Milling piston dome?

[Beekeeper]

So just a quick measurement on the hole I pulled the piston from it’s a 4.250 stroke. I measured the length of total ring travel from the top to the bottom
of the cylinder then deducted the the amount from the top of the top ring to the bottom of the bottom oil ring to come up with the stroke.

 

[Hemirunner]

So just a quick measurement on the hole I pulled the piston from it’s a 4.250 stroke. I measured the length of total ring travel from the top to the bottom
of the cylinder then deducted the the amount from the top of the top ring to the bottom of the bottom oil ring to come up with the stroke.

So that combined with the nominal deck height and your known rod length should let you make some preliminary calculations. Diamond has a really good compression ratio calculator on their site.

 

[Beekeeper]

So that combined with the nominal deck height and your known rod length should let you make some preliminary calculations. Diamond has a really good compression ratio calculator on their site.

I did try a few calculators and with a .060 gasket it comes in around 13 to 1 if I plug in a .100
gasket it comes to 11 to 1. so I think I may be able to make it work without milling the domes or changing pistons. The bore is 4.310 on this block which looks
fairly fresh to me with no ridge at all at the top

 

[Fran Blacker]

With a .100 head gasket intake fit will be critical.

 

[Beekeeper]

I’ve tried to get a rough measurement on deck height and it seems there’s around .080 cut off it. I could mock it up with some super stock heads I have along with a manifold to check the fit.

 

[33 IMP]

Not yet I will pull the No 1 main cap and get the info. I can’t see all of the part number
what I can see is 440425022 but can’t see the last two digits

You had enough there. 440, (440 mains)obvious,4250 next is the stroke, 22?? will be 2.200 big block Chevy rod journals. (Very likely because of the 7.1 rod length.)

 

[Ceedawg]

Real easy to get stroke, run the piston down to bottom then to top and measure.

 

[Beekeeper]

I contacted Diamond this AM and they made the pistons. 108cc dome and 1.377 deck height
so next thing I need to measure is block deck height this thing is like solving a puzzle

 

[33 IMP]

By my calculations those pistons are almost .125 in the hole. Your compression might not be as high as you think.
Edit: assumptions..... 4.280 bore, 4.25 stroke, 170 cc chamber, 100 cc dome , .050 x4.350 head gasket, and the biggie, a .125 deck height (half stroke, 2.125 plus 7.1 rod, plus 1.377cd, =10.602, standard deck for a rb, 10.725 if blueprinted to stock.... .123 deck), i get between 9.5 and 9.75.

 

[Beekeeper]

By my calculations those pistons are almost .125 in the hole. Your compression might not be as high as you think.
Edit: assumptions..... 4.280 bore, 4.25 stroke, 170 cc chamber, 100 cc dome , .050 x4.350 head gasket, and the biggie, a .125 deck height (half stroke, 2.125 plus 7.1 rod, plus 1.377cd, =10.602, standard deck for a rb, 10.725 if blueprinted to stock.... .123 deck), i get between 9.5 and 9.75.

thanks for the math but the deck height is nowhere near 10.720 is more like 10.620 I got
a pair of 12” calipers today So I’ll be checking the block deck height and will report back.

 

[33 IMP]

Same as above, with a 10.620 deck height.....12.07

 

[BSB67]

thanks for the math but the deck height is nowhere near 10.720 is more like 10.620 I got
a pair of 12” calipers today So I’ll be checking the block deck height and will report back.

If the crank and bearing are out, don't forget the thickness of the bearing or radius of the saddle in your math.

 

[Beekeeper]

So here’s the block and piston measurements. Bore is 4.310 deck height is 10.612
4.250 stroke crank with 7.100 rods 108cc dome and 1.377 CH.

 

[33 IMP]

496 inches. With your numbers(.010 deck) and a .041x 4.35 head gasket, i got 14 to 1(actually 13.95), with a .100 thickx4.375 gasket, i got 11.91 to 1. Edit: also assuming 170cc head.
( a .125 head gasket will effectively just be putting back the material cut off your deck.)

 

[Beekeeper]

Here’s the info I plugged in the Diamond calculator

 

[Beekeeper]

So with .108 removed from the deck would it be safe to say that a .125 thick gasket or a combination of steel spacer and gaskets would work out with an uncut intake? I know I will have to use spacers on the China walls as well to seal the valley.

 

[33 IMP]

Theoretically, an unblueprinted rb block (spec of 10.725, plus who knows how much, maybe .015?,) so 10.740, plus a composite head gasket of .041 compressed, the head bolts on 10.781 from the crank centerline.
With your deck of 10.612 plus .041 you are at 10.653., maybe .130 less than stock. A big ,fat, thick head gasket might just get your intake alignment better and your compession down to where you need it. It's a hemi, so you don't have to worry about loss of quench like the wedge guys do.
I'm just spitballing here, i'd talk to your machinist and see what he says.

Edit. Both your last two posts were posted while i was typing mine. Sorry my typing is so slow!

 

[Beekeeper]

Yea I keep forgetting about the quench thing with a hemi. The block doesn’t need any machine
work I just need to get the right parts to assemble it. I would like to get it to 11.5 to 1 or close
or to put it another way I want to run 93 pump without fighting detonation issues.

 

[33 IMP]

With a .125 x4.375 gasket, i got 11.25

And i would be tempted to make friends with somebody who has a private plane. I do love my avgas. 91 plus 10% is the best pump here, but five gallons of 100LL was only 22bucks (NOT in california).

 

[Beekeeper]

I would be happy with that for sure