Are these numbers real?

[SilverXJ]

yes, 9.3 SCR, .055 quench, 0 advance on the cam (not 100% sure), comp cam 68-231-4. These are the numbers the machine shop gave me, they put it together not me. I can't run 89 octane or it will ping, I have to make sure I run a good quality 93 fuel.

FYI: use a double roller timing chain.

I was running a similar combo (9.5 SRC, 8.29 DCR) . I had a .044" quench. With the 68-231-4 cam. I never got around to messing around with the tune that much, but IIRC if it was running rich I could run midgrade (didn't try 87). But when I started to tun, getting closer to 12.5-13:1 afr it started to ping and I had to run premium.

[SilverXJ]

That's strange, I'm running 9.25 SCR, .043 quench 214 @ .050 duration cam advanced 3 degrees, ford cobra xr3e fuel injectors, and I can run 87 octane with no ping...hmmm?

I'd be interested to know what your AFR is.

[YJason]

with anything less than 92/93 octane it will ping 2000-2800 rpm with a AFR between 14.1 and 14.5. I'm having trouble at WOT with it wanting to run a AFR of 12.8 - 13.2.

[yuppiexj]

yes, 9.3 SCR, .055 quench, 0 advance on the cam (not 100% sure), comp cam 68-231-4. These are the numbers the machine shop gave me, they put it together not me. I can't run 89 octane or it will ping, I have to make sure I run a good quality 93 fuel.

FYI: use a double roller timing chain.

That's strange, I'm running 9.25 SCR, .043 quench 214 @ .050 duration cam advanced 3 degrees, ford cobra xr3e fuel injectors, and I can run 87 octane with no ping...hmmm?

Atlanta is 1000 ft above sea level could that be enough of a difference?

[Jak Flash]

Yes to both without a doubt. For mine the difference in torque was most noticeable at low/medium rpm compared to my old modded 4.0 and that's a difference you can really feel in normal daily driving.

Perfect Thanks I will be building one. Just want to make sure its not wasting time and just jump to V8 power. Not to mention I like the Kewl factor.

It would seem that the .010 tighter quench makes the difference

Does this little change affect your performance that much? what is the best way to measure quench?

I'd be interested to know what your AFR is.

Pardon the Newbie in me but WTF is AFR?



So a brief update:

this Build was supposed to happen this February as the 4L in the Jeep was real sick. well apparently I underestimated how sick it was. On friday at lunch it Finally Shit the bed and since it is my DD at this point it was necessary to do an immediate transplant. I picked up a Low millage used 4L and installed it last Saturday.

Kind of a double edged sword, I now have the time to spend more time researching the necessities of building the right Stroker. But I really was looking forward to doing it this winter. I'm kind of relieved and disappointed all in the same breath. But I do Have a busy bild shedule this winter as it is. So kind of a blessing all the same.

[John]

"Pardon the Newbie in me but WTF is AFR?"

That would be air fuel ratio.
John

[Cheromaniac]

Atlanta is 1000 ft above sea level could that be enough of a difference?

No. At 1000ft the air is only 3% thinner than at sea level and in any event, the MAP sensor will compensate for altitude changes by maintaining the same A/F ratio.

[dwg86]

That's strange, I'm running 9.25 SCR, .043 quench 214 @ .050 duration cam advanced 3 degrees, ford cobra xr3e fuel injectors, and I can run 87 octane with no ping...hmmm?

I'd be interested to know what your AFR is.

I would also like to know what my AFR is. I don't have a AFR gauge installed yet. My plugs look good, maybe a little on the light side. It would be nice to know the DCR limits of 87, 89,and 91 octane fuel.

[Jak Flash]

That's strange, I'm running 9.25 SCR, .043 quench 214 @ .050 duration cam advanced 3 degrees, ford cobra xr3e fuel injectors, and I can run 87 octane with no ping...hmmm?

I'd be interested to know what your AFR is.

I would also like to know what my AFR is. I don't have a AFR gauge installed yet. My plugs look good, maybe a little on the light side. It would be nice to know the DCR limits of 87, 89,and 91 octane fuel.

As we all know Octane controls the preignition of the engine as the cylinder compresses the fuel/air mixture. the higher the compression the more heat that is generated the higher the octane level required.

therefore, It also contols the level of heat that the Air/Fuel mixture preignites at.

Now if your engine is running lean it will generate more heat in an engine cycle. And the higher the heat the more octane to control the pinging.

you should determine if your running lean. you could lower your octane and save.

[SilverXJ]

you should determine if your running lean. you could lower your octane and save.

However, even with stock injectors a standard stroker will run 14.7:1 until it goes into open loop. No way to control that unless you want to go to a completely aftermarket EFI system.