Building a 505 mark IV BBC. Long story short, the original machinist botched an .080 bore on the BBC and now I'm sitting at .100 over. New machine shop says it's good to go but obviously needs new pistons. If I'm buying new pistons I might as well stroke it and get all I can out of it. Stroker kit only comes with 20 cc dome forged pistons so I'm looking at 12.4:1 or 10.5:1 compression depending on which heads I use. The small chamber heads are matched to the cam and freshly rebuilt. Comp cams says I should be in the 600s for HP regardless of heads and that means it won't spin past 6000 rpm (if my pump is tight). Less compression means less HP but should I push the block at .100 over and go with the higher compression or even forced breathing? E85 is plentiful here in corn country but I'd prefer to run a pump gas motor. I'm thinking studs all around and see what she'll do. Cam is a hydraulic roller lifter cam from Comp. With all the aftermarket blocks people rarely run .100 over on a stock block any more, so I'm looking for guidance from those that have been there.
Push it or Pamper it?
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obnoxious001
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I had answered you on PB the other day. I will repeat here that I use Racetec for pistons, and have them make the piston to give the compression ratio that I want.
Note that I don't select a cam until I know the rest of the combination.
Nothing wrong with .100" over if the block has been tested like yours is marked. I ran a 505 combination in my ski race boat for many years, first with a blower, and later with a turbo set up on higher boost with race gas. It never failed, and in fact was freshened up and sold separately from the boat, now with another pump gas blower set up. I didn't have the block or heads studded, bolts worked fine even though I was told I "had to have" head studs. Noting that you have at least two helicoils, I would probably consider studs. There are some less expensive ones I have used on a few engines that work fine.
Note that I don't select a cam until I know the rest of the combination.
Nothing wrong with .100" over if the block has been tested like yours is marked. I ran a 505 combination in my ski race boat for many years, first with a blower, and later with a turbo set up on higher boost with race gas. It never failed, and in fact was freshened up and sold separately from the boat, now with another pump gas blower set up. I didn't have the block or heads studded, bolts worked fine even though I was told I "had to have" head studs. Noting that you have at least two helicoils, I would probably consider studs. There are some less expensive ones I have used on a few engines that work fine.
Thanks for the reply. I called Racetec today and they agree with the recomendation of Auto Tec pistons. They have a ready made flat top that might put me just a touch over the 9.5:1. I'll have to see where everything sits with it in the block to know for sure. They even recommended a shop to buy from close to here (3 hrs away) rather than just ordering on the phone, which is amazing customer service. It not only sells their parts but creates a potential gain for both their customer and vendor. That's a sign of a 1st class business.
obnoxious001
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Who did you talk to there? I should have told you to mention my name.
For the 3 hour drive I would just make sure you have all your numbers right and get them shipped. I trust them enough to just have them send the pistons straight to the shop I use for balancing.
For the 3 hour drive I would just make sure you have all your numbers right and get them shipped. I trust them enough to just have them send the pistons straight to the shop I use for balancing.
Since I need the crank and rods to go with the pistons, him referring someone that had good pricing and was close seemed very good. But, the number to the shop in MN is apparently not in service and there has been no response to email. Perhaps I should ask if you have a 4.250 crank and rods you want to part with. The pistons they recommended were Part #1000263. Flat with -3 cc for valve relief. I figure if I build it right, even if the block doesn't work out, I might have something to work with on the next build. He did say it should make really good torque numbers and said running the Berkley in a boat is like running an engine on a dyno. So hopefully once the parts are rounded up, I can get this one back together. Maybe the wife will get the itch again and want her's finished too.
obnoxious001
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Summit is pretty good for crank and rods (with free shipping). If you are going to keep it pretty mild, you can run a cast crank that probably only costs around $300 or so, and check out the new Eagle I beam rods, they are also just over $300 or so, I forget. They rate those at 850 hp, but at any rate better than just reconditioning stock ones. For a standard deck stroker engine, 6.385" rod is very common (1/4" longer than stock), just make sure pistons get ordered for correct bore, stroke and rod length. Hopefully your local machine shop can do a nice job of balancing.
