Slant 6 Turbo 68Dart Project
I say supercharged motors are the only ones you have to worry about, but I guess if you built a super duper lotsa money turbo motor with the most efficient turbine, so on and so forth, and then ran low-ish amounts of boost then you may have problems. The turbo graph in the below post is a very efficient setup. I think most have more exhaust pressure than inlet pressure, or equal (I'm talking higher in the rpm range, toward/after peak power). This is the reason of the old 'dont have overlap' train of thought, it wasn't cuz of boost blowing out (though it seems to have morphed into that.) Don't worry Bill, you're not the only one I've seen say that. Appears to be a common misconception. Tis true when referring to supercharged setups, just not so much on turbo setups.
From Billy Godbold (A Comp Cam Lobe designer)
Older turbo systems often needed cams with almost no overlap because the backpressure was much higher than the inlet pressure and the systems were prone to reversion issues
Here's a couple of articles to go over (You may have read them before though)
http://www.hotrod.com/how-to/engine/ctrp-1106-turbo-camshaft-guide/
http://www.hotrod.com/how-to/engine/hrdp-1011-cams-for-turbocharged-engines/
Serj, heads don't really matter themselves when talking cams I don't think. What I mean is, I believe you can put the hydro setup on your nice head. I think you need the rocker setup, pushrods, lifters, and cam... maybe somethin else to. It's been detailed more over at .org. I'm not really sure which would be better, I think if I were to build one I'd lean towards the hydro, but that's just me. I think it may be one of those personal preference type deals...
Huh, I haven't compared the stock hydro cams and mech cams too much. That is interesting that you say they differ so much though.
I know of a few turbo builds using the old MP 244 stick (don't be fooled, this isn't much like the stock 244 cam at all. More lift, aggressive lobes, unsure of LSA) and having wonderful luck, also there is a fellow that runs a 264 cam on 114 and has wonderful luck. I've always thought a 252 cam (like the OCG818 cam) on a 112lsa would work nicely for a turbo cam. I've got the 819 (264*) on a 109 and it's got a little bit of lope. Me thinks that may be a little too much overlap, but it would work if need be (46* overlap) it wouldn't be ideal though. I would use Oregon Cam Grinders for a cam, they can either regrind yours (if I could go back in time this is what I'd do) or grind on a new blank (i went this route, I feel like it was money that could've been spent better elsewhere) and they have TONS of different lobe profiles, not to mention more grinds than anyone else for the slant (I think they have 50 or more :glasses7: ) Or, you might give Comp a call and have them custom make you one for your app. That would be a fine way to go as well, as they would actually know what they're talking about lol.
More on pistons; Your spare motor already has the 'perfect' compression ratio. My late 70's cast motor had somewhere around 8.1:1 actual SCR right from the factory. The 80s one may be a touch closer to actual spec, but a dished piston shouldn't be
needed. Now, you could get a taller piston, and then get a dish to drop compression back down to where you started in hopes that you'd get a better shaped combustion chamber, but now you're getting into engine theories that may or may not have any noticeable effect. No way do you want a dome. Higher comp and a poorer combustion.
My thoughts on the 1200 dollar forged piston kit was along the lines of what you stated, buy a package and save money. However, the more I got to looking I noticed something.
Other than the pistons, the only thing the HP kit has different than the master kit is:
Moly rings (unknown rings in master)
High Volume oil pump
And 'Performance' wrist pins
Also, it says:
Some master engine kits can have parts upgraded or even deleted from the kit. Items like timing sets, oil pumps, cams and pistons can be upgraded to performance or aftermarket including forged pistons (not applicable to all kits) Call us for details on your kit at (603) 378-0090
So, I'm thinkin you should call them and discuss deletin the cam and tossin in the forged pistons and goin from there. The forged pistons they have aren't "off the shelf" I don't think, I was under the impression that they just ordered them for you or sumthin, that's how you could get different comp heights, have them made 'for most aftermarket heads' and so on.
Lastly, You may want to ask about the Master Kit w/out pistons and rings, and the price actual custom piston mfgrs like Probe, Ross, etc.
Oh, and there may be some stuff I am not completely key-rekt on. I'm still learnin too!