'66 with a 2.73 in the rear?

[Rich 5150 69]

You have throttle linkage issues you need to resolve first, either your trans kickdown or throttle linkage has slop in it, or its binding up...then adjus idle speed in neutral or park, then set timming initial first / then vaccum dash pot, a small allen head wrench will slide into the dashpot turn clock wise to decrease advance which sounds like what it needs with manifold vaccum.

[Str8axle]

Originally Posted by C10Slim

I let it run for a few seconds and then slowly backed out the choke.

When you say this, are you pushing the choke knob IN or OUT?
IN should be choke off
OUT should be full choke

Also, is the engine stone cold or warmed up?

You shouldn't have to choke it if it's already warm.

[C10Slim]

Rich: I have been through the linkage several times. Its tight and smooth. I can just place a finger on the cable between the bracket and the linkage and notice the RPMs come up. This was part of setting up the TV cable. You put a gauge on the trans and are supposed to see a pressure change just by putting your fingers on the throttle cable. No kick down because of the 700r4.

I am convinced it is in timming because the only thing changed was the port used. Fixed one problem but created another. Once I get my light back I am going tog to re-time everything. I am also going to try and re-adjust the a/f mixture screws.

St8: yeah in taking the choke off(pushing the cable in). The motor was cold. Really only gave it half choke and it fired right up(first time ever!). Like I said before changing to manifold vac, even ice cold you couldn't give it any choke and get it to start.

I am pleased with the progress we are making. I really want to go drive it I am sure it hase helped the low end I originally started this thread with. I think with just a little fine tuning it will be perfect. Funny how this went from a gear question to engine tunning 101, but thanks again everyone for the input and helping me think through this problem. The input has been invaluable. That's why I love this forum!

I will get my time light back this week and keep everyone posted of the progress.
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[C10Slim]

Ok so got my light back today. Plugged off the vac ports and started her up. It would barely run the rpms were so low like 300-400rpm. I put my hand on the linkage and brought it up to about 800-850 which should be a good street idle. Well I had 4* ATDC. Yes, 4* AFTER TDC. don't know what happened there. So just for chuckles I hooked the vac line back up and checked timing again. At idle I get 12* and at 3500 I get 36* which is just about right. So maybe when we initial timed it I had the vac advance on and thought "oh it's damn near perfect."

Now my only question is... If I go back and reset the initial timing with out vac to 12* is that going to push the total timing way out of spec? Meaning I am going to have to push initial timing from -4 to 12 so is that going to add 16* to the total timing making it 52!?!?

[erock805]

Sounds like you found your culprit. Vaccum shrinks or stops under acceleration but is strong at idle. Set the mechanical as recomended by your engine builder, then you can dial in the vaccum by using the small allen wrench to total timing. Also I cant rember if you have an adustable mechanical advance timing as well? YOu can adjust when the timing comes in by using harder or softer springs, or total timing by adjusting the stops in the distributor. All this stuff takes experience and you only learn by doing. You can watch someone but it will never be as good as doing it. Keep going man...you can do it!

[fleetsidelarry]

Originally Posted by C10Slim

Ok so got my light back today. Plugged off the vac ports and started her up. It would barely run the rpms were so low like 300-400rpm. I put my hand on the linkage and brought it up to about 800-850 which should be a good street idle. Well I had 4* ATDC. Yes, 4* AFTER TDC. don't know what happened there. So just for chuckles I hooked the vac line back up and checked timing again. At idle I get 12* and at 3500 I get 36* which is just about right. So maybe when we initial timed it I had the vac advance on and thought "oh it's damn near perfect."

Now my only question is... If I go back and reset the initial timing with out vac to 12* is that going to push the total timing way out of spec? Meaning I am going to have to push initial timing from -4 to 12 so is that going to add 16* to the total timing making it 52!?!?

slim, you need to know what each of the 3 components of your advance is. you know what your initial is (-4°) and what's in your VA can (16°), now you also need to find out what your total centrifugal advance is.

with the VA unhooked and plugged off, slowly rev the engine and record the advance degrees at several RPM stages, continue increasing the revs 'til the advance stops. Normally you would subtract your initial (-4°) from this number, but in your case, since your initial is negative, add it. This is your total centrifugal. the other values you recorded will tell you (and us) what your curve looks like.

to answer your question above, yes you may end up with 52° at light-throttle cruise. This isn't necessarily bad, just maybe not optimum depending on your specific engine. as you may already know, when you hit the throttle or put a load on the engine, you will lose the vacuum portion of the total, and be at whatever your total mechanical is (initial + centrifugal). That's one of the purposes of a "vacuum advance" mechanism--to actually RETARD the ignition under certain conditions to avoid detonation. If I'm telling you stuff you already know, I apologize. and if I've steered you wrong, I'll hear about it

[C10Slim]

No guys keep the info coming! The more I read the more I learn. This has definately been a great experince for me. All my other cars are computer controlled so the tunning is done with a laptop or handheld. This is really my first experince tunning with my hands. It's fustrating at times, but very rewarding when I get something right or it starts heading in the right direction. So I apperciate it very much!

Today's update. I turned the Dist as far as I could but basically only got +4* before the vac can hit the intake. So it's basically back a 0 BTDC. I guess I am going to have to move it back a few teeth so I can get more room to adjust.

So, my question now is... If I mark the rotor location on a stationary object like maybe the linkage, a bolt or something on the fire wall. I should be able to pull the dist turn it back a few teeth and as long as I get the rotor back on my mark everything else should be ok right?

Again thanks for all the info!

[C10Slim]

I read on another forum I can just move all the plug wires over one post Counter clock wise. Would that work as well? That may actually work better for me as it's a bit easier to do.

[fleetsidelarry]

Maybe, but it may actually move your timing too much. one position on the cap is 45 distributor degrees. That's 90 crankshaft degrees! you may just go from one extreme to the other. But I'd give it a try. It's easy and you may actually end up right where you need to be. I've done it before. if you do try it, it's probably best to move one wire at a time, going around the cap, rather than pull all off at once. easier to keep the proper order.

did you make an effort to find out what your centrifugal advance is yet? if you are truly at zero initial right now, it would be really easy to read your total centrifugal

[C10Slim]

Houston we have lift off!! Switched the plug wires over one post, turned the dist back so the rotor was under the new number one. Fired it up and got it timed. I went with 17* at idle and 35* at 3500 with no vacuum. First thing I noticed was it idled much better. Then when I put it in to drive no more 400 rpm drop. Maybe fell about 150 rpm and idled perfect, no surge or anything. Then I took it for a short drive up and down the block. Pulled much harder! I still don't know if it's 400 HP hard but much harder. I u-turned at the end of the block and then stomped it. Took off with no stumble or hesitation. Again pulled hard, but not exactly what I was hoping for, BUT I looked in the rear view and there was a huge white cloud! Not sure if it was tire smoke or something burning, but I will go look for rubber later.

Man I can't thank you guys enough!! So nice to have a it running right and know it's right because I did it. So thanks!

So 2 final things. Now it seems to be running a little bit hotter. Any reason for that?
I guess I should also hook the vac back up and double check where the timing is at?

[fleetsidelarry]

if you're intent on running 17° initial, I wouldn't hook the vacuum advance up.

you've previously shown that you have 16° of advance in the vacuum can, and just stated that you have 18° of centrifugal at 3500 rpm. if you hook the VA up now you'll have 33° at idle! It may not even want to start like that.

yes engines like the advance at idle. normally on a street driven vehicle you'd get this advance from a combo of initial AND the vacuum advance so you wouldn't run so much initial.

it's not clear why you're not getting more centrifugal out of that MSD unless it's sprung too heavy right now or so light that it's already coming in at idle.

I'm sure when some of the others see these specs they'll have something to say

Glad it's getting better!

[Rich 5150 69]

Maybe his idle was to high when he set his initial timing....if not may have to change springs in dizzy to one heavier.

[fleetsidelarry]

Rich, I agree. could be either too stiff or too weak. To me, based on the chart that came with my MSD recurve kit, it's like the distributor already has stiff springs, not allowing the full available centrifugal to come in. then again, if, at idle, he's already 7° into the available 24° does that mean he only has 17° left?

'Course, there's no guarantee that my recurve kit is the same as his MSD distributor.

[fleetsidelarry]

Or, DUH Larry, it could be right in the middle.

C10Slim, sorry for the distraction I just caused. if you want to "dial-in" your timing, you'll need to know what's in the distributor.

For right now, if you want to try running with vacuum advance (as most would recommend), I believe you'll have to reduce your initial timing.

[C10Slim]

Ok so something aint right. I hooked up the vac to manifold vac and I am getting 32* at idle. Starts fine and idles nicely, but when I start giving it throttle it just keeps climbing it hit like 42* as 2000 rpm and I shut it down.

I switched to ported vac and again started and idled fine. Again throttled up and timing kept climbing and hit 42* at 2000 rpm.

What's up with that? And my can my setup be so different from what they dynoed it with. I mean they had to set the springs and vac advance. Now I can't get it to match up!

[Rich 5150 69]

Slim let me throw a Monkey wrench in here, you bought a complete drop in motor from blueprint, now I`m not bashing anybody here, but what I`m thinking is they put together a known build, that they`ve done so many times, originally they might have dinoed it 400 motors ago, they buy all the same parts throw it together and call it done. Now what you have is a motor that needs fine tuning, drive habits, available gas, gearing, vehicle weight all add to the total. it just sounds that the mechanical advance is comming in to soon, mine did MSD street fire, pulled one yellow spring from my box of crane cams advance kit and put it in, fixed my problem. You`re real close here, either one heavier or lighter. Then you need to dial in the vaccum can, mine I turned in ( clockwise four full turns), it would ping at load up a hill at full temp on a hot day, kept turning it clockwise til it quit, done deal.

[fleetsidelarry]

Slim, I guess you didn't read this previous reply.

Originally Posted by fleetsidelarry

if you're intent on running 17° initial, I wouldn't hook the vacuum advance up.

you've previously shown that you have 16° of advance in the vacuum can, and just stated that you have 18° of centrifugal at 3500 rpm. if you hook the VA up now you'll have 33° at idle! It may not even want to start like that.

with your initial set at 17 and your can hooked up its going to immediately go to 33°. then as you increase revs, your centrifugal advance will start adding to that. since you've already established that you have at least 18° in centrifugal to add, it's doing exactly what one would expect.
do what Rich suggested above:

it just sounds that the mechanical advance is comming in to soon, mine did MSD street fire, pulled one yellow spring from my box of crane cams advance kit and put it in, fixed my problem. You`re real close here, either one heavier or lighter. Then you need to dial in the vaccum can, mine I turned in ( clockwise four full turns), it would ping at load up a hill at full temp on a hot day, kept turning it clockwise til it quit, done deal.

[C10Slim]

Cool thanks! I will give that a shot.

[fleetsidelarry]

Slim, to answer your other Q about when you had it hooked to ported vac (vrs manifold), the basic difference is manifold vac is there when your carb butterflys are closed at idle so it's activating your vac advance even at idle. the ported source is above the butterflys and is not getting any vac signal at idle. But as soon as you start opening the throttle even just a hair, the ported source comes "online" and and activates the vac advance, so at that just off idle both manifold and ported are behaving similarly.

Again, I still think you need to dial back your initial from 17° if you're going to run vacuum advance