Here's a question no one's asked

rob ss - I agree with you that waisted bolts are not as important on cast iron parts but you still see them in cast iron engines and there are plenty of aluminum cylinders out there and they're getting more popular. A reduced shank bolt is generally considered to be better and thats why you see them being used for heads and rods. The Carrillo rods are all steel and the bolts are high grade steel with reduced shanks. This gives them some more stretch than bolts with full thickness shanks and so they have a wider range of elasticity - their tension is more consistant. See the reduced shank rod bolt and chart below where the bolts can be torqued according to the bolt stretch. Many builders prefer to measure the amount of stretch on the rod bolt.








Below is a video I made showing how to install thread inserts with a common drill press so they are installed deep enough and come out straight.

A bolt or stud that is not stretched is not tight and will vibrate loose. The waisted section on waisted bolts & studs is usually about the same diameter as the minor diameter of the thread, so is not a weak point. Waisted bolts, regardless of length, will stretch more than standard bolts for the same torque and will stay tight for longer, especially on an engine that vibrates a lot, like a Commando. Graham.

SteveBorland said:

My experience was that prior to using the Comstock (CnW) bolt kit, I had problems with the fasteners loosing tension and oil leaks around the pushrod tunnels.. After converting, both problems solved. YMMV of course,

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Steve
I use them too (ARP version/cNw) but not for the applications above that Jim is trying to sell
Next he'll have special waisted triangular bolts for engine to cradle fixing.
Cheers

velo54 said:

A bolt or stud that is not stretched is not tight and will vibrate loose. The waisted section on waisted bolts & studs is usually about the same diameter as the minor diameter of the thread, so is not a weak point. Waisted bolts, regardless of length, will stretch more than standard bolts for the same torque and will stay tight for longer, especially on an engine that vibrates a lot, like a Commando. Graham.

Click to expand...

Interesting, the entire world is falling apart because standard nuts and bolts are used - who knew!

Cut away about 25% of a bolt's shank and it's not weaker - who knew!

SteveBorland said:

My experience was that prior to using the Comstock (CnW) bolt kit, I had problems with the fasteners loosing tension and oil leaks around the pushrod tunnels.. After converting, both problems solved. YMMV of course,

Click to expand...

The kit that cNw sells, as best I can tell, does not include wasted studs for the three head studs being discussed here, and it does not include wasted versions of the 5/16" studs screwed into the barrels. The 5 head bolts are wasted, ARP style, but not the triangular style. So, I'm confused about what is stopping your pushrod tunnel leaks. BTW, it takes nothing special to prevent those leaks - simply follow AN's recommendations for composite head gaskets and do the required retorquing.

Also, cNw states: "Manufacturer: cNw / ARP" for these. When Jim Comstock designed something that cNw sells, cNw states: "Manufacturer: cNw / Comstock Engineering" So I don't know where the "Comstock(CnW) bolt kit" came from.