Recommend Spark Plugs

[spdbrake]

I think you missed my point the 605 plugs you have installed are too short and have the the wrong mating seat for your heads. Most likely the cause of your exhaust popping due to incomplete fuel burn.

The conical (tapered seat) plugs are usually found on GM engines. The 605 plug you are running do fit 4 cyl Ford Rangers and some V6 Mustangs Taurus cars though.

[169mph]

Originally Posted by spdbrake

I think you missed my point the 605 plugs you have installed are too short and have the the wrong mating seat for your heads. Most likely the cause of your exhaust popping due to incomplete fuel burn.

The conical (tapered seat) plugs are usually found on GM engines. The 605 plug you are running do fit 4 cyl Ford Rangers and some V6 Mustangs Taurus cars though.

I didn’t miss your point I missed your entire response. I planned to call Roush next week. I compared the 605 to the 3926 on Autolite’s website yesterday evening and I snipped the comparison because of the differences you stated. I was hoping Roush would point me in right direction. I did confirm that the plugs installed are the plugs the engine came with. Strange?

Thanks again

[spdbrake]

Good plan Mike,

I was making my recommendation based on someone else's post, which I don't normally do since it could steer you wrong.
It is quite possible Roush counterbored the spark plug holes to accommodate the 605 plugs.