datsun-roadsters
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Re: u20 startup help

To: JCLAY510@aol.com
Subject: Re: u20 startup help
From: "John F Sandhoff" <sandhoff@compctr.ccs.csus.edu>
Date: Tue, 12 Oct 1999 12:13:56 PST8PDT
It was asked, presumably by Jimmy but it may have been Sara:
> I need some u20 help. I am firing this motor for the first time. The 
> tensioner makes noise for a few seconds until oil pressure builds up.

You said all parts were replaced - does that include the chains and
gears? How much chain slop is there - enough that the chain can
hit the upper guide? (Put the car in gear, roll it backwards just a
nudge, and that'll shift all the chain slop to one side).

If the chain's about to touch the guide, then it sounds like the head was
milled. With a thinner head, the cam is 'lower' and adds slop to the
chain. The cure is to add shims under the cam towers, equal to how
much was shaved off the head in the first place. This brings the
cam geometry back to expected placement.

Two things to remember:

1) When the bottom of the head is milled to flatten it, the top also needs
to be milled. When the head warps, it all warps - bottom AND top.
If the top is still curved, the cam will flex and ultimately may break.
Ouch!

2) If you remove the lower cam towers, the manual warns to have the
bearings align-bored by a machine shop (is that the right term?) Anyways,
the idea is that those bearings better be dead-on in alignment. If you're
feeling lucky, grease it all up, bolt it together without rockers, and see
if the cam turns freely. If it binds at all at any point, something's not
aligned well enough.

-- John
     John F Sandhoff   sandhoff@csus.edu   Sacramento, CA


> parts have been replaced and the motor was assembled by a reputable shop. 
> However it has been sitting for a number of years until I rescued it a year 
> ago. Any ideas would be helpful
> 
> Jimmy & Sara Claypool   
> 2 roadsters
> 2 2002's
> 1 cat
> 

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