262 Vortec V6 timing issues, sorry a bit long

[John_S]

Re: 262 Vortec V6 timing issues, sorry a bit long

Also can you use a V8 module on a V6? I don't know how the module knows wether it is on a V8 or a V6. It simply reads the pules from this distributer and fires the coil. (ok, it does a little more but that covers it input and output)

Thank you all very much,
Cameron

The modules don't know what they are installed on. A V6 will work on a V8 and visa versa. The amount of advance and the actual curve does change a little, though. That is because the counter/divider is different. 6 pulses = 2 rpms on the V6 module. There was info in Dennis Moores book on using the V6 module on V8's. Using a V8 module on a V6, I think would have a slightly delayed timing curve.

Timing curves: http://www.boatfix.com/merc/Bullet/95/95_11.pdf

 

[Cameron351]

Re: 262 Vortec V6 timing issues, sorry a bit long

Yea your right about the delay in the advance curve. I didn't think about that. With the V6 giving you 3 pulses per RPM and the V8 giving you 4. That would delay full advance on a V8-24 module (mounted on a V6) to a little over 4900 RPM. That would require about 320hp to turn the jet at that RPM; I don't think that's gona happen.
Great input, thank you.

What about installing a mallory marine distributor? Anyone want to weigh in on that thought?

Thanks again to everyone,
Cameron

 

[wca_tim]

Re: 262 Vortec V6 timing issues, sorry a bit long

Actualy you get about the same advance curve whether you use the module on a v6 or v8... the reason to use a v6 module on a v8 is so you can run a lot more advance at idle when running a long duration camshaft or especially with a blower. I run a v6 16 module on my v8 so the idle is at much more advance than 8 degrees and so it's all in by 2500 rpms... it runs a good bit better this way.

the distributer is also interchangable between 4.3 and 5.7, what's different is the cap and rotor. (everything else is interchangable between the two mrecruiser set-ups). The pulses spaced by the rotor in the distrbuter... not the module.

I'm thinking that the big difference is where in the rotation maximum cylinder pressure is achieved in a v6 relative to a v8. The name of the game in engine design based on my niave understanding is to achieve maximum cylinder pressure at the point in rod to crank angle where the greatest amount of work can be done by that cylinder when it fires and in between the point where the previous cylinder fired and the next cylinder is going to fire. For a v6, the next cylinder will be firing at another 120 degrees of rotation, while in a v8 it will be only 90 degrees later... in a v6 each cylinder must provide the torque for a longer at a given rpm than in a v8 and thus would be more efficient if max cylinder pressure was achieved a little later than

I need to read and chew on this a bit more.... but those are some of the factors that I'm certain have influence...

 

[John_S]

Re: 262 Vortec V6 timing issues, sorry a bit long

Actualy you get about the same advance curve whether you use the module on a v6 or v8... the reason to use a v6 module on a v8 is so you can run a lot more advance at idle when running a long duration camshaft or especially with a blower. I run a v6 16 module on my v8 so the idle is at much more advance than 8 degrees and so it's all in by 2500 rpms... it runs a good bit better this way.

I had to go recheck DM's book. He indicates that running the V6 module on a V8 will lower the advance considerably. It says somewhere around 6-10 degrees.

It wouldn't be the 1st error I found in his book. Not sure how that could be, based on what little data the module has to work with. Timing curve shift seemed to make the more sense.

 

[Cameron351]

Re: 262 Vortec V6 timing issues, sorry a bit long

If I wanted a fully adjustable advance curve; what are my options? I only want marine grade options. I know mallory made a dist. are they adjustable and reliable? Also I really don't want to do the points and condenser thing.

So what I am looking for is a fully adjustable electronc marine distributor, that is reliable and inexpensive. That's not asking too much is it?

Any suggestions?

 

[wca_tim]

Re: 262 Vortec V6 timing issues, sorry a bit long

I had to go recheck DM's book. He indicates that running the V6 module on a V8 will lower the advance considerably. It says somewhere around 6-10 degrees.

It wouldn't be the 1st error I found in his book. Not sure how that could be, based on what little data the module has to work with. Timing curve shift seemed to make the more sense.

it's not an error, it just reflects that the v8 modules are 20-24 degrees advance and v6 is 14... the difference is 6-10 degrees. His point was that if you are running a fairly hot camshaft or a blower, coupled with efficient heads and a tight quench (will want less total advance for max power, but need more advance at idle to run right), you can run a v6 -14 module on your v8. The other reason would be running forced induction and needing toi retard the total timing to ward off detonation yet still have enough advance at lower roms for the engine to idle and run right.

to the OP, if you really want to spend money on your ignition, and are pretty sure you need a variable advance curve (I have a strong feeling with your current set-up there is little to be gained), I would probably see if you can find one of the crane HI-6M CD boxes and run it with your stock coil and distributer (ignition module no longer needed). That gives you multiple spark below 3000 roms, programmable advance curves and an adjustable rev limiter. all for something shy of 300 bucks...

Personally, in your situation I would run the factory thunderbolt ignition. You'r enot going to get anything more reliable, parts are easy to find and cheap used, and you'll be very hard pressed to improve on performance in any noticable way...

Just my opinion...

 

[John_S]

Re: 262 Vortec V6 timing issues, sorry a bit long

it's not an error, it just reflects that the v8 modules are 20-24 degrees advance and v6 is 14... the difference is 6-10 degrees. His point was that if you are running a fairly hot camshaft or a blower, coupled with efficient heads and a tight quench (will want less total advance for max power, but need more advance at idle to run right), you can run a v6 -14 module on your v8. The other reason would be running forced induction and needing toi retard the total timing to ward off detonation yet still have enough advance at lower roms for the engine to idle and run right.

..

I understand why they would want to use them on a V*, but the way I read it, it is specificly talking about the advance difference. Read page 191, the text at the bottom of the shaded box. He is specificly talking about the V6-14 module having less advance on a V8. "They give considerably less than 14 degrees when used on a V8, somewhere around 6-10 degrees."

 

[wca_tim]

Re: 262 Vortec V6 timing issues, sorry a bit long

I understand why they would want to use them on a V*, but the way I read it, it is specificly talking about the advance difference. Read page 191, the text at the bottom of the shaded box. He is specificly talking about the V6-14 module having less advance on a V8. "They give considerably less than 14 degrees when used on a V8, somewhere around 6-10 degrees."

You're right, the wording is confusing. I guess I read that in the context that no one would ever consider putting a v6 in a boat... or at least that he's not talking about v6's. I assumed that he meant ignition modules for v6's have less advance than those used with v8s... and since the module works based on the signal sent from the distributor, which is the same for v6 and v8 aside from the cap and rotor, it is silly to think that the module would work differently between the two. oh, I know that the advance on my v6 module flattens out at 2500, exactly where it is supposed to.. and that's with it installed in my v8.

btw. I realize you know why and when one would want to use a v6 module on a v8, I was giveng more explaination for someone else that might not.

 

[Aloysius]

Re: 262 Vortec V6 timing issues, sorry a bit long

Crank fired ignitions do not "advance" timing..think about it...it's physically impossible to make an event occur in the future. The crank position sensor tells the brain where the crank is so it can compute the settings for the NEXT cylinder in rotation.

In any case, timing requirements are virtually identical for both engines. 4,6,8,12 cylinders..won't make any difference IF they cylinders of all are identical. Same ignition curve, same injector pulse width, same power per cylinder, same torque from each cylinder.

Why the difference in advance curves? My guess is, typical Mercury marine "cheap way out". Sacrifice power for cheap parts.

 

[Cameron351]

Re: 262 Vortec V6 timing issues, sorry a bit long

I expect the engineering team decided they were making enough power out of the V6 and didn't have the need, time nor funding to develop further performance. After all it is a V6 (not offense to V6 owers but it's 2 cylinders short of an engine)

Anyway; On a drag racing engine you can find best total advance by raising the advance 2* at a time watching the MPH increase at the top end. Once it hits max MPH or starts to drop you have found the sweet spot. This has to be done very carefully or you will be going home early.

I don't know why this couldn't be done on the water. Adjust the total timing, then make a short run to top MPH. Document the results and make the next adjustment and go again. It's a stock engine which is much more forgiving than a blown alky motor. Of course the environmental conditions is a huge variable which would require me to back off from this sweet spot say 4 or 5* to provide a margin of safety.

 

[John_S]

Re: 262 Vortec V6 timing issues, sorry a bit long

The only input to these T4 ICMs is the distributer ignition sensor, that fires from the rotor window passing in front of it. I have not figured out a way that the ICM could detect if it was on a V6 vs V8. There is not a jumper or switch setting. While it must have an internal time base, it also needs to know for how many pulses equals one revolution. There are not any crank position or distributer position sensors on these carbed motors. Later EFI and MPI, yes. The only thing I can think of is, it detects the difference in the open to closed window duration of the rotor. I think that is grasping though.

 

[Aloysius]

Re: 262 Vortec V6 timing issues, sorry a bit long

I'm not familiar with the absolute operating logic either, but common sense tells me that, even if the trigger is in the distributor, the sensor has to be for the NEXT cylinder, and timing is computed backwards.

Import, you're not grasping. let's see..a v8 fires every 90 degrees(720/8). A v6 fires every 720/6 or 120 degrees per firing, if it's even firing. 30 degree crankshaft difference, equals 15 degrees distributor. hmmm..not 10 degrees. Help me out here.

Don't look at it as "advancing". You simply can't say.."this is TDC..fire the cylinder 30 degrees BEFORE this point..."

 

[John_S]

Re: 262 Vortec V6 timing issues, sorry a bit long

I agree that it is probably triggering off the prior window, and just delaying the firing. But, regardless it has to understand revolutions per minute, so it can adjust the amount of delay. An internal crystal would provide the timebase, but still needs to know how many pulses equal one revolution.

I was refering to the recommended total advance timing difference of 8-10 degrees. As stated earlier, I don't know why that is, but also don't believe GM/Merc/Volvo all intentionally killed hp output by that much. If that were true, there would be a long list of threads on how to get "free" hp from every 4.3L out there. IMO, there is a reason, and wca has probably come the closest for an explaination.

As far as the OP ability to run at that advance, I suspect the engine is not as stock as it would seem, and/or something else is going on. How a jet drive loads the engine, vs a prop? Something.

 

[Aloysius]

Re: 262 Vortec V6 timing issues, sorry a bit long

The "event duration" issue is an interesting aspect. Requires extremely accurate time measurement for accuracy. From what I figgered above, in the same time increment, the event duration between a 6 and 8 cylinder engine would be 15 degrees. Now, there's certainly a pulse count factor to determine rpms, so maybe the logic circuit compares rpms to pulse width time.....

Hey, I rebuild and curve distributors..I've gotta good basic understanding of digital management, but I live in an analog world.........

 

[Cameron351]

Re: 262 Vortec V6 timing issues, sorry a bit long

I'm guessing here but I believe the V6 module expects 3 pulses per crank rpm and the V8 module expects 4 pulses per crank rpm. I thought about using a V8 module but with only receiving 75% of the expected pulses the full advance wouldn't be in until about 4900 RPM. The module doesn't know anything except the rate of pulses it receives. It must have a crystal as a refferece. It really not that fast of an event; a V8 running at 5000 rpm with 4 pulses per rpm is only 20 Khz.

 

[wca_tim]

Re: 262 Vortec V6 timing issues, sorry a bit long

note that the distributer is interchangable... what is different is the cap and rotor and the sensor that attaches to the rotor... I think John hit it on the head above.

I noticed and will check later if no one chimes in that knows for certain, but it looks to me like the gaps between metal are the same number of degrees each on both the v8 and v6 rotor - about 24 degrees of rotation for each gap. A hall effect switch, is very accurate in terms of measuring degrees of rotation (used on many crank and cam position sensors) and is an on and off switch - it shows a square wave if you look at it on an o scope. This is also why the sensor has to be precisely aligned on the rotor for the distributor to work properly... The favct that we're using a different sensor wheel in the v6 and v8, each of which has gaps corresponding to exactly the same degrees of rotation, makes it unnecessary for the ignition module to know how many events to count per revolution, it knows how many degrees of rotation the hall effect trigger is on for with respect to each event based on the rotor sensor. (the hal effect switch is on, except when blocked by the sensor blades, so it is the oenings that dictate the amount of time it is on for each pulse - very precisely so.

So do you know off the top if when you set timing with one ignition module, and then swap to the other, what changes? initial timing or total timing? I bet it is initial timing and that total timing remains exactly the same. Again, I don't know for certain, but it makes sense to me that you're actually setting timing for total advance and the ignition module retards it the maximum amount at lower rpms, and retards it less and less until it sees the full advance at whetever rpm the curve for that module dictates. You're delaying spark at low rpm ,not advancing it at higher rpm...

That's my current guess at how this works, but I need to do some more digging to be sure, or hopefully someone will chime in that knows precisely how it the system is designed...

 

[Cameron351]

Re: 262 Vortec V6 timing issues, sorry a bit long

I contacted Berkley and told them I had a 262 V6 and a Berkley model 12JC-B jet pump and asked them for initial timing, what rpm should the advance be all-in and what the total advance should be.
Here is there answer:

"I would use 8 to 10 degrees on the initial timing you can go to 12 if needed and have the curve done by 2500 rpm and if possible a total timing of 34 to 36 degrees would be great."

 

[Aloysius]

Re: 262 Vortec V6 timing issues, sorry a bit long

I contacted Berkley and told them I had a 262 V6 and a Berkley model 12JC-B jet pump and asked them for initial timing, what rpm should the advance be all-in and what the total advance should be.
Here is there answer:

"I would use 8 to 10 degrees on the initial timing you can go to 12 if needed and have the curve done by 2500 rpm and if possible a total timing of 34 to 36 degrees would be great."

Why am I not surprised? I also wouldn't be surprised if Mercury didn't have a misprint in their literature.

What works for a 350V8 works for 3/4 of a 350V8.

 

[John_S]

Re: 262 Vortec V6 timing issues, sorry a bit long

Why am I not surprised? I also wouldn't be surprised if Mercury didn't have a misprint in their literature.

Well, they made allot of timing modules wrong, over many years, as well??? Volvo too?

 

[whitney]

Re: 262 Vortec V6 timing issues, sorry a bit long

Interesting discussion. I thought I would throw out one easy to check thing: Are you sure you have the right spark plugs? When Chevy went to the Vortec heads, the threaded plug depth got a lot longer than the pre-vortec. The threads on the Vortec-correct plugs are like 2x the length.

I had this problem on my 92 with a 96 block ... mechanic used the old plugs. The affected timing since the flame front was starting from inside a deep hole and would need more timing than spec.

Just an idea I had while reading this thread... $0.02