Block # gurus...

[1 Wild R/T]

Your 2.285 number isn't accurate.... I've been looking but haven't found the spec... I recall it being something like 11cc...

 

[jeepthrills01]

Ive been out of school for over 25 years...and i havent use the math like that in just as long. If some one knows better please chime in..lol...

 

[33 IMP]

69bee had that formula as ...im guessing ....a TLAR...(That Looks About Right) estimator...i guessing we can assume 10-15% error in it? Id like someone else to run those dish numbers...see how far off base this really is.

Dish is 2.88 diameter x .09 deep.

I got 9.609 cc.s . It's probably a little less than that, due to the slanted walls of the dish. I would probably use 9cc's in my calculator.
Are you trying to calculate what you have now, or with the rpm heads?

 

[jeepthrills01]

I got 9.609 cc.s . It's probably a little less than that, due to the slanted walls of the dish. I would probably use 9cc's in my calculator.
Are you trying to calculate what you have now, or with the rpm heads?

Either one...with the volume of the dish both are attainable


Thanks for the info

 

[jeepthrills01]

Ok..8.9...soggy little bottom 383...lol

 

[jeepthrills01]

Ive got a line on a set of used std bore hp pistons....or for 2x the price...the KB400 or kb167...if they fit with the closed chamber

 

[33 IMP]

Okay, i used the same formula for cylinder displacement .bore x bore x stroke (or in this case, depth) x number of cylinders (does not apply) x .7854 (functional constant).
Got .586297etc cu.in. Conversion factor from cu.in. to cc'c, x 16.39 gives 9.609xxxx.

 

[1 Wild R/T]

Ok..8.9...soggy little bottom 383...lol

View attachment 1063525

Those numbers are still optimistic... You've entered 82 cc for the chamber volume.. 906's are closer to 88-92... Even the Edelbrocks are 84.... Your showing the piston at .007 in the hole, I suggest you measure that, cause it'll almost certainly be deeper.. Cheap and easy use a decent straight edge & feeler gauges....

 

[jeepthrills01]

I did measure all 4 on the one side...pretty even..almost no variance

 

[jeepthrills01]

And the eddies will be right about 82 after the cleanup cut...they were previously enjoyed..lol..i got them second hand

 

[1 Wild R/T]

Ive got a line on a set of used std bore hp pistons....or for 2x the price...the KB400 or kb167...if they fit with the closed chamber

The 167 will fit but isn't much better... I don't believe the 400 will work with closed chamber heads & if it does you'll likely be to high on C/R..

 

[jeepthrills01]

Yeah...thats got me back to those roll the dice used HPs

 

[jeepthrills01]

Or...8.91...good flowing heads...decent small cam...headers and 2.5 exhaust..let it rip...Jim (IQ52)might even approve..lol

 

[69Bee]

r=1.44"
h=0.90"
dish vol=5.860cc

Gasket Vol:
G=(d/2)^2 * 51.48 * t

Where:
d=gasket hole dia (4.250")
t= compressed thickness (0.027")

G=6.277cc

 

[69Bee]

My compression calculator I built in Mathcad14
These are NOT his numbers, just an example. I made it calculate both dish & dome, you just have to use the correct answer for your situation

 

[jeepthrills01]

I think lll lay this to rest...69bee, 1wild, 33imp, mike...thanks for the efforts...if its 6ccs or 9ccs...this motor is still basicly a 9ish to 1 SCR....and about 8.8 DCR with good heads and a Harold Berkshire design cam...itll run decent.i can live with it

 

[33 IMP]

These are the numbers i got, using wallace's calculator, and LOTS of assumptions.
Roughly what you have now, stock bore and stroke, assuming 90cc for the 906s, 9cc for the dish, 039 compressed head gasket with a 4.375 bore (typical composite hg, big enough for a .060 over 440) and a .010 deck height, i got 8.08 - 1
Same as above, with 82cc heads, got 8.63 - 1
82 cc heads with a .020 x 4.310 steel shim (guessing on the bore size) 9.01 - 1.
All the above could be much more accurate with actual measured dimensions.

 

[jeepthrills01]

If you start at page 1..thats all explained
.027 cometic gasket with 4 25 bore
.007 below deck piston
And eddie rpms cut to 82cc

 

[jeepthrills01]

Wallace

 

[1 Wild R/T]

Wallace

View attachment 1063556 View attachment 1063557

What camshaft?