Cylinder head volumes?

[Rumblefeesh]

I can't recall finding info on combustion chamber volumes of different heads anywhere - I am not setup to measure volumen on different heads accurately - does anyone have info on the volumes for the different factory heads, and/or for STD and S&S?

[shovelbill]

i know a guy that may know the cc #'s of some different heads. i'll give him a shout and see what i can find out for ya.
                                                                          bill

[crazycanadian]

I'll give you some really good free advice! NEVER EVER accept what is written on paper to be what the heads are ever! OR what the piston SAYS you will have !!!!..  I built race engines for a living and I would honestly say 7 times out of 10 they are never as advertised.. that goes for car engines to.! I did a 396 last summer that all the pieces claimed 10.4 compression.. when actually measured.. it was 7.5 .. same for a 331sbc.. he had an actual 7.8 compression. I just finished a twincam that used screaming eagle 10.25 pistons.. when measured out it had 9.3!!!!!.

All you need to cc is a basic 60cc syringe and alil baby 3cc for the final air bubble and a piece of plexiglass with a small hold drilled in it nothing more!  For shovel heads I have a round one to fit inside the fire ring hole to give me an accurate reading easier. If you need help I'll gladly walk you through it! Your giving up free horsepower and fuel economy and throttle response! and YES it matters lol!!

step one..

get your head and ur piece of plexiglass.. take some grease and lightly grease valves.. drop em in and run grease around to seal them.. put your spark plug in and then take and lube the top of the deck surface liberally with grease.. then put your plexi piece on and squish it around so it seals.. then fill with colored water and record your measurements

step 2

get your cylinder and put your piston in with a top and second ring. push it down about 3 inches . now run some grease around the cylinder and push the piston so it's exactly 1inch from the top of the bore. gently wipe the grease around to get it out and seal up the rings.. now put ur plexi on top and do same thing.. measure..

step 3

gimme the measurements with your head gasket thickness and what your piston squish band is. your bore and stroke and i'll figure out exactly what your compression is..

skip any of this and your just guessing.. and pretty much guarantee it'll be less than you think!   

Also you should really check your piston height as this affects many things including squish and compression... This is a major important deal and has a major impact on the output of the engine, fuel economy, ablility to handle low octane before encountering detonation.  I generally run most of my engines with 11.1 compression on pump gas with no problems and have a 93" shovel making 114hp on 87 octane pump gas with 11.1 compression.!

It's also been my experience that stock cases are never machined accurately and I have cases that the piston was different almost .045 in height!!!! That's massive!

What style of head do you have that your enquiring about.. shovels generally run about 129ccs

evos can be anywhere in the 80cc and up

[Rumblefeesh]

I agree to not take anything for gospel - however, I am looking for some general guidelines as I have about three different projects going and am looking to make some general decisions, late heads, early heads, aftermarket heads, etc. My question is spurred by comments from one manufacturer saying that their pistons provide 9.5:1 compression with 135cc heads, and another respected on-line site saying "late model heads had combustion chambers upwards of 165cc".

That got me to wondering how big a (nominal) difference there was between late, middle and early series heads, and how they compare to S&S and STD. Just looking for the nominal values since I cannot find any source quoting actual cc's for any of these.

[otis]

Most piston manufacturers use 135cc for ther dome height calculations. 

I agree with the crazycanadian, can't trust anything but your own measurements and that the advertised compression is usually less in reality.  I had to cut 0.100" off my cylinders to get the 9:1 advertised by the KB.  CC's must be thouroughly check for any good engine build.

Good luck,
Patrick

[MBSKEAM]

I know that this is not a shovell but the theroy is the same...





found a cool comp. ratio calculator:

http://www.rbracing-rsr.com/comprAdvHD.htm

Camshaft, Rod Length, Boost and Altitude Correction to Compression

Your engine summary is as follows: Bore 3.5 inches,stroke 4.625 inches, rod c-c length 7.470 inches, with a static compression ratio of 9.48 :1.
Your camshaft specifications call for an inlet valve closing of 43 degrees ABDC (after bottom dead center).

Your chamber volume is 85.99 cc's. With this camshaft your dynamic, or effective stroke is 4.17 inches.
Your dynamic compression ratio is 8.65 :1 corrected for cam timing, altitude, and rod length. Your dynamic cranking pressure, corrected for cam timing, rod length and altitude is 175.86 PSI. Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and 0 PSI is 8.65 :1.

Knowledge is power.

old build with KB pistons

Camshaft, Rod Length, Boost and Altitude Correction to Compression

Your engine summary is as follows: Bore 3.5 inches, stroke 3.968 inches, rod c-c length 7.470 inches, with a static compression ratio of 9.94 :1.
Your camshaft specifications call for an inlet valve closing of 43 degrees ABDC (after bottom dead center).

Your chamber volume is 69.98 cc's. With this camshaft your dynamic, or effective stroke is 3.56 inches.
Your dynamic compression ratio is 8.92 :1 corrected for cam timing, altitude, and rod length. Your dynamic cranking pressure, corrected for cam timing, rod length and altitude is 182.94 PSI. Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and 0 PSI is 8.92 :1.



I know that this is a real accurate program because it got within .1cc I got by bolting on a head at TDC, and tilting the engine till the spark plug hole was level then CC'd it, I found it to be 86cc. since the program did not ask me for this info, but told me I can only think that it is right on. some other compression calculators kinda vary. I also did it by math and get the same numbers

a side note about KB pistons .......

http://kb-silvolite.com/cycle.php?action=details&P_id=15

these are the ones that most pan guys are using.......

CC'd the heads and then I go and CC the pistons 1" down the cyl. so how does KB come up with a 57CC dome when I only come up with about 33CC:

3.5 bore, piston at 1" down it took 125cc to fill. that is 7.625 CI, then I figure the volume without piston 9.621 CI. 9.621-7.625=1.996/.0610=32.72CC
so what am I missing? are they using the head of the piston all the way to the 1st ring? or am I missing the secret number?
my S&S pistons come up with a 28CC head.

did come up with 120CC's on the STD panheads,

mbskeam

[Hillside Motorcycle]

I'll chime in and make mention not to get overboard on the squeeze, but do squeeze as needed.

[crazycanadian]

sounds right on the std..
evo head should be around the 80ish mark

I run as much compression as possible. You just have to know how to build the engine right.. I routinely put my twinkies at 11.1 to 11.5 on pump gas  with a 256 duration cam.. and non of them knock... it's knowing how to build it right and to what clearances.. and that is the difference between a mediocre engine and one that kicks ass.