Manifold Vacuum Advance what am I not getting?
Well Turk.
Describe an engine YOU built that idles best at 12* & would not benefit from more timing at idle, whether by MVA, locked timing etc
Heads, cam, etc give us a parts rundown to all of these enquiring minds the magic numbers of this mystical engine. Now is the time to put or shut up.
I’ve never said I build engines that run on 12 initial. Never said that.
What I’m saying is regardless of what Vizard said, jacking initial timing with MVA is the WRONG way to do it.
As for what GM did or does I do not care.
This started because a guy has an engine that runs like sour owl ****. And what do we know about it?
Well, it’s down in compression and some hero put a big, sloppy and probably a slow lobe as well cam.
That’s a recipe for junk. Can you hook it to MV and make it run? Sure. Is it correct. Not even close.
Even you know why they need a that timing.
It’s because the chamber has so little combustible mixture (plus a giant assload of EGR from the stupid cam selection) that it burns like old people screw.
Slow and incomplete (don’t bother to ask how I know that…my lips are sealed on that) so you have to add all that timing just to get some kind combustion done.
It’s a poor way to fix a hunk of **** engine build.
Unless of course you like engines with horrible low speed response. It just kills power.
And for the record (going off rough numbers because I’m not at home and I haven’t done all the measuring yet..you do measure what you build don’t you??) I’ll be between 12.1 and 12.3:1. If I can it will be 12.3:1 but I’m not sure if I can get that with the head gaskets I need. That’s because some idiot blew the chambers out on these heads and I’m going to live with it until I build the W2 stuff.
Iron heads. Tunnel ram with two 800’s. Real 800’s not some silly Carterbrock ****.
Quench will be .040.
SFT Racer Brown cam. 255/255 .620/.620 105 in at 105 but I may move it ahead two but I doubt it.
That’s it. I suppose 18-20 initial, maybe and maybe 24-26 at peak torque, which should be around 5000 rpm.
Peak power should be 6600ish and I’ll shift at 7ish.
It should be no more than 32 total. Of course in low gear I’ll add 4-6 degrees of timing and in high gear I’ll pull 3-4.
That’s on pump gas.
I’ll be dropping the fuel pressure at least 2 pounds at a cruise and I’ll run ported vacuum advance. I suspect it will only take 10-12 degrees of VA.
That’s it. Nothing special and it won’t rattle its brains out. It will idle down to 750 (probably slower) if I wanted it to.
Of course, I could drop the compression to a pump gas “friendly” 10.5:1 and jam a bunch of initial in it but to what benefit?