225 Pro xs spark plug threads

[scotty34]

0T997921
Anyone know if you can chase the threads on these heads due to the casting angle ? #5 &#6 need dressed up to get new plugs started, old ones came out fine with piece of rubber hose after I loosened them and they felt fine. The new ones are giving me a hell of a fit getting started, I even split the lower cowl to get a straight shot on them.
Thanks Scott

[EuropeanAM]

Scott:

STOP where you are at... you don't want any aluminum flakes or fragments getting into the cylinders (or more likely, the direct injectors on the next startup attempt).

Proper method is to remove theads, repair or sleeve threads (note- NO "helicoils"). Angle is very important... you have about 1.5 degrees to play with (max).

[scotty34]

I looked closely at the threads ans it appears the first 3 are the problem, my plan was to load the tap with grease and only make 4 turns to dress up the first couple.

[EuropeanAM]

Be careful- I know that I personally would not attempt that.

[lpugh]

I looked closely at the threads ans it appears the first 3 are the problem, my plan was to load the tap with grease and only make 4 turns to dress up the first couple.

I agree with Don, You would be extremely lucky to get a Tap to start in perfect alignment as well as the risk of even a very small piece of metal being pushed into the direct injector ruining it. I think they are around 500 bucks a piece. You could also render your head unusable or even unrepairable with the smallest of errors. If you insist on doing this yourself you should remove the head and use a thread chaser from the chamber side. Please Don't take this as a insult in any way but just the mention of using a tap to correct this problem makes me feel that you should take this to a Pro that has experience in this type of problem. I will also say there are many marine techs and almost all automotive techs that would take the wrong approach to this. Cylinder head off this would be very easy to repair with almost no risk involved
As Don mentioned above and many do not think about esp. with heli-coils is the heat transfer rates, Thus the plug may run to HOT if not done right.

[boatwrench]

Snap on makes spark plug thread chase tool that works from the chamber side out. It works very well for this problem. Lower ceilings need to be removed for good access. Tool is about 50$ I have used it many times for this problem. Be aware it will straighten and clean up threads, not manufacturer threads that are there.

[Savage]

Cylinder head needs to come off. You will not be able to match up to the good threads that are still in the head.

[scotty34]

I'll check out the snap on tool.

[Savage]

I'll check out the snap on tool.

No tool can synchronize with the un-damaged threads.

[lpugh]

Cylinder head needs to come off. You will not be able to match up to the good threads that are still in the head.

This tool is 5 1/2 inches long, not so sure an amateur should be attempting to use it though, can be inserted into the area of good threads and expanded till proper fitment then backed out of the hole to straighten threads, still there are several risks involved of causing further damage. WARNING: If you have no experience with this type of operation you could easily turn this into a major expense
I was not going to bring this procedure up but someone else has already opened that can of worms

[boatwrench]

I'll check out the snap on tool.

Mactools has them also

[billnorman1]

Yeah, a tap is probably the worst choice for a tool here. If the outside threads are good a thread chaser is a good friend. Sounds like a job for a professional with the right tool, if there is cowling in the way you could remove it to save yourself some money so he could get a straight shot with the tool.

[Gamblinman]

I've never tried this....pull the heads and start the chase from the inside? I can't remember if those are tapered threads or not, but that would solve the alignment problem.