340 camshaft question, yea another one.
My timing is set at 16* initial, mechanical is 18* at 3400 and the vac can is 14* at 14 inches. I have it connected to manifold vacuum so it had 21* total at idle.
I have been looking at the stock 340 cam for my car, I'd be fine with that.
There it is
The 21 at idle is killing it. Put that Vcan back on the spatk-port, the 274 is waaaay too small a cam to be able to run that way.
When you remove the vcan the idle speed will drop, then when you put it into gear, there won't be as sudden nor as huge an airflo decrease through the carb nor will there be a sudden drop out of timing due to the Vcan backing off when the manifold vacuum drops.
That's probably the biggest contributor to your problem.
If you remove the carb right now and flip it over you will probably see the T-ports as good as covered, and SHAZZAM that is the problem! That is exactly what I've been talking about. Now go look! If I'm right, put that 274 back in!
Now heres the deal with the factory 340 cam, listen carefully;
IT WILL NOT MAKE ONE SINGLE BIT OF DIFFERENCE
And here's why. Your 274/110 cam in at 106* has an ICA of 63*, and
the 340 cam is 268/114 in at 110 has an ICA of 64*
Exactly 1 degree later, so the idle torque is likely to be exactly the same! Now the 340 cam will idle slightly smoother on account of the overlap is only 44*.
But sliding one in there will make ZERO idle difference.