My Engine build R&D thread

[Evil_Fiz]

I originally posted these questions on The Samba but recognize that many here may greatly assist with my efforts. This thread intends to facilitate a dialogue on the best choices for my engine build. Motivated by the feedback thus far (on TS), I have dedicated time to researching said input. I have settled on three possible engine choices: a 2110 (90.5 x 82), a 2109 (94 x 76), or a 2180 (92 x 82), listed in order of perceived preference.

My reasoning based on the findings:

2110
- It's a popular choice for low to midrange torque and MPG (Street/Hwy driving)
- 90.5 P&Cs provide better cooling, due to greater fin area, and good longevity
- 82mm CW crank provides good leverage with reasonable case and cam clearance needs

2109
- It's not as widely used as a 2110 but should have similar performance and longevity
- 94 P&Cs provide less cooling and durability, but greater force due to increased piston crown surface area
- 76mm CW crank provides less added leverage but requires less case and cam clearance and affords a higher rod ratio

2180
- Another popular choice but unsure if I really need it (Mo-Bigger is Mo-Better?)
- Is a mix of the Pros and Cons of the other two options
- Is of similar cost and reliability as the others
- There's no replacement for displacement = less stressed

Once I decide, I will be back for advice on the particulars but for now, I need answers (opinions) on the following questions to help me make the best choice:

- Is the extra cooling of the 90.5s significantly better than the 94s? (assuming a complete set of tins, doghouse shroud, the large (36mm) fan, flaps, thermostat, and external oil cooler)

- Is a rod ratio of 1.671 (82mm crank x 5.4" Rod) considered low, mid, or high?

- Would durability and longevity be substantially improved by a rod ratio of 1.803? (76mm crank x 5.5" Rod)

- Which of the following should I prioritize for maximum longevity, better cooling (90.5 P&Cs), or reduced ring and cylinder wear (High rod ratio)?

Cheers and thanks,
Emil

[Bruce2]

IMO, the 76 stroke is a waste of time. By that I mean it takes a significantly greater amount of time to build the engine because nothing fits. If you use "A" pistons, the engine will be quite a bit wider than stock. Custom pushrods, tubes, linkage, exhaust, cylinder tin, head studs, etc. Nothing will fit.
If you use "B" pistons, you'll have too much deck height so you'll have to shorten your cylinders. When you use shorter cylinders, again, (see list above) nothing fits.

If you use a 78 stroke crank with stock rods, the engine builds like a 1600. Everything fits.

An 82mm crank will make more bottom end torque than a 78.

If you want it to last, use 90.5s. It's not just the greater fin area, the cylinders are thicker. Run it for 100k miles if you want. Something else will fail first.

If you want to make power, use 94s. But beware, you'll be putting in a new set of P&Cs at 30k miles if they even live that long.

I haven't seen any results with the new thicker wall 92s. They have the same OD as 94s, so they should last a lot longer than 94s. But will they last as long as 90.5s?

[Evil_Fiz]

Thanks for the details. Engine width is something I am struggling to find data on and I don't trust my math enough yet. Here are some questions I have not been able to answer during my research.
- If I use an 82mm crank with "B" pistons and stock (5.4"?) rods, will I be able to keep my stock engine width?
- How does fitting an exhaust work when dealing with an engine that may deviate slightly +/- from the stock width?

Cheers,
Emil

[Bruce.m]

Merged exhausts with slip joins with allow for width differences