whats the first steps toward more performance

[Street Ryderz]

It prevents crack out. A non smoothed hole will eventually crack and start walking. Same with the Pistons, bevel the edges. Piston is more likely to crack, for obvious reasons.


Don't have to be a big bevel, just enough to knock the edge smooth.

Pistons have a huge shoulder built up around the hole's face to keep it strong and I've never seen one crack in over 40 years building engines even when things went terribly wrong at the wrist pin/bearing, the cranks holes have no pressure other than inertia on them and again I have cranks that I've been using since 07 still in service without any issue.
I don't think it will make any real difference honestly but I do know that the chamfer in the crank holes is not a common practice due to the afore mentioned.

 

[Street Ryderz]

Street Ryderz did you just take the casting line off your rod? Or is your connecting rod actually knife edged? Your pic look like its knife edged.

It's knife edged to reduce the turbulence it creates going through the charge.

 

[DieselTech]

It's knife edged to reduce the turbulence it creates going through the charge.

Thanks @Street Ryderz I appreciate everything,

 

[DieselTech]

It's knife edged to reduce the turbulence it creates going through the charge.

Yeah when building small block chevys I used truck 4bolt main connecting rods because the beams were wider in them, they had the casting flange down the center of the rod & if you didnt remove & smooth the connecting rod there, that's usually 9 out of 10 times if they had a connecting rod failure it was due to the casting line in the rod is where they broke.

 

[Karl Snarl]

Pistons have a huge shoulder built up around the hole's face to keep it strong and I've never seen one crack in over 40 years building engines even when things went terribly wrong at the wrist pin/bearing, the cranks holes have no pressure other than inertia on them and again I have cranks that I've been using since 07 still in service without any issue.
I don't think it will make any real difference honestly but I do know that the chamfer in the crank holes is not a common practice due to the afore mentioned.

I was talking when we window them. From stock all the holes are smooth. In aluminum it happend worse than in steel, but steel will still crack out. Industry standard for any industry that drills holes in metal, bevel/countersink the edge. Only from india and china do you find any thing real built, with no beveled edge or cheap arse companies. Then again, that's one reason why their crap falls apart faster then the rest of the worlds crap. lol. If you cut a window and do not bevel it, I'll put money down it will crack out. The crank can probably get away with it because it is spinning, instead of up and down, and the part that takes the most stress is below the drill holes in the meat of the cheeks. It will eventually crack to from the heat cycling. Will take a lot longer than a non beveled window piston hand made, though. Now if you leave a burr all the way around, Ironically it will stop cracks from spreading and forming too. lol.

 

[Karl Snarl]

Yeah when building small block chevys I used truck 4bolt main connecting rods because the beams were wider in them, they had the casting flange down the center of the rod & if you didnt remove & smooth the connecting rod there, that's usually 9 out of 10 times if they had a connecting rod failure it was due to the casting line in the rod is where they broke.

Crack out, from stress. Aluminum has to be smooth, or it will crack from shock.

 

[Jaycee604]

This is my thinnest flyweight thickness crank.

View attachment 164119

Thats weird. All three of mine are 15mm . Are yours stock 80cc s ? (66)

 

[DieselTech]

Thats weird. All three of mine are 15mm . Are yours stock 80cc s ? (66)

There all CDH Power 100cc/ true 79.5 or 76.5cc engines, except the 1 crank I got that is almost 20mm wide is from idk what but is old. They are 66/80cc bottom ends though. The pic of crank that is 18.94mm thick is from a 66cc engine.

 

[Karl Snarl]

There all CDH Power 100cc/ true 79.5 or 76.5cc engines, except the 1 crank I got that is almost 20mm wide is from idk what but is old. They are 66/80cc bottom ends though. The pic of crank that is 18.94mm thick is from a 66cc engine.

Thats weird. All three of mine are 15mm . Are yours stock 80cc s ? (66)

All the ones I get from CDH are thick cheeked. I have a thin cheeked one from a 6mm single piece 66cc. Wasn't a bad motor, didn't vibe all that much till higher rpms.