[david jensen]

i recentlty bought a 69 cougar xr7 with what i thought was a 351.
i had valve seat problems so i removed the heads and had a valve job done. I thought that i marked the distributor right but i must of screwed that up. When i went to do the firing order i found that the distributor turns in the counter clockwise rotation. The book says 351' s are clockwise ? i set the order for 351 and motor wouldnt run. set it to 302 firing order and now she runs. but at light acceleration the motor back fires and hard it dosent. it doesn't seem to have the power that it had before, i cant even spin the tires. any help appreciated! i tried to adjust the valves for 351 and for 302 no difference in performance. how can i tell if somone put a 302 in this car. it has the dooe 351 heads edelbrock intake.

 

[modifiedmark]

Sounds like someone might have put a 302 cam in it. The cams will interchange except the fireing order is different between the two. mm

 

[sixt9coug]

yeah, sounds like a 302 cam in the 351. if you have a pic of the engine that will help tons. in the mean time, heres my 351W... they are wider than the 302 by about 2 inches. heres the other thing you might want to try, i think that the rotor turns counterclockwise in the engine. set the firing order for the 302 but make sure that its going counterclockwise as well. see what happens. and let us know
oh yeah i almost forgot, count the bolts on the intake manifold. i THINK they have 16 on the 351 and the 302 has less. CORRECT ME IF IM WRONG people

 

[david jensen]

why would someone put a 302 cam in it?,, i set the firing order for 302, and the motor ran. but the problem now is under light acceleration the car backfires, not sure if it is a lean pop or back fire. did not do this before.
thanks
dave

 

[modifiedmark]

Ok the fact is dont get too confused here, both the 302 and 351 dist rotates in the counter clockwise direction. I'm going to assume that you did not remove the wires from the cap when you pulled the dist, right? If thats so, ask yourself why do you need to change the fireing order now? It run before. My guess is you put the dist in 180 out to begin with and thats what started your trouble. Are you sure the dist is in right now? If not get after that and make sure you got it right.

Bring the motor up on TDC on compression stoke. Remove #1 spark plug while turning it over by hand and make sure that its comming up on the compression stroke when it hits TDC. You can remove the valve cover if your not sure to make sure both valves on #1 cyl are closed. Now make sure your dist is set in right and the rotor points to where the #1 plug wire goes. Now starting with #1 cyl go ahead and route the wires counterclockwise on the dist. If it was set at a 351 order before thats where you should be or vice versa.

Why would someone put a 302 cam in it? Walk around a swap meet some time and count the 302 cams compared to 351's. If someone got the cam they wanted cheap, Viola!!! there you go.

6t9 I will correct you although your half right. The EARLY 351 W's used 16 bolt intake manifolds. By early I mean 69 and 70 for sure, but my memory is bad and I'm not for sure anymore and don't have the gumption to care but 70-72 may also been 16 bolt. All the rest used 12 bolt intakes. You can use 12 bolt intakes on the early 16 bolt heads but not the other way around.