My Combo, Manifold Or Ported VAC Advance, We'll See...
With the Predator, 15 mpg may be a dream, but one I'll aim for.
I am going to play with the rate the manifold vac advance comes in, and ported may be the better option.
Yes you are right about the distributor, and I may at some point change it. In fact I would much prefer one I could put a curve in, but for now I'm stuck with this one.
Thanks for the comments.
Just so you know, I just went through a similar thing like MVA today. My friend has a 73 Duster with a 340 I did.
A measured 10.64:1 and a little 280/.480 lift Chrysler circle track cam.
I would rather he had a cam that had LESS seat timing with the same at .050 timing. Or quicker.
Anyway, his cousin is a true bubble gummer. And he reads forums and takes every word as gospel.
So when said cousin was helping him last year, he did a “POWER TIMING” thing…some bull squirt nonsense like that.
I had no idea what he had done.
First he went down a plug range. Then he set the timing “by ear”. And he did by that by doing what I detest.
He set the idle low, then he just turned the distributor until his EAR said it was set. He never hit it with a timing light and didn’t have a clue what the total was.
I fixed the **** I had to and we took it for a drive. I’m thinking this thing idles like straight garbage and it feels like it’s down on power.
I’m trying to figure out WTF happened since the last time I drove it.
I pull a plug and it’s the wrong heat range. And I say who the frick put these plugs in? He says his cousin.
So I put the correct plugs in and it’s a bit better but the idle is crap on a cracker.
So I take out the timing light. I’m STUNNED when it says 30 initial at 900 RPM. And 40 total. Unreal.
Now I’m doing the Daffy Duck, loosing my mind. I’m thinking the distributor came loose so I try and tighten it up. But it’s tighter than (add in whatever you want here) so I asked just what went down after the last time I drove it.
That’s when the story comes out. So I said WTF is he doing. The upshot is he’s an idiot.
So I reset the timing at 24 initial and 36 total at 6k. Right where it should be.
And guess what? It now idles nicely at 1k and when it drops into gear it goes to 900 rpm.
It didn’t want all that initial. Why? Because the cam matches the compression ratio.
I’d bet everything I have that if I picked a different cam it would take even less initial timing and maybe a bit less at rpm. To really sort it out it shoud be on the dyno.
Like I say, MVA is a bandaid for a build with two much cam, not enough compression or both.
Too bad his bone headed cousin doesn’t have the common sense God gave a hammer. He’d be better off if he was as smart as a hammer.
A ball peen hammer, not a carpenters hammer. Those hammers are pretty dumb. No offense to carpenters here.
Edit: I forgot to point out that that 6 degrees of initial pissed it off at idle. My friend is a car guy but not a tuner. Even he could tell as soon as it fired up it was idling better than it was before.