Can I save Engine that has Spark Plug cross thread damage on the Cylinder thread??

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pfrederi

Well-Known Member
Messages
91
Sooo I managed to damage the cylinder head where the spark plug threads into the engine. Im not quite sure how but i must have cross thread it when i last installed it because it was difficult to unscrew out. Once out, i noticed i could not fully thread a new spark plug back in there. It would only thread part of the way but it did not seem seat all the way down. It started and ran ok until i noticed some power loss and noticed that the engine was losing compression. This is an expensive engine too. Its an OBR 30.5 Reed Case engine. I dnt understand how the thread could have damaged so easily. Im careful when i thread the spark plug in. Anyways does anyone know if theres anyway to get this fixed or rethreaded?? It appears some of the thread on the cylinder head is gone.

Thanks
 
Sooo I managed to damage the cylinder head where the spark plug threads into the engine. Im not quite sure how but i must have cross thread it when i last installed it because it was difficult to unscrew out. Once out, i noticed i could not fully thread a new spark plug back in there. It would only thread part of the way but it did not seem seat all the way down. It started and ran ok until i noticed some power loss and noticed that the engine was losing compression. This is an expensive engine too. Its an OBR 30.5 Reed Case engine. I dnt understand how the thread could have damaged so easily. Im careful when i thread the spark plug in. Anyways does anyone know if theres anyway to get this fixed or rethreaded?? It appears some of the thread on the cylinder head is gone.

Thanks
Try running a tap through it the same thread as the plug, maybe you will get something.
 
Sooo I managed to damage the cylinder head where the spark plug threads into the engine. Im not quite sure how but i must have cross thread it when i last installed it because it was difficult to unscrew out. Once out, i noticed i could not fully thread a new spark plug back in there. It would only thread part of the way but it did not seem seat all the way down. It started and ran ok until i noticed some power loss and noticed that the engine was losing compression. This is an expensive engine too. Its an OBR 30.5 Reed Case engine. I dnt understand how the thread could have damaged so easily. Im careful when i thread the spark plug in. Anyways does anyone know if theres anyway to get this fixed or rethreaded?? It appears some of the thread on the cylinder head is gone.

Thanks
Well plain and simple either you initially cross threaded the plug (and you should have felt a lot of unusual tightness as you continued to thread the plug in) or you over-torqued the plug when it was fully seated (and you also should have felt the plug tighten and then all of a sudden slip and feel loose again)
My best advice is to contact OBR and explain you have a stripped plug hole. I'm willing to bet they can Helicoil repair your stripped threads.
 
Funny how it only happened when u took it out 🤔
The damage was done on the way down... only shows itself when you remove it.... seeing as heads are relatively cheap and of cast aluminum id just replace the head as it gives you a reason to upgrade... if it was a actual vehicle by all means try and repair the threads
 
I bet it was over tightened. Take the head off and send it to obr to get it fixed, or maybe a machine shop can do it for you.
Yeah Ill call Dan over at OBR and see what he says. hopefully its doable. Thx
Thanks Guys!!!
You All touched on good points which may have happened. Im gonna call DAn over at OBR and see what he says. Ive rebuilt the top end before but not on a Reed Case with the plates on it. And this engine the intake is situated weird. Im sure i can do it if needed but ill have to do some research. When i installed the spark plug there was little resistance nothing more than normal but man when i tried to get that sucker out it was hell which is weird. Anyeways like you guys said its likely it crossthreaded on the way in. Whe i was unscrewing the plug in noticed some the thread shaving off and thread shavings almost fell in the cylinder thats how bad it was. Theres still some thread left on there though about 60% from what i can see.

Thanks Again!!!
 
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Yeah Ill call Dan over at OBR and see what he says. hopefully its doable. Thx
Thanks Guys!!!
You All touched on good points which may have happened. Im gonna call DAn over at OBR and see what he says. Ive rebuilt the top end before but not on a Reed Case with the plates on it. And this engine the intake is situated weird. Im sure i can do it if needed but ill have to do some research. When i installed the spark plug there was little resistance nothing more than normal but man when i tried to get that sucker out it was hell which is weird. Anyeways like you guys said its likely it crossthreaded on the way in. Whe i was unscrewing the plug in noticed some the thread shaving off and thread shavings almost fell in the cylinder thats how bad it was. Theres still some thread left on there though about 60% from what i can see.

Thanks Again!!!
So your spark plug threads are steel and your head's threads are aluminum. What im guessing happened is you over-torqued the plug which caused the aluminum threads to strip and embed into the sparkplug threads. When you removed the plug the embedded aluminum threads galled and just tore out more aluminum threads as you removed the plug. This is what happens with "dissimilar" metals. I always make good use of Antisieze on engines. I always use antisieze on plugs. Do yourself and your OBR reed engine (which you spent huge money on) and spend a small amount of money on a 1/4 or 3/8 torque wrench to ensure you don't go through this again. Here's one for $29 bux . Another life long tool that you will be using until you die on many different projects.

https://www.amazon.com/EPAuto-8-Inc...hvlocphy=&hvtargid=pla-4584413735682365&psc=1
 
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So your spark plug threads are steel and your head's threads are aluminum. What im guessing happened is you over-torqued the plug which caused the aluminum threads to strip and embed into the sparkplug threads. When you removed the plug the embedded aluminum threads galled and just tore out more aluminum threads as you removed the plug. This is what happens with "dissimilar" metals. I always make good use of Antisieze on engines. I always use antisieze on plugs. Do yourself and your OBR reed engine (which you spent huge money on) and spend a small amount of money on a 1/4 or 3/8 torque wrench to ensure you don't go through this again. Here's one for $29 bux . Another life long tool that you will be using until you die on many different projects.

https://www.amazon.com/EPAuto-8-Inc...hvlocphy=&hvtargid=pla-4584413735682365&psc=1
LOL That was gonna be my nxt question what torque wrench size and brand do u guys recommend? I guess this will help from over tightening but anything to help crossthreading is a plus as well. I think someone rec anti-sieze which i will get and start using as well.

Thx
timesert’d mine and works fine.
poop Rovan cylinder though, but i worked a lot on porting and did not want to throw it away
View attachment 76052View attachment 76053


Thanks szaki75.
So timesert vs. helicoil. Pros and Cons. based on your pics Im starting to lean towards the timesert. It looks like a complete new sleeve vs a heliucoil which does not appear to be a full sleeve but just actual threads which in my opinion the timesert looks like it might last longer and not be prone to craoss threading as easily. Am I off here?? May not sound like a big deal but I would like to base my decisin on one that last the longest nd lest prone to damage if possible so my engine last longer.

Thanks
 
The reinsert takes a special set of tools to cut and Install, I use to use them quite often at the machine shop. They are without a doubt about the best way to go. Buying the kit to replace one spark plug isn't cheap. A helicoil is simple enough to use and pretty cheap, it replaces the poop threads with stainless steel threads. Once properly installed you won't have any more issues. The timesert is the better option imo, but cost alone wouldn't justify it. We're not working on something expensive. I'm talking a $150.00 kit vs a $20.00 odd dollar kit. If you have a local machine shop that has the tooling for it I would expect the timesert repair to be in the $20-30 range. You really need to look at things in perspective of time/cost vs return on Investment. Helicoil is the way to go in these things plane and simple.
 
Thanks szaki75.
So timesert vs. helicoil. Pros and Cons. based on your pics Im starting to lean towards the timesert. It looks like a complete new sleeve vs a heliucoil which does not appear to be a full sleeve but just actual threads which in my opinion the timesert looks like it might last longer and not be prone to craoss threading as easily. Am I off here?? May not sound like a big deal but I would like to base my decisin on one that last the longest nd lest prone to damage if possible so my engine last longer.

Thanks
hi there,

my repair kit was this one:
1626717034649.png
cost about 22usd.
i was suffering a lot to cut this thread to the insert. w/o experience (like i did not have), it is really challenging to push the tap, twist it and keep its alignment until you cut through. the fist few thread on the top was fek, but the rest OK'ish. probably this set is a crap... i do not know..
i used JB Weld to fix it in the cylinder, and even with that it is very advisable NOT to remove the spark plug until the cylinder is hot. else the timesert comes off with the plug. happened ones and my smile was not honest. :confused:
also, since i have this repair on the cylinder, i just tighten the spark plug a hair more than i believe there will be no blowing-by.

if i we about to decide again, i think i'd give a try to the helicoil.
 
Appreciate it guys.
I spoke with Dan at OBR and i think ill just send it in and have them do the helicoil after talking with him. I could try it myself but i dnt want to muck it up even further (mis-aligning, etc.). Ill also see possibly have them do an upgrade on the top end haven't decided yet though on maybe some porting or something. if its too expensive ill just stick with the helicoil repair. But All in All thanks again.
 
hi there,

my repair kit was this one:
View attachment 76089
cost about 22usd.
i was suffering a lot to cut this thread to the insert. w/o experience (like i did not have), it is really challenging to push the tap, twist it and keep its alignment until you cut through. the fist few thread on the top was fek, but the rest OK'ish. probably this set is a crap... i do not know..
i used JB Weld to fix it in the cylinder, and even with that it is very advisable NOT to remove the spark plug until the cylinder is hot. else the timesert comes off with the plug. happened ones and my smile was not honest. :confused:
also, since i have this repair on the cylinder, i just tighten the spark plug a hair more than i believe there will be no blowing-by.

if i we about to decide again, i think i'd give a try to the helicoil.
That's not a timesert brother......
https://www.amazon.com/dp/B01ETNH6IM/ref=cm_sw_r_cp_awdb_imm_CPSS3C3BGWNFMR5DQJB0
 
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