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Re: U20 drivability help needed

To: Roadster List <datsun-roadsters@autox.team.net>
Subject: Re: U20 drivability help needed
From: cbreaul@banet.net
Date: Mon, 19 Apr 1999 20:05:19 -0400
I had the same kind of problem with my R16. What I found was that I was actually
running on one carb as the needle valve had stuck on the other one. Just a
thought
Charlie
69 1600

Ronnie Day wrote:

> >Hi everyone;
> >I had a great weekend - spent Friday getting the car in order, and Saturday
> >and Sunday bombing around town....  what fun!
> >
> >I am still trying to figure out something with my de-smogged and
> >header-equipped U20.  I've posted about this before, but now that I have
> >some bugs ironed out, maybe someone can give me better direction.  The car
> >is a '69, but I can't say about the engine - I think the engine number is
> >something around 11,xxx...  (IOW, it's an unknown hodge-podge engine)
> >
> >Basically, the car feels like it's running out of gas at 5000 rpm.  It will
> >pull pull pull like there's no tomorrow, until it hits 5,000, then it's
> >just like the carbs are blocked - no more flow, the exhaust tone changes,
> >and the car slows down.
> >
> >I thought it might be float settings (enough gas to get me to 5K, but then
> >no more), but *gently* taking the car to 4000 and punching it yields the
> >same result.
> >
> >The valves have all been adjusted, the timing is about 10BTDC.  I have set
> >the carbs and balanced them.  I pulled the breaker plate from the dist and
> >cleaned it up and relubed it.
> >
> >Nothing I've done has made any difference.
> >
> >I'm just about going nuts here - the car is fast and strong, but it would
> >sure be nice to get some more revs out of it.
>
> I wouldn't be at all surprised if you're running out of gas due to low
> fuel pressure, at least at higher RPM. This is best checked under load,
> at speed. Of course, that's not too easy, either, but it is doable. Are
> you running just the OEM mechanical pump? Carter (I think) makes a
> relatively inexpensive electric (around 4.5 PSI) which works very well
> when combined with the Holley adjustable low pressure regulator.
>
> >My only thought is that the distributor is either not functioning properly
> >or needs modification for improved performance.  The vac advance (as viewed
> >from the indicator tab sticking in from the advance body) moves, but not
> >much, as the engine is raced about.  Of course, this is under no load, so I
> >don't have a clue as to what it's supposed to do.  Can someone help me out
> >with the proper action of the vac advance, or a vac spec (duh, shoulda
> >thoughta that - probably in my manual)...
> >
> >I've heard of recurving the distribtor - what's involved?  Is is as simple
> >as replacing the mechanical advance springs or what?  Is it a DIY, or a
> >send-it-out-to-some-pro-who-knows-what-he's-doing modification?
>
> I doubt the problem is the distributor. Even a recurved distributor
> should be fully advanced well before 5K, usually all advance is in by
> 2500-3K at most. The specifics of recurving have been discussed before. I
> seem to remember a reference to info on Gordon's site?
>
> HTH, Ron
>
> ________________
> Ronnie Day
> rday@airmail.net
> Dallas/Ft. Worth
> '71 510 2-dr (Prepared class autocrosser)
> '73 510 2-dr (Street Toy)




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