LukeZ28

I am just trying to get used to the calculator, so trying stock CR.
Where am i wrong.

Cylinder head Volume (CC) = 54.40
Piston Top Volume (CC) = 0.00
Cylinder Bore (Inches) = 4.0
Cylinder Stroke (Inches) = 3.48
Deck Height (Inches) = 0.030
Head Gasket Thickness (Inches) = 0.039

Computed Compression Ratio is 11.4 to 1

Thanks for the help.

1racerdude

You didn't add your CC's for valve reliefs,and no intake valve closing point.
If you give me that info I will run it on my program and give you the complete results.

LukeZ28

Well, i am trying to find stock specs/numbers for the CR on my engine to have numbers to go off of, and not having the best luck searching.

Thanks

dano73327

Your numbers are about right depending on what you used for head gasket hole diameter.

Mindgame

You need to enter a piston relief volume of 7ccs. That sets you at 10.5:1 static.

-Mindgame

1racerdude

In the piston volume (which means Valve reliefs) put 4-6CC's maybe 8 and see what you come up with.I know the stock pistons have 4 relief's but I have never bothered to CC them. The number for piston clearance is a + .030 which means it is in the hole .030.The compression for an LT-1 is 10.5X1

LukeZ28

Now looks better.

Cylinder head Volume (CC) = 54.40
Piston Top Volume (CC) = 7.00
Cylinder Bore (Inches) = 4.0
Cylinder Stroke (Inches) = 3.48
Deck Height (Inches) = 0.030
Head Gasket Thickness (Inches) = 0.039

Computed Compression Ratio is 10.5 to 1

would be stock CR

If i went with
SRP Forged Piston Set Reverse Dome -24cc
4.030" bore x 3.48" stroke, for 5.70" Rod

machining to a 355, at stock deck height would result

Cylinder head Volume (CC) = 54.40
Piston Top Volume (CC) = 24.00
Cylinder Bore (Inches) = 4.0
Cylinder Stroke (Inches) = 3.48
Deck Height (Inches) = 0.030
Head Gasket Thickness (Inches) = 0.039

Computed Compression Ratio is 8.8 to 1

Thanks for the help!

Mindgame

Are you looking to build a boosted engine?

That compression is ok, just make sure you don't end up with a quench height of .069" like in your example (.039 gasket + .030 deck height). Any reputable builder should know this but just thought I'd give a heads up before you start buying parts. I'd shoot for .035-.045 quench to get the turbulence up and help fend off detonation. Just a FYI.

-Mindgame

LukeZ28

Thanks mindgame,
I am trying to look into everything before getting into the rebuild, and i am not familiar myself with quench. Those are stock specs so, if i was to go with the felpro 1074 (.039") gasket, i should deck the block/head to reduce the height, which would help quench in a boost application. Stock valve clearance problems?

rskrause

That gasket is the correct thickness for a "zero deck" block as the resulting 0.039" quench height is just about ideal.

Rich Krause

kmook

Not sure why this is in Adv Tech, transfering to LT1 Tech. Thanks.

LukeZ28

Thanks Rich,
So it looks like with the setup above and zero deck;

Cylinder head Volume (CC) = 54.40
Piston Top Volume (CC) = 24.00
Cylinder Bore (Inches) = 4.0
Cylinder Stroke (Inches) = 3.48
Deck Height (Inches) = 0.000
Head Gasket Thickness (Inches) = 0.039

Computed Compression Ratio is 9.4 to 1

which is now running a bit high for FI, and i was looking for around 9.0.

Mindgame

This is why SRP makes the 31cc inverse dome pistons.

Same calcs with the -31s and you're at 8.8:1.

Are you using a virgin block (4.0) or is this a rebuild/rebore? I assumed 4.030 for my calculations.

-Mindgame

LukeZ28

I will be working off a stock probably high milage block, either mine or might be picking up a used long block. So i noticed most of the SRPs are for 30 over, and thought to go ahead on a used block and bore it out. I didnt see the 31cc, thanks, sounds like the best option.
Bore block 30 over
Machine to zero deck
Felpro .039
Eagle 5.7 forged rods
SRP 31cc dished pistons SRP-37557-31 (are those for stock stroke?)
JE hellfire ring set
federal mogul bearings

Sound good?
Thanks guys.

rskrause

If you can spring a few extra dollars, consider going 10 over instead of 30. With boost, you want the cylinders as thick as possible.

Rich Krause