Spark plug hole cracks in highriser heads

[tomsfe64]

I was turning over my as yet unstarted freshly built 427 with high riser heads and I noticed some excess fuel was escaping In a fine mist from 2 plug holes. Could these plug holes be cracked and if so what's the fix?

[jayb]

You will sometimes see that issue on high risers and tunnel ports.  I've been told that pinning the cracks is a good solution; the cracks don't extend into the water jacket, so you can drill them, tap them, and put in a threaded pin to seal them up.  Usually it will take more than one pin, so you overlap from one pin to the next to create the seal.  Gotta have the heads off to do that, though...

[tomsfe64]

These heads were magnafluxed but maybe they didn't check the plug holes. Thanx for the info.

[fekbmax]

Have they been helicoiled ?
This may sound dump but I seen this very thing on a 4.6 mod motor.  Fuel was misting out around it just cranking it over because it hadn't been repaired properly. I told him he should probably take the head off and have them Czech it or replace it because It was a re man head but sometime after I had left my genius know it all nephew put pipe dope all around the sparkplug threads.  LoL. Needless to say it finely fired the plug out of the head . For the life of me I don't know how he got lucky enough that the fuel spray didn't catch afire. He's lucky it was still up on jack stands in his side yard instead of driving down the road.. it was one of those  classic SMH moments.

[e philpott]

plugs blow out all the time on 4.6 ... there are not many threads holding the plug into the head to begin with  , they don't crack , the threads just don't hold the plug tight , we have a kit that repairs the threads while on the vehicle , no taking it apart ...... the High Rise head are cast iron , totally different deal

[fekbmax]

Many a cast iron head has had to be repaired with helicoil in the spark plug aera  as well as aluminum,  all I was getting at is sometimes there not installed properly, leak or back out causing problems.  The on the engine fix it kit for the 4.6 sounds pretty trick. That's got to save you guys alot of grief and head ache.  I been lucky so far I guess, 94 T Bird with 4.6 and 226k miles on it and no plug failing. .

[Nightmist66]

plugs blow out all the time on 4.6 ... there are not many threads holding the plug into the head to begin with  , they don't crack , the threads just don't hold the plug tight , we have a kit that repairs the threads while on the vehicle , no taking it apart ...... the High Rise head are cast iron , totally different deal

Yep, I've done several spark plug repairs on those 4.6s at work. Not much fun of course, but it is do-able. I use lots and lots of grease on the tap. A few shavings inside are inevitable, I blow out with compressed air and crank over a few revolutions.

[Stangman]

Yeah done a few of them also had a few customers that wouldnt change their plugs unless they had a problem almost always the second or third on pass side