setting timing on my 340

[505challenger]

how do i set the timing on my 340?  i have read that i dsconnect the vacuum to the dist, then set the timing.  but then when i plug the vauum back in wont it just pull out more timing?  i know this is a very stupid question but i just need someone to tell me how to set my timing

[dodge freak 2]

The most important part of the timing is the total amount without any vacuum advance. Most shop manuals like just go by the factory settings and the factory was worry about it passing the smog standards when they came up with the specs.

The total timing should be around 32-34 degrees. Better with the low octane gas we have to set it lower . If cheap racing gas was still sold at the local gas stations 36-38 degrees might been best.

The amount at idle really doesn't matter unless you have a big camshaft, then you might want 18-20 degrees but it would cause the total advance to be too high. This is were a aftermarket dist is nice, like the MSD (I have a big buck E-curve dist, super nice but $400--brought back in the good old days, lol)

How do you set for say 33 degrees total. Get some timing tape and motor off, place tape on damper and with white paint mark a line at 35 and just guess from there. You can time by ear too. Start the timing low at 30 degrees and keep advancing while hearing the motor increase in rpms then once it seems to stop back it off a tad but it might put it at 36 degrees, a bit too much.

Also the motor has to be turning, 3,000-4,000 rpms for the advance to be all the way in, means you have to gun the throttle while looking at the timing until it stops advancing.  I wear ear muffs for gun firing to protect my ears or they ring for hours after ward.

Watch out for the fan and your timing wires, don't ask how I found out long ago, ha ha. 

[Chryco Psycho]

total timing seem to work best in the 36* range , 2 3/8 " clockwise from the TDC line on the damper is 36* , most engine seem to run best in the 12-16* area at idle but idle is less important than total is .
the Vacuum can be left disconnected or you can insert an allen wrench into the vacuum canister & turn the screw counterclock wise to reduce vacuum advance , you looose approx 1* / full turn , it will go 14 turns from 14* advance down to 0 , you can play with what works best sometime you need the initial reduced to 12* or so to kil the pinging & need 2-4 * of vacuum to get the full 36* at higher RPM for example ,

[505challenger]

thanks for the help this is GREAT info!!

[dodge freak 2]

Notice in another thread you say gas mileage isn't a big deal. Then maybe try running no vacuum. advance. It just helps out part throttle and sometimes can cause problems-like pinning that weakens the rod bearings.

With no vacuum advance you might be able to quicken up the mechanical advance, like have it all in by 3,000 rpms. Lighter springs in the dist will do it, there is two springs, first try just one light spring, likely it be very close.

I am assuming the motor has iron heads and 10 to 1 compression, if its 8.5 to 1 then try to use both lighter springs in the dist.

You do know how to change those springs    

[UKcuda]

With no vacuum advance you might be able to quicken up the mechanical advance, like have it all in by 3,000 rpms.

I believe the 340 distributors had a very steep advance curve from the factory, all in well before 3K.  On the early ones anyway.

If this is a high compression 340 it will be quite sensitive to ignition timing so it is worth making sure you have the lighter springs in the distributor and how much mechanical range it has.  If someone has swapped in a smoggy distributor it will probably be giving way too much mechanical (they are stamped on the underside of the slotted plate - the amount of advance is 2 x the number stamped).

[vinb]

Everyone's engine combo is different, but most 340/360 like 30 to 34 degrees,
36 or 38 is a bit much...

[UKcuda]

Everyone's engine combo is different, but most 340/360 like 30 to 34 degrees,
36 or 38 is a bit much...

The point I was making is that a lot of the stock SB distributors have like 30 degrees mechanical built in.  So if you use a stock distributor and set for 30 to 34 degrees total then you might have to live with hardly any advance at idle, which can be tough, so you need to check what distributor set up you have in case you need to fix that problem internally.

[dodge freak 2]

The point I was making is that a lot of the stock SB distributors have like 30 degrees mechanical built in.  So if you use a stock distributor and set for 30 to 34 degrees total then you might have to live with hardly any advance at idle, which can be tough, so you need to check what distributor set up you have in case you need to fix that problem internally.

Very true and with these motors being 40 years old no telling what parts have been changed over the years.