400M cam question

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Mar 30, 2013 | 11:29 PM

Chevmn56

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400M cam question

Hello all, I was watching one of these automotive shows they have on the weekends........and in my limited knowledge they comitted a cardinal sin, they changed a cam out in a engine to give it a little more power.

What they didnt do was change the cam bearings ,rods, lifters or rockers......I always thought that these parts had to be changed because of the specific wear patterns that take place . If you didnt change all the wear items would they not just destroy them selves pretty quickly????

I am going to change the cam in the 400M i have and go to a RV cam......i was budgeting in new bearings, lifters, rods and rockers.......after watching that show im not sure i need to.

Any help or sugestions would be appreciated

Mar 30, 2013 | 11:57 PM

devino246

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From: Lynchburg, VA

Lifters with a new cam, yes. Bearings, push rods, rockers, no.

As an aside: you know you need a special tool to replace cam bearings in an OHV V8, right?

Mar 31, 2013 | 12:08 AM

redroad

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From: Pa.

Quote:

Originally Posted by Chevmn56

you definitely need lifters and cam bearings and if your changing to much with the cam over original springs etc. should be changed also .. The push rods you could skip if they spec out but why ..

Get a kit that includes the 0 degree timing set .. with push rods you looking at about $475

Mar 31, 2013 | 12:14 AM

devino246

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From: Lynchburg, VA

Quote:

Originally Posted by redroad

you definitely need lifters and cam bearings

I'll have to disagree about the bearings. If the cam journals and bearing faces look good, there's no reason to go through the trouble.

Mar 31, 2013 | 12:26 AM

tbear853

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Joined: Feb 2004

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From: The Shenandoah Valley

Quote:

Originally Posted by Chevmn56

I've done many cams changing only cam and lifters, and often while I was there .... timing chain or timing set usually, especially if slack or high miles or etc.

If upgrading the push rods and rockers along with springs, retainers, it was because I was swapping on another set of heads in my case, never just because I did the cam unless the cam specs told me I needed to. If I had tired springs or stock springs and was going wild on the cam, then new springs and retainers and keepers along with stem seals. I have done such a swap with heads in place on a BB in my 67 Chevelle using air but I had not long earlier built the motor and had broke the new cam in with weaker stock springs .... after a few miles I swapped on the new stronger springs and keepers / retainers.

Cam bearings ..... only times I've ever (since 1970) changed them was always after hot tanking a block and doing a rebuild as the hot tank's caustic fluids eat on them.
Anything less, I just inspected the cam journals ... never had reason to look further as a cam just isn't hard on bearings.

Every engine build is a series of compromises, decisions made based on intended and use and conditions expected and chances the builder is willing to take. In my truck's case, long ago I knew that my 351M was not gonna be reved 5000 rpm plus, I just wanted more mid range with my cam change. I must say, those old stock valve springs have done OK for my truck's use. When I swap in the 400, I'll do a new matched cam & kit .... them old springs gotta be gettin' tired!.