Can anyone tell me the chamber cc, or the compressed thickness of our headgaskets? I found the thickness of a cometic gasket, but i figure that is uncompressed thickness, so if anyone knows how thick it is compressed, or the head cc, I would greatly appreciate it.


Thanks

Beecher

 

all i can find is swept volume at 1598 cc . one of the racers is bound to wade in .

 

Well, by the math, each cylinder swept volume is 399.5 cc.
(swept volume + chamber volume)/(chamber volume) = C.R. ... so ...
(swept volume)/(C.R.-1) = chamber volume.
For the R50 MC 10.6 CR yields a combustion chamber volume of 41.6 cc per cylinder.
For the R53 MCS 8.3 CR - 54.7 cc.
For the R56 MC 11 CR - 40 cc.
For the R56 MCS 10.5 CR - 42.1 cc.

 

nice job!!!

 

but you didnt factor in the head gasket, plus the r50 and the r53 actually have the same chamber cc, the r53 has dished pistons to drop the compression. By the numbers i arrived at, the cc is 26.75, but that was using what i assume is the uncompressed thickness of the cometic gasket, so it is wrong as well.

Thanks for the formula tho, but im affraid it only works in theory

I really need the numbers from a head that has been CC'd or the compressed thickness of a head gasket. Either will work for me.

Thanks again

Beecher

 

there should be a thumbs up smiley after theory, but its not showing up, again....

 

Sorry, I assumed the combustion chamber volume meant the portion
between the top of the cylinder head and the top of the piston at TDC.
You're right - the volume in the cylinder head is the same for MC and MCS
since the heads are the same except for valve material.

 

thats a fair assumption. And acctually, something seems weird, because your measurements are alot bigger than mine, and i did it your way, and got the same answer, so that is right, but there is no way that the head gasket takes up like 15cc is there? I didnt really think so. This might come down to just pulling my head and ccing it. I will let you all know when i find out tho! This is weird. I dont see why our numbers were so different. If yours was like 31, i would say, ok, head gasket, but the jump to 41 seems extreme. I will get to the bottom of this one tho, i assure you.

Beecher

I dont really know how to cc a head gasket tho, at least not accurate to the degree that would be acceptable, so i supose i cant prove anything, but the cc of the head alone, which i will do.

 

Just remember that there will be an extra tad of volume as the cometic gasket is 1.5 mm greater in diameter than the bore. I would just call Cometic and ask what the compressed thickness is and do the calculations then.

Jeremy

Jeremy

 

There's also a little volume under the head gasket between the piston and
the top of the engine block.

for a .065" gasket (let's guess .05" compressed which may or may not be close),
that's .127 cm and a bore of 7.7 + .15 cm, so the volume is 6.14 cc in the head gasket.
and leaves another 7-9 cc under the head gasket for the MC's and the R56 MCS,
and about 22 cc under the head gasket for the R53 MCS with its dished pistons.

 

gasket according to their catalog is .027 (!!!) which means the cc should be 38.5, which is awfully close to the 41.6 you said! but 41.6 would still make a compression of 9.93. why are these still off? I want them closer yet. What are we missing? could that 1.5mm make that difference, cristo, you seem to know more of what your doing, would you mind figureing that one out? im very confused right now.

 

it's the only way....

Matt

 

The combustion volume in the head gasket then would be Thickness*1/2*pi*(bore/2)squared.
.027" would be 0.686 mm or .0686 cm
77 mm + 1.5 = 78.5 ... /2 = 39.25mm or 3.925 cm
then the volume would be 3.3 cc in the gasket.
if the cylinder head has 26.75 cc that leaves 10-12 cc under the gasket for
all the models except the R53 MCS which would have about 24.5 cc.
I'm pretty sure the pistons don't come completely up and flush to the top
of the cylinder head even in the MC. According to the calculations above,
they probably come up to about 2.4 mm shy of flush in all models except the R53.

 

i think i got it. Your numbers is overall, mine is just the head alone. Combining my head cc (38.5), plus the volumn in the gasket (3.3) would give you 41.8.

NOw where have we heard that number before??? (well, 41.6 actually, butagain, that .027 is probably uncompressed, so that is probably the 2pt difference) hahah, weve got it!

thanks so much for everyones help, especially you cristo!

Beecher

 

here's a nice calculator (there are many on the net, some even figure in the cylinder/piston clearance and
distance from top of piston to first ring!):
www.mopar1.us/compression.html

 

Hey! Lookie! Lookie!

From this old post dated 12/2003: https://www.northamericanmotoring.co...ad.php?t=34061

engine measurements
I am bringing this over here as a general FYI:
engine measurements

I've compiled some info from my spare engine and since questions arise, thought I would put them in one place: (maybe this should be a sticky?)

Block:
bore: 77mm (3.03"), piston area: 46.5 sq cm,
stroke: 85.8mm (3.380") (from the Mullet link to Tridec; not personally measured)
displacement per cylinder: 399 cc (1600cc total)
bore-to-bore centerline: 85.34mm (3.36"), web between bores: .330"
rod length: 130mm (5.11") (eye-center to eye-center)
Rod/Stroke ratio: 1.53
deck height: -3.6mm (-.145") piston is below deck surface;
head gasket: .025"( compressed)
piston: flat with .020 depression to 1/2" of perimeter


(comment: a 1mm ovebore gives 1640cc, about 40cc increase and recuces the web to about .290".)

Head:
intake ports: 1.675" x .85"
exhaust ports: 1.348" x .8"
intake valve: 30.2mm (1.189"), throat below seat: 25.9mm (1.02")
exhaust valve: 23.3mm (.918"), throat below seat: 18.8mm (.74")
rocker ratio: intake 1.65:1; exhaust 1.43:1

cam: base circle 1.185" dia
lobe lift: intake .202", exhaust: .217"
valve lift: intake .333" exhaust: .310"

(PROMINI cam: base circle 1.145" dia intake, 1.132 dia exhaust)
lobe lift: intake .228", exhaust: .240"
valve lift: intake .378" exhaust: .343")

valve adjusters are hydraulic piston, located in the rocker, dia .47"
cam followers are rollers

header ports: 1.366" x .975" (Supersprint is 1.60" x 1.05")
header primaries: 1.36" (Supersprint is 1.63")
header secondaries, Supersprint is 1-3/4"
header collector: 2.3" (Supersprint is 2.5"")

intake runners:
-valve back to flange: 3.5"/4.6" (bottom of port/top of port);
-intake flange to manifold interior plenum: 4.0"/4.5"
total, plenum to valve: 7.5" along port bottom, 9.1" along port roof.

exhaust runners:
-valve back to flange: 2.6"/3.45"

 

Plug these numbers into the calculator and you get a cylinder head
combustion chamber volume of 33.24 cc for a 2003 MCS.

It also means that if the R50 MC has a deck height of -1.14 mm if it has flat topped pistons,
or -0.79 mm if they are dished as the R53 MCS ones are (either way, the MC has taller pistons than the MCS).

The two inaccuracies that could be present are:
1) C.R listed is probably rounded off to the nearest tenth of a point
2) I'm assuming the head gasket bore is 78.5 mm

 

.

 

wow! info ive been trying to find for a long time in there! Thats good stuff. Thanks so much. Im going to print that off and stick it in my bently. im going to be drooling over all that stuff for a long time! thanks There somuch stuff in their of searched for and never came up with any results (largly because cr, cc, are too short to search for in vB). Thanks alot for that stuff, a great help

 

You're very welcome.

 

Ok so what's the goal of your head job/rebuild then Beecher? A higher CR?

Jeremy

 

X2 on that... Beecher, I think we might be planning something very similar..!

 

yeah, i want a higher compression. I want 12:1, but by the looks of it, i will have to settle for 11.5 to one by only changing the gasket. To get more i would have to mill the head, and that is not going to happen right now, next winter maybe, but i doubt it, i would rather leave the head alone as far as that goes. I will probably just settle on 11.5 for now, once my motor sees some more displacement, i will have to crank the compression back down some anyway, so there really is no point in milling the head.

chad, what are you guys doing?

thanks for the help again guys

Beecher

 

Is this for a race application? Or are you going to run 94 octane or octane booster full time?

Jeremy

 

i run 94 all the time as it is. I just wish the station that sold 100 at the pump was closer to me (its about 45 minutes, and in the states, and i live in canada). If it was local, i would get the head milled and run alot more compression yet. Its not really a race aplication, but this last year most of my milage was put on going to and from races, haha. I spent 3 months putting the car together, took it to the track for one day and took it apart again. that was 3 months ago again already, hahah. Its SUPPOSED to be my daily driver, but, i got a little cought up inthe mods, and the car sees more time undergoing mods than it does driving, hahah. To give you a hint at what im like, i was rebuilding a motor that was supposed to be stock, and it turned into a full blown race motor. I cant keep myself undercontrol!