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I say get the nicest welder that you can afford. I recently upgraded my TIG because I decided that being able to weld aluminum was important to me. I’m glad I spent the money on it. Welders are kind of like air compressors in the regard that you can’t have too good if one, but you can dang sure...

Just take the adapter to you local parts store, but a radiator hose that fits and a couple of hose clamps. Then you cut a piece of the hose and couple the two with it. I like to butt the carb up to the adapter, so it being flexible isn’t a problem.

Yes, 500cc. I think I could get by with the extra .13cc

Long intake runners are conducive to building torque, so I’ve always been a fan. I’d run a slide carb with a common plenum and long runners if I were the one doing it.

I ordered it from the zongshen site, and it shipped out of Florida. I played with the idea of building a 625, but it wouldn’t have been legal for UAS.

I’m going to say 60+ on horsepower. I run a blend of 75%methanol and 25% nitromethane, and the fuel makes quite a bit of power on its own. I’m thinking there will be a lot of throttle control involved in driving this one effectively.

Yep, unlimited modified. I’m keeping it at 500cc so that it’ll still be legal for the unlimited all stars in case I want to race with them again.

According to the math on mean piston speed I should be safe at 7500. You’ve nailed my whole reason behind doing this with the RPM. My thought is that if I can make enough torque that I won’t have to rev the engine nearly as much, so it should last better. I blew up 3 really nice small blocks...

The head is on its way to North Carolina to spend some quality time with Johnnie at Laid Back Racing. He’s built several heads for my unlimited karts, and I’ve always been very happy with the results.

Custom copper gasket with an o ring.

I use a 3/8 drive snap on digital torque wrench with a shallow 1/4” 12 point that I bought at O’rielly

I couldn’t resist a test fit with the stock wrist pin since I knew there was only .005” difference, and it seems that I won’t have to wait for the reamer set to know what rod I need after all. It looks like it’ll be a stock length rod, and the piston will be going for a ride in my larhe.

And just like that I have a 96mm bore GX390. With the 69mm stroke crank it works out to be 500.13cc. Now I’m just waiting on my new reamers to show up so that I can mock it all up with a stock rod so I can get an idea of what to order for rod length.

Went to the shop and grabbed my 1/2” drill this morning and chucked up my micrometer hone.

Next, I bored it to .008” under where it needs to be for the finished product. I’ll get my big drill from work tomorrow and chuck up the micrometer hone to finish it up. After that, I’m waiting on a set of adjustable reamers to come in so that I can increase the bore of the small end of the rod...

After about 500,000,000,000,000 passes taking off .010” per pass, it was all nice and flush.

Next, I mounted it back up in my mill and inserted my 6” face mill.

After the hour was up, I dropped the sleeve into the block, and it fell right in with a solid “thunk” on the shelf while the alcohol sizzled and spit. I gave it a couple of good whacks with my 3lb deadblow hammer to make sure it was good and seated.

After it got up to temp, I chunked the block in there and let it roast for about an hour to make it expand while the sleeve was chilling out in the garage.

Then I fired up my pellet grill and set the temperature to 500F.