262 Vortec V6 timing issues, sorry a bit long

[Cameron351]

Hello,
I have a 262 Vortec V6 that isn't making much power after the original heads were rebuilt. This is not the original engine for the boat and I am not even sure if it is a marine engine or a car engine or wether it even matters. BTW it has a Berkley Jet on it.

So here's what I know. The engine runs smooth however takes awhile to get on plane. It feels like it's only getting part throttle. I checked the throttle and the primarys are opening all of the way. I checked the vaccuum secondaries and they only open about half way on accelleration. You can force them open with your finger but you don't get any additional power. This pointed me to ignition timing.

On the lake without a timing light I gave the distributor about 1/8" turn in the advance direction and the engine came alive. It sounded crisper and really accellerated well. I only did a couple of hole shots and put the boat back on the trailer.

Now that I am home with a timing light here is what I find.
My initial timing is sitting at 20 BTDC and with the Thunderbolt IV advance it adds 14 deg. making a total of 34 deg advance. The engine runs pretty dang good here, although steep for initial timing.

The Thunderbolt IV timing for a 262 shows is should have the initial set at 8 deg and the Thunderbolt IV will add 14 deg for a total of 22 deg.

I am not an expert boat mechanic (that the reason for my post) but, on most stock Chevy V8's they like 32 to 34 deg total timing. Why would a boat engine differ so much from a car engine for total timing?

I verified the TDC mark on the ballancer is correct using the positive stop method. I have also verified that 8 deg initial + Thunderbolt IV gives me another 14 deg as per the book. The problem is this leaves a bunch of power on the table.

So, could I have a car engine that has a magical difference from a marine engine?
Should I a after market distributor and curve it my self?
I see that the Thunderbolt V has a Acceleration Advance Envelope that pushes up to 34 deg total timing. Should I change to a Thunderbolt V distributor?

I have spent a bit of time working on magnitos and disturbutor in my life so I don't understand why you wouldn't want more than 22 deg total timing. But before I go burning up an engine out of ignorance to the marine industry; I am asking for some expert opinion and advice.

Thank you all in advance,
Cameron

 

[pwpns]

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

Cameron, Were you having this problem before the heads were rebuilt? You said you are not sure if the motor is original or not. You might have a aftermarket cam in it which could require a bit more initial timing. The cam could also be degreed in with an extra 4 deg of advance which could be pushing your initial timing out further. However 20 deg intial timing is getting out there. Is the motor hard to start or does it start easy. What kind of carb do you have on it. You want to make sure the throttle cable opens the throttle linkage on the carb all the way open. Your cam might be big enough to cause you to lose some vacuum and not fully operate your secondaries. I dont know what type of exhaust you have but you want to be careful about reversion if your cam has to much LSR. Changing from t-bolt IV to t-bolt V would be expensive because you would also have to change the ICM and your wiring and you would not receive any extra benefits to offset the cost in my opinion. If you have a bunch of automotive parts on your boat you will need to change them over to marine parts for safety issues.

 

[Brucetafer]

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

my volvo goes to 36*, and my 454 goes to 32*, so i dont think thats the issue...

if it came to life when you changed the timing on the water, theres your issue...

 

[Brucetafer]

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

my old chevy used to run at 16 bdtc and 32 at total advance..

how is your advance controlled???

 

[Aloysius]

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

Are you confusing crankshaft degrees and camshaft degrees? 14 degrees of camshaft/distributor degrees equals 28 CRANKSHAFT degrees.

Has your damper slipped?

Isn't there a "spout" wire to disconnect/short out to get true base timing?

 

[Silvertip]

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

You have "air valve" secondaries -- not "vacuum" operated secondaries. This means air pressure above the plates opens the secondaries when the pressure below them is less than that. The amount they open depends on demand. As such, they will rarely be fully open.

 

[John_S]

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

The initial and advance timings you have stated are correct for stock Mercruiser V6 and V8 propped I/Os. Why the difference between them? Don't know, but expect there is a reason for it.

Why yours seems to come to life at that much advance could be a reflection of how the engine was built up. What kind of rpms are you hitting? Most jets run higher rpms than propped drives that top out at 5K.

I can't say I've seen any V6 jet drives, usually it is a large built big block. ie something that has gobs of hp that most standard drives are hard to match it to. Maybe this is in a river runner? Jet drives are nowheres near as efficient as a prop. They typically take 25-30% more engine hp to get the same performance of a prop. They do take more to plane out than a prop as well.

 

[Cameron351]

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

Sorry my post was a little confusing. I will try to clear things up.
The factory settings for the TB IV ignition is 8 BTDC and it electronically advances 14 deg for a total of 22 deg. This is by the book and this is what it does in the boat.

I have verified the ballancer has not slipped, using the positive stop method.

The motor has a holley 4bbl carb on it and stock mercruiser exhaust. The bottom end of the motor is all stock as far as I know.

The engine was installed by one mechanic and the heads replaced by another. My guess is the first mec had the timing cranked up a bit and the second set the timing to spec.

My issue is: why in the world would the total timing be limited to 22 by mercuiser? Why wouldn't it be in the low 30's? I know when you advance the timing to 34 total the engine sounds clean and pulls really good. The problem is that pulls the initial timing up to 20 deg. The TB IV advances 14 so when you subtract that from the total of 34 you end up with 20 and yes it makes it hard to turn over.

I would like to yank that distributor out and install something that has more advance but, I don't understand why Mercuiser designed it that way. My experence has taught me that anytime you think you are smarter than the engineer that designed something you better watch out. It doesn't mean they are always right but you better have your s#it together.

That's what I am doing here; I am seeking advice from people that know the marine industry better than I.

Thank you.

 

[Don S]

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

Long post, lots of replies, and no hint to vintage of the engine. No year no SN, nothing.

 

[Cameron351]

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

I beleive the engine is a 1996 or 1997 at least that is when it was installed. On the valve cover there were some numbers:
8LK
108LK T712150897

And the block is stamped just behind the head with:
G04774

That is all I got for numbers.

With the timing set to spec ie 22 deg total, the engine turns right around 4000 maybe 38 or 3900 at WOT. With the total timing at 34 deg the engine turns 43 to 4500 RPM at WOT. Sorry I didn't record the numbers exactly, I failed to document the test runs, my bad. There is a very noticable difference in power.

Thanks everyone for the help.
Cameron

 

[Don S]

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

What year is the igntion system. It really doesn't matter what the block is in this instance, but what ignition system you have and what year.
You may have had a 96 or 97 long block put in and you installed the original ign. system, or it may have been a bobtail engine, which would have included wiring, distributor and ignition system.
We can't see what you have, we can only go by what you tell us.

 

[Aloysius]

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

22 degrees total is not enough advance for a stock engine..34 degrees should be about right. There are different advance modules for those things.

 

[Don S]

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

22 degrees total is not enough advance for a stock engine..34 degrees should be about right. There are different advance modules for those things.

Think I made the same mistake as you. Stop thinking V8 and think V6.
He is within specs for a V6.

 

[wca_tim]

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

even a somewhat hot v6 (4.3) runs great at about 24 degrees total timing.. and the stock module as noted is nearly always a 14 degree advance so running with 8 degrees initial is perfect and it'll have all 22 in by about 2500. I run a v6 module on my v8 so I can run more advance at idle and lower rpms...


and no way on after,market distributer - the tbolt 4 ignition is an oustanding set up and based on my personal experience is about bullet proof and easily supports A LOT more horsepower than any stock engine makes.

Have you checked to be sure that everything else is right? vacuum leaks (ie intake)? valve lash set right?, carb still working properly (as in no crap, fuel mixtuer on target?), what do the plugs look like? did the same engine under the same conditions run as well before? just looking for alternative explainations. timing and ignition sounds like it's fine...

do take a minute to be sure that the contacts are clean in the ignition modeul plug... don't ask me how I know this can do kind of strange things...

Good luck with it!

 

[Cameron351]

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

I think the ignition system is the original system. The boat is a 1989 so I am guessing the ignition system is 89'. Assuming the TB IV was in production then. The ignition module has two numbers on it. 5L03A and V6-14.

Now I don't understand why a V6 or V8 would take a different advance. That is assuming same combustion chamber profile, piston shape, compresson and same fuel is used. It really comes down to how fast the flame front propagates across the cylinder; Light the fuel too early and you create negitive torque; too late and you don't build the optimum pressure in the cylinder.

Is this common for the V6's to have a total timing of 22 deg? I sure wish I had this engine on a dyno; then you could advance the timing until you start to loose power and then back it off to allow for environmental differences.

The best I can tell is this engine wants more advance and 22 deg doesn't seam like enough. On a car; as a rule of thumb for smooth accelleration, you need about 10 deg advance for each 1000 RPM up to the maximum.

If I wanted to get more advance; what would be the best way to do this? do they make a V6-24 module?

Thank you all very much for the help,
Cameron

 

[wca_tim]

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

once you get it close if you have it proped right, you pretty much have a dyno when you put it in the water....

once you get it running pretty well, then we can bum the timing up 2 degrees at a time until you get detonation or quit picking up more speed at wot... (more power)

and then back off.

if it's pinging as I thought you mentioned, then its too far advanced...

my 4.3 ran great with 22-23 degrees total timing...

 

[John_S]

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

He does ask a very good theoretical question: a 4.3L is 3/4 of a 350 sbc, with same bore and stroke, and combustion chamber being similiar, why the 10 degree difference in total advance? I initially thought it might do with V6 firing order or 6 cyl vs 8, but couldn't come up with a rational explaination.

On the other hand, if you assume the 22 degrees is set to produce good power with decent detonation protection, why is his supposidly stock 4.3L running so well at that much more total advance? and it looks like he has made the obvious check with the TDC to balancer TDC check.

 

[Aloysius]

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

v6-v8...same engine, just different number of cylinders. Pistons, heads, displacement, are identical. There is no reason timing should be different. None.

 

[Cameron351]

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

I had no signs of pinging and I was up at 34 deg. It may give me more power with more advance but I didn't check it. I would be happy with 32 deg. and be a bit more on the safe side.

I also under stood the this V6 was essentially a 350 V8 with two cylinders cut off. Although it should have been a 60 deg block to run smoother. I guess the later years they installed a counter ballance shaft to smooth things out.

Does anyone have a listing for all the Thunderbolt modules and there advance curves?

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

 

[FreeBeeTony]

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

Spoke with a friend about the difference in timing curves between a V6 and V8, BTW...he is not a marine guy.

He thought the difference in timing curve (less advance for the V6) might be related to the difference in the amount of torque produced between the V6 and V8.........

Make any sense?