valve lift?
Thread Starter
Safety Car
Joined: Jul 2001
Posts: 3,921
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From: York PA
valve lift?
How much valve lift will the stock heads/springs on a '81 vette handle. I am looking at a crane powermax H-278-2 cam that has .467 intake/.494 exhaust lift. Will this work, or will I break stuff?
Safety Car
Joined: Aug 2001
Posts: 3,683
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From: Waterford Mi
Re: valve lift? (stickboy)
The heads should be ok but you should plan on upgrading the springs. The stock springs are a little weaker than the ones recommended. You should replace the rocker arms as well. The stock old rockers will have a ware pattern different than the new cam will create.
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: valve lift? (stickboy)
I never screw around when it comes to springs. You have too much to loose if one fails. The price of that nice cam and kit isn't that much more than the cam alone.
When you have your heads refurbished you should go with PC Seals for your valve stems. The shop will know how to machine the guides and pockets for them. The next thing to install with any hotter cam is lightweight Chromemoly retainers and good keepers. I had that cam and with good heads it's 7000 rpm capable in a 355 ci. If you intend to run over 6000 rpm 10 degree keepers will keep you from ruining the valve stems. I would not run that cam with less that 125 - 135 lbs closed. It will keep you out of valve float.
With that cam, port work, 2.02/1.6 valves, 10:1 or slightly higher compression, and headers you can exceed 400 hp. I also used 1.6 roller tip rockers. It was really solid bracket race motor for me in the 12.60's
[Modified by gkull, 4:47 PM 2/12/2003]
When you have your heads refurbished you should go with PC Seals for your valve stems. The shop will know how to machine the guides and pockets for them. The next thing to install with any hotter cam is lightweight Chromemoly retainers and good keepers. I had that cam and with good heads it's 7000 rpm capable in a 355 ci. If you intend to run over 6000 rpm 10 degree keepers will keep you from ruining the valve stems. I would not run that cam with less that 125 - 135 lbs closed. It will keep you out of valve float.
With that cam, port work, 2.02/1.6 valves, 10:1 or slightly higher compression, and headers you can exceed 400 hp. I also used 1.6 roller tip rockers. It was really solid bracket race motor for me in the 12.60's
[Modified by gkull, 4:47 PM 2/12/2003]
