5.7 vortec in 72 c10 issues
 

Hi guys. This is my first post, but I have been reading through this site for some time now. I recently bought a roller 72 c10 long bed. I had a 98 5.7 vortec from a truck that I put comp cams magnum 280, comp cams bee hive springs with required hardware, aluminum dual plane intake, holley 750 vacuum secondaries, hooker super comp 1 7/8 headers and jegs quite flow fuel pump. I installed cam straight up as per comps tech line. IM having trouble with backfiring through carb and exhaust. It acted like the valves were to tight, but I just ran them again to zero lash plus 1/4 turn. Also I have played with timing and all the same. Has anyone had this popping, backfiring issue. Thanks in advance . Oh yeah all parts are new and the long block was running strong before it was pulled.

Re: 5.7 vortec in 72 c10 issues
 

What method did you use to run the valves?
The spin the pushrod or the wiggle the pushrod method.
It's likely you have a couple valves hanging open!
http://www.crankshaftcoalition.com/w...raulic_lifters

Re: 5.7 vortec in 72 c10 issues
 

Hi there. I first set them on stand. Then I ran then with engine runnin .

Re: 5.7 vortec in 72 c10 issues
 

What are you running for timing?
Have you proven your timing tab/balancer are accurate?

Re: 5.7 vortec in 72 c10 issues
 

Yes it doesn't matter where timing is. Initial set at 10. Then total 38. Then moved dist. Around. No changes with backfiring

Re: 5.7 vortec in 72 c10 issues
 

Running the valves with the engine running is pretty fool proof imo so they must be adjusted close enough. If you are positive that you don't have a spark plug wire crossed, then you must have a cam/lifter problem and will have to have a closer look. I crossed a couple plug wires a few years ago and it ran pretty decent until I got on the throttle and I got nice machine gun backfires. I ran it like that for a couple weeks because I was positive the wires were on correctly and an old dog like me couldn't make such a rookie mistake.

Re: 5.7 vortec in 72 c10 issues
 

x2 on the crossed wires, especially 5 and 7. could be a bit much on the total timing for a vortec

Re: 5.7 vortec in 72 c10 issues
 

I'm gonna change cap when I get to the shop if no good I will measure all valve travel. Thanks for all replies.
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Re: 5.7 vortec in 72 c10 issues
 

Look for coil bind too!
Vortec's don't like more than 32 degrees too!

Re: 5.7 vortec in 72 c10 issues
 

I know you said it's a '98 block, but is that magnum 280 a hyd flat tappet or hyd roller?

Re: 5.7 vortec in 72 c10 issues
 

Did you break in the cam properly and use plenty of assembly lube? Did you use a zinc additive during break in. If that cam is a flat tappet cam I really hope you didn't fire that engine up and let it idle while you attempted to adjust the valves. The first 20 minutes of a flat tappet cams life is the most important. If you didn't do proper break in I would suspect that you wiped the cam out.