitting the guide bosses.
I had to have my factory heads clearanced for the ZZ4 cam @ the guide bosses and spring pockets, and for teflon seals.
Factory heads are good for aprox .480" lift only.

 

I've had my heads machined for the extra lift as well. I used the beehive springs though. The heads had to be machined for the proper shims to fit. Now I think I'm just going to go with the 986 spring, keep the ZZ4 cam, and spend the money elsewhere.

 

I think .375" of lift at the cam is pushing the limits for factory roller setups. This is due to the lifters dropping out of the "wishbone" retainers. Which could cause a lifter to rotate and immediately destroy the cam and possibly more.

 

Well, I've decided against swapping the cam. Mainly because the seller never replied back to me..

I'm keeping the ZZ4, and have already removed the heads.