What is initial timing on 4.3GL & can I advance it to improve performance?

USA_boater

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If I ran super unleaded instead of 87 octane, can I set the timing more aggressively? On an EFI 5.0L Camaro I used to have, I set the initial to 10* from 0* and put super unleaded in it and no pinging or anything and it felt quicker when combined with K&N filter, and other bolt-ons etc... Would this be possible in my boat to improve performance since it is just basically a carbbed version of the same style Chevy small block motor?
 

jimmbo

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You need to get the volvo service manuals to get the timing spec.
As for comparing your Camero engine to your boat engine... what works in a car/truck usually doesn't work as well in a marine engine. But it is your engine, so crank away with the advance, but when it grenades...

Maybe a 4.3 is too small of an engine for your boat. Myself I wouldn't buy an 18ft with less than a 5.7. and a longer than a 22ft a 7.4
 
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Scott Danforth

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Your 4.3 is already pushing the same power your camaro 5.0 was pushing. The Marine 4.3s are pushed to their limit

Not much you can do. If you need more power, you need more motor
 

Maclin

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If the Camaro had one, I bet the knock sensor working with the computer kept the timing at bay.
 

tpenfield

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As the others have said, probably not going to amount to much messing with the timing. Funny thing is that the manufacturers of the engines have already figured this stuff out and set things the best possible way.
 

Lou C

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I think the 4.3s were more sensitive to detonation judging by what I see in my OMC shop manual, the V8s both can run with more total advance than the 4.3 which is more limited:

4.3: base timing 6* BTDC, total advance at 3200 rpm = 18* (6 base + 12 mechanical)
5.0: base timing 10* BTDC, total advance at 3200 rpm = 22* (10 base, 12 mechanical)
5.7: base timing 8* BTDC, total advance at 3000 rpm = 29* (8 base, 21 mechanical)

BTW the gas pumps we have at the 2 gas docks close by only sell 93 octane gas anyway, but in my shop manual it indicated if your are running lower octane gas the 4.3 should be timed at 1* BTDC.

Before doing anything to your base timing you should use an advance timing light to check your full advance with the boat in the water so you can run it up to whatever the full advance spec is (if you can't find it use 3200-3500 rpm) boat anchored or tied up lol!
You do not want to get into a situation where you have detonation but due to the noise inherent in running a boat you never hear it before its too late!
What ignition do you have (Delco EST?) and is this carb or throttle body injection? Pay close attention to the color of the center electrode insulator of the plugs....you don't want it to be blistered white.....light tan or grey is good.....
 
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Lou C

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You will get more out of making sure your ignition and fuel systems are up to snuff and your prop pitch is properly selected to allow it to reach the specified max rpm at WOT, than changing the timing.
 

USA_boater

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I wish I knew how to use multi-quote so I'll respond without the quotes:

- I got the boat for 8500 bux from a cousin so I wans't going to shop for another '04 with a V8 (but yes of course I wish it had one).

- Interesting you say the 4.3 is 6* BTDC, everyone on this forum tells me 87 octane is fine (4.3GL vortec heads), but Lou seems to indicate either 87 octane isn't okay OR my boat was set to 1* from the factory?

- Good point on the knock sensor, the Camaro had one but I didn't feel it retard the timing or hear any pinging so I still think 10* was fine. DOES THE 4.3GL have a knock sensor? There is a sensor on the lower block with no harness attached and I thought perhaps that could be a the knock sensor and just isn't used on the carbbed short block?

- I cant't say the boat is under powered, I just have always liked performance so a timing advance is a cheap way to increase it a bit.

- Can anyone tell me if there are any special things to do to set the timing? On the Camaro I had to unhook a wire in order to set initial timing accurately.

- yeah Lou, the plugs looked good (platinums came on vortec motors which of course last a long time) but I am going to replace the cap & rotor and maybe the wires eventually. I'd love to do the Edelbrock 4 barrel and intake too but its money!
 

harringtondav

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Setting timing depends on your engine's ignition system. You'll need a manual. But if you tinker with the timing, fuel and power, you may have the chance to buy that larger engine.

A boat engine is worked much harder than an automotive engine. That is why my 4.3 only averages 3 mpg, 4 on long trips, vs. 20+ mpg if it was in an S10. Even a lead foot car driver only uses full power for a short time. Once up to speed, an auto engine barely works. With a boat, it's full time.
 

Scott Danforth

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your motor is designed to run on 87 octane. increasing timing would increase octane requirements, however increase vacuum at idle and introduce reversion (bad)

your factory service manual will have the timing for your particular volvo and the ignition that is on your particular volvo 4.3

generally the 4.3's are on the raged edge. increasing timing, simply mean that you either burn holes in the pistons and replace the motor or you suck water in the motor, hydro-locking it and then replace the motor.

remember, your 4.3 is prop rated, where the camaro was crank rated. if you want more performance, get more motor.
 

Maclin

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Regarding your Camaro engine with the knock sensor, the computer works very fast to retard timing to where you would not hear pinging. You could probably have set it to 15 and had exact same results. The initial timing from idle until 1500rpms or so is what your butt dyno is reading.

For your particular 4.3, a knock sensor would only make a difference when used by an external computer controlled ignition of some sort with the port for it. Does your carbed 4.3 have TB4/5? Or just distributor controlled timing?
 

USA_boater

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Not sure what TB4/5 is? I did see a GM ignition module on the distributor so it appears to be one of the newer kind.
 

Lou C

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I think that is mercruiser terminology....Thunderbolt 4 or 5....
going back to the original question, the info I gave you was for OMCs specs, make sure you are using Volvo's specs for your engine...they may not be the same due to the differences between the older 1st gen 4.3 that I have vs yours which is much newer.
As far as what fuel octane is adequate, that is an individual thing to an extent. In that an engine might run well (ie no pinging/detonation) on 87 octane when new but as it ages and accumulates carbon build up, the octane requirement of the engine changes so it needs a higher octane gas for it to not ping or detonate. The problem is that pinging or detonation is very destructive and it is hard to hear in a marine engine. So I have always used premium gas and never had pinging or detonation. In fact even though I had two blown head gaskets at the end of the summer of '16, when I took it apart, there was no burning on the tops of the pistons, valves etc.
 

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Maclin

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TB4/5 sorry, got mixed up as to which forum I was in, I will retire from this one.
 

USA_boater

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Thunderbolt Ignition...I'll always remember that term from the 80hp Merc OB on my uncle's old '78 Monark tri-hull when I used to ride in it as a kid in the early 80's. It just sounded cool!

Anyway, as for the octane, I've used super unleaded (91) the only 3 times I took the boat out before the summer ended. However, people on this forum say I only need 87 Octane for that boat? Furthermore, the 87 octane is a minimum rating and the actual octane is closer to 88 or 89 at the pump? My compromise was I was going to start using 89 octane just to be safe since it should be closer to 90 actual at the pump? But I would like to know, how many are using 87 octane and is it "really" okay?

EDIT: For carbon removal, I think seafoam through the intake can remove a lot of it and help stop pre-ignition...at least in cars I've used it a lot; wonder if the boat would be the same?
 
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Scott Danforth

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All I use is 87 octane with exception of the motors I build that require higher octane
 

aimlow

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I think that is mercruiser terminology....Thunderbolt 4 or 5....
going back to the original question, the info I gave you was for OMCs specs, make sure you are using Volvo's specs for your engine...they may not be the same due to the differences between the older 1st gen 4.3 that I have vs yours which is much newer.
As far as what fuel octane is adequate, that is an individual thing to an extent. In that an engine might run well (ie no pinging/detonation) on 87 octane when new but as it ages and accumulates carbon build up, the octane requirement of the engine changes so it needs a higher octane gas for it to not ping or detonate. The problem is that pinging or detonation is very destructive and it is hard to hear in a marine engine. So I have always used premium gas and never had pinging or detonation. In fact even though I had two blown head gaskets at the end of the summer of '16, when I took it apart, there was no burning on the tops of the pistons, valves etc.

that you Bubba? Looks like it. Billinstuart here.

Is that a CSFI injected engine with the dreaded flat top distributor?
 

aimlow

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Some 4.3's used a unique intake port design..high swirl or something. Greatly aided turbulence, which resulted in less ignition advance being needed than most SBC's. Same with vortec heads, but that's a separate issue. Seems total advance should be less than 30 degrees total, but maybe Lou is more familiar with those puppies.
 
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