Why would you reverse the firing order on a 350? - Chevrolet Forum - Chevy Enthusiasts Forums

Why would you reverse the firing order on a 350?

Old  March 3rd, 2009, 4:38 PM
  • Junior Member
    Join Date: Mar 2009
    Posts: 2
    Tacoma, WA
Why would you reverse the firing order on a 350?

So, my father in law gave us his 1983 Chevy 1/2 ton. He bought a crate motor and had it installed, drove it for 6 months. Then the TH350 gave out so he bought a rebuild and had it installed. After about another 6 months of driving, gas prices forced him to buy a Toyota, and park the Chevy. Here we are a year or so later and the truck runs like a raped ape (idling @ around 1300 rpm <low> and 1800rpm <high>). It's sputtering and missing, so I remove and clean the plugs. Write down the firing order (which is reversed form any other Chevy firing order I've evr seen). Pull the cap and rotor, clean and replace. So, now, it won't start at all. I've tried setting it back to T.D.C. and setting the firing order as they had it, tried advancing and retarting the distributer till my hands bled, all to no avail. Please help.

Old  March 3rd, 2009, 9:51 PM
  • CF Monarch
    Join Date: Jul 2007
    Posts: 6,151
    Princeton, NC, USA
It would also help to know the type of Chevy crate that was installed. Small block, LSx, pre-Northstar?

Not saying you are ignorant, but here is a rundown on firing orders-

GM small block V8 engines are 1-8-4-3-6-5-7-2.
GM LS V8 engines are 1-8-7-2-6-5-4-3

Its also important to note that the cylinder numbers alternate starting from the left side of the vehicle as pictured below. This is true of all GM engines EXCEPT Northstar and some Pre-Northstar engines which are opposite.

(photo from CraigBlock)

Old  March 8th, 2009, 2:07 PM
  • Junior Member
    Join Date: Mar 2009
    Posts: 2
    Tacoma, WA
Father in law is still looking for the build specs and paperwork on the engine. A radio auto-show host says it may be a ?reverse grind marine cam? I'm assuming that the engine is of earlier model and so that the standard small block Chevy firing order is the one it SHOULD be using. 1-7-5-6-3-4-8-2 is the firing sequence that the engine was running on. It was also running about 16 degrees advanced, with the fuel mix screws opened 6 1/2 turns, on a 4 barrel Edlebrock carb/intake ( I don't know the model # off hand ).

Old  March 8th, 2009, 5:36 PM
  • CF Active Member
    Join Date: Oct 2007
    Posts: 116
i may be way offbase here:

it seems like it is also running wayyy rich. 16 degress ahead is quite a bit. i usually dont run more then 8. i have found FOR ME that 8 seems to be the best for my setup. as every setup is different. for the edelbrock 6 1/2 turns seems a little on the rich side to.

like i said i may be way offbase. but i know for my chevy setup i am at 8 degrees advance and 1-2 turns rich.

Search this Thread