Advanced Hemi 212cc Predator Build

[bob58o]

Black Mamba Jr Cam Card Specs and Event Timing at 0.050"

I can never find this when I need it because the picture of the Cam Card is in Buggy thread. Appearantly Cam event timing needs to be considered when considering optimizing CR for a given octane.

Maybe a 9 : 1 Corrected CR is OK? I've read shoot for 9.2 : 1 Corrected CR, but think it was for a v-twin Harley?
Working with some online calculators now.

Black Mamba Jr Cam

Lobe Center : 104 deg
Duration : 230 deg (both intake and exhaust)
Lift : 0.275" (both intake and exhaust)

INTAKE (0.050" Lift Event Timing)
Open : 11 deg BTDC
Closes: 39 deg TBDC

EXHAUST (0.050" Lift Event Timing)
Open : 39 deg BBDC
Closes : 11 deg ATDC

 

[bob58o]

Corrected Compression

Maybe I'll be filling up at Chicagoland Speedway in Joliet?
Maybe this is a torque cam? Looks like I'm very close to the limits of 93 octane!

Intake closes at 39 degress ABDC

18cc
0.027" gasket
11.11 : 1 Static Compression
10.3 : 1 Corrected Compression
220 psi

18cc
0.045" gasket
10.33 : 1 Static Compression
9.6 : 1 Corrected Compression
201 psi

18.5cc Polished Head
0.027" gasket
10.87 : 1 Static Compression
10.10 : 1 Corrected Compression
215 psi

18.5cc Polished Head
0.045" gasket
10.13 : 1 Static Compression
9.41 : 1 Corrected Compression
196 psi


Not sure the exact "compression vs octane required" for this specific head, so I'd rather error on the side of caution.

It looks like the thick gasket and polishing are in my near future. Hopefully 93 octane will work????????????????????????

Still will labor through the P2V clearance measurements so I know I have room for the cam's lift.

 

[bob58o]

So the closest to concrete numbers for 93 octane I could find were 9.2:1 corrected compression or 190 psi?

I've heard Aluminum head and hemispherical chambers are better for allowing more compression without knock/ping/detonation/pre-igntion? I've heard people running 9.5 corrected compression and also people shooting for 200-210 psi for a 93 octane build?

What could I do???????????????
- Retard Timing - less power - less GAB
- Enrichen the Mix - less power - less GAB
- Enlarge the Chamber - less power - less GAB

- Use 100 octane - Maximize the power of the beast I built - More Power - MORE GAB!

I think you guys can see where I am leaning.....
Please correct any of my obvious flaws or suggest ideas, but without changes that will cost power, I see 100 octane as my best option????????????????????

 

[Poboy kartman]

So the closest to concrete numbers for 93 octane I could find were 9.2:1 corrected compression or 190 psi?

I've heard Aluminum head and hemispherical chambers are better for allowing more compression without knock/ping/detonation/pre-igntion? I've heard people running 9.5 corrected compression and also people shooting for 200-210 psi for a 93 octane build?

What could I do???????????????
- Retard Timing - less power - less GAB
- Enrichen the Mix - less power - less GAB
- Enlarge the Chamber - less power - less GAB

- Use 100 octane - Maximize the power of the beast I built - More Power - MORE GAB!

I think you guys can see where I am leaning.....
Please correct any of my obvious flaws or suggest ideas, but without changes that will cost power, I see 100 octane as my best option????????????????????

This is going beyond my limited knowledge...maybe FreeRunner can help.

 

[bob58o]

This is going beyond my limited knowledge...maybe FreeRunner can help.

Well I don't plan to drive to TX anytime soon, so I'm not that worried about the price of the fuel. A few gallons at $7.50?? (don't really know the price) won't break me and would give me comfort and allow me to start my engine without fear!

 

[ezcome-ezgo]

There can't be less GAB at this point. You're all in. "I've heard" of people scratching an itch till they bleed to death too.

 

[bob58o]

There can't be less GAB at this point. You're all in. "I've heard" of people scratching an itch till they bleed to death too.

Nope no itches. All cleared up.

---------- Post added at 02:08 PM ---------- Previous post was at 02:06 PM ----------

Stressful math puts me in my happy place. (I know... I'm sick)
But here is some comic relief for y'all.
https://www.youtube.com/watch?v=3WyMSrAgPKc&list=PL9iqmrHcvcZ8sV5bl-6VjpWP-hIB3CCG3

---------- Post added at 02:24 PM ---------- Previous post was at 02:08 PM ----------

OK. Time to shine! Future so bright, you're going to need shades! lol

---------- Post added at 02:27 PM ---------- Previous post was at 02:24 PM ----------

Ok, last one. LOL
https://www.youtube.com/watch?v=Dd7FixvoKBw

 

[bob58o]

Some time with the 120 grit flap wheel makes me wish I started with the 80.

Getting there!?
Looks like something scratched though the intake???

 

[bob58o]

I'm not very good at this. I may need another 120 flap wheel. It seems like it's going OK?

 

[bob58o]

No more time before work...
I'm training a bouncer to be a bartender. They are probably training him to replace me. Let's see how much I share... Job Security!!!
TBC

 

[bob58o]

Just lean in a lil closer now..
A few more drinks and she'll be pretty enough to take home! JK

 

[bob58o]

Progress report

 

[Poboy kartman]

Progress report

Maybe back up on the drinks there Bob!

 

[Denny]

At only 9.5-1 you should be good to go with pump gas premium. At 10-1 go with the 100 octane or aviation gas.

Denny

 

[bob58o]

At only 9.5-1 you should be good to go with pump gas premium. At 10-1 go with the 100 octane or aviation gas.

Denny

Thanks, I will be looking at racing fuels near me.

I was spending time reading about static vs dynamic compression and I this is what I found.
http://www.yellowbullet.com/forum/showthread.php?t=472656

Given the same static compression, one cam could have much higher dynamic compression than another. Depending on how long the intake valve closes after bottom dead center.

If the intake valve closes right at BDC, then the whole 212cc could be compressed and Static Compression Ratio would equal Dynamic Compression Ratio.

Since the intake closes after BDC, the actual Dynamic compression is less.


My intake closes at 39 degrees (0.050") ABDC and calculates a corrected compression of 9.4 : 1.

Hold the intake open longer and close it at 59 degrees ABDC and now the only getting around 8.5 : 1 corrected compression.

This is only important at low RPM with no Ramming effects. Higher RPM operation makes use of Ramming more air in after the piston starts moving up.


I believe it is called Volumetric Efficiency - it is better at higher RPM but at low RPM (2000), the dynamic compression drops. This is why some racing cams can't make good power at low RPMs???????????

Also when in the powerband, (not idling), Volumetic Efficiency can increase to 100% or more (if forced induction is used). Meaning that that dynamic compression is equal to (or more) than static compression.

Just sharing!

I will use some good stuff to be safe.

 

[bob58o]

IIRC, my first post was about a chain roller guide...

I was wondering who responded cause I did't know anybody yet...

First Response Team. Thanks for the help Poboy! LOL

 

[bob58o]

Free Engine Analyzer Pro Demo.

IDK how close it? Doesn't ask about valve springs. Can't start a build from scratch - must modify an established engine.

15HP at 6000 RPM! but I guessed on some flow data and stuff and figuring out the cam event timing. Just starting to play with it.

 

[rk970]

You cannot use the .050" cam timing values when calculating dynamic compression ratio!... compression starts when the intake valve closes. Not when it is still hanging open .050"..
This is what tim sent me
(For F*** sakes)
RK
"Hi Robert,

The NO LASH valve timing at .006" lifter rise on the mamba JR is:

intake open 29.275

intake close 57.275

exhaust open 57.275

exhaust close 29.275

Thanks,

Tim"

I can never find this when I need it because the picture of the Cam Card is in Buggy thread. Appearantly Cam event timing needs to be considered when considering optimizing CR for a given octane.

Maybe a 9 : 1 Corrected CR is OK? I've read shoot for 9.2 : 1 Corrected CR, but think it was for a v-twin Harley?
Working with some online calculators now.

Black Mamba Jr Cam

Lobe Center : 104 deg
Duration : 230 deg (both intake and exhaust)
Lift : 0.275" (both intake and exhaust)

INTAKE (0.050" Lift Event Timing)
Open : 11 deg BTDC
Closes: 39 deg TBDC

EXHAUST (0.050" Lift Event Timing)
Open : 39 deg BBDC
Closes : 11 deg ATDC

 

[bob58o]

You cannot use the .050" cam timing values when calculating dynamic compression ratio!... compression starts when the intake valve closes. Not when it is still hanging open .050"..
This is what tim sent me
(For F*** sakes)
RK
"Hi Robert,

The NO LASH valve timing at .006" lifter rise on the mamba JR is:

intake open 29.275

intake close 57.275

exhaust open 57.275

exhaust close 29.275

Thanks,

Tim"

Thank You very much. I went back to look for that post from a while back. It was even more confusing back then, but I think I got it now.

Thanks for taking the time to read along! What is your opinion about DCR equals SCR at an RPM when ramming effects allow air to be forced into the cylinder even after the piston has started back up???

---------- Post added at 01:55 PM ---------- Previous post was at 01:48 PM ----------

Using 57 instead of 39 degrees, I get 8.5 instead of 9.4 DCR, but the Hammer Performance Calc I found asks for 0.053 close timing??? so I used the 0.050" Timing on the card?

 

[Poboy kartman]

Ramming effect? Not happening...What DOES. happen is overlap...The exhaust valve is still open at the point the piston is starting up....the scavanging effect of the exhaust gases exiting helps suck more fresh fuel charge in...once that exhaust valve closes...it's all over...only bad things can happen after that.