Author Topic: ignition timing on the 340? (Read 21009 times)

miketyler · « **on:** October 24, 2005 - 10:30:52 AM »

I was reading the manual on timing specs on the 340. I believe it is 2.5^oBTDC and to take the reading idle. I have read others on here time your engines at 2500-3500RPM? Is that a high performance thing or what?

dgc333 · « **Reply #1 on:** October 24, 2005 - 11:08:41 AM »

If your engine is stock then the factory specs at idle are just fine. However, if you have made mods especially a cam change then the it's very likely the distributor needs to be tweaked to get maximum performance.

A rule of thumb for a performance small block mopar engine is total mechanical advance should occur some where in the 2500-3000 rpm range an it should be around 35 degrees. The rpm range is controlled by the springs on the advance weight and the total is a sum of the intial and the number of degrees in the slots. More agressive cams typically require more initial advance for good throttle response and idle quality. If you tune for this number then a stock distributor will give you too much total. Change parts or or reducing the slots can bring it back. The vacuum advance is applied to the sum of the mechanical and initial and should be in the 50 degree range for maximum economy. The vacuum advance has a fixed amount of degrees bulit in (stamped on the arm) and most mopar cans can adjust the point at which the vacuum advance starts to work and when it's full with an allen wrench in through the vaccum connection. You want it in as soon as possible with out casuing deontation problems.

MEK-Dangerfield · « **Reply #2 on:** October 24, 2005 - 03:30:42 PM »

Well put dgc333, (thumbs up smiley). The timimg at idle will advance some if you have gone to a bigger cam. The best bet is to tune by total advance, as was described. I have a big block, but I found it tricky to get my vacuum advance adjusted so that I didn't have a detonation, or miss problem. For now, my vacuum advance is disconnected, but I'll get back to the problem some day(LOL).

Mike

dodgetkboy78 · « **Reply #3 on:** October 24, 2005 - 04:35:06 PM »

Quote from: MEKrunner on October 24, 2005 - 03:30:42 PM

Well put dgc333, (thumbs up smiley). The timimg at idle will advance some if you have gone to a bigger cam. The best bet is to tune by total advance, as was described. I have a big block, but I found it tricky to get my vacuum advance adjusted so that I didn't have a detonation, or miss problem. For now, my vacuum advance is disconnected, but I'll get back to the problem some day(LOL).

� � �Mike

Hook it up to the manifold vac and try, it is what I do once a bigger cam is installed.

MEK-Dangerfield · « **Reply #4 on:** October 24, 2005 - 05:27:37 PM »

Quote from: dodgetkboy78 on October 24, 2005 - 04:35:06 PM

Hook it up to the manifold vac and try, it is what I do once a bigger cam is installed.

Thanks for the advice. I didn't try that(red-faced-smiley).

Mike

matt63 · « **Reply #5 on:** October 24, 2005 - 06:42:59 PM »

While we are on the topic, does anybody know which distributors have adjustable mechanical advance? I see that the MSD units do. It seems to me that welding and grinding the slots is a tedious trial and error method.

Chryco Psycho · « **Reply #6 on:** October 24, 2005 - 11:09:41 PM »

all the new Mopar performance dist have adjustable Mech advance now as well
I find that by adjustingor unhooking the vacuum advance & increasing the advance at idle the car will get better milage & power / response will improve also so I set the total timing at around 36* & wrok with the idle advance to add more initial advance without over advancing at 3000 RPM up

matt63 · « **Reply #7 on:** October 25, 2005 - 07:58:58 PM »

How is the mechanical advance adjusted wiht the MP units- bushings? I wonder who makes them for MP.

Chryco Psycho · « **Reply #8 on:** October 26, 2005 - 12:39:29 AM »

mallory supposedly makes them

basement · « **Reply #9 on:** October 26, 2005 - 07:14:39 AM »

You'll have to excuse my ignorance but no where on my dampener is there a 35degree setting. How is the achieved, sounds like another gadget for the tool box though.

Chryco Psycho · « **Reply #10 on:** October 26, 2005 - 11:37:06 AM »

measure 2 3/8 " clockwise from the TDC mark this is 36*

Author Topic: ignition timing on the 340? (Read 21009 times)

miketyler

ignition timing on the 340?

dgc333

Re: ignition timing on the 340?

MEK-Dangerfield

Re: ignition timing on the 340?

dodgetkboy78

Re: ignition timing on the 340?

MEK-Dangerfield

Re: ignition timing on the 340?

matt63

Re: ignition timing on the 340?

Chryco Psycho

Re: ignition timing on the 340?

matt63

Re: ignition timing on the 340?

Chryco Psycho

Re: ignition timing on the 340?

basement

Re: ignition timing on the 340?

Chryco Psycho

Re: ignition timing on the 340?