Hello Group
I recently traded brands- I sold my Chrysler, - owing to no time to fix it- and bought a Desoto S-11 (baby Chrysler) that needed much less work (seemed to me)(Groan).Brought it home and discovered it was actually pretty cranky.
I have finally gotten the time to dig deeper into its troublesome '47 flathead. (I was told by the seller that he thought it had low miles on a rebuild (no receipts)).
Background data:
Great bottom end; quiet, 40 psi oil pressure.
Compressions (hot, plugs out, wot)all near 95 psi at cranking RPM.
Adding 20W-50 boosted it by a just few psi.
Vacuum 18", w/ a drop of 1" on one cyl., and an occasional drop of 3".
Runs ok when cold, but just horrible when hot. If you drape a piece of paper over the tailpipe, it occasionally sucks back against the opening, at idle.
The oil in the crankcase has quickly turned black. Slight blowby visible from breather and road draft tube.
Everything I checked was already in specs - valve lash, points gap, timing, float level, etc. etc.
If you dribbled a little gas into the carb when running, its rough, ragged running smooths out considerably. The same if you close the choke part way, after warmup. I have already replaced the manifold gaskets, as I suspected an intake leak. Seemed to me it was a case of running too lean.
No improvement, at all.
I tried 3 carbs, including the NOS from my '46 Dodge, and they all were equally lousy.
New coil, plugs, wires were previously installed.
Someone tried to get this car running well, and gave up. So did the next owner. Now I'm on the spot.
After my external probing, etc. did not identify the problem, I pulled the head yesterday, and removed the valves.
It does appear to be a very low time rebuild.
New valves (laser-etched part nos. on some, others made in Brazil)
+.020 o/s pistons, etc. Crosshatch still visible in cylinders, no ridges at all. Very slight scuffing on valve stems, and they mike out at NEW diams.
BUT - all the valve heads are caked with wet or sooty carbon, ditto the valve pockets. Carbon on valve stems extends up into some of the valve guide areas. Valves seem loose in guides with springs released.The head has quite a bit of carbon build-up, as do the piston tops.
Seems like it's really rich,(?????), or getting oil on all the valves somehow? Everything is black, or wet, or both.
Does anyone really know what amount of side-to-side play is acceptable for the valves, with the springs released?
I have no way to ck. for bellmouth, etc.
I took lots of photos. I need advice as to my next step. I suppose it's time to pull it out for new guides and to ck. the bores for taper and out-of-round.
Ideas?
Thanks
Ward d.
