Back to my story...

The machinist says the cylinders cleaned up nicely at 0.030. I plan to have him take about 0.050" off the deck and just clean up the surface of the head. That should give me about 8.8:1 static, to go with the RV-10RDP camshaft. We're also replacing the exhaust valves and guides, and I cleaned up the rough edges on the ports and valve bowls. For now I'm sticking with the stock electronic ignition, 1-barrel carb (Holley 1945), and the stock 2" exhaust. After I see how it runs I'll probably want to upgrade all those things, but I want to do one thing at a time.

Sounds like a great plan.

Lou

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Home of Slant6-powered fun machines since 1988

My son and I got the cylinders installed today. We didn't have a depth micrometer to measure the deck height, so we stacked feeler gauges on the piston until a straightedge went across evenly, then used a digital caliper to measure the thickness of the stack. The new deck height is 0.127" or very close to that on all cylinders. The machinist took off 0.050" so it seems the experienced posters were right that the original height must have been close to 0.180". When I measured it before, I was using the caliper's built-in depth gauge, but I have now realized that the Harbor Freight caliper is cut unevenly on the end, making it useless for depth measurements.

Next step is to decide how much to shave off the head. The cylinders are now 0.030" oversize and the static compression goal is 8.8 or so. I measured the combustion chamber at 59 cc, but I'll ask the machinist to double check, as the head is still with him.

Here's a shot of my son torquing down the #2 rod bearing cap.

You are working a good plan.
To calculate how much to trim the head, for every .0069 cut you will lose 1 cc
You can play with an online compression calculator and determine how many cc’s
it takes in the combustion chamber to get to your desired static compression ratio.
Then using the .0069 per cc ratio determine how much the head needs to trimmed.

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Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

I ran the numbers based on a 0.040" thick head gasket. Came up with removing 0.022" from the head to get 8.8:1

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Sounds and looks good to me!

Lou

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Home of Slant6-powered fun machines since 1988

The head gasket is right around 0.040" thick, plus some metal and silicone (?) that I assume will compress down. I don't have specs on the compressed thickness; I'm waiting for a response from the manufacturer (EngineTech). Based on 0.040", the calculator says the required head cc is 54.5. So I take it the combustion chamber diameter is a bit less than the cylinder bore? From that, if I need to remove 4.5 cc, I should cut about 0.030". Again, I'm not totally confident the original volume was 59 cc. How do you figure?

Here are the numbers I'm using.

It's going to be a week or more before I get the head back. If I want to continue building up the bottom end in the mean time, I will need to degree the camshaft. I don't have a spare cylinder head to follow the procedure in DD's book, but I think I could do it with a rod of the right length and diameter and a dial gauge. Any suggestions for the rod, given that I don't have machine tools?

I do still have my old lifters. I could glue them together into a tall stack. Hmm...

I made a plate that bolts to the deck and holds a pushrod straight and centered. Just a piece of flat stock with 2 holes in it.

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Official Cookie and Mater Tormentor.

Here's my glued stack of lifters. I'm giving a day for the Super Glue to cure before I try to use it.

I degreed the cam. It's within 1-2 degrees at 0.050" lift, which is probably as good as I could get it. Question: how much slop is acceptable in the timing chain? Here's a quick video of my brand-new timing set. https://youtu.be/PY6Ii0oLHNc

That's not great, but it will live a long time that way. I had this happen once years ago and it turned out the cam and crank bores were closer together than they should have been. I tossed that block.

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Joshua

I got the head measurements today from the machine shop. 62 cc's on #2 chamber now that everything is cleaned up. The chamber measures 3.450" across and 3.500" lengthwise, so the area is about 61.2 sq cm. To remove 1 cc of volume, I need to mill 0.016 cm or 0.0064" (pretty close to DadTruck's number of 0.0069").

I want to get to 54.5 cc for 8.8:1 static compression (EngineTech says the gasket compresses to around 0.038"). To remove 7.5 cc's, 7.5 * 0.0064" = 0.048". So I think I'll start with 0.045" and remeasure the chamber cc's. I expect we'll end up milling off another 5 thousandths after that, but as the machinist said, it's easy to take more off, not so easy to put it back on.

The machinist pointed out if the distance between camshaft and crankshaft is short by 5 thousandths, you'll get a half-inch of slop. When the engine is running, centrifugal force keeps the chain tight anyway.

I'm wondering what temperature thermostat I should use. I was going to use a 195 for best combustion, but my machinist recommended 160 to avoid detonation on regular gas with the higher compression I'll be running now. Static compression ratio will be 8.9:1 (he ended up milling 0.047" and the combustion chambers are now 53.5 cc). I don't know what the dynamic compression will be with the RV-10DP (Oregon 2106r) camshaft. My driving will be mostly low RPM around town with occasional highway trips, with ambient temperatures mostly between 30 and 90 F.

I guess my question is, how concerned should I be about detonation?