I think you should torque the head and go over the valve adjustment
again. I am always amazed at how loose the head bolts are after running
a new motor. A compression test is a good idea I am betting you do not
have much or any compression on 1 and 2. Jim E
Jan Eyerman wrote:
>With the engine warm, run a compression test on cyl 1&2
>
>Jan Eyerman
>
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>John Slade <edalsj@igs.net> wrote:
>I have run into an engine problem that I can't diagnose, and am
>wondering if any out there have had a similar experience.
>
>Situation....freshly restored car with essentially a brand new engine.
>New 1725 factory short block, which I have been carrying around with me
>for the last 25 years, fitted with all overhauled/reconditioned
>accessories. Head and cam overhauled by a reputable machine shop, engine
>built up by me (I've done several before), distributor and Stromberg
>carbs overhauled by me, etc, etc. New spark plugs, clean fuel lines with
>an in line filter. Various vacuum hoses checked and found leak free.
>Points and spark plugs correctly set, as were the tappets.
>
>Engine initially started, and distributor set to approx 70 BTDC. Carb
>mixtures adjusted to give reasonable running. Car idled at about 1200
>rpm. Drove car for about 2 miles at modest rpms, then shut down.
>
>Next day, started car OK, went for a drive, and after about 2 miles,
>engine started to miss, and get a little rough. Got worse as I returned
>home. Found that I could remove number 1 and number 2 spark plug wires
>with no change to engine running, though still with a big spark on the
>leads. Fiddling with throttle and choke had no positive effect. Both
>carbs seemed to be working, i.e. as I blipped the throttle, both pistons
>raised a little.
>
>Let engine cool down, then attempted to restart. Started fine, ran
>smoothly for about two minutes, or until things started to get warm.
>Then the misfiring returned, same symptoms...nothing from #1 and #2
>cylinders.
>
>Let the engine cool down, and repeated. Same results as before...ran
>fine for a couple of minutes or so, then went off.
>
>I assumed that the front carb was acting up, so removed the carbs, and
>replaced the front one with another which had not been overhauled, but
>which had worked successfully on a 1725 a couple of years before.
>Replaced the carbs, and started the engine....exactly the same symptoms.
>While fiddling around in this condition, I blocked off the air intake to
>the front carb with a leather work glove....the engine smoothed out
>noticeably (perhaps not completely), but at a lower rpm than when the
>engine was started.
>
>At this point I am a bit stumped. Perhaps I have some sort of vacuum/air
>leak which only occurs as the engine warms up, perhaps there is
>something I haven't thought about. If it is a leak, how come it only
>affects the front two cylinders? The problem does not appear to be
>electrical, since there continues to be good sparking at the front two
>cylinders. Since I replaced the front carb with another, it seems not to
>be directly front carb related.
>
>Any comments and/or advice will be appreciated. I'd like to get this
>sorted so that I can go driving this weekend!
>
>John Slade
>Manotick, ON
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