New Motor Build Question - Stroker (Flat tapper) or Stock Stroke (Roller)?

[WPP-Bill]

This is an interesting topic.

Would someone mind explaining the pros & cons of using the original crank plus a girdle vs. using an after-market crank?

What about using steel main caps?

I avoid purchasing Chinese products as much as possible. Are there any after-market cranks & rods that are completely manufactured in the USA?

Thank you

Many stock cranks, which are pushing 30 years old, have been abused over the years - detonation causing the caps to dance and an already brittle crank to endure stress. If/when the crank splits in two it can take out other components including the block. A girdle will not turn back time and eliminate the past stress cast cranks have been put under. Additionally, grinding the crankshaft will remove some of the rolled radii and reduce the strength of the crankshaft.

Two center billet caps is a must for every engine we build as it is the weakest point that needs to be corrected. Next comes a forged crank and then girdle.

USA made/finished cranks and rods are available in billet steel, though will cost in the range of $4k+ vs forged $1,300.

 

[~JM~]

Thank you for the information. I had thought about the remaining lifespan/strength of my original crankshaft. My car has been adult owned, driven lightly & maintained well since new, but it does have an excess of 100K miles on it.

I'm inclined to replace the crank, rods, pistons, just don't want Chinese parts. That's a big price difference that you listed though.

I had heard that the Chinese cranks are substantially heavier. Any truth to that & if so, how much heavier? How does this extra weight effect throttle response?

Aside from an align hone, what are some of the typical machining procedures & expenses involved with installing the billet main caps & girdle?

 

[84BuickGNYorkPA]

As a member of the broken crank club, I would replace the stock cast iron crank and connecting rods with forged parts as Bill from Weber stated. I found out it less expensive to something once than it is to do it twice. Good luck with your new build.
Chuck

 

[ek02]

Thank you for the information. I had thought about the remaining lifespan/strength of my original crankshaft. My car has been adult owned, driven lightly & maintained well since new, but it does have an excess of 100K miles on it.

I'm inclined to replace the crank, rods, pistons, just don't want Chinese parts. That's a big price difference that you listed though.

I had heard that the Chinese cranks are substantially heavier. Any truth to that & if so, how much heavier? How does this extra weight effect throttle response?

Aside from an align hone, what are some of the typical machining procedures & expenses involved with installing the billet main caps & girdle?

There is a sticky on line boring and honing the block with billet main caps. The block needs to be align honed with a girdle. There are a few ways to do a girdle. RJC recommends using the spacers and shims after the main caps are machined flat to get the clearance right (.005) between the girdle and pan rail. Others machine the caps, pan rail, and front cover down to eliminate the shims and spacers with the caps a few thousands higher than the pan rail. I have had 4.1's done this way and it worked out OK, but the front cover will only work on that block. Another method is to square up the pan rail and front cover and just use the spacers with no need for shims to get the clearance. It can be hard to find a machinist to do a girdle, and the girdle takes more time when assembling the short block or checking bearings or clearances. Billet center caps and line boring usually cost less than a girdle and the installation labor.