Originally Posted by
telekenfun
If you read through this forum, you'll find a lot of great ideas of what to do. I would recommend starting with a 263. Find a good one, complete as possible. You can use your compound manifolds on it. Don't go crazy with milling unless you want to get custom made pistons. I didn't cut but .020 from each surface just to straighten things up. Bore it as big as you can but be carefull there. Make sure your block never had a mud ring around the water jacket because that causes pinholes reaching into the cylinder walls. If you're going more than .030-.040, you better have it sonic tested. Primarily checking for wall thickness and core shift. A good block can get you out to 300 cubes but I haven't found a block that good yet. More than larger displacement you need to make it breath, The real improvement will be in the combustion chamber and valve bowls. You can get very little increase in port runner size because of the thin walls. Just smooth them up and do the port matching on the head and the manifolds. Get rid of the stock valve guides, install 5/16" guides with tapered stems where they protrude into the bowl, use 1.60 & 1.40 valves with 5/16" stems. Do a lot of porting work around the guides, streamlining the flow, remove restrictions and open the bowls in a tapered fashion, matching up to the new larger valve seats. Too big of a bowl on the valve side of the guide and you'll lose intake velocity. Carefully ease and round the short turns in the ports and in your intake manifold if you can reach them.
Get some custom pistons made if you can afford them, They'll want a mold of your combustion chamber and the "cc" volume if they're going to do it right. Try for a .040 fit to the chamber on the back side of the piston away from the sparkplug to shorten the flame travel and provide as much squish and quench as possible. Don't go past 9.0:1 unless you want to use racing fuel.
You'll need a reground camshaft with as much lift as you can get. The trouble here is: the base circle can only be reduced so much and there isn't much material to cut the new profile for way longer durations and narrower lobe centers. Durations of around 200 degrees @ .050 is about all you can get without making the cam so skinny there is a risk of it breaking. The solution to this is to use higher ratio rockers and less lift at the cam. A 200 degree cam is about all that is needed since these are low rev motors no matter what. 5000 RPM max. 2-4 grand is what you're going to use most of the time unless it's going to be a race motor.
Your combound intake manifold is about as good as you can get if you clean it up and smooth the short turns other than making a custom tube equivilent. Their runner length is sufficiently long to creat a pretty good ram effect in the mid band. Get a couple of AUUVB-267 Aerotype Strombergs from 53 Buick V8s. They are cheap and slightly larger than the AA1 & AA16s. They are about all the motor can really take and too many people make the mistake of using too much carb. You'll need to make adapters from 1/2" aluminum for the four bolt bases but it will use two of the existing studs, really simple. The Aerotype Strombergs use many of the same parts as "97"s so jets and stuff are easy to get. Eliminate the progressive linkage and run them syncronous.
You also need to do distributor work to delay the advance and increase the advance amount as the centrifical will only get you 10 degrees and you'll need nearly twice that much.
EGGE Machine has all the stuff you'll need to do a stock rebuild if that's the way you decide to go, and it will probably be around $2500 when you're all done if you assemble the engine yourself. Expect to spend another $5 grand if you want to embarrass a 57chev with a Powerpac.
I hope this gives you some more ideas and good luck with whatever you endeavour. TELEKENFUN
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