Which thread replacement?

T

Truckphone

Member
Hey fellas I havta fix my outside head bolt next to the exhaust valve. What is the insert of choice? I have available an insert style and two heli coils. I read something recently that it would be a good idea to stack the helicoils but is that even necessary? All opinions appreciated, Ale. 5C929753-3568-44E7-8C49-A9059548ECAF.jpeg
 
i believe if you went with the heli coil .
if it failed you could the go too the keen sert type .
Material thickness would be a consideration .
stacking would be a benifit .
 
Okie dokie, I will stack the helicoils, and because I'm not going by any rules except trying to keep this puppy alive I can use studs, right flattop?
 
Yes, you can stack heli-coils. Be careful breaking off the tangs and keeping the threads timed.
For a head bolt, you will want as much thread contact as you can get (even with a stud,) as it pulls/distorts the cylinder more evenly.
For a sidecover bolt, one heli-coil will be sufficient as you're only pulling it to 80-85 inch pounds.

-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
33 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
There are longer helicoils.
McMaster Carr is one example:

Inch
18-8 Stainless Steel—Right-Hand Threaded
Thread
Size		Installed
Lg.		Drill
Bit
Size		For Max.
Hole
Dia.		Specifications
Met		Pkg.
Qty.		 Pkg. Each Each Each Each
Inserts
Through-Hole
Taps		Closed-End
Hole Taps		Installation Tools
Prong
Break-Off Tools
5/16"-18
click to learn more about 5/16-18
5/8"Q0.332"MS122-1621091732A740$9.0491709A106$30.1791709A443$26.0790261A156$138.9092955A113$130.00
5/16"-18
click to learn more about 5/16-18
0.781"Q0.332"MS122-2021091732A22417.2091709A10630.1791709A44326.0790261A156138.9092955A113130.00
5/16"-18
click to learn more about 5/16-18
0.938"Q0.332"MS122-242591732A7418.1591709A10630.1791709A44326.0790261A156138.9092955A113130.00
 
To install stacked heli-coils, can you pre-break off one tang, stack them on a bolt with a "stop nut" prevent it from moving "up" the bolt, then install, and break off the lower tang? That would keep the "timing" close to perfect. Let set with loctite on outer threads, then remove inner installation bolt...
 
Ted Hamilton said:
To install stacked heli-coils, can you pre-break off one tang, stack them on a bolt with a "stop nut" prevent it from moving "up" the bolt, then install, and break off the lower tang? That would keep the "timing" close to perfect. Let set with loctite on outer threads, then remove inner installation bolt...
Click to expand...
I've always had to install them individually. They are bigger than the threads and torsion into place to secure them. It you stack them, the outer one can't compress to install.
 
Truckphone said:
Hey fellas I havta fix my outside head bolt next to the exhaust valve. What is the insert of choice? I have available an insert style and two heli coils. I read something recently that it would be a good idea to stack the helicoils but is that even necessary? All opinions appreciated, Ale.View attachment 19567
Click to expand...
I have gotten into the habit of putting Time Serts in all my flatheads And Animals . Never felt that the heli coils were a permanent? solution. Never used the other insert you have a picture of. And Plus I build all of my header braces. Or should I say , overbuild them.
 
One Fast Kat said:
I have gotten into the habit of putting Time Serts in all my flatheads And Animals . Never felt that the heli coils were a permanent? solution. Never used the other insert you have a picture of. And Plus I build all of my header braces. Or should I say , overbuild them.
Click to expand...
I used helicoils on this one but I’m planning on leaving studs in it, not thinking I should havta worry about them coming out with the bolt. Usually I throw the poor things away when there’s too many messed up threads but this one is special. I sure appreciate all the responses from people who know the right ways.
 
Last edited:
Consider the length of the threads on the bolt and the threads in the block.
When you torque that bolt, the pull is on the entire length of the threads of that bolt and the distortion of the cylinder is somewhat limited due to the length of the thread contact.

Not convinced? Try honing a cylinder without a torque plate and bolts.
Then try it with the torque plate but using shorter bolts.
Now hone the cylinder with the torque plates and the right length bolts...You will visually see the difference in how much the cylinder distorts.
There's a reason you hone with a torque plate and the right length bolts and threads.

For exhaust and intake thread replacement, one heli-coil is enough.
If you're pulling them, you're gorilla tightening the bolts. :)
 
@Pete_Muller gives some advice on the KT-100 exhaust studs -- just snug enough to seal and then double-nutted to prevent loosening. Anything tighter pulls the bore out of round. I don't know that the 4 cycles suffer the same issue to that degree, but it's illustrative that when you're chasing perfection (read: efficiency) when it comes to engines, every little bit affects something else. I know that I prefer running studs when possible, sometimes simply because I worry about the aluminum threads failing long before the steel...

Another option that hasn't been covered here is the "alumifix" or "dura-fix" option -- filling the hole with a alloy "stick" that then can be rebored and rethreaded.

https://www.durafix.nl/en_US/c/Welding-Rods/14
 
CarlsonMotorsports said:
Consider the length of the threads on the bolt and the threads in the block.
When you torque that bolt, the pull is on the entire length of the threads of that bolt and the distortion of the cylinder is somewhat limited due to the length of the thread contact.

Not convinced? Try honing a cylinder without a torque plate and bolts.
Then try it with the torque plate but using shorter bolts.
Now hone the cylinder with the torque plates and the right length bolts...You will visually see the difference
Click to expand...
I've honed cool bores without a torque plate and then put the headbolts with washers. You can see the deflection or whatever you call it in the bore. Actually see the warping!
 
You must log in or register to reply here.
Back
Top