Dwell and timing set. Crisp take off and power! BUT rattles on acceleration.

I set the dwell to 30, and the initial timing to 9 degrees.

I have a stock 1973 vaccuum advance and stock distributor mechanical advance.

I tried the vaccuum advance on manifold vaccum and also tried it on ported vaccum. I got less rattle on the constant manifold vaccum. I think the power was a little better too.

I read that article on timing. It says all the timing should be dialed in at 2500 rpm. I didnt even wind it out and it was rattling at 1500 - 1800. Im sure the mechanical advance wasnt even half in at that rpm and it was already rattling.

If I get softer springs and get all the timing in by 2500 it will be rattling like box of rocks. What to do?

 

no there is no EGR, its a 1970 manifold

 

Larry, good call. Wouldn't an EGR tuned carb be lean without EGR present? It's been too long since I worked on one.

What carb are we talking about here?

Devon

 

yes I just swapped out the 2bbl pollution control manifold for the 1970 quadrajet manifold. and rebuilt the Qjet too.

The car runs great, drives great, good acceleration, was sluggish off the line until i adjusted the timng, now has a good head snap feeling but rattles. thats in another thread. I will definitely spray around the edges tomorrow while its running and see if I can find a leak.

TY

 

the Q jet is also 1970.

 

I had pinging on acceleration aswell on my nailhead and it turned out to be Accel counterweights on distributor.I changed back to original ones and it was remedy.aftermarket weights seems to be much to heavy.Just my 2 cents but might be worth to try.

 

Are you running the highest octane fuel available at the pump?

 

Did he ever say what the total advance moved to after he made the initial adjustment?

Perhaps moving the initial back one degree at a time until the pinging ceases is another corrective measure to be taken.

 

What Octane Are You Running?

 

The correct octane fuel for this engine is 87. If you must run anything higher then you have a problem.

 

Im running 87.

Why would running higher octane fuel cause a problem? What problems could/would result?

I havent checked the total timing yet but whatever it is the only thing I see can be done to change it is.

1. adjust the initial timing.
2. move the vaccum advance to port or constant manifold
3. buy special springs for the mechanical advance. 3 choices. weak, medium, strong.

4. modify the vaccum advance linkage.

Everyone says to get all the advance in by 2500 rpms about 32 to 34 degrees.

The only way to do this that I can figure out from the discussion is to get weaker springs for the distributor.

So it seems i should modify the vaccum advance so I can keep the intitial advance up there where the peformance is good, but limit how much it comes in so it doesnt start pinging, and then get weaker springs for the mechanical advance so it is all in by 2500 rpms.

Ill put a mark on the balancer at 30 degrees today and see what rpm it takes to get it up there. I read that in the timing article.

gary

 

Gary,
On 87 octane you might not be able to run 32-34 degrees total, on my 73 Electra I'm only running 25 total and that is actually more than the manual recommends. I'm looking at the page right now and for your engine it is 14-18 degrees at 2900 rpm. I put a recurve kit in my distributor and have 13 degrees initial and 25 degrees total and I'm making good power and still able to run 87 octane...of course this is a 455. I am still tinkering to get the best combo though but want to make sure I can still run 87 octane. You will have to go to a higher grade fuel if you dial in more timing and if I'm going to do that I'm going to bump up my compression and make it worth my while.

 

Kurt,

do you have your vacuum advance on port or manifold?

 

Larry, could he be missing the bushing on the pin that rides in the advance slot?
Adding the bushing will allow him to run a little more initial advance without having too much total advance.