Irocss85

iTrader: (1)

is this accurate? I guess'd at 2cc for the reliefs and 63cc comb. chambers since 853 heads milled .030, and I polished the chambers, and sunken valves after valve job. someone else mentioned to use the .006 #s instead of the intake closing point but what do you mean? looking at the cam card (custom comp cam) I got duration at .006 is 285 on the intake, no mention of intake closeing point at .006". the closing point is (at .050" ) 47abdc. which I used in the below calc. is this accurate (ofcourse assuming my guestimates are right) or did I do something wrong here? if so wouldnt I want to use the GM MLS gaskets instead to lower that a tad for pump gas use? it will always use 93octane, and it will be dynotuned, but I dont want this thing creating spark knock/detonation either.

if I swap the .040 head gaskets for .054 MLS, I get 8.68 DCR.
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ENTER YOUR DATA CALCULATED DATA
Cylinder Head Volume (cc) 62
Piston Head Volume (cc) Piston Head Vol 2cc

Gasket Thickness (in.) .040"
Gasket Bore (in.)3.90?
Cylinder Bore Diameter (in.)3.90"
Deck Clearance (in.) -.007?
Stroke (in.) 3.62"
STATIC COMPRESSION RATIO 11.061

OPTIONAL DATA
Rod Length (in.) Adjusted Stroke (in.) 02.873
Intake Closing Point (degrees)
ABDC @ 0.050 lift plus 15 degrees 47+15=62degrees?
DYNAMIC EFFECTIVE COMPRESSION RATIO 08.985

TIA
chris

Irocss85

iTrader: (1)

ok, searched and found this guys formula for calculating .006 duration #s, but my cam card does not have advertised #s. only duration at .006 lift. and if i use that # (285I/291E @ .006"), it seems to be very low. so doesnt seem right to me. my ICL is 110.


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You'll also need the formula for calculating IVC at .006". It's not on your cam card. That formula is : Advertised duration divided by 2, plus your ICL, minus 180. That will give you the IVC for the last blank. The site says just add 15 to .050", but that is horrendusly off, and basically a guess.
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Smitty's '04 GTO

iTrader: (5)

When I got my cam from T.R., it had a Cam Pro Plus report which included IVC @.006. (Mine is 71.9*ABDC) This is the number I used in that calc and I believe the results to be pretty accurate.

When I used your formula above, plugging in my Ad. duration, ICL, etc.; I got a number of 70.25*ABDC. So, I'd guess the formula you have for figuring IVC @.006 to be just a tad off, but a whole lot closer than the calculators formula of IVC@.050+15*.

Also, when filling the fields of the calculator, you may want to use 3.91 as the Gasket diameter (info from Cometic), and the factory cylinder bore is 3.898 and the stroke is 3.622. Are you using the factory flat-top pistons? If so, Piston Head volume should be 0, a negative number if you have valve reliefs in the piston (ie. flycutting) and a positive number if using a domed piston.

Plug those numbers in and see if you don't get some more reasonable results...

Good Luck with it!

Smitty's '04 GTO

iTrader: (5)

on a side note, "advertised duration" is considered by the industry standard to be the duration @ .006, so your 285/291 numbers are your advertised duration numbers. An exception to this is that Crane Cams uses duration @ .004, as does the factory cam specs. The difference is negligable.

Irocss85

iTrader: (1)

ahh, thanks guys, I'll redo this when I Get hom on my pc.

Irocss85

iTrader: (1)

62cc head volume
2cc piston volume(valve reliefs Im cutting into pistons)
.040" cometic head gaskets (F... it, Im goin to try them out)
3.91 head gasket bore diameter
3.898" bore diam.
-.007 deck clearance (maybe I'll actually measure mine since it varies)
3.62" stroke
6.098" rod length
72.5 deg. is the icp @.006"lift according to this fomula of Ad. Dur. 285/2 +ICL[110]-180=72.5

I get 11.05 SCR and 8.227 DCR.


not too shabby right? please anyone correct me if I got something mixed up still. I love this forum.