360 Ignition timing help

[Deleted member 49442]

Hi Guys,
Looking for some assistance in tuning my LA 360 short block.

What I have:
Mopar LA 360 it has a 9.5 compression ratio
Comp Cam #20-221-3
20-221-3 - Xtreme Energy™ Hydraulic Flat Tappet Camshafts
stock j heads
Mopar Orange box ECU with new distributor (haven't touched the vac advance adjustment)
318 exhaust manifolds (Truck)
Rebuilt Thermoquad Carb
I usually run 87 octane
Torqueflight transmission
3.55 gearing
Tire size p225 70R15
Bosch Platinum plugs

What I'm experiencing:
Terrible gas mileage 8mpg
Light pinging under load, up long steep hills
Also seems like this should have more power than it does.

From my service book with a Mopar 360 8.6 compression ratio it says timing should be set to 4 degrees btdc (The sticker for my vehicle states it should be at 10 degrees btdc)

What I did:
I started by leaning out the carb.
Took the fuel enrichment screws in ½ turn each are now out 1 & ½ turns
Took it for a test drive and it was majorly pinging

I checked the timing (with the hose pulled off the vac advance and plugged)
and found it was set to > 10 degrees btdc (off the scale)
I changed the timing to 8 degrees btdc

It was back to Light pinging but now dieseling
I think my dad slowed down the idle to remove the dieseling.


So my questions are:
With my setup with a higher compression ratio engine than stock what should the timing be set to? (I'm thinking it should be lower than 8 degrees, maybe around 4 degrees btdc)

Should I be running higher than 87 octane?

When I have initial timing set do I need to mess with the vacuum advance timing adjustment?


I bought some timing tape so I can dial it in with more accuracy.
Its winter here in PA, so I wont be able to take it out for a test drive for a while, just wanted to get on top of this asap.

Thanks
Michael

 

[yellow rose]

Sounds'ike you need to start by putting some fuel in at a cruise and post what your timing curve is. What spark plug are you using.

Also, did you measure your CR or are you assuming it is what it is?

 

[MOPAROFFICIAL]

Hi Guys,
Looking for some assistance in tuning my LA 360 short block.

What I have:
Mopar LA 360 it has a 9.5 compression ratio
Comp Cam #20-221-3
20-221-3 - Xtreme Energy™ Hydraulic Flat Tappet Camshafts
stock j heads
Mopar Orange box ECU with new distributor (haven't touched the vac advance adjustment)
318 exhaust manifolds
Rebuilt Thermoquad Carb
I usually run 87 octane
Torqueflight transmission
3.55 gearing

What I'm experiencing:
Terrible gas mileage 8mpg
Light pinging under load, up long steep hills
Also seems like this should have more power than it does.

From my service book with a Mopar 360 8.6 compression ratio it says timing should be set to 4 degrees btdc (The sticker for my vehicle states it should be at 10 degrees btdc)

What I did:
I started by leaning out the carb.
Took the fuel enrichment screws in ½ turn each are now out 1 & ½ turns
Took it for a test drive and it was majorly pinging

I checked the timing (with the hose pulled off the vac advance and plugged)
and found it was set to > 10 degrees btdc (off the scale)
I changed the timing to 8 degrees btdc

It was back to Light pinging but now dieseling
I think my dad slowed down the idle to remove the dieseling.


So my questions are:
With my setup with a higher compression ratio engine than stock what should the timing be set to? (I'm thinking it should be lower than 8 degrees, maybe around 4 degrees btdc)

Should I be running higher than 87 octane?

When I have initial timing set do I need to mess with the vacuum advance timing adjustment?


I bought some timing tape so I can dial it in with more accuracy.
Its winter here in PA, so I wont be able to take it out for a test drive for a while, just wanted to get on top of this asap.

Thanks
Michael

It can be hard to know which way to go with numerous people giving advice...so try YR suggestions first if you like.
I want to know what the total timing is, full advance without vac adv hooked up. We know the initial timing is low, yet its dieseling ...that isn't a good thing, high heat and unburnt fuel/end gases.
I would think you would want to start around 32 degrees full advance and move up till it starts to ping under load again then go back 2 degrees.
You are going to have to look up re curving the distributor so that you can limit the advance and raise up that initial timing.
One thing that keeps bugging me....is that you are running a 318 exhaust manifold, that has to be backing it up , chamber temps rise, and if thats the case....doing all the right things else where won't make much diff mpg wise especially and will make it ping. But I guess best thing at the moment would be to address the timing issue first, drive it and see if it surges at cruise speeds like 45-50 mph ,if it does its lean, if not...check the plugs and see where its at and go from there...and if your compression is what you say it is, and let's say you just stabbed the cam in dot to dot...could be advanced, then the dynamic would exceed 160 psi and on un preped chambers with tons of end gas...not good. btw you could run 89 octane, needing 91 is iffy imo.

 

[AJ/FormS]

I want to say that this is easy, but that would sound harsh., but really it is.

You just gotta start with the T-port sync.

 

[AJ/FormS]

This should be easy,start with the T-port sync.

But really you need higher octane gas. With a 9.5 Scr, your Dcr is looking like 8.17@164psi.
With a stock TC and 3.55s,you will have to slow your advance curve way down. The T-port sync will set the idle-timing. Then you have to limit your power-timing. Then you will have to spend some time slowing the curve down. To prevent PT pinging.

Better it will be to run 91 gas cuz, 164 psi is running on the edge, with iron heads and 91 gas; never mind 87.

Or you could upsize the cam to drop the Dcr to right around 8.0. You will have a much easier time to put a tune on it.

Ima thinking the terrible mileage is telling you a story. If you're engine is into pinging, even tho you may not always be hearing it, pinging is creating cylinder pressure at the wrong time and that means the energy lost. Energy lost means gas burned that did not make it to the rear tires. Furthermore with retarded timing, the butterflies have to be opened further than necessary for the engine to idle. This exposes more transfer slot than necessary, and that puts more fuel through the engine than necessary. But hold on, that same retarded timing is causing the rich running. all the time, on account of the extra transfer exposure is not just at idle,but all the time. You can lean out the idle with the mixture screws, and you can lean out the mains with jetting, but the transfers are much harder to adjust. The transfers are flowing all the time and are most effective from idle tip-in to about 1/4 throttle or a bit more, until the mains come on line. And on the hiway, your carb will be on the transfers, and needing in excess of 48 degrees at 2200 rpm for cruising. With retarded idle timing, and a wussy factory Vcan, this is usually not possible. My engine likes close to 60 degrees. Most like 52ish or a bit more. If you cannot give it what it wants, cuz the timing is limited on account of detonation on the 87 gas, then it will not make decent fuel mileage. Again;up the octane and up the cruise advance.
With 3.55s and 26.5 tires say; 60mph=2700rpm at Zero-slip. The cruise-timing is gonna need to be up there. The factory tune will be woefully inadequate. The absolute very best that is possible would be 36* plus 18ish in the can=54*. But if you run 36@2700 on the mechanical with 87gas, your engine will not last long under detonation. In all likelihood, with 87 you will be hard pressed to run 25* at 2700, and most Vcans are probably down around 14 or less;so the total cruise-timing might be down around 25+14=39,woefully inadequate. Running like this,with inadequate timing, the fire does not start soon enough, and the pressure peak arrives too late and is soft, And it is possible for not all the fuel to finish burning inside the engine. This all adds up to poor fuel economy, AND poor power.

So the cure is a tankful of 91, and getting the T-port sync established. That is job #1.
Job #2 is to make sure the vacuum advance can is hooked to the spark-port, and not directly to manifold vacuum.
Job #3, is to set the power-timing to 34 to 36 @ about 3400rpm.
Then come the roadtests.
The roadtests will tell you if you can bring the power timing in sooner. So you work on that for awhile.When you get that close, then, you can dial in the mains, and then the PV.
Then you can start running some power through it and maybe more timing changes.And then maybe the fueling needs more changes.
After you think you got her understood and have met all her needs, THEN
You can switch to a lower grade fuel, and start all over

And finally you will be able to drive more miles on a dollar, by running a correct grade gas and proper timing, than trying to set up an engine to run on a less-than-optimum grade of gas. Retarded timing is to be avoided.It sacrifices power and economy, and will just burn more cheap gas than if you tune for and run the correct grade gas.
I would also do a cylinder pressure test, to verify that you will be able to someday run on less than 91 gas. If you are pushing 164 psi, then you may not be able to; that cam has a pretty small ICA of about 54 degrees. It's gonna be a bit of a battle. But cheer up; that cam with appropriate gearing and TC will someday get fantastic gas mileage,point to point, on the hiway.
So,to recap, start with top grade gas and get the T-port sync established.I could tell you what idle-advance to start at, but no matter what number I throw out, it will likely be wrong. Let the T-port sync establish it. Forget the factory specs. Forget what you might think you know. Forget what others might have told you. Let the T-port sync establish it.

 

[yellow rose]

Did the OP say he had the vacuum advance was hooked to manifold vacuum or were you just letting him know to check it?


Seems to me that the new deal is to hook the VA to manifold vacuum rather than timed vacuum. I have no idea why this is ever good but it seem to be the in thing lately.

 

[crackedback]

One of the ignition guys likes to do recommend the VA to manifold vacuum.

Get initial set to most the starter can handle when hot and tune it from there. That should be the first step.

Most SB mopars like anywhere from 12-20 in not too crazy of a build like a XE256h camshaft.

 

[yellow rose]

One of the ignition guys likes to do recommend the VA to manifold vacuum.

Get initial set to most the starter can handle when hot and tune it from there. That should be the first step.

Most SB mopars like anywhere from 12-20 in not too cray of a build like a 221 camshaft.

Hmmmm. What is the benefit of manifold vacuum? Every time I tried it, I was bit in the ***. But, I can say I probably have not tried it since the late 1980's so maybe there is now a place for it.

 

[crackedback]

I guess he likes to have the extra advance at idle, but, it dumps right out when you step on the gas.

It's a three letter company that suggest and I refuse to mention them by name as he thinks he's the only one to ever make a MSD advance bushing!

 

[yellow rose]

I guess he likes to have the extra advance at idle, but, it dumps right out when you step on the gas.

It's a three letter company that suggest and I refuse to mention them by name as he thinks he's the only one to ever make a MSD advance bushing!

Got it.

 

[AJ/FormS]

YR
no he didn't say. But unless we start from a known point, we will be running around in circles; and this cam is too small to need to run the can basackwards. This happened to me in another thread,cuz I didn't ask, and it wasn't volunteered until a long list of dead-ends was pursued.
But I'm sure you know all about such things. This said in all honesty, no smartassedness.

 

[TF360]

Are you sure you have 318 exhaust manifolds on it. Take them off first! The opening is a different size

 

[Deleted member 49442]

Sounds'ike you need to start by putting some fuel in at a cruise and post what your timing curve is. What spark plug are you using.

Also, did you measure your CR or are you assuming it is what it is?

I will check the plugs tomorrow. I didn't measure the CR of the engine, but its a reman Mopar performance short block, with stock heads its listed to have 9.5.

Sorry I know the basics but how do i find my timing curve?

 

[Deleted member 49442]

Are you sure you have 318 exhaust manifolds on it. Take them off first! The opening is a different size

I'm fairly certain they are, but they are truck manifolds, on a 79 Red Express

 

[Deleted member 49442]

YR
no he didn't say. But unless we start from a known point, we will be running around in circles; and this cam is too small to need to run the can basackwards. This happened to me in another thread,cuz I didn't ask, and it wasn't volunteered until a long list of dead-ends was pursued.
But I'm sure you know all about such things. This said in all honesty, no smartassedness.

I'm 99% certain that the vacuum lines are hooked up correctly. Will check tomorrow.

 

[AJ/FormS]

As to the timing curve; you will have to generate your own.
You will need a timing lite, and a tachometer.
>First you have to prove that your timing mark on the balancer is in the exact right spot. Then you can install the timing tape; exactly right. Then you need a pencil and paper, and a helper is nice to have.
Job one is to disconnect the VCan, and plug the port at the carb.
Then you set the timing to say 10 degrees at 800rpm or less.
Then you are gonna check the timing at every 400 rpm; so like 800,1200,1600 and so on until the timing stops advancing, and one more to be sure it has stopped. On the piece of paper you will record each block of 400 and its related timing number.
Then you generate a graph; with rpm along the bottom axis, and advance along the left-side vertical axis, and with the start point for both at the bottom left corner.
Map out the horizontal in 400 rpm blocks , each division equal and about 1/2 inch wide.
Map out the timing in 2degree blocks, each division equal and at least 1/4 inch tall.
Transfer your data with dots, and voila, the curve is visible.
>If it appears to be a straight line, draw a straight line among the data points to average them all out, connecting as many dots on the line as you can.
But if the line is not a straight line but appears to have a kink in it, and each line is more than two dots long, draw the two lines as best as you can. Stop where they cross.
But if you have a single data point up near the top that appears to be rather far off the line, then go back and get one or two more data points, near that errant one. Then connect those as best as you can.
Now the analysis can begin.

 

[Deleted member 49442]

It can be hard to know which way to go with numerous people giving advice...so try YR suggestions first if you like.
I want to know what the total timing is, full advance without vac adv hooked up. We know the initial timing is low, yet its dieseling ...that isn't a good thing, high heat and unburnt fuel/end gases.
I would think you would want to start around 32 degrees full advance and move up till it starts to ping under load again then go back 2 degrees.
You are going to have to look up re curving the distributor so that you can limit the advance and raise up that initial timing.
One thing that keeps bugging me....is that you are running a 318 exhaust manifold, that has to be backing it up , chamber temps rise, and if thats the case....doing all the right things else where won't make much diff mpg wise especially and will make it ping. But I guess best thing at the moment would be to address the timing issue first, drive it and see if it surges at cruise speeds like 45-50 mph ,if it does its lean, if not...check the plugs and see where its at and go from there...and if your compression is what you say it is, and let's say you just stabbed the cam in dot to dot...could be advanced, then the dynamic would exceed 160 psi and on un preped chambers with tons of end gas...not good. btw you could run 89 octane, needing 91 is iffy imo.

Sorry if my questions are basic, much of this seems way over my head. So to find total timing I should increase the RPM to the point where the timing no longer seems to be increasing?

When you say re curving the distributor, is that adjusting with an alan key in the vacuum advance, or tearing down the distributor and changing springs etc, in the distro?

Sorry should have specified its got 318 truck manifolds, I'm sure I can find 360 replacements, if needed.
I don't think it ever felt like it was surging.
Not sure what you mean by un preped chambers?
I think I will be running premium in it from now on.

 

[MOPAROFFICIAL]

Sorry if my questions are basic, much of this seems way over my head. So to find total timing I should increase the RPM to the point where the timing no longer seems to be increasing?

When you say re curving the distributor, is that adjusting with an alan key in the vacuum advance, or tearing down the distributor and changing springs etc, in the distro?

Sorry should have specified its got 318 truck manifolds, I'm sure I can find 360 replacements, if needed.
I don't think it ever felt like it was surging.
Not sure what you mean by un preped chambers?
I think I will be running premium in it from now on.

Total timing "minus" vac advance is reving it up till the mechanical advance stops increasing. For what you have going on setting the total to 30-32 degrees would be a good starting point.
Recurving means how fast a rate the mechanical timing advances, with marginal octane you would want a slower curve, again, in your possible case. Then there is the adjusting the amount of mechanical advance in the distributor which also involves pulling it out and removing the advance plate that holds the pick up, and don't forget to pop off that reluctor wheel, few screws on the side of the housing including the vac can. It's easy, once its apart ...you get out your welder , which of course you have...jk you can buy an adjustable advance plate.....or if you have access to a welder...just weld the slots a 1/3 of the way closed.....now if you have no octane issue, you can do a little trick that will give something close to shortening the mechanical advance, and that's removing the heavy advance spring and just leaving the other lighter spring in place. That gives about 18 initial and 35 ish....because the advance weights will be partially extended at idle from lack of the stiffer spring.

 

[AJ/FormS]

Click to expand

Sorry if my questions are basic, much of this seems way over my head. So to find total timing I should increase the RPM to the point where the timing no longer seems to be increasing? Yes; job#3, with the vcan disconnected

When you say re curving the distributor, is that adjusting with an alan key in the vacuum advance, or tearing down the distributor and changing springs etc, in the distro?Leave the advance can disconnected during the initial tuning so as not to confuse things. That was job #1

Sorry should have specified its got 318 truck manifolds, I'm sure I can find 360 replacements, if needed.IMO, if there is a port mismatch,this is gonna be a deal later on once you get the low speed stuff figured out. I agree with MoparOfficial, that at some point they should probably come off.A large mismatch is most definitely gonna affect power in a bad way.
I don't think it ever felt like it was surging. 1.5 turns out on the idle mixture screws out is about normal.This adjustment affects the idle quality almost exclusively.
Not sure what you mean by un preped chambers?Stock J heads per post #1
I think I will be running premium in it from now on.That was mentioned on posts 2 and 3

 

[Deleted member 49442]

this is the location I have for the Vac advance hose, looking at my docs, it looks like the correct location.

 

[Deleted member 49442]

The plugs I have are Bosch Platinum, my tire size p225 70R15

 

[AJ/FormS]

What in the World?! Ohhhhhh, platinums.I have never run those.

The thing about the exotic tip plugs is, they were designed in conjunction with lo-perf coils ,starting with 2 plus per coil, then COPs. They were designed to work together. Because the exotics have a low firing voltage requirement,and the engines had multiple coils,the coils could be wussy, and get the job done.

but that same low low firing voltage, means, in a hi-compression engine, the flame-kernal is relatively weak, And It don't matter how hi-perf your coil is, it only puts out enough juice to get the job done.
The exotic tips last a Bazillion miles, running on this reduced tip voltage.
That's why I don't run those plugs.
I believe in a massive spark, that is impossible to blow out. I don't care if the plugs only last half as long. And I believe that a large plug gap fired by a welding coil will more than get the job done. Wide gaps require more voltage, so you better have a decent coil.
I am a big fan of the Accell Super Coil; the big square one Mopar PN P4120889, and Copper plugs. Now, if your current system is not misfiring, I'm not telling you to go out and buy a replacement. I'm just offering an option if yours cannot keep up.I understand that the MSD stuff works too, and it is a great builder system for track-guys. I install those all the time,for guys. I just feel that the Accell coil is a much more affordable system and for a streeter, with a decent fuel tune, it is all you will ever need.It is all I have ever needed.

But yeah, there is no color on that plug that I can see; not on the sidearm, nor on the insulator.And I can't see the center electrode at all.

 

[yellow rose]

The plugs I have are Bosch Platinum, my tire size p225 70R15

View attachment 1715015148

Not sure without other pics bu that plug looks pretty damn hot.

I'm not a big fan of a tip that long. Ever.

 

[Deleted member 49442]

What in the World?! Ohhhhhh, platinums.I have never run those.

The thing about the exotic tip plugs is, they were designed in conjunction with lo-perf coils ,starting with 2 plus per coil, then COPs. They were designed to work together. Because the exotics have a low firing voltage requirement,and the engines had multiple coils,the coils could be wussy, and get the job done.

but that same low low firing voltage, means, in a hi-compression engine, the flame-kernal is relatively weak, And It don't matter how hi-perf your coil is, it only puts out enough juice to get the job done.
The exotic tips last a Bazillion miles, running on this reduced tip voltage.
That's why I don't run those plugs.
I believe in a massive spark, that is impossible to blow out. I don't care if the plugs only last half as long. And I believe that a large plug gap fired by a welding coil will more than get the job done. Wide gaps require more voltage, so you better have a decent coil.
I am a big fan of the Accell Super Coil; the big square one Mopar PN P4120889, and Copper plugs. Now, if your current system is not misfiring, I'm not telling you to go out and buy a replacement. I'm just offering an option if yours cannot keep up.I understand that the MSD stuff works too, and it is a great builder system for track-guys. I install those all the time,for guys. I just feel that the Accell coil is a much more affordable system and for a streeter, with a decent fuel tune, it is all you will ever need.It is all I have ever needed.

But yeah, there is no color on that plug that I can see; not on the sidearm, nor on the insulator.And I can't see the center electrode at all.

I would like to stay as stock as possible as its a show vehicle, I currently have the stock Mopar round coil, i could get you a part # if it helps.
What plugs would you recommend?

Isn't it good that the plugs have no color? I can get you a better pic of the top of them.

 

[yellow rose]

I would like to stay as stock as possible as its a show vehicle, I currently have the stock Mopar round coil, i could get you a part # if it helps.
What plugs would you recommend?

Isn't it good that the plugs have no color? I can get you a better pic of the top of them.

Yes, post some pics of the firing end of the plug. As far down the ceramic and you can get. Still, I say that plug is pretty dang hot for your application.