I'm just playing with numbers... whats the max CR you'll set your engine using iron heads, Hiper pistons, on gas pump ( 91-95 octanes )

Max static CR single choice
	10.1-10.3
	10.3-10.5
	9.7-9.9
	9.9-10.1
Votes accepted starting: 07/26/11 10:26 PM You must vote before you can view the results of this poll.

Depends on the cam. Stock cam and it'll be less CR than any of those #'s you posted. Aggressive cam and you can crank it up pretty high.

383man was running either 10 or 10.5 compression in his iron headed 440 with the mp .557 cam.

Depends on application, engine/chamber/quench design and altitude.
A heavy RV/Truck engine with alot of load and small torque cam, operating in the lower RPM range at sea-level, will need a much lower compression ratio (maybe 8.5:1 or less) compared to a lightweight race car with a 5,000+ stall converter, and large cam running at 6,000+ ft altitude which may run fine with over 12:1 compression ratio?

More specs then:

street use, B body, cams to use are MP 280/.474 OR Crower 282HDP. 727 MP175 converter, on the 400 block being stroked with stock 440 crank and KB215 ( 444 since I'm keeeping standard bore ) AC car.

Caracas altitude is 900 to 1000 meters over the sea level ( around 2700-3000 feet ? ), but I like to drive the country when I can, so that changes, going to sea level.

recently got damaged my new MP cam ( badly rusted front journal ) because the box got wet and noticed too late. I want to try to save the cam though. Anyway, just in case, got a Crower 282HDP what must being shipped today.

also have a NOS resto Mopar HP camshaft on the line, but not the one to be installed.

I'm playing with numbers using metallic gasket or composite. Need to CC the chambers on a NOS pair of 452s I'm porting though, but last time I CC'd a pair of 452s got 92 cc. Wish to use the metallic one... but will depend on heads ccs

With 92cc heads, 10cc head gasket (typical 0.040 thick big block gasket) and stock 9.980" deck height, that calculates to 9.53:1 compression.
The quench dome KB piston will give some quench effect to the chamber too.
With the cams your looking to use you should be fine with regular pump gas.

Static compression means next to nothing......dynamic compression is the real number that tells you where you can push the limit. Shoot for 8.5:1 dynamic with a iron headed motor and 9:1 with aluminum.

http://www.projectpontiac.com/ppsite15/compression-ratio-calculator

all what I have said is what I have, no less no more... well, bigger valves too ( 2.14/1.81 ).

-stock 452 NOS heads being ported.
-KB215 pistons ( 0.95 quench pad, -1.5 cc piston volume due the pad )
-KB crew told me piston sets 0.025 below the deck. My block has been milled down for sleeves instalation 10 years ago so maybe now closer to 0.020 than 0.025 KB crew told me
-Engine being built with pistons/cilinder and rings clearences limit ( in opposition with some members opinion, sorry about that ), just removing the close to 0.001 ridge ( total bore is standard +0.002 ) and a light hone job more on bottom than top... on top just to finish the ridge reaming job.

Pistons are not in hands yet, arriving to Florida today with luck, then 2 weeks more to have them in hands ( once the cam also arrives )

still unsure about the cam to use, one of those for sure. I wanted my engine the more Mopar as posible, but dunno if the MP cam I got will be posible to be saved.

making several combinations, playing with cc ( from 92 up to 88 ) gasket numbers and final piston to deck clearence ( around 0.015-0.020 ) what still I can't determinate due pistons are not in hands and block was slightly milled to match the sleeves, I have got ( on calculators ) from 10.08 to 10.58

Combustion chamber measures THE SAME ( 0.94-0.95 ) than the KB215 piston quench pad height stated by KB, so 0.020 gasket and 0.020 piston deck clearence, will give me the theorically "perfect" 0.040 quench. Thats why I would like to keep metallic headgasket and that could give me 10.27 CR on 90 cc. 92 cc drops to 10.08. 88 cc raises to 10.46 so maybe on that moment, composite will be better ?

so, I'm hearing based on this, whats the max I could set my compression, to, once get all the parts involved, which way to go if some of the numbers differs, going composite or metallic etc...

Combustion chamber will be polished so maybe will add some CC. ( what will be maybe fine on this case ).

I'm just thinking forward about this

its amazing how votes are splitted!

You will need to check the depth of the open chamber cylinder heads where the quench pad will be.
When I did my 360 one head was 0.010" different than the other, but I was using the KB232 pistons which have a short 0.050" quench pad, so I gad to mill the block to get the piston closer to zero deck, then mill the heads. I think one head was cut 0.030", and the other 0.040". Then I cc the heads, and polished the chambers to equalize the chamber volumes.
I ended up with 9.5:1 compression, and dynamic compression of 7.5:1 (using a RV cam.) Engine runs fine on pump gas, but the lowest altitude I have had it was 4,500 ft.

If your block has been milled to 9.960" (about 0.020"?) that should put the piston at -0.005" below deck at TDC, and with the 92cc heads, resulting in 9.94:1 compression ratio, and with the Crower 282hdp cam, installed at 106 degrees results in a dynamic compression ratio of 7.52:1.

actually you really think the deck height it was blue printed at 9.980 ? naaaaah, after the heads experience and deception where everywhere says open heads are on 84-88 cc rate and they are really on 90-92 I don't think the 9.980 is for real. How its measured ? I could try to check that

the "milling" block job was just for decking the sleeves, not actually a mill job. I don't think a machine job will cut 0.20 on a decking job

heads measured on quench area 2.5 mm average... will check further though

nice, will give a try but I don't think will have a long caliper like that handly

about both sides being the same lenght... it looks to be the same. Cilinder ridges from the old pistons looks to be the same wide on both sides.

My perfectly adequate Chinese 12" dial caliper cost me $49.00, and came in a case.
R.