I have -4cc pistons right now. Don't know if I can get anything more than that to lower my compression. They are probe pistons, I'll review their website. My heads are 61cc heads. Can I increase my gasket thickness some more, with that I can be closer to 9-ish.
The drawback to increasing the head hasket thickness is you're also increasing the quench distance at the same time, which increases the engine's tendency for pinging and a corresponding appetite for higher octane fuel. You've stepped into the avoidable scenario as to why I advise everyone who's building an engine to do in doing all the homework in parts selection (especially piston choice) before buying or ordering anything. I advise you to heed Blown5.0's advice on cam selection now, that's going to make or break you on fuel requirements now with a blower.
I think I'm going with the piston swap, thanks for the advice. Gotta call the engine dude and tell him not to balance things until I get him the right pistons . . . When I was envisioning this engine I was going for close to 10:1 compression, didn't think I'd be going forced induction one day.
If I can find pistons with -11cc volume I would be at 9:1. That should be pretty safe. I'll call Probe Monday morning.
Well, talk about "Pot calling the Kettle black" Anderson's not the only cam tha'll rev past 6500 without floating the valves. How about 7 grand with a Ford Z303, 1.7 rockers and the springs that were std on Canfield heads ? And I've seen split blocks at the 500 hp level.
OK, so you've proved you can reprint the specs on a cam. What's that got to do with the price of eggs in China ? Want to try a little harder on showing everyone that you can reprint cam specs and little else ? So far, all you've accomplished here is to quote specs and information posted somewhere on the net. You've failed to prove your point in any of it. And your stating that any one of the things I pointed out, that added together can end up with a split block, cannot do it by itself. That tells me you're shootin blanks here. Along with believing that just because a cam's specs and the published description that it'll only pull to 6500 is something that's indisputable, tells me you haven't a clue as to what you're talking about. No two engines are alike. Anyone with a lick of common sense and who's been around engines would know this. Just because your engine quits at 6500, means absolutely nothing when that cam is used in a completely different build. How any one part is designed to function in an engine can and will change in character when used with any other number of parts combos. Just because yours won't doesn't mean someone elses engine will.
This seems to be turning into a "whose got the biggest wiener" contest then an actual help thread for mashori.... Im not trying to make anyone mad, but if you guys want to compare pictures then take it up in PM, dont keep the drama out here, because its off-topic and its not helping the OP at all
So Greg is the machinist over at Total Performance. I spoke to him today, he has had experience with building supercharged engines. With the roots blower we decided to go with an 8.7:1 compression. We picked pistons from Probe with -20cc. Tomorrow I'm taking my engine block to him to look over.
The machinist dude was talking about "20 in the hole". I have no idea what he meant and I was in a rush talking to him so didn't get him to explain it. What's that?
WOW, I'm impressed. My last 302 would spin up to 7500 with a B303. With the same Canfield heads and 1.7 rockers, topped with a Vic Jr and a 700 Holley DP carb.. You want to go further ? You haven't the slightest clue as to what I've done with engines in the past 35 years. Now you're laying claim to winning the Engine masters challenge For every contestant there, there are at least a dozen more guys building engines in fly over country who have done the same with less. It's just that not everyone who knows his s--t wants to or has the means and time to compete in these contests. Some of us have a life, obligations & priorities that tend to get in the way of things. And we laugh at prima donna's like yourself that insist that what they know, is all that needs to be known on any given subject. With your way of thinking, we'd have never gotten past the early 1800's when the going thinking said that man couldn't survive going at speeds in excess of 15-20 mph. Or reached the moon.
Twenty thousandths of an inch down the bore at TDC. That's more than I like to see, but some of the off the shelf 302 pistons are that far down the bore at TDC. .020 adds up to an extra 4.5 ccs in compressed volume. Doesn't sound like much, but the smaller the engine is, the more it makes a difference in compression ratio. And it decreases the quench factor to where an engine's apppetite for higher octane fuel increases.
