|Topic Review (Newest First)|
|06-08-2019 12:07 PM|
As always thank you for your advice/insight. The C&B cam appears "fatter", not so "pointy" as the stock Jetronic cam (with VVT). I am assuming greater duration = greater cylinder filling.
In the past I recall using a clay/play doh material for measuring piston/valve clearance. Can we assume a minimum of .06"
|06-08-2019 08:49 AM|
The cams (109 280s 10.9mm ) are made from billet (same as the factory) so testing isn`t necessary. They are a smaller BC so you will need a supply of shims(thicker).
Cam followers are a different matter. With the poor quality aftermarket followers I suggest using the OE ones if they are still flat and smooth. Use a flat edge (like a machinist rule) against the top surface leld up to a light. If you see light between them don`t re-use it.
The only aftermarket ones I will use are the Eagle brand, and they are about 2x the cost of common aftermarket ones.
But ignore the C&B set-up specs. The 110/110 LCs are to prevent the typical buyer from having piston to valve clearance issues.
Lash of .015" (2.3mm) intake and .012"(2.5mm) exhaust
I suggest using lobe centers of 105 intake and 105 exhaust. Before starting the motor follow the instructions (below) to insure no P to V issues.
Below is my PDF file I furnish my cam customers.
CAM SET UP NOTES
Piston to Valve Clearance Check
This is very important since when cams are advanced the piston clearance reduces dramatically,
and Lobe re-design can effectively advance the valve opening.
Set Intake and exhaust cams at initial LCs as indicated by provider`s set up instructions, and lash
By running the .050 plastic wire-tie between the Intake valve & piston, and .075 - .080 on
the Exhaust side you can check if there is any interference and see that you have adequate
clearance between piston & valve. If by turning motor over by hand you feel some interferance
using a .050 thick wire-tie, (or .075 on the Exhaust) but the motor continues to roll through, you are
at the limit! YOU MUST ROLL THE MOTOR OVER OVER BOTH FORWARDS &
BACKWARDS TO BE SURE THERE IS CLEARANCE AT THE LIMITS!! REMEMBER,
WHEN OFF THROTTLE THE CHAIN TENSION REVERSES!!
If it locks up, retard the cam on the intake side, (or advance on the exhaust side) to get more
clearance. and try again until the clearance is found. Each hole on the vernier sprocket changes
the cam timing 1.5 degrees at the cam (3 degrees at the crank).
I suggest as a test to find this limit, you advance the intake cam until you do find the minimum
needed clearance, and permanently mark that point on the cam cap. That will be the point where
the cam must NOT be advanced past. Then do the same with the exhaust only retarding it until
the limit is found.
Timing initially is dependant on design of cam lobe. Aggressive large duration cams will be more
retarded.(intake) and advanced (exhaust) because of ramp & valve lift in order to fit in a engine
that is already assembled and valve relief's not designed for large cams.
Tighten and install lock nut on intake and bolt through sprocket and cam nut. Inspect carefully.
Roll the crank over by hand to verify timing.
When the intake cam is at the limit, or LC setting whichever is less advanced. You are there!
|06-07-2019 05:05 PM|
I am considering installing a C&B intake camshaft that has been laying around for a year or two. After reading another thread regarding a higher flow intake vs the exhaust flow. I cannot locate the thread, but sounds interesting. My question is it recommended to test the surface hardness of the camshaft in comparison with the buckets? The intake cam I have is labeled C&B 109xxxx. The lift and duration is greater than the original and could be fun. Engine is 2.0 Weber carbs with a two into two factory exhaust setup.