[christianchevell]

Your DIY is not such a good idea now …….let alone if you had the perfect right information or skipped some critical stuff to keep you from majorly screwing the pooch.

Hopefully you knew the thread pitch for setting your preload is around.048 so one turn too much to get to around .045-.060 ls3/7 lifter preload tightening it down from zero lash..... and should be thought of as .048 x 1.7 ratio of rocker ( a Fulcrum) = .81 distance moved adjusting preload with one complete turn...overly tight even for a ls7 that takes .070 the max preload.

Hopefully your pushrods were measured/ heavily recommended; and with smaller most likely base circle on a aftermarket cam your pushrods are slightly longer than stock as .050 difference in the circumference of the base circle means on one side of the cam a .025 difference in the length the pushrod needs for the same top end architecture/ angle of the dangle etc...… hopefully you presoaked your lifters, installed your cam right at the right timing....and a whole bunch of other things ….and have plans to immediately tune it while breaking it in...yes I break mine in with Driven racing BR30 something people may scoff at as its a roller...but hey its gone to 8620 cores for a friggin reason etc..... stupid is not a thing a old hot rodder wants to say about their own lack of prep...…


You sound like you need help desperately before your trashing something...… back firing can destroy a engine BTW, with the age of your car you most likely should have done new head gaskets, new lifter baskets, new TTY head bolts new lifters if your mileage was more than say 20k and maybe even then its all in lifter condition old cam condition/tracking etc....

If you changed out your oil pump you had to change the dangerous to replace o ring and get the height perfect for the pick up tube something you can sneak in by loosening the pan for a DIY but my tuner does with a cradle drop....

This is not your old daddies Chevy the distributor could be 180 degrees out on as you know..... I would myself have to go back through things.....to find what's wrong even if I did it perfectly with every reference manual sometimes they miss a step or take for granted knowledge a person not a mechanic does not know...… of have just a timing wheel around or understand a cam with +4 comes with four degrees advance already ground in etc etc

So you may need help professionally in your area from a real good corvette type mechanic......IMO as you should not even with no tune be backfiring...…...your engine is with its ECU trying to adjust air/fuel , timing ;etc to avoid any detonation which is backfiring and it comes in two varieties....one with internal engine backfiring which is very harmful, and one in the exhaust which can be harmful also especially if its happening right out of the combustion chamber. Its totally different also from exhaust Burble or Decel Popping which occurs at the fuel cut off in a tune and the excess gas is then ignited making mild popping further down the exhaust than a back fire. Fuel cut off is of course from not stepping on it anymore or downshifting to higher revs not accelerating particularly.


Good Luck to you, so much to check ...every ground, every preload, every thing..... a canned tune in a handheld may stop some problems but its not going to most likely be perfectly good for your engine as that specific cam and your individual mods ; it makes saved tunes by tuners ,( that can be preloaded in handhelds), that much more important ;in a library of tunes even for tuners with dynos....to even be able to start with dyno tuning with HP tuners etc...…and lots of people then go on to data log, dyno Steve is a good remote tuner also used frequently on here; Frankly it would be hard not to keep tinkering with it yet even as a old experienced build many SBC?BBC engine guy I did not mess with the install myself.

I went to the best I could find for my install around here Thomas Wong after reading a ton and then buying parts over a long time and reading more constantly on here over the years and consulting with him over and over and I am on my second engine and understand springs have limited life, a over rev can trash a engine if not caught soon enough, push rods can bend and the engine is strong enough to be sounding just fine, etc etc etc.

And yes I know the faults to the DIY on here by Robert Way; and his short coming with being able to measure his Pushrods and set his preload....and most likely it came back to bite him as it was a work in progress for the DIY...I have not heard of him in years and years...…… IMO I would be for towing it to someone good and letting them take it over and spare yourself grief with just some cash. Specialty tools a timing wheel etc are not things I have just laying around for other than SBC BBC and then I have ….a timing gun, a pre oiler I made from a old distributor, hell I even have topless valve covers to adjust flat tappets running, do a break in /fluid drains etc etc etc lots of tricks just for much less complex builds. Good Luck again. Your new LSA is vastly different than the stock huge LSA and timing.