I have a 69 mach1 with a 351W and I cant get it to stop backfiring out of the carb. I've replaced plugs wires points checked and rechecked firing order and timing. It only seems to be runnung on 4 cylinders. checked compression and all are between 145 and 155 lbs Any advice would be greatly appreciated.
Help
- Thread starter redneckjeff
- Start date
69 Rustang
Member
Do you know the history of this motor--could it have a cam with a 302 firing order? If the cam was ever swapped, that could be possible. Otherwise, the distributor off a tooth, timing chain jumped, or???
SoCalCruising
Founding Member
Hopefully it's just timing or firing order, even though you have checked this, because it otherwise sounds like fuel reversion through valves that aren't sealing. They could be bent or ?.
dennis112
15 Year Member
Need is a strong word because ALL factory 351w motors from 69' to their demise in the late 90's used the 13726548 firing order. This same firing order was also used in the 5.0 motors from the 80's.
As was mentioned by a previous poster, it could be 15426378 IF someone swapped in a 302 cam.
I am not a pro when it comes to all this engine building, all I know about my 351w is that is what I have and when I ran the 13726548 firing order it did the same thing that his was doing and I was told by a very good engine builder that 351w did have two firing orders, so I went and changed the plug wires to 15426378 and it pered like a CAT! But who knows I just might have a 302 cam, it sounds like it.
ALL 351's (W, C and M and also 400) had the 13726548 firing order originally. i'm sorry but your engine builder either doesn't WTF he's talking or he assumed that you might have a 302 cam and just explained it wrong. just FYI
dennis112
15 Year Member
Not to bust your balls, but a good tech website does their best to separate facts from hearsay. We want to put out as correct information as is possible.
The correct firing order for a Factory 351w is and has always been 13726548. Need concrete proof? Go to the library and find the Automotive repair section. Open up any Automotive service manual that includes a 351w motor, and you will find only ONE firing order for 69's and up. I have yet to see one bone fide publisher list the 302 firing order as available or as an option for a factory 351w . . . . . . .
A quick web search should provide the same information:
http://wiki.answers.com/Q/How_do_you_find_the_firing_order_for_a_351_v8
As mentioned a 302 cam can be installed in a 351w and will work correctly, as long as the 302 firing order is used. Ford did not produce them this way.
Similar threads
