The Stovebolt Site Forums The Shop Area Engine Shop timing, dwell, and backfiring

> I'm working on a 49 3600, my new project. 216. I have rebuilt the
carb
> (Rochester) and got it to run. If anybody has a CarterW-1 that
they'd want
> to turn loose of I'd love to get it to replace the
rochester.Anyway. I have
> replaced points, plugs, condendor, cap, rotor, wires and it runs
ok, but
> seems a little down on power. I'm getting a timing light and dwell
meter
> today. I know you can ck dwell with the plugs out, can you ck
timing the
> same way?? I'm hoping the timing and dwell with a valve adjustment
will help
> it run better. It ran for 45 minutes and went for a mile ride, then
I did
> the valve adjustment. Exhaust were all tight and intake were loose.
When I
> pulled the plugs(new) they were very black and soot covered. Any
thoughts?
> I'm going to set dwell and timing, run it again for 45 minutes and
then
> re-check valve adjustment. Also, the idle adjustment screw on the
linkage
> work it self loose very quickly. How can I help it stay in
position? I know
> I need to get a vaccume gauge to set the idle accurately, I'm
planning that
> for this weekend. I've also rebuilt the M/C and got the brakes to
work
> fairly good.

Went home last night with my new dwell meter. Already had plugs pulled, spun over motor, dwell was @ 40. Readjusted points a couple of times got dwell to 33-34. Also cleaned flywheel, found BB, marked it with white paint as well as tip of pointer, checked head bolt torque all ok but one a little loose, checked rocker shaft nuts torque. ok, carefully lubed each valve stem with tranny fluid and squired a little on the rocker shaft itself. Reinstalled plugs and cap carefully checking firing order. Tried to start, wouldn't. Checked carb, bone dry. grrrr.. added gas to tank, fired right up, ran for a couple of minutes. I decided to ck dwell one more time while engine was running, 40. Pulled plugs, reset points dwell w/o plugs in to 33. Reinstalled plugs, carefully rechecked firing order, fired up. After it ran for a minute or so it started backfiring VERY loudly and quit. Rechecked firing order, ok. noticed a little gas on the front of the carb. seemed to be coming from the fitting on the fuel line. Went ahead and pulled off top of carb to recheck float drop. Was @ 1 7/8 reset to 1/34, put Teflon tape on fitting. Got dark.
I don't understand why it is backfiring. I'm positive the cap and wires are right. 153624. I do notice that if you are looking at the dist cap at the wire clip that holds the cap to the dist, #2 is just above the clip on the r side of the dist, #4 is just below the clip and them # 1 is below #4 pointing at the ground. This is how it was when I got the truck. It ran for 45 minutes the other day and NEVER backfired. Never got to ck the timing. Where do I go from her??

Did you get the cap cinched down correctly? If it is loose it will have problems.

The firing order is clockwise, it will run the other way but poorly, so check that. I have gotten it wrong.

Finally, check your distributor cam for wear. If the cam is worn out you will be able to adjust the dwell OK but the gap will end up way too narrow and the thing will misfire.

After thinking over every thing I've done I realized that I had NOT run the truck after I did the initial valve adjustment which was done after "normalizing". The backfiring didn't appear until After I adjusted the valves. I'm thinking that if it ran before albeit down on power but with out backfiring why won't it run now. I did a quick cold ck on an exhaust valve That I had adjusted hot to .013 and I could not get the feeler guage inserted. I may have a distributor problem, but I'm thinking about doing a cold valve adjustment in the neightborhood of .009 intake and .018 ex ( I had set them .006 in .013 ex). The rockers all move smoothly and I did soak all the valve stems with tranny fluid after I did the adjustment. I do have another distributor out of a 235 that ran fine before I pulled the motor out of my old 50, but I want to settle the valve question first. I'm basing my guess on cold adj on just a guess, so Please express yourselves.
Dave

Yes, if your valves are too tight you will definately have problems.