My potential compression ratio

[moper]

Moper,
I feel that in the long run I have an advantage in that I am building the power plant last.
I can not tell you how many cams, "new and improved" I have plugged into the engine dyno, including all sorts of roller cams, and nothing happens to fit my combination like the 285. Now the 295 gives me more power but the power band climbs up into territory im not interested in going to.
I also have to agree with DGC333, in that chart is pretty much a worst case scenario put together by people who are not taking into account such things as quench and coatings which we have access to today.Its just a baseline reference when talking about true or Dynamic Compression. It also takes no account of altitude adjustments.
Andrew

My own order of operations is once the powertrain is "up" (meaning chassis/bodywork/paint/etc is done) the whole driveline has to be done at once to get the most from it. Engine would be first, then trans and final gearing in that group. Because so much depends on the camshaft. The main issue I have with the calculators are they are just like fantasy football. They have only a part based on reality, the rest are mathematical estimates and compromises to get the result anyone can interpret. So while you run a dozen cams and they show little difference on the dyno program, you could swap in 12 cams and see drastic differences in the empiric results of a dyno session. That's one of the reasons I tend to recommend cams I know yielded results I want. I've gotten away from saying "run this cam" and more into "run a cam around these specs" because of that. People have favorite brands or part numbers, some only have one or two points of reference, some have no idea how they work but read a lot, some simply don't know and don't want to, they just want an engine that works...lol I also think Dave's (DGC333) build is a great one to copy.

 

[octanejunkie]

I'vwe always found it safer to err on the side of lower than higher dynamic because I never know what altitude or the quality of fuel available where-ever the engine ends up. I do think many people overthink a lot of things...lol. But there's making a decision, and hemming and hawwing and never making a choice. Overthinking is only overthinking when you can't make a choice.

Agreed, and I am making a decision, I am just not there yet, so I am getting my hemming and hawing out of the way before it holds me back

Moper,
I feel that in the long run I have an advantage in that I am building the power plant last.
I can not tell you how many cams, "new and improved" I have plugged into the engine dyno, including all sorts of roller cams, and nothing happens to fit my combination like the 285. Now the 295 gives me more power but the power band climbs up into territory im not interested in going to.
I also have to agree with DGC333, in that chart is pretty much a worst case scenario put together by people who are not taking into account such things as quench and coatings which we have access to today.Its just a baseline reference when talking about true or Dynamic Compression. It also takes no account of altitude adjustments.
Andrew

The 285 fits numerically for me too, but not in drive-ability or manners, at least not on paper. I am leaning towards DGC333's advice and just going with it, but I also wonder what if I took my quench distance to .050? My SCR would drop to 10.56 and my DCR to 8.50 - what would I "loose" having an .050 quench vs. an .039 to .040 quench?

I also think Dave's (DGC333) build is a great one to copy

Agree again, and that is what started this epiphany-of-sorts for me - if I zero-deck my block and throw the same XE268H stick in there we'll have twin engines - which, for my sanity's sake, is probably the best plan for now

 

[MopaR&D]

I know this is an old thread but I just wanted to see if the OP made any progress since the last post... I'm also building a 360 with Magnum heads much like dgc333's build and I'm stuck on cam choice. One I've been looking at is the Comp 270H, I know it was mentioned that Magnum heads have better crossflow characteristics and might not benefit from dual-pattern cams. I'm interested to see if a single-pattern like this one would produce better breathing efficiency compared to its closest dual-pattern cousin the XE268... also the slightly lower lift on both lobes and higher duration on the intake might make it even less detonation-prone than with the XE268 which dgc333 said wasn't even bad in the first place. Have you been able to play around with this yet octanejunkie?

I'm also looking to run ~3.2 gears and a 2800-stall converter so I need to find that delicate balance between keeping detonation at bay and having enough low-end torque for cruising and gas mileage.