cylinder pressure and dynamic compression with different camshafts`

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elitesrock2

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building a solid roller 416 stroker motor and i was wondering about cylinder pressure and dynamic compression and what i should shoot for. wanna run it on 92 octane pump gas. is a 416 with heavily ported iron x heads. looking at the horsepressure article on hughes they shoot for a 165 cylinder pressure with iron heads which put me at 10.5:1 compression and 8.17 dynamic. so is this what i should be looking for or what compression should i play with. inputs are 8 cylinders, 4.070 bore, 4 inch stroke, 6.123 rod length, 10.5:1,63 degrees abdc and 1800 altitude
 
abdc is what to look at.
 
Read this article. You can download the calculator.
I run a 340 10:1 J head at sea level on 93 with 282S, 185 crank psi
You need the extra compression at higher elevation to make good power.
 
Read this article. You can download the calculator.
I run a 340 10:1 J head at sea level on 93 with 282S, 185 crank psi
You need the extra compression at higher elevation to make good power.
Interesting, do tell what pistons and timing...
 
building a solid roller 416 stroker motor and i was wondering about cylinder pressure and dynamic compression and what i should shoot for. wanna run it on 92 octane pump gas. is a 416 with heavily ported iron x heads. looking at the horsepressure article on hughes they shoot for a 165 cylinder pressure with iron heads which put me at 10.5:1 compression and 8.17 dynamic. so is this what i should be looking for or what compression should i play with. inputs are 8 cylinders, 4.070 bore, 4 inch stroke, 6.123 rod length, 10.5:1,63 degrees abdc and 1800 altitude
If you have a tight quench you can run over 8.5 dynamic. For instance I run 8.8 @185 with quench dome pistons and in the guy aboves post , he says he runs about the same. If you are talkng about flat tops with the x's open chamber, I say stay about 160-165 @ sea level w/91 , in line with Hughes, cause I don't want to put you in a stressful spot...but I would go for 8.5/172 Cranking@1800ft and that would take ivc 58, but unless you're making records...kind of small to go changing the cam, just use a thin gasket or mill the heads .018
 
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L2316F40 deburred and polished top
66 cc chamber deburred
25 initial 35 total mechanical
run a good cooling system and proper AFR
Show your work for me if you can, because something's not adding up there.
Who did your math?
I get no where near the dynamic you say. I could run that high of timing too, but not under wot, and its not about afr...I even question 93 making the diff, polished piston tops or not, the chamber is where the trouble really lies...but hey..... I think your math is quite possibly jumbled. Because I'm coming up with your dynamic in the 7's and 155ish cranking.
But I won't call you a liar, I'm not there to see, check , or disprove it, so good job on whatever you got there!

I did go out and recheck mine yesterday during a break in the rain and with the carb pinned open have 190 cranking, yikes.
 
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Show your work for me if you can, because something's not adding up there.
Who did your math?
I get no where near the dynamic you say. I could run that high of timing too, but not under wot, and its not about afr...I even question 93 making the diff, polished piston tops or not, the chamber is where the trouble really lies...but hey..... I think your math is quite possibly jumbled. Because I'm coming up with your dynamic in the 7's and 155ish cranking.
But I won't call you a liar, I'm not there to see, check , or disprove it, so good job on whatever you got there!

I did go out and recheck mine yesterday during a break in the rain and with the carb pinned open have 190 cranking, yikes.
I never stated my DCR, simply wrote what my last compression check was. A compression gauge is for checking engine health. My gauge is not calibrated and the only use is are all the cylinders even. Every motor I've built is measured by me. This motor is 7.81 dynamic.
4.08 bore flat top .018 above deck +7.5 cc valve relief 3.31 stroke 6.123 rod
66 cc head felpro 1008 .039 x 4.180
282S ICA 67*
 
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this is an engine i'm in process of building currently. It will be in a 4x4 ramcharger. But i have ported x heads, performer rpm airgap intake, fitech efi, headman headers. the cooling system will be top notch. so im just trying to figure out the compression and all before i put this engine together i have yet to get pistons or head gaskets
 
I never stated my DCR, simply wrote what my last compression check was. A compression gauge is for checking engine health. My gauge is not calibrated and the only use is are all the cylinders even. Every motor I've built is measured by me. This motor is 7.81 dynamic.
4.08 bore flat top .018 above deck +7.5 cc valve relief 3.31 stroke 6.123 rod
66 cc head felpro 1008 .039 x 4.180
282S ICA 67*
So now your mill is 9.18 static and ivc 67 making 7.15 @ 138 , whatever you say.
Your post is hurting my eyes to read, so I'm pulling the ejection seat lever. Good luck op...over n out!
 
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So now your mill is 9.18 static and ivc 67 making 7.15 @ 138 , whatever you say.
Your post is hurting my eyes to read, so I'm pulling the ejection seat lever. Good luck op...over n out!

i just ran his numbers on the csg engine calc tool and it's showing 10.04:1 static.
around 9.2 if his piston were below the deck by .018...
 
Bingo! Pistons are .018 above deck. 10:1, 7.81 DCR car hauls the mail.
I use the Wallace calculators, I got you at 10.01 static...but the ivc is not giving the quite the DCR you claim. First is was .019 now its .018 doesn't even matter when you edit every post you make till makes sense ....but still doesn't make sense, the cranking doesn't match.imo Whatever you have you have, now have fun!

2017-02-08_13-43-36.png
 
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building a solid roller 416 stroker motor and i was wondering about cylinder pressure and dynamic compression and what i should shoot for. wanna run it on 92 octane pump gas. is a 416 with heavily ported iron x heads. looking at the horsepressure article on hughes they shoot for a 165 cylinder pressure with iron heads which put me at 10.5:1 compression and 8.17 dynamic. so is this what i should be looking for or what compression should i play with. inputs are 8 cylinders, 4.070 bore, 4 inch stroke, 6.123 rod length, 10.5:1,63 degrees abdc and 1800 altitude

Let's start over.
First decide at what rpm you want the power to be and the width of your powerband requirement.Your vehicle weight,gears and TC will all need to be taken into consideration before making these decisions.
From that you can select a cam. From that you get the ICA. From that you target the Dcr. Once the Dcr is targeted, you can adjust the Scr to get that Dcr. Then you find out if it's possible to do what you want to do. If it isn't, then you have learned what won't work, and start over.
 
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I never stated my DCR, simply wrote what my last compression check was. A compression gauge is for checking engine health. My gauge is not calibrated and the only use is are all the cylinders even. Every motor I've built is measured by me. This motor is 7.81 dynamic.
4.08 bore flat top .018 above deck +7.5 cc valve relief 3.31 stroke 6.123 rod
66 cc head felpro 1008 .039 x 4.180
282S ICA 67*

That clears that up.
Go get a new gauge and next time, if you know its not calibrated...don't offer it's reading as some bases of advice.
 
That clears that up.
Go get a new gauge and next time, if you know its not calibrated...don't offer it's reading as some bases of advice.
You need to read, not make assumptions, and stop calling me a liar.
I will post whatever I want if I think it will help someone.
 
You need to read, not make assumptions, and stop calling me a liar.
I will post whatever I want if I think it will help someone.
If you don't wanna own up to your misinformation then you're not trying to help anyone and i will call you a liar. You knew the gauge was bad yet offer its reading....why? It's worthless!!
How are you helping by specifically telling the op you have 185 cranking when clearly your gauge is ****, you admit it and the math shows you in the 155 range...which is 87 octane territory...how is that helping.
It isn't, you don't run that on pump without good quench and careful tune.
Stop arguing against truth and hi jacking the thread.
 
All this info could have quickly been found anyway using the search feature as it's been pounded and pounded into the pavement. Now we have another stupid thread too end up 15 pages worth of arguing and dick swinging.
 
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