stuttering and backfiring
 

Hey all first time poster here.
I've been working on my 71 scamp for almost 2 years now, just updating things in hopes to make it some what reliable. So here's the break down, its got a 1980 318 with 360 heads not sure on cam probably a stock 360 but I'm not sure I bought it this way and the guy didn't know what it had in it. So far I've switch to fitech efi, msd box, msd dis., msd coil, msd wires, and a 76mm turbo. I got the car far enough along to start driving and find any other issues I might find and fix. There have been a few. So all is going well, the turbo system is working really well and so is the fitech at controlling afr. I was having some decel backfiring and wanted to do some adjustment in the fitech to get that to go away. So took it out a few Saturday's ago and doing some pulls and adjusting the decel in the fitech and it seemed to be helping with the backfiring when letting off the throttle after a pull. Then a few minutes later the car started to hesitate a little, then progressively get worse where it was backfiring with just a small touch of the gas. Now at idle if I rev the engine it will start backfiring. I pulled the timing cover just to make sure I didn't skip a tooth and all is well there. I did a cold compression test and all cylinders where fairly close in numbers to each other. My fitech was giving a O2 sensor fault, the first time I drove it my O2 wire fell down and the connector layed on the exhaust and melted a little but it didn't seem to effect how it ran and the fitech's ability to adjust the afr, but I went ahead and ordered a new O2 and connector and redid that with no effect. And the crappy part is it was running strong for the first few week, my brother was coming up for work training and I wanted to give him a ride cause he is always talking trash about his c4 vette being faster and the weekend before he was coming down is when it started running bad. So far I've ohmed the plug wires, checked timing and changed the plugs. Any help would be awsome.

Might just get a valve spring checker and make sure the springs are all about the same and have not gotten week... I'm just taking for granite that every thing else is in good working order.
I would say you were on the rite track on getting ride of the back fire.. Not sure what the adjustment was. But if I recall reading on one of the other sites, it was ether Return to idle number was raised or it was timing retard? Not 100% sure on my part... Now I do think that cam will make a difference in helping with the back fire issue also.
Keep us posted on what you find...

Is that something that a auto part store rents out. I just got done doing a smoke vacuum leak test and the only smoke was coming from the fitech around where the wires exit the unit.

Take a close look at the rotor and dist cap !!! There are super cheap caps out there that are junk.. MSD should be ok...

It is a Msd. It did have some crust or what ever its called on the rotor and points in the cap. Cleaned it off I'll take a closer look at it today, but at first glance it didn't look to bad.

core -

Oh, it's an MSD, and where is the rev limiter set???

Archer

Flat cam or springs, nothing else.

Not that I know of.....
Not sure what you where going after with the vacuum test and the smoke test? Smoke test is mostly an emission systems test... Dose not work well with crankcase, because of open ended ring gaps.
But will just stay on topic for now...

6500

Would it still idle normal if the cam was flat or a worn spring?

Just check to make sure the intake isn't leaking

Perfect..