Retired Marine
New member
Good Evening,
I just bought a 4Runner and today I had a Doug Thorley Header installed at the local muffler shop. Upon driving it home I noticed a pre-ignition knock upon heavy acceleration or going up a hill. It did not do this before installing the header.
The header is chrome and not ceramic coated and no longer has the heat shields that the manifold had.
I pulled one of the plugs tonight and it has a heat rating of 5 or hot. I'm thinking the knock may be cured by changing to a 6 or 7 plug.
Has anyone has this experience? For those of you with headers, what heat range plug do you use?
I appreciate any assistance or advice on what it could be outside of the spark plugs.
Thanks!
I just bought a 4Runner and today I had a Doug Thorley Header installed at the local muffler shop. Upon driving it home I noticed a pre-ignition knock upon heavy acceleration or going up a hill. It did not do this before installing the header.
The header is chrome and not ceramic coated and no longer has the heat shields that the manifold had.
I pulled one of the plugs tonight and it has a heat rating of 5 or hot. I'm thinking the knock may be cured by changing to a 6 or 7 plug.
Has anyone has this experience? For those of you with headers, what heat range plug do you use?
I appreciate any assistance or advice on what it could be outside of the spark plugs.
Thanks!
