Well I finally finished my truck yesterday, after 3 months of being down. Assembled the 6.0 and installed, fresh heads, ported ls6 oil pump, ls2 timing chainset, arp rod bolts, 222/224 cam, 918 springs, hardened push rods, new tranny, 34" radiator, and 05 e-fans.
Well I crank engine to build oil psi, then install spark plugs, connect injectors and coils and went to start it.
I turns over and studers, try it agian and does the same thing, it finally cranks and starts but is back firing to the intake. RPM tries to level off but then it just raves high and I turn off the key. Went home pissed!

I am trying to figure out what the problem might be. The timing chain comes to mind but I checked that thing three times. In a previous truck I had a similar problem, it would sputer like it was missing but no back fire, turned out to be that 2 or three of the injectors had clogged up, it really sucked that i removed the timing chain again and checked it only to find out that it was the injectors.
I have a new set of 42lbers, should I try them?
What else could it be? I dont want to take it apart to check the timing chani agian till I narrow it down.

Help please.

 

so it starts, sputters, then revs out of control, or does it level out? make sure that all of your vacuum lines are connected.

When I swapped mine, it wouldn't stay running unless I had a valve cover breather opened.

 

I starts sputters then revs high, but I am concerned about the back fire to the intake.

 

how did you set your timing? I didn't degree my cam, but I'm wishing that I had. I did the dot to dot, it's dead nuts on. Are you positive that's like that.
How about your plugs. Are you sure that they're all ok, none of them questionable?

The only time that I've see backfires out of the intake is from having the distributor 180degrees off. We cranked and cranked . . .got nothing, added some fuel in the carb, then it tried to start, and the next thing was a huge fireball came out of the carb.

 

Believe me I am kicking my self in the *** right now, but I am 99% sure the timing is right unless I had a brain fart.
Would the LS2 timing set have something to do with it?
I did dot to dot and this was the cam that was in my 5.3.
I will take it apart tonight, if it is dead on shoudl I do a 180 on the set?

 

yeah, by brother said the same with a beer in his hand when he put the head gasket on backwards, it'll either line up or it won't it's pretty obvious.
No I did the same, the chain is the only difference, it's thicker, way beafier !
no way, don't even think of doing that, you'll bend valves and everything else. What cam did you go with, is there any advance ground into it?

 

I did install the heads, I just hope the gaskets aren't on backwards. I there a way to tell with out taking off the head?

 

your starting problem would have nothing to do with what you're having issues with. But if you'd like to check. . . take off the water pump, and the top holes of each side should be free and clear. Removed the water pump, and stuff your fingers up the top ports, you should be able to touch the head.

I had a cooling problem, you can search my posts and find it if you'd like.

 

So if the gaskets were on backwards it should still start, right.
Well on the good side of things it was nice to see my truck put back together after 3 months of it sitting there with no trans or motor. Just glad I did not loose and bolts, lol,
Hope to have the problem solved tonight.

 

How old is the gas? 60 days is a rule of thumb for gas although I have used older gas than that. Old gas can cause backfiring and al sorts of weird ****.

Were the injectors sitting around dry for 3 months? I've heard it is not good for injectors to sit. I once installed a used set of injectors and couldn't get them to fire. I even removed the fuel rail w/ injectors installed, not even a drop when cranking.

I'm no expert but I would start w/ the easiest things to eliminate first. check fuel pressure while you're at it.

good luck.