[Fot] Spitfire Misfifre Part 2

[Tim Murphy]

Have you tried the old trick of spraying carb cleaner around the intake
manifold and carb mounting on #1 and #4 to see if you somehow have a massive
intake leak causing a very lean mixture and the misfire?

Tim

-----Original Message-----
From: fot-bounces at autox.team.net [mailto:fot-bounces at autox.team.net] On
Behalf Of robertten1 at aol.com
Sent: Saturday, August 04, 2012 6:55 PM
To: fot at autox.team.net; net at newenglandtriumphs.org; nedyno at gmail.co
Subject: [Fot] Spitfire Misfifre Part 2

Thanks to all who responded to my problem here.  I'll be heading to the dyno
shop on Friday next, hopefully to get baseline and a/f readings.  This in
hopes of solving the misfire problem a a little break-in time on the new
engine.

To recap :  Removing the #1 or #4 plug wire there is no difference in engine
note.  If remove the #2 or #3 plug wire the engine stumbles.  I've checked
the
timing, tried rotating 180 degs ( will not start ).  Swapped the plugs
around
and the same 2 cylinders misfire.  Swapped the plug wires around and no
change
in results.  Checked and cleaned all the engine grounds and the connections
at
the battery.

I have swapped out complete ignition systems, one is Mallory Dual Point the
other is a PerTronix conversion in the factory Delco Distributor.  The
PerTronix is all new parts the module, cap rotor, wires and coil.  The
Mallory
is as was before the engine rebuild.  There was no noticeable change in my
problem with either system.  Re-checked all connectors and connections for
both complete ignition systems found nothing faulty.

I have done a compression test and all cylinders seem OK.  I did a leak-down
test and nothing stood out there either.  I had hoped If there was a problem
I
would get some direction in one of these tests.  Next I removed the valve
cover brought the crank to top dead center, removed the plug to #1 cylinder
to
verify and checked the lifters for #1 - both are loose ( suggestion from Kas
)

I re-torqued the head, checked the valve clearances ( nothing out of place )
reassembled.  Then changed from Platinum plugs to NGK V-Groove plugs and
started the engine.  Still a misfire at #1 and #4 ???

I have checked the Weber carb, knowing it will need some tuning as I made
some
changes to the engine during the rebuild.  The biggest is a custom cam from
Rick Cline.  I found I need to lean the Idle Jets as both Idle adjustment
screws could turned in all the way without changing the idle note.  A 2 step
leaner jet did result in backing these screws out almost 1 full turn.  But
no
change to effect the misfire problem.

And yes, in all kinds of testing there is spark going to #1 and #4 plugs
just
no change in engine note. A couple good zaps made me feel wide awake
performing those tests,   Hmmmm ??

So I am going to order another rotor for the Mallory dizzy ( at some one
here
suggestion ) as I grasp at straws for a solution to this misfire problem


Engine - .'73 1500 Spit  Bored .040" over  (recessed blocked)
A/E flat top pistons  +.040
Head -  Milled .125" ( big valve head )
6.5 to 1  roller rockers   Race Push Rods
10/10 crank polished and balanced
Lightened flywheel  @ 12 #
Duplex timing chain set-up
Cline Cam  lightened and drilled lifters
Tri Y  Headers   2" exhaust
Single Weber 45 DCOE 13 carb   Cannon Manifold


Stumpdified,
Bob T.
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