[Roadsters] U20 - Cam Broke - Valve Worries

[robert k. smith]

hi nath., usually, when the cam breaks on a u20, the head is, or



was warped. that is,top of the head is warpped, and the cam towers



are not in a straight line any more. possibly the head was warped



(SP.?) and was milled only on the bottom side. this happened to me



one time only,( i eventually DO catch on). you probably have at



least 1 or 2 bent valves,(on the cyl. where the cam has stopped).



usually,the valves might mark the pistons,but, rarely, have i seen



a cracked piston.

you need to remove the head and ck. to see if the bottom of



the head is warped. if not, you can fix the warp problem,one



of two ways. take everything off the top of the head, and have



it milled. or, you can use shims under the cam towers, so, when



you use the correct shims, you will be able to rotate the cam



by hand.   on the bent valves: i have replaced the valves, and



left cracked valve guides in the head, to no ill effect.(no



smoking) or you can have the valve guides replaced.



if you want more specific details, call me. ive fixed this problem



4 or 5 times, over the years. regards, bob smith 614 418 9911



( ohio).





> Date: Sun, 12 Jul 2009 19:30:58 -0400
> From: nmleeds at mindspring.com
> To: datsun-roadsters at autox.team.net
> Subject: [Roadsters] U20 - Cam Broke - Valve Worries
>
> All,
>
> Continueing on the saga of the U20 -> U10. It wasn't the carb. It wasn't
electrical. So I took off the valve cover and found a broken cam. The video is
good for laughs.
>
> That raises a couple of questions:
>
> 1) Any ideas why my new cam, on my freshly rebuilt (5,000 mile) engine
broke? What should I look for and address before putting a new one in?
> 2) Should I be worried that the snapped cam might have caused the pistons to
hit the valves? I noticed a the sparkplugs on the 3 and 4 cylinders were wet,
and worried about valve, valve guides . . .
> 3) Any thoughts about what cam I should put in as a replacement?
> 4) And, does anyone have one cheap they would sell me?
>
> Nathaniel
>
> '69 U10
>
> Status: Parked.
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