Everything but the cam

[mtnrat]

I have pretty much decided on everything but the cam for my 383 build
The block is at the machinists getting worked on.
Parts.
Enginequest Heads 200cc and 72cc combustion chamber.
SB Chevy 383 Mahle -16cc Dish Top Pistons or equivalent.
Scat 383 4340 Standard Weight Crank - 3.750" Stroke - 6" Rods.
Scat 4340 Forged Pro Stock SBC 6.000" I-Beam Rods - 7/16" Cap Screw.
Roller retrofit lifters.
Clevite 77 bearings
etc etc.
Static compression of 9.1:1
I am looking at two cams from comp cams.
1) CS XM 270HR-12
Duration At 0.05 218 224
Gross Valve Lift 0.495 0.503
LSA 112*
2) CS XM 264HR-12
Duration At 0.05 212 218
Gross Valve Lift 0.488 0.495
LSA 112*
Low speed idle is important. I want an engine that idles and runs quiet but still gets up and goes. I think I can get that with the 264 but will I give up too much not going with the 270, which I understand idles well in a 383 as compared to a 350?

[ck7684]

I like the first one, but these numbers are pretty close to each other. Not sure there'd be a huge difference between the two...

[cstraub]

I have pretty much decided on everything but the cam for my 383 build
The block is at the machinists getting worked on.
Parts.
Enginequest Heads 200cc and 72cc combustion chamber.
SB Chevy 383 Mahle -16cc Dish Top Pistons or equivalent.
Scat 383 4340 Standard Weight Crank - 3.750" Stroke - 6" Rods.
Scat 4340 Forged Pro Stock SBC 6.000" I-Beam Rods - 7/16" Cap Screw.
Roller retrofit lifters.
Clevite 77 bearings
etc etc.
Static compression of 9.1:1
I am looking at two cams from comp cams.
1) CS XM 270HR-12
Duration At 0.05 218 224
Gross Valve Lift 0.495 0.503
LSA 112*
2) CS XM 264HR-12
Duration At 0.05 212 218
Gross Valve Lift 0.488 0.495
LSA 112*
Low speed idle is important. I want an engine that idles and runs quiet but still gets up and goes. I think I can get that with the 264 but will I give up too much not going with the 270, which I understand idles well in a 383 as compared to a 350?
Number 1. She will still be very well mannered in a 383 and give you some very good mid range. With a 6" rod be sure you go with a small base circle on the camshaft or their is a chance 2 and 6 rod will not clear the cam.

[Ryan00TJ]

Of the two choices I would go with the XM270HR. It will be a baby in your 383. Stockish idle and well mannered. I run a 226/230HR in my 355 and it idles decent. 750 rpmsN, 650rpms In gear. Like CStraub noted it should give you a nice powerband with good midrange cruising. I would like to see higher static compression to get your dynamic compression up but for your goals it will work fine. I'm going with those same rods and they are stroker profiled to clear the cam unless you are running a big solid roller.
Your a good ways ahead of me on the 383 project. I'm still deciding on which engine to build over the winter.

[bajarunner]

Another vote for #1. I just finished close build to yours, different cam and heads. That 270* will idle like grandmas Cadillac and still pack a decent punch. As said go small on the base circle with those rods or there's a very good chance of hitting rod to cam.