alkemyst
07-17-2008, 07:22 PM
My other post is about my car being way down on power. I am opening it up saturday morning, but i did double check the alignment of the two cams...the one thing I didn't double check was if I moved at all from TDC at the crank while doing this...I doubt this is the issue as I don't think it would be running so smoothly...
I am trying to do the math and based on what my 232 cams do..if I move an exhaust cam to intake it's going to be about 75.8 degrees off, this is '4 teeth' (each cam tooth is 18.95 degrees)...so moving the cam 4 teeth ccw brings the timing back to what it should be.
Now I am looking at my 248 exhaust cam being practically on the money with the four tooth method and any advance or retard will move the cam out of this spec.
If I am right (which would show why many that just throw the 248 cam in without any gears is why they are making decent power and why I am not with my 2.5 deg. advance) then while using my 232 exh as an exhaust cam.:
248 at 4 teeth is opening 1 deg ADTC with 3 degs overlap closing 69 deg ABDC
adv 2.5 degs would be 3.5 deg ADTC with 50 deg overlap and closing 71.5 deg ABDC
retard 2.5 degs would be 1.5 BTDC with 5.5 deg overlap and closing 66.5 ABDC
Adv seems like there is noway it'd make power.
Now some others are saying even with the 4 teeth method you are still 1.5 degrees off...that could well be, here are the numbers in that situation...
248 opens .5 BTDC with 4.5 deg overlap and 67.5 closing ABDC
adv 2.5 -2 ATDC with only 2 deg overlap and closing 70 ABDC
retard 2.5 degs would be 3 deg BTDC with 7 degrees overlap closing 65 ABDC.
All cam setups I looked at stock have 3 degs overlap and open 1 deg ATDC...closing events for the intake cams take place between 51 and 63 degs ABDC.
I don't see how anyone can say they are making power with adv. the cams 2.5 degs on a 248/232 setup with the 248 from a 91-93 S13.
It seems not retarding or advancing will put you closest to stock timing.
Maybe my math is off...anyone else know more? Not looking for links to other threads as I have seen them...looking for anyone else that knows the math here.
Å
I am trying to do the math and based on what my 232 cams do..if I move an exhaust cam to intake it's going to be about 75.8 degrees off, this is '4 teeth' (each cam tooth is 18.95 degrees)...so moving the cam 4 teeth ccw brings the timing back to what it should be.
Now I am looking at my 248 exhaust cam being practically on the money with the four tooth method and any advance or retard will move the cam out of this spec.
If I am right (which would show why many that just throw the 248 cam in without any gears is why they are making decent power and why I am not with my 2.5 deg. advance) then while using my 232 exh as an exhaust cam.:
248 at 4 teeth is opening 1 deg ADTC with 3 degs overlap closing 69 deg ABDC
adv 2.5 degs would be 3.5 deg ADTC with 50 deg overlap and closing 71.5 deg ABDC
retard 2.5 degs would be 1.5 BTDC with 5.5 deg overlap and closing 66.5 ABDC
Adv seems like there is noway it'd make power.
Now some others are saying even with the 4 teeth method you are still 1.5 degrees off...that could well be, here are the numbers in that situation...
248 opens .5 BTDC with 4.5 deg overlap and 67.5 closing ABDC
adv 2.5 -2 ATDC with only 2 deg overlap and closing 70 ABDC
retard 2.5 degs would be 3 deg BTDC with 7 degrees overlap closing 65 ABDC.
All cam setups I looked at stock have 3 degs overlap and open 1 deg ATDC...closing events for the intake cams take place between 51 and 63 degs ABDC.
I don't see how anyone can say they are making power with adv. the cams 2.5 degs on a 248/232 setup with the 248 from a 91-93 S13.
It seems not retarding or advancing will put you closest to stock timing.
Maybe my math is off...anyone else know more? Not looking for links to other threads as I have seen them...looking for anyone else that knows the math here.
Å