2FastZeder

Hello
And great forum
I've been trying to find out the SCR and DCR for my engine but every damb online calculator gives me a different answer.
Can some one help my specs are.


Cylinder Head Volume (cc) -->52cc milled head
Piston Head Volume (cc) -12cc Mahle
Gasket Thickness (in.) .016 modded gasket
Gasket Bore (in.) 4.100
Cylinder Bore Diameter (in.) 4.030
Deck Clearance (in.) 0.027??????? not sure yet
Stroke (in.) 3.875
Rod Length (in.) 6"
Intake Closing Point (degrees) ABDC @ 0.050 lift plus 15 degrees =84

if you need more info please let me know

Any help would be greatly appreciated
thank you

bw_hunter

Wallace racing calculator puts the compression ratio at 12.5:1

2FastZeder

Well, that sucks when I bought the parts it was supposed to be around 10.75-1

The highest octane gas I got to run on at the pump is 94 octane.

what would the compression be if I put in a .041 head gasket???

Thank you so much for your expertise, Hunter.

Best Regards

PS
I don't understand why I keep getting different answers from the comp cals.????

2FastZeder

I tried that calculator at .041 gasket thickness and it came out to 17.84????

2FastZeder

I was adding minus "-" in front of dished piston relief volume without it the numbers are more accurate not the same but close. I don't know what I'm punching in the wrong?

what the highest ratio I can run on Sunoco Ultra 94 octane???

Thanks

Injuneer

Octane requirement is determined by DCR, not SCR.

How sure are you of the 52cc figure on the combustion chamber? In your earlier posts it appeared you had not actually measured it, but were trying to calculate it based on how much the heads were milled.

2FastZeder

This is a different engine, the last engine your referring to is a 350 this is a stroker 395. The head has been milled a little over 1.25mm.

I'm just wondering how much octane will I need to run on this setup with around 12-1

time to do a bit more research
the last engine ran like a fn bat out of hell I can't imagine what this forged stroker will run like, I just don't want to detonate.

Is there also a better cam choice than the XFI292 for mid to upper-end power like in the 7 grand range?

2FastZeder

OK i'm getting the right answers now.

STATIC COMPRESSION RATIO 11.244

DYNAMIC EFFECTIVE COMPRESSION RATIO 7.498

NOW HOW HIGH OCTANE DO I NEED???

THANKS

Injuneer

What input did you change to get the "right answers"? Which calculator did you use?

DCR looks low.... Why do you add 15-deg to the intake closing? The cam card on the Comp Cam website indicates "Valve Timing @ 0.006" lift", not 0.050". The 292 XFI HR13 IC is 75-deg ABDC. And events are based on a 1.6X rocker. I think the 15-deg adder only applies to a cam card based on 0.050" lift. Educate me.

2FastZeder

WOW at 45,000 posts you do your homework!!!

I did not notice the .050 and .006 lift so I'm off again F@$&!

Why is this so hard last time the machine shop guaranteed mee the results and I came up with the same answer using an online calculator?????

So I don't know WTF is going on know this IS NO HILARIOUS BUT YET AGAIN IT IS.

ARRRRRRR

Please Help

2FastZeder

OK according to the Wallace Racing Calculator I have a DCR of 8.59:1 HOW much Octane Can I run would I be safe at 94 Octane before the computer retards it?
"INJUNEER" you were right it was kinda low! Nice one! Now Whats the lowest octane I can run???

Thanks

Injuneer

Just to make your quest even more unpleasant ... answer is never absolute. But you should be fine with 91-92 octane pump gas. Other factors affecting detonation - high coolant temps, high inlet air temps, lean A/F mix, too much spark advance, quench issues, too hot spark plugs.

And the altitude where you drive makes a difference. Did you use the Wallace DCR calculator? Did you enter the correct altitude (Wallace calls it "Target Altitude")? If you are at or near sea level, enter "0".... always safe. If you are in Denver, DCR would only be 80% of what it is at sea level.

2FastZeder

WOW Again Thanks, A lot FRED
I got a 160' thermostat and engaged the fans earlier.
I got a Moroso CAI kit
12.5 A/F Ratio target
Spark retarded due to nitrous but off nitrous not sure yet
Spark plugs are two steps cooler E3.108 race plugs was warned about fouling up street driving,
Not sure about quench got to look that up and measure it out.
Yes, I used the Wallace DCR altitude is less than 1000'.

Thanks again Fred now on to study quench height.

2FastZeder

So at 94 Octane, I should not experience retard issues?

Injuneer

Sounds like you are headed in the correct direction.

94 will be fine. Sunoco used to sell 94 at the pumps in NJ, but it disappeared about 10 years ago. They still have 93, as far as I know. I haven't had my car out of the garage in at least three years. I was running VP Fuels C16 (117 MON) blended with a bit of VP Air Race with the 300-shot. Last time I bought a drum it was $12/gallon. Probably up to $15 by now.