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Old 05-12-2004, 12:49 AM
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SBC Head Question?

I pulled my valve covers tonight and looked things over. I found several of the rockers loose enough to move side to side. I could also move the push rod up and down on the loose rockers. I know a serious valve lash adjustment is in order, but if the rockers are that loose do I need to check for bent push rods or cracks in the cups on the rocker arms from the push rod slamming into them?

I looked at the head numbers and here is what I have 458642, I thought it read 8842 but I can't find a reference to them anywhere. SO it must be 8642. don't know valve size or year I keep reading different dates off the web.

Regards
Mark

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Old 05-12-2004, 01:16 AM
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It would be a good idea to check over the push rods with a straightness checker and check out the rockers. The casting numbers pulled up as
458642.....75-84...350..........350
468642.....76-up...350/400

These heads were the common smogger heads of that era. likely have 1.94 1.50 valves, 76cc chambers.
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Old 05-12-2004, 10:09 AM
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OK Thanks DV
I think they are a set from 1979 which would make them 350/400 heads.

As far as the push rods go couldn't just roll them on a hard level surface and look for any abnormality in to rolling?

Also on these heads are all the rockers 1.5? There was a web site that had all sorts of mixed rocker setups for these heads.

Regards
Mark
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Old 05-12-2004, 10:48 AM
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I hope this is a solid lifter cam. . if not and it is hyd. you may have some lobes going down.

Chris
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Old 05-12-2004, 11:10 AM
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Hey Double Vision.
I was browsing the web and a post came up on Hot Rodders from you saying that the 458642 heads were crack prone. Could you elaborate on this please.

Regards
Mark
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Old 05-12-2004, 12:53 PM
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I know that my rockers move side to side too. And have that nice clickety-clack when it idles. Runs like stink...

Never was able to find out what cam it has. The guy who replaced the racing cam (before I bought it) says that he got a stocker from Autozone back in 02 right before the tranny went...but I find it hard to believe that it's a hydraulic cam. Dart Iron Eagle 200cc heads...but it's been sitting for over a year so the cam is still new.

A little movement is normal...Lot's of movement and you need to adjust. I too would see if your pushrods are straight, but it may just be a case of "wearing in" over the years and your rockers just need to be tightened.
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Old 05-13-2004, 10:35 PM
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Could be collasped lifters, bad cam lobes, bent pushrods, just loose rockers arms or any combination of these. Best thing to do is start from the top and check the whole valvetrain just to be sure. The old school back yard mechanic way to check pushrods is to roll them on a piece of glass.
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Old 05-13-2004, 10:50 PM
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Well I went out tonight to check out the setup. I checked the pushrods and they are perfect, then I pulled the rockers and they to look good. So it's on to my first valve lash adjustment. It took me a couple times to get it close. I'm not sure it's perfect yet. But the rockers are fairly tight with very little side to side movement. I think I'll read up on doing valve lash again, and do it again tomorrow.

Thanks to all for the info.

Regards
Mark
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Old 05-14-2004, 06:50 AM
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http://www.angelfire.com/tx5/randysr...Headguide.html
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