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**Urgent help please** with BC cams and JWT sprockets

Posted: Sun Sep 01, 2019 9:47 am
by scoobydo
So currently they are as follows

intake opens 3.8 ATDC (cam card calls for 12 ATDC), Closes 38 ABDC (cam card calls for 50 ABDC) all at 50thou lift
Ex opens 16.7 BBDC (cam card calls for 47 BBDC), Closes 12.5 ATDC (cam card calls for 9 BTDC) all at 50thou lift

I am not quite getting the sprockets or what I am to do. Intake looks like I need to either retard the cam or advance it by 7.5 so hole 4 or C cannot get it straight in my head what the relationship is between the cam and the crank. Exhaust cam looks like 1 tooth out 18.95 degrees (is this forward or backwards) plus either hole 5 or hole d for 10 degrees making it 45.65 degrees.

Please help :-)

Re: **Urgent help please** with BC cams and JWT sprockets

Posted: Thu Sep 19, 2019 4:25 pm
by scoobydo
So in the end it was hole 3 on the inlet and hole 4 on the exhaust

inlet opens 14.2 ATDC, closes 49 ABDC
ex opens 44.6 BBDC, closes 15.3 BTDC

Cam card wants

inlet opens 12 ATDC, closes 50 ABDC
ex opens 47 BBDC, closes 9 BTDC

Running this through the calculator I get

Intake Duration is 214.80 degrees.
Exhaust Duration is 209.30 degrees.
Installed Intake Centerline is 121.60 degrees ATDC.
Installed Exhaust Centerline is 119.95 degrees BTDC.
LSA is 120.8 degrees
Overlap is -29.50 degrees.

Anyone got any insight into setting it up as my torque was dropping of early . Note ex manifold is log style

Re: **Urgent help please** with BC cams and JWT sprockets

Posted: Thu Sep 26, 2019 12:16 pm
by adamky
This gives you some basic info on how cam tuning affects your powerband: ... uning.html
For more top end, you want to decrease overlap. I'd start by retarding the intake cam 2.5-5* and advancing the exhaust 2.5-5*. That will give a better idle and more top end power, but u might lose some mid-range torque