2270 Build thread, Looking forward to making all of the mistakes! Options

[vjb206]

Hey folks! I've got...

• Case halves from an old 1.7 (cleaned as best I could)
• 2270 crank + P&C kit
• #163/86b Web Cam
• 2.0 heads with 44X36 valves, where I'll be installing dual springs and 38mm exhaust valves
• Upgraded oil pump and other goodies

So my first question for the community has to do with ensuring the rotating mass is spinning freely/correctly…

I started by measuring all of the the main journals on the crank and I got a range from 2.358” - 2.360” (I used a digital caliper and I'm pretty sure I did this correctly).

Then I “dry-fit” Silverline STD/STD main bearings into the case (sans crank), torqued everything down, and got 0.003” in radial play (I used a cylinder bore dial gauge for the first time, and I think I did it correctly).

The spec-sheet says radial play should be between 0.06” - 0.10” (0.03” - 0.09” for #2); and I have 0.003." I'm a MINIMUM of 0.057" off, is that normal? What's my next step?

1. Stop pretending I know what I'm doing and take it to a machinist for test-fitting and honing (I'd like to keep cost down so this is my less preferred option)
2. DIY: hone 0.06" off all bearings (what's the right honing tool / approach here?)
3. Order different bearings (if so, which?)

[technicalninja]

Just looked through that. Thanks, cgnj!

Rod mods look fine (if you're reusing stockers)
I believe you should either have spray from a rod-based hole or dedicated piston crown sprayers.

Thier suggestions regarding shims/head fire rings should be taken with a grain of salt, especially if you're building a non-stock motor.

I believe you should choose your deck height via measurements during your build.
Just saying use a 1.6mm ring under the barrels is not enough in my book.
You should end up with the perfect spacing via dial indicator and only THEN should you look to what is available.
Choose what is closest, make your own, machine barrels, what every it takes to get close to your chosen deck height.

Deck height varies for different alloys. Forged with low silica will require more bore and deck clearance vs a hypereutectic cast piston.
Look to your piston manufacture for their suggestions.

The original clearance in the TSB (technical service bulletin) are WAY tight in my book.
Original bore to piston is from .00086" to .0015".
This is a "9 tenths" clearance!!!!
Less than a thousands for an air-cooled motor!
Freaking tight!
They had problems accordingly...

Cast I'd expect to be running at least .002" and more likely .0025".
I like tight quench motors and I'd run more that .035 but less than .040 on cast.
Forged would be higher. At least .004" P/C and .045"+ quench.

The rod idea has merit, the suggested deck height changing procedure is not really applicable to a "built" motor in my book.