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Combustion chamber volume?

Performance mods and Advanced Stroker discussion.
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str8-6
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Combustion chamber volume?

Post by str8-6 » February 9th, 2015, 1:24 am

I've read on here that the size of the combustion chamber is 57 cc,but when You look at the chamber size in the comp.ratio-calculator it says that 58 cc's is the most common size,is that with a 0630 head or is it the same for all types of head?

Milled 0.00669 off on a 7120 head to get some more room for decking the block without getting way to much compression,still getting 10.62 static/8.83 dynamic in comp ratio,should be a bit less after polishing and smoothing out the chambers,aimed for 10.4 but then the quench got to high,now the quench is in the .055 "area"

If I had stopped with a .020 decking the comp.ratio would have been 10.36:1 static and 8.6:1 dynamic but in that case the quench had ended up at .066 ,I think that is to high to have some good use of the quench,well things are what they are so 98 swedish octane,here we go...

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Cheromaniac
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Re: Combustion chamber volume?

Post by Cheromaniac » February 9th, 2015, 2:10 am

str8-6 wrote:I've read on here that the size of the combustion chamber is 57 cc,but when You look at the chamber size in the comp.ratio-calculator it says that 58 cc's is the most common size,is that with a 0630 head or is it the same for all types of head?
The quoted combustion chamber volume for 4.0L heads of all years is 55.2-58.2cc (median value 56.7cc) so there's quite a wide variation. The only way to know for sure is to cc each individual head.
I used the plexiglass method to cc two heads that were in my possession (as well as two sets of pistons). The first (on my old 4.0) was 56.5cc while the second (on my stroker) is 57.0cc.

http://www.summitracing.com/search/part ... nVT85FjbcQ

An economy kit would do fine for our purposes.
1992 XJ 4.6 Stroker - 5MT - Sold :cry: Stroker build-up, Stroker "recipes"
2006 Mustang GT - 5MT - Midlife crisis car :D with Mods

str8-6
I think I'll order a "tab"
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Re: Combustion chamber volume?

Post by str8-6 » February 9th, 2015, 5:44 am

OK,thanks Dino,suppose it's time to go trough the shack to see if I can find the meassuring stuff somewhere in all the junk that mysteriously pile up there as the years go by...

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SilverXJ
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Re: Combustion chamber volume?

Post by SilverXJ » February 9th, 2015, 11:34 am

I CC'd the chambers on my polished chamber 0630 head:
1: 57.2 cc
2: 58.4 cc
3: 58.6 cc
4: 58.2 cc
5: 58.0 cc
6: 58.4 cc

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Re: Combustion chamber volume?

Post by Cheromaniac » February 9th, 2015, 8:48 pm

Looks like you gained about 1.5cc with the chamber polishing.
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Russ Pottenger
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Re: Combustion chamber volume?

Post by Russ Pottenger » April 1st, 2015, 8:43 pm

Only thing I'll add is if your doing your own chamber work and later your
going to take your head to your local machine shop for a min surface, figure
into your calculations that every .006 surfaced from the head surface you'll lose
about 1cc.

My chambers when done are usually 62 to 63 and shoot for .035 to .045 piston to head.
.028 to .032 on the race engines with bushed rods.


Russ

str8-6
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Re: Combustion chamber volume?

Post by str8-6 » April 2nd, 2015, 2:19 am

Thanks Russ,Silver and Dino,if my calculations is right I will have a quench of .055 (decked .031+head milled .007) would have liked to get a .43 quench but then the comp.ratio would have ended up at 11."something" so we stopped at those values,comp.ratio is now (acc. to Comp calculator on here) around 10.6

I haven't done any work to the bowls yet,waitng for some spare time to get the head over to my machinist-buddy so he can get the valveseats and valves done,ports are done and despite the fact that I've only done a couple of heads before and that was 25 years ago they look pretty good for a homeported head got some buddys that's been porting heads way more than me and they have given me a thumbs up for the port work made by me ,myself and I...,rather even in size's and form so they think I did good :D .

Not flowed and will not be,it is what it is and not a bit more... A buddy that has a flowbench did hit the famous wall sometime ago and is not well yet so I will not push him to flow my head even if he promised me to do it,it's better to let him get well without pressure from me about my stuff and his promises...

And in the matter of polishing combustion chambers;I not sure that a highly polished surface in that area is all that good,when looking at comb. chambers from "the big guys" doing heads for racing,they often leave the chambers quite coarse,some of them even suggests that IF you have to grind the surface and it gets too smooth You should use a punch and make dimples all over the chamber to make it easier for the mixture to let go of the chamber walls,I dont know if thats just for racing stuff but whats good for racing usually works for street-engines to. And tests done by a Swedish muffler-manufacturer (Apple Racing) shows that their muffler which is punched with all the holes in the tube going trough it actually flows more air than a straight pipe of the same lenght and dimension without holes.

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Re: Combustion chamber volume?

Post by Brianj5600 » October 4th, 2019, 4:29 pm

Russ Pottenger wrote:
April 1st, 2015, 8:43 pm
Only thing I'll add is if your doing your own chamber work and later your
going to take your head to your local machine shop for a min surface, figure
into your calculations that every .006 surfaced from the head surface you'll lose
about 1cc.

My chambers when done are usually 62 to 63 and shoot for .035 to .045 piston to head.
.028 to .032 on the race engines with bushed rods.


Russ
I am curious why you run the quench tighter on a race engine? Just more time consuming?

Russ Pottenger
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Re: Combustion chamber volume?

Post by Russ Pottenger » October 7th, 2019, 10:28 am

Correct.
Any engine with a closed combustion chamber cylinder head will benefit from a minimal piston to cylinder head clearance at TDC.

I have and will build Jeep Strokers that are as close as .026 but It will Require close tolerance Machine work.

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