I have a '72 that is probably an 8 out of 10, 99.5% rust free 240Z 82k original miles. I have had this car for 10 years and have rebuilt the suspension (all new poly, shocks, NOS euro springs, factory bolts etc. etc.), added a ZXb (close ratio 5-speed) and R200 3.90 rear end, toyota 4 piston calipers up front, pertronix ignition and Accel Super Coil, and MSA 2.5" exhaust (which was added before the R200 and now barely clears the R200 - more on that later) with stock L24 exhaust manifold.
I have tuned this car by following the Z-Therapy video (i.e. checked cam timing [now on third mark), valve clearance hot, ignition timing at 10BTDC, then carbs). Also found out that ATF is way too thin for the dashpots and am now running 10-30 in them (summer).
I would like to get the most out of this setup first and have it in the best state of tune possible. Then, perhaps look at another cam etc. I am looking for input on the following and any other suggestions from people who have a similar setup:
1. Will my cam timing being set on the 3rd mark, meaning the chain is stretched but still able to be adjusted out, cause issues (i.e. if I replace the timing chain and put it back to the 1st mark or 2nd as some people have suggested for more torque)?
2. In terms of cams, has anyone had experience putting the "C" cam (this was suggested by Robello Racing) in this engine? So far I cannot find any posts that tell me the different cam profiles for stock Nissan L6 camshafts (I have heard there is an A and a C).
3. I have read the stock manifold is very good unless you do some major changes to this engine in terms of flow, is this your experience -- even if going to the "C" cam? Keep in mind I have pretty low backpressure with that 2.5" exhaust.
4. What would be the effect of adding SM needles to this (my current) setup?
I typically drive the car between 2-4k rpm (will accelerate to 5-5.5k if I get on it). The 5-speed helped the mileage as the car tacs about 3.9k at 75mph in 5th for cruising.