Bone$

Hey guys I need some LS guru help . I bought a 2000 ls from a guy it was open header and I got to ride in the car before I bought the motor . It ran great . I swapped it into my 1954 gmc open header and it would start and run . I drove it onto the ramps for the exhaust shop this morning . When I picked it up this afternoon and tried to start it .. It cranks and stutters like it might fire but nothing .
The shop said maybe it the motor was tuned open header and now the back pressure is messing with it . ????

I checked all my grounds and power sources but still can't get her to fire .. $600 in exhaust and can't even hear it run .

Any help would be great..

Thanks

usnfenix

iTrader: (11)

Sounds like BS from the shop. They messed something up and they need to fix it i hope you didnt let them off the hook

RPM WS6

iTrader: (3)

Agreed. Some definite BS from the shop, unless they sold you mufflers that are stuffed with dead rats and other debris causing a no-flow situation. Absolutely no where on earth will being tuned on open headers equal a no start condition once a complete exhaust system is installed. If they actually believe what they told you, they shouldn't even be in business.

gametech

iTrader: (1)

Did they weld any part of the exhaust while on the car? It is exceedingly rare to cause a problem, but technically there is a reason the service manuals say to disconnect PCM/BCM/etc. while welding on a car. You could "in theory" have corrupted data or damaged electronics in the computer.

Jay-P

iTrader: (16)

That was my first thought as well...

psychosid30

iTrader: (7)

Exactly what these guys said. Back pressure would cause it to act up once to put some RMPs to the motor, but at idle it is not restrictive enough to cause an issue. They damaged something when they installed your exhaust.
If you want to fully test their theory though, just remove the bolts from your exhaust flanges and open it up a bit and hold it open with a wedge of some sort and try to fire it up.