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Backfires are often caused by either a timing issue,wrong firing order,or a lean out. Does the carb accellerator pump squirt fuel? You could have a vacuum leak somewhere.
Good luck.
I think the engines and drive trains were great if properly maintained. I think the old big gear reduction starters were junk and often failed in just 2-3 years.
Ballast resistors failed often and most Mopar guys carried a spare as i still do. Mopars were often more cold blooded/slow to warm up...
Seems like you might need to just lose the vacuum advance because its aparently advancing your timing well past 36 causing pre-ignition. I would think that running say 18-34 would work quite well using only the mechanical, although you likely only need about 15 at idle for good response. Depends...
I would check the lifters for crown as described above. Then install them in the block along with the heads,pushrods,and rocker arms making sure cam and lifter bottoms are properly lubricated. Then mark all the pushrods and rotate the engine by hand about 20 or 30 revolutions. If all the...
Comp sells a simple tool for grooving the lifter bores to provide direct oiling to the lobes. I have one and use it every time now. Still had 1 comp lifter fail.
Now using dedicated break-in oil without detergent in it,n.o.s. lifters,old weak valvesprings for 20 miniutes at 2000 rpm. Listening...
I dont know 100% how good the Johnsons are. I do know that comp lifters have a very bad reputation with a lot of people who have had failures including myself. Comps stuff used to be all good for many years,but i think they were bought out and the new owner proceeded to unleash the bean counters...
I dont trust comp or summit lifters. Highly recommend you find at least 20 year old nos lifters or buy Jonson lifters from Hughes Engines. Otherwise......your chances of lobe/lifter failure [which fills your engine with metal shavings] is quite high.
Good luck.
Never seen the notch around the outside;strange. Normally the top ring has a bit more tension but its not easy to judge the difference.
Its an odd bore size but maybe you can find something new to be sure? Molly is far better if available as the bores wont wear nearly as much.
good luck.
If the top rings are molly, they will be shiney and the 2nd rings will be dull. A top ring w/bevel on the inside of the ring goes on the piston bevel side up.
A second ring with a bevel around the inside goes on the piston bevel side down. Generally, if one ring has a bevel around the inside...
A breakdown/analysis of what portion of the 1/4 mile you were slower [if not every segment] might shed some light on the reason. For example....sometimes a smaller carb will produce better torque resulting in better e.t.s at 60 ft, 1/8th etc. . I think using an air-fuel ratio meter to tune both...
The main limitation is hydraulic lifter pump-up,followed by the strength of the stock stamped rocker arms and stock 5/16 pushrods. Bottom end is mainly limited by oil pan capacity and whether a windage tray is present. Next is the strength of the stock rod bolts. I would avoid 6000 with stock...