Engine: R1 into R2

[SN-60]

Does anyone know if there's enough 'meat' in an R1 cylinder head's combustion chamber to safely allow enlarging it to R2 combustion chamber specs?

[bezhawk]

I doubt you could lower the compression a whole point by grinding. However if you used composition gaskets you could. But,doing that, it would make it MORE prone to detonation by having too much quench, and dead air space. You can end up about 60 or 61 cc if you grind,starting with a 58 but not 68 or more.

[StudeRich]

Heads are Ported all the time, my "Racing Heads" (537555) also 8.5 to 1 with Full Dish or 10.25 with Flat Tops, are old school, they have all of the shrouding around the Valves removed and smoothed for somewhere around 1 1/2 to 2 Points decrease in Compression IIRC, so one would think that could work.

But the most common solution is simply use the Shallow Dish Avanti Pistons to get to about 9.0 to 9.5 to 1.
I have those in stock in +.030 and can get +.040 or +.060.

Or of course, just use the "Truck" Heads is another option.

[PackardV8]

Yes, and by using the thick head gaskets, but only if your labor is free. It's tremendously labor intensive and requires a few tools not everyone owns:
Sonic tester, depth micrometer, burette, stand, cover plate, die grinder, carbide burrs.

1. Finish bore and hone the block. Mount the heads on the bare block and from the bottom, scribe the outline of the finished cylinder bore.
2. Assemble the short block and measure the deck height.
2. Using a burette, measure and record each combustion chamber volume.
3. Find an on-line calculator which accounts for gasket thickness, crevice volume, deck height. I use https://www.uempistons.com/index.php...tors&type=comp and determine the current compression ratio.
4. Determine how many CCs need to be removed to achieve your desired compression ratio.
5. Use a sonic tester to measure chamber wall thickness.
6. Enlarge the area around and above the intake valves.
6. Measure thickness and CCs again, calculate again, grind again.

jack vines

[SN-60]

WOW!....I think we'll continue to look for truck heads!! (How about starting with '55-'56 heads?)...Or go with Rich's advice and use dished pistons.

[Mike Van Veghten]

Remove and blend all sharp edges.
Lay back the " eyebrows" adjacent to the valves at about a 35 or so degree angle.

That'll go a long way in removing cc's AND make a better working chamber.

Mike

[PackardV8]

Remove and blend all sharp edges.
Lay back the " eyebrows" adjacent to the valves at about a 35 or so degree angle.

That'll go a long way in removing cc's AND make a better working chamber.

Mike

MVV has inhaled enough cast iron dust that his suggestions are to be taken as fact. He also knows the time involved. Mike, how much would you charge to enlarge a pair of heads to 68cc?

jack vines

[SN-60]

So 68cc is the magic number?

[bezhawk]

Roughly.....67.7cc is the Stock R2 volume