I Need help 410 Stroker timing Carb Education
@AJ/FormS why do you drill the primary throttle plates for bypass air instead of cracking the secondaries?
On a regular carb, that does
not have 4-corner idle; when you crack the secondaries for idle-air; that air is dry and has no fuel in it. So the back cylinders go lean, and the engine idles rough.
It will always have a rough idle, cuz the front cylinders are not only doing most of the work, but are also dragging the back ones along..
To compensate, you have to either
1) add more fuel in the primaries, and then the front cylinders go rich. or
2) increase the timing, or
3) crank the idle speed up.......
all of which are bandaids,
Yeah with an automatic, you can make that work, cuz you have the fluid coupling. But the final result is, the engine will not idle down sufficiently for first gear operation with a 4-speed at very low rpm. With an automatic, you can get away with a lot of things, that you cannot, with a manual trans.
So if you have a 4-corner idle carb, that's cool, you can crack the secondaries and or introduce idle-fuel thru the rear mixture screws.
But your cam size (274/110) is on the borderline of being too small for use with a 4-corner idle system, because; you will have to adjust the screws so small and so fine, that you may not be able to get the transfer slots set right. So what usually happens is the guys will just live with it.
I'm not that kindof guy. I'm the other one, that tries to idle it down to 550 (or less) and still have enough power to idle around the parking lot. I can only do that when the transfer slot exposure is just right, otherwise she stalls under load.
But hang on; with an automatic, it only has to idle slow enough,
> that it doesn't pull too hard when stopped
> doesn't stall going into gear, nor bang hard
> is free from the dreaded tip-in sag.
But it never fails to impress me when I hear an automatic chugging across the parking lot, just above stalling, going
ka-chunkachunk-ka-chunkachunk..... cuz I know somebody put some time into making that happen.
BTW1
I've been drilling those holes since the 70s. I can't say right or wrong, but it works with no downside. If you can figure out how to get fuel into that dry air, without affecting the primaries, I'm all ears. The proof that whatever you are doing is working, is by how slow you can make it idle, and she won't stall going into gear, nor hesitate when you tip the throttles in.
BTW2
Some guys worry that at too slow an rpm, the oilpump will not supply sufficient oil.
I think that is a valid worry.
But to that I counter this; every time you start your engine, it has zero oil pressure, and all the oil has drained out of the rods, or at least most of them. Yet we do that hundreds of times every summer, for many many summers..
At 550 rpm, my 367 has just enough power to pull itself on flat level hard ground, and if I turn too sharp, the SureGrip slows her right down. My first defense is to crank more timing into her, and if I have to, I toe the clutch. She will chug, down to 500, but she may not recover.
