Total Ignition Timing 440 Street/Strip

[ykf7b0]

i have recently sought to fine tune my street/strip 440 by finding true top dead center on the balance then removing it to install timing tape. I now have it running like never before and it is STOUT! My timing numbers are as follows; Initial 12 Mechanical 38 Total 58. I'm using a MP electronic conversion set up with a Holley 850. From reading post on the internet I'm thinking the total is much to high. Should I be concerned with this and if so what do you recommend to reduce total? Thanks!!!

 

[dvw]

36-38 total with factory heads, 32-34 with aluminum heads.
Doug

 

[dieseldazzle]

If you have 12 degrees of initial plus 38 degrees of mechanical advance isnt that 50 degrees of total timing? At WOT I cant see you getting an additional 8 degrees of timing out of it

 

[Badvert65]

36-38 total with factory heads, 32-34 with aluminum heads.
Doug

X2
Remember, this is TOTAL advance. I been running this way since the 80's (along with my other Mopar buddies) You can't go wrong with that setup.

 

[dieseldazzle]

X2
Remember, this is TOTAL advance. I been running this way since the 80's (along with my other Mopar buddies) You can't go wrong with that setup.

I thought the aluminum heads typically allow a little more total timing than iron heads????

 

[lewtot184]

58 degrees? sure not including the vacuum advance? that thing will self destruct at 58 degrees total at WOT. total timing depends on how efficient the combustion process is. the more timing you need the worse the process. 34-36 with good quench, proper plugs and fuel. i don't think head material is a big factor. where the plug is located, chamber and piston configuration are things that i look at.

 

[ykf7b0]

Vacuum Advance

Let me clarify. With vacuum unhooked and plugged I am at 12 degrees idling at 600 rpm, 38 degrees 3500 rpm still with vacuum plugged off, and with vacuum connected at 3500 rpm I am at 58 degree's. I know the 38 degree's is within reason but the 58 degree's with vacuum advance connected is my concern even though she runs really, really well. Again, I have just recently re-connected the vacuum advance after many years of having it plugged and have learned my 440 is much more responsive with the vacuum advance working. What is the maximum total advance with vacuum advance working should I shoot for without any fear of detonation?

 

[dieseldazzle]

You will have some advance pulled in at part throttle and you can adjust that via your vacuum canister if thats what your engine likes. Evidently yours is working well. I would leave it all alone if its not pinging. 58 degrees at part throttle at 3500 rpm doesnt sound unreasonable to me. If you go WOT it will immediatley drop to your mechanical advance total so its working correctly.

 

[Cranky]

Timing depends on the combination and low compression engines like a lot of timing. The cam also plays a big part in the equation. So far over the years, I've tuned two engines that liked 50 total and both had low static compression and fairly long cams. Cams with long duration usually bleed off cylinder pressure at lower rpm and that just adds to low PSI pressure test and those are the ones that benefit from a lot of timing. What do your plugs look like after making a pass? If it's not burning off the ground strap, you are probably safe but man, never seen one needing 58 total before. What's the cranking PSI on that thing?

 

[dieseldazzle]

He is not talking about WOT or mechanical advance

 

[ykf7b0]

He is not talking about WOT or mechanical advance

True. Thanks!!

 

[lewtot184]

58 degrees at cruise/high vacuum may be a little high. this means you have a 10 degree vacuum advance unit. you can reduce how soon the advance comes in by turning the adjusting screw in the vacuum pod counterclockwise. there were 7,8,and 9 degree units made that will reduce total advance. i'm running a 10 degree unit on one of my engines that a siliconed a .055" shim at the notch of the vacuum pod arm to reduce total. about .012" reduction in travel will reduce timing about 1 distributor degree.

 

[Cranky]

He is not talking about WOT or mechanical advance

Most usually set their engines to have total timing all in by a certain RPM regardless of WOT.....

 

[dieseldazzle]

Most usually set their engines to have total timing all in by a certain RPM regardless of WOT.....

I agree and they also have their vacuum advance plugged when doing so..........

 

[Dodge 330]

36° total is what I've always run on 440's. lightweight Mr. Gasket spring kit #925B to mainly make starting easier and its all in by ~ 1800 rpm. Never worried about the slot length either and always capped off vacuum advance as I'm not doing economy runs! LOL

 

[dvw]

Let me clarify. With vacuum unhooked and plugged I am at 12 degrees idling at 600 rpm, 38 degrees 3500 rpm still with vacuum plugged off, and with vacuum connected at 3500 rpm I am at 58 degree's. I know the 38 degree's is within reason but the 58 degree's with vacuum advance connected is my concern even though she runs really, really well. Again, I have just recently re-connected the vacuum advance after many years of having it plugged and have learned my 440 is much more responsive with the vacuum advance working. What is the maximum total advance with vacuum advance working should I shoot for without any fear of detonation?

If it 's not pinging at light throttle or on tip in, run it. Vacuum advance has no effect t WOT.
Doug

 

[kidmopar]

58 is really unheard of for me i dont see higher than 40 in bb mopar race motors much less street are u sure timing tab is perfectly on tdc when it reads 0 degrees?

 

[ykf7b0]

58 is really unheard of for me i dont see higher than 40 in bb mopar race motors much less street are u sure timing tab is perfectly on tdc when it reads 0 degrees?

This is vacuum advance (58 degrees) we are referring and not mechanical advance which is 38 degrees. I used a piston stop and found true top dead center by rotating the engine both ways then measuring the distance and then splitting that distance before marking it. I then removed balancer and installed timing tape with top dead at 0 so I'm positive I have it marked correctly. I think I might try adjusting the vacuum cannister to reduce the vacuum advance a few degrees, if this is possible, just to be on the safe side even though I have not heard any pinging.

 

[dieseldazzle]

This is vacuum advance (58 degrees) we are referring and not mechanical advance which is 38 degrees. I used a piston stop and found true top dead center by rotating the engine both ways then measuring the distance and then splitting that distance before marking it. I then removed balancer and installed timing tape with top dead at 0 so I'm positive I have it marked correctly. I think I might try adjusting the vacuum cannister to reduce the vacuum advance a few degrees, if this is possible, just to be on the safe side even though I have not heard any pinging.

Why?

There is nothing wrong with that kind of advance when the engine has no load on it and definitely helps economy and street manners and remember you can change the vacuum canister to different rated vacuum pods as well. Some dont do **** until 10 inches of vacuum anyway to be honest.

I know most will argue that a 3 speed automatic car with no lock up converter and numerically high (3.00 and above) rear gears behind of a BIG BLOCK is not "economy" but when you actually DRIVE your car like I do, it is nice to have enough fuel when out on a cruise or headed to a show or even the track and believe me it helps economy.

If you have a car that is borderline pump fuel friendly or any kind of forced induction or even nitrous really, then I would be concerned but still even those can be tuned around to use vacuum advance.

Locking out the timing and all of those other tricks are for purpose oriented engines, not street cars.

 

[dvw]

58 is really unheard of for me i dont see higher than 40 in bb mopar race motors much less street are u sure timing tab is perfectly on tdc when it reads 0 degrees?

Re read my post. 58 degrees vacuum with vacuum advance has NO effect at WOT. Vacuum advance retards when the vacuum level drops, IE opening the throttle.
Doug