2.7RS build / aluminum-oxide hone

[Bobboloo]

Thought I would post a couple jpegs of some Nikasil cylinders that I recently de-glazed with an aluminum oxide grape style "hone". Hone is really a misnomer for this tool since aluminum oxide isn't hard enough to actually cut Nikasil but just de-glazes the surface similar to Red Scotchbrite. Engine Hone sells this tool specifically for Nikasil cylinders.

I was very pleased with the results. I gave the cylinders about for strokes with the hone and some WD-40. They cleaned up very nice.

The cylinders are from a 90mm Mahle Euro RS P + C set that I used for a 2.7RS motor I built last month. They were used but mic'd out as virtually new in spec.



Might as well post a few pictures of the motor. I know how we all like pictures.

The motor is really nothing exotic. Just your basic tried and true 2.7RS replica motor but with carbs instead of MFI. It's going into a 69' Light Ivory Coupe. A cafe style racer.

Cams are Webcam Early S replicas on 4 bearing billets.

Deck height was set at 1.1mm. I used a dial gauge for setting deck height. Crushed solder or veneer calipers don't yield as good as results IMO. The dial makes easy to double check for repeat readings.

Pistons, wrist pins and rods were all balanced within 1 gram of each other.

Dizzy re-curved to RS spec.

The case, a 75' 7R, was farmed out to Henry at Supertec. Almost everything that could be done was done to this case short of shuffle pinning. It came out fantastic.

1. Case halves were shaved case and then line bored back to standard.
2. Cylinder spigots resized and decked
3. Through bolt holes spot faced
4. Intermediate shaft stud timeserted
5. Oil bypass mod
6. Case perimeter studs helicoiled


Checked the main bearing clearance with Plastigauge and it was right on the money for all the main bearings. Gotta love good machine work.



Valve covers are aluminum.

Valve covers and fan shroud are powder coated flat black.

Headers are ceramic coated flat black as well.


Engine tin, crossbar and cradle are Satin Black.

Engine shroud is Getty Design.

Carbs still need to be rebuilt and set up. Tony at TLG will be doing that. Besides doing the carbs Tony also rebuilt the tranny, a 915, for the client. I just did the motor rebuild.

[herman maire]

Beautiful job, the detail is great.

I dont quite understand what you did to the cylinders... was it just to prep them for new rings?

You think a 72 T case would be good enough for a build like this or is a 7r case really needed?

[Bobboloo]

Originally Posted by herman maire

Beautiful job, the detail is great.

I dont quite understand what you did to the cylinders... was it just to prep them for new rings?

You think a 72 T case would be good enough for a build like this or is a 7r case really needed?

Yep. Prep for new rings.

There has been long threads in the past on this forum about what is the proper prep for Nikasil or Alusil cylinders when rebuilding.

In re: Nikasil I don't believe aluminum oxide hones ever came up in the discussion. Probably because I think it's use for Nikasil cylinder prep is a fairly recent development. I read up on it recently on some motorcycle forum and decided to give it a try.

In the past some have tried Silicon Carbide hones and from what I've read the results have not been good. It's hard enough to mar the Nikasil but not actually cut clean cross hatches. To actually be "honed" Nikasil needs to be cut with a diamond hone machine like a Sunnen that can apply enough pressure in a controlled manner. Then the cylinder is deburred. I believe with aluminum oxide but don't quote me on that.

As far as your 2.4 case you should ask someone like Henry (Supertec) or Steve Weiner (Rennsport). I've built a handful motors but don't have the experience of those guys. I've heard of people building a 2.7 on the 4R/5R cases (early 2.4) but don't know how they held up over time.

[TVRLOTUSTR3]

Nice! Which grit did you use? Egine hones web site (enginehones.com) shows that the sell three different grits.

[techweenie]

Spectacular, Bobby.

[Bobboloo]

Originally Posted by TVRLOTUSTR3

Nice! Which grit did you use? Egine hones web site (enginehones.com) shows that the sell three different grits.

240 grit 95mm.

[jaybird840]

Would you be interested in selling me (or renting) your hone? I'm right behind you on the build. Also, have you fired it off yet?

[Bobboloo]

Sure. Maybe a rental. I'll be needing it again in the very near future.

The motor is very close. Carbs are almost done and then it'll be time.