Correct tension ???

[mcbob]

Well another question i have just obtained the better conrod big end bolts and need to know the torque setting to suit these in the Copperhead/Vintage US820 ENGINE
These are the bolts Dave Bonbright supplies (rod bolts 500,000psi ) for these engines
and since emailing Dave gets no responce then this forum is my best bet.

Mc Bob.

[Dick Teal]

Mc Bob,

I have the Vintage version of the 820 and the spec sheet has the connecting rod torque at 80-90 In. Lbs., the flywheel at 420 In. Lbs., the head bolts at 90-100 In. Lbs. and the spark plug at 120-180 In. Lbs.

Hope this helps,

Dick Teal

[mcbob]

Thanks Dick but i wonder if the new hi-po rod bolts are torqued the same ?

Bob.

[Dick Teal]

Mc Bob,

The vintage engine has the Hi Pro rod bolts so I would think that they are the same. In general the guts of the Copperhead and the vintage engine are the same. I also use the same components in some of my old blocks.

The other option if you want to do it is how I build all of my own high RPM 820's. I use red LocTite and torque the bolts to 120 In. Lbs. The LocTite acts as a lubricant on the threads when they are being torqued so I use a higher number. The old high strength rod bolts are still available from GEM but the Hi Pro bolts are probably better.

The reason we went to better bolts a long time ago was for street races and then enduro races. The highly modified 820's didn't want to stay together for too many of the hour events. The Copperhead and vintage engines are ported just like we used to do them but they have a better rod and piston assembly and the block and head are heavier construction for durability. They also have electronic ignition. The other main difference is that the cylinder is plated after the port work is done. We didn't have that option back in the day unless we wanted to spend a lot of dollars.

I would think that you're not going to run them for very long when you are racing chainsaws so they should last you a long time. If you're like me you will take them apart at the end of the season just to check on them and to put new seals and gaskets in.

Have fun,

Dick Teal

[Jeff Campbell]

Dick,
I always wondered if using loctite on those rod bolts would be a good idea. My concern was that the loctite might get in between the rod and cap joint and not allow them to fully seat (creating an out of spec, oval shaped bearing surface on the big end). But, I would imagine if the loctite got in between the rod and cap, that it should just squeeze out of there under the torque of the screw, as long as the assembly process is done swiftly, the loctite used sparingly, and it is all put together once with no reassembly while the loctite is still liquid.

Do you have to heat the rod to disassemble when using the red loctite?

Jeff

[Rob Voska]

I've always used 1 small drop of RED locktite. You have to make sure your have clean threads and surfaces before you even start. Also I never reuse rod bolts.

[mcbob]

Thanks for the advise fellas ........................

Mc Bob.

[louie figone]

McBob, Bonbright recommends 105-110 in. lbs. torque on the new type rod (ARP) bolts. They can be re-used many times. Loctite not required but can be used. Lube the threads if you don't use the Loctite. Dave checks his email about every two weeks.

Louie

[Dick Teal]

Jeff,

The way Rob does it by adding one drop of Red LocTite to the threads of the screw works OK and I've never had to use heat to get them apart. I clean the bolt and rod with CRC contact cleaner first. Make sure the LocTite goes around two or three threads.

I'm not sure it's necessary but it doesn't hurt anything. It always feels better when you are taking the engine apart.

Dick Teal

[Tom Smith]

correct torque with some light wt. oil is all that's needed for rod bolts unless they are titanium and then white lead is used for the lubricant.
Loc-Tite used correctly is applied to the underside of the fastner head and/or only the last couple of threads that engage, like a nyloc nut. For countersunk fastrners all that's needed is a drop or two on the bottom side of the countersunk flush head, not on the threads. That way you don't have to mangle the threads or use heat to disassemble stuff. I didn't make this up, I attended a Loc-Tite seminar for dumb mechanics like myself at the Indianapolis 500.