Well last night didn't go so well.

I went out to set the timing at 12* advanced and then try to set total timing out to 32-36* advanced. About the time I was just finishing up swapping the springs in the distributor so that the timing would be all in by 3000 RPM my neighbor came over. He's very helpful most of the time and I've learned a lot of good things from him but he doesn't agree with what I'm thinking on how the car should be timed.

If I've read everything correctly, then I want to set the timing without the vacuum advance hooked up and get a total timing around 32* to 36* advanced. Some people say to set the initial timing and others say initial doesn't matter but I figured I'd set initial to 12* and go from there. Then, after the timing is set, when the vacuum advance is hooked up it will add an additional 10* or so advance depending on the vacuum available at the moment.

Where my neighbor is having the problem is adding the initial timing (say 12*) plus the centrifugal advance (say 21*), plus the vacuum advance (say 10*) and coming up with a number around 43* advanced. He says that is way too high and will start tearing up the pistons. However, if I understand what I've read then that's not true. The vacuum advance changes based on engine load and when running WOT there won't be any vacuum advance. The vacuum advance only kicks in under partial throttle and the engine can stand more advance during those times right?

Anyway, he was helping me set the timing to where I wanted it and at the point where I think we were at 12* initial and the distributor should have added another 21*, we were only measuring about 24* total timing at 3000 RPM. Then, when we went to shut it off it continued to run for a few seconds and shook pretty vigorously before spitting fuel out the top of the carb. That got my attention! My neighbor felt like that was because we had the timing too advanced. Ultimately he wanted to set the total timing with the vacuum advance connected and since my brand new engine had just puked on itself I went along with it. Unfortunately we ended up with the initial timing being 2-3* retarded now and a total timing of about 34* advanced at 3000 RPM with the vacuum connected. I know this isn't right but at least the engine didn't sputter and jerk when we shut it off that time.

So, I'm hoping somebody can reassure me of what I'm doing here. I think the timing should go back to 12* advanced initially and then shoot for 32-36* advanced total with no vacuum hooked up.

I'm also concerned about the carb running way too rich. It blows black smoke when you rev the throttle and the fumes in the garage when it is running will literally make your eyes water. Other than that, and the red hot headers, the engine seems to be running great and sounds healthy.

I pulled one of the spark plugs tonight and it was very black and covered with soot. My neighbor says that confirms that it is running way too rich. Most of the running the engine has done so far has been at 2000 - 2500 RPM; it hasn't been idling much at all.

Will correcting the timing fix the overly rich carb problem or will I need to change jets in the carb? Also, in which order does it make the most sense to fix these problems; carb first or timing first?

Sorry again for the long post; I feel like a newb all over again. I've learned so much about engine building and now its like starting all over again to learn how to tune it right. I feel like I have a good healthy engine at least but that it just needs to be tuned right now.

 

Man, ya gotta get this guy away from your car. I don't wish to be impolite, but his knowledge of how an engine works is lacking.

 

How many turns out (counter clockwise) are your fuel idle mixture screws on the bottom front of your carb?

 

Yes, YOU are fine - you just need to do it without the neighbor around!

Unhook the vacuum and set it to the 32 degrees all in by 2500-3000. Then hook up the vacuum and take it for a ride and burn off that extra fuel (from being so retarded!). Give it a good run - warm it up real good an get a little highway in. See how it runs and do any fine tuning from there.

As was mentioned, you may need to close up the idle mixture screws, but you really do need to "clean out" the engine. Give it a good run.

 

I run 24 initial and 46 total on pump gas. Your combo is everything. Fix the fueling first by rejetting. then fine tune your timing and recheck the fueling. If the inner 2 pipes glow then the outer 2 on the other side may as well if you have a dual plane intake. This also indicates the need to cut out your plenum, add a carb spacer, or custom jet left and right banks.

Just get a wide band o2 sensor or read your plugs, but fix your fueling to 13.0ish at WOT. 14.7 at cruise with vac advance working. Make sure your vac adv is plugged in into thecorrect place as well (carb base plate ususally).
Good luck

 

Also, basedon a DCR of 8.3:1, it sounds like you have a pretty small cam for your compression. ~224@.050? If so, you may not want more than about 28* at WOT with vac adv unplugged.

 

It's in the middle of a frame off so no highway runs on it for a while. I'm going to try to get some time on it without the neighbor and set the timing, then make sure all my carb settings are right. I'm not sure where the needles are right now but I'm going to find out.

 

I'm running a Comp Cams XE274H. I put it in to get the DCR down from 8.5:1 on the XE268H I was going to get. I know 8.3 is kind of high still but we'll see how it goes. I've got a Dewitts radiator and dual spal fans that were amazingly bringing the temp back down to 165* yesterday even after the engine had run up to 210* and with a 180* thermostat. Hopefully I can keep the engine cool enough to avoid detonation issues with this DCR.

 

I have to disagree with that. The only reason that you would want to run 28° total is if you cant run the proper amount of advance without pinging.
But that still doesnt make 28° optimal, only what you can get away with. I would try at least 34° to start with, and adjust from there if you have to.

I am sure your distributor has an adjustment for total mechanical advance. Do you know how much is supposed to be in it as it sits?
From what you were saying it could be adjusted for only 12° of mechanical advance. If thats the case, you will probably want to change that. Adjust it where you have about 20° of mechanical advance.
Did you rev the motor higher than 3000 to see if it kept advancing more? If you at least temporarily run the lightest springs it is easier to find the total advance.
That way you can easily adjust total, and then worry about the curve. Absolutely do not connect, or concern yourself with the vacuum advance while you are setting total timing.
At WOT you engine wont see enough vacuum to cause vac advance to occur. Part throttle is where vac advance is important.
After you get the total advance where you want it, you can play with springs to get it to be all in around 3000 rpm.
Then connect your vacuum advance canister and see how everything works. It could need some adjusting to.

I suggest you do this while your neighbor isnt home.

 

MSD directions say that the bushing that comes in the distributor out of the box is the 21* bushing. I'm going to have to confirm that is actually what is in there though. I put the two blue springs in which should bring the timing all in by 3000 and it seems to be doing that. When I rev up to 4000 RPM the timing doesn't go any higher than it did at 3000 RPM. I'm going to double check it with my timing light though. We were using the neighbors timing light the other day. Hopefully I can get out there tonight and work on it some.

Thanks again for all the good replies.