Initial base timing vs. total timing

[powbmps]

First time posting here, so let me know if I am doing it wrong.

Which is more important, initial base timing or total timing?
5.7 Vortec (remanufactured) with new Edelbrock 1409 carb and 2116 intake. Original 1995 Thunderbolt V ignition with new coil, plugs, wires, rotor, cap and sensor. It is my understanding that base timing for the Vortec is 10 btdc with 28 total advance by 3k rpm. I checked total advance out of base mode and was only getting ~25. Advanced distributor until I was getting 28 (I brought it up to 4,000 rpm and it stayed at a constant 28). Shut off motor, connected jumper wire, and started it back up. At 650 rpm's, in base mode, I'm at almost 14 btdc. Went full throttle a couple times with no noticeable issues. For what it's worth, I only run 93 octane in the motor.

So I suppose my actual question is....Am I better off worrying about the total timing staying at 28, or the base timing staying at 10, because I can't seem to achieve both?

Thank you!

 

[oldjeep]

First time posting here, so let me know if I am doing it wrong.

Which is more important, initial base timing or total timing?
5.7 Vortec (remanufactured) with new Edelbrock 1409 carb and 2116 intake. Original 1995 Thunderbolt V ignition with new coil, plugs, wires, rotor, cap and sensor. It is my understanding that base timing for the Vortec is 10 btdc with 28 total advance by 3k rpm. I checked total advance out of base mode and was only getting ~25. Advanced distributor until I was getting 28 (I brought it up to 4,000 rpm and it stayed at a constant 28). Shut off motor, connected jumper wire, and started it back up. At 650 rpm's, in base mode, I'm at almost 14 btdc. Went full throttle a couple times with no noticeable issues. For what it's worth, I only run 93 octane in the motor.

So I suppose my actual question is....Am I better off worrying about the total timing staying at 28, or the base timing staying at 10, because I can't seem to achieve both?

Thank you!

4000RPM isn't in your WOT range. What happens when you bring the motor all the way up to 4600-4800 which should be in your WOT range.

 

[powbmps]

I'm barely hitting 4,400 rpm with this motor (and I've gone through the "List of possible causes of low WOT rpm" on the forum ). I was pretty close to that and still holding at 28.

 

[Silvertip]

I'm barely hitting 4,400 rpm with this motor (and I've gone through the "List of possible causes of low WOT rpm" on the forum ). I was pretty close to that and still holding at 28.

So after going through the list of things causing low WOT rpm, what did you determine? 1) did the engine EVER get to the upper end of the rpm range before the rebuild? 2) What prop is on the boat (probably the issue in the first place), 3) Carb primary throttle blades opening fully, 4) if a Quadrajet, do the secondary air valves open under full throttle operation (you cannot check this unless the engine is under load -- on the water). As for the base difference -- if you moved the distributor to gain advance timing, you also gain in the base timing. Is the bottom of the boat clean and free of algae buildup? Lots of things other than the engine can be causes for the inability to reach WOT recommendation.

 

[powbmps]

So after going through the list of things causing low WOT rpm, what did you determine? 1) did the engine EVER get to the upper end of the rpm range before the rebuild? 2) What prop is on the boat (probably the issue in the first place), 3) Carb primary throttle blades opening fully, 4) if a Quadrajet, do the secondary air valves open under full throttle operation (you cannot check this unless the engine is under load -- on the water). As for the base difference -- if you moved the distributor to gain advance timing, you also gain in the base timing. Is the bottom of the boat clean and free of algae buildup? Lots of things other than the engine can be causes for the inability to reach WOT recommendation.

I may be burying my head in the sand, but I'm assuming that 4,400 may be it for this motor. We only ski and cruise around the lake (Malibu Response), so I'm not too bothered by the 43 mph top speed. Of course I would like to know that I was getting everything out of it that I should.

1) It was a re-manufactured replacement for the motor that was originally in the boat, so it had not been run before. The literature from the company I bought it from listed max. hp at 4,800 rpm's. Per ACME's recommendation I am running a 515 prop, which Malibu was using from the factory in more recent years. It should not be holding back the rpm,s.
2) The boat originally had a Carter 9770, 750 cfm carb, that I rebuilt and reused on the new motor. I replaced it with a new Edelbrock 1409, 600 cfm carb. This did not affect the max rpm's at all. I have checked, and believe that the primary and secondary air valves are opening all the way. I will re-check the next time I am out.
3) The hull could use a waxing, but it is very clean. Boat is kept on a trailer in my driveway.
4) I understand that increasing advance timing increases base timing. I am just wondering if I am better off running a higher base timing to get the proper total advance, or vice versa.

 

[NHGuy]

I have experience with this issue..
You don't need to set the timing ahead with TB V as the onboard control will find the best advance for you. it has smart features. So just set it to 10 degrees warm with the base mode enabled. Then shut off the engine, detach the base ground, and when restarted it will constantly maintain mean best timing.
If you watch it at idle, you will think something is wrong because the timing moves all over, but that's how they work.

I have a 600 cfm Weber, they are the same as an Edelbrock 1409. I have a new engine too and I've been working out the jetting difference. You really ought to do the setup that Edelbrock recommends. Once it's jetted in you will probably get a couple of more "ponies" but more importantly you will have enough fuel going in there to avoid detonation.
If you like I will look up the jetting that Mercruiser uses in your engine when I get home later, it will be a good baseline for you.

The ignition system listens for ping and retards the timing if it happens, but if you get the engine enough fuel (via proper jetting) you will get all your power in a safe manner. avoiding detonation.

 

[powbmps]

I have experience with this issue..
You don't need to set the timing ahead with TB V as the onboard control will find the best advance for you. it has smart features. So just set it to 10 degrees warm with the base mode enabled. Then shut off the engine, detach the base ground, and when restarted it will constantly maintain mean best timing.
If you watch it at idle, you will think something is wrong because the timing moves all over, but that's how they work.

I have a 600 cfm Weber, they are the same as an Edelbrock 1409. I have a new engine too and I've been working out the jetting difference. You really ought to do the setup that Edelbrock recommends. Once it's jetted in you will probably get a couple of more "ponies" but more importantly you will have enough fuel going in there to avoid detonation.
If you like I will look up the jetting that Mercruiser uses in your engine when I get home later, it will be a good baseline for you.

The ignition system listens for ping and retards the timing if it happens, but if you get the engine enough fuel (via proper jetting) you will get all your power in a safe manner. avoiding detonation.

Thanks NHGuy. I'll bring it back down to 10 at idle in base mode, and let it do its thing. I spoke with someone at Edelbrock yesterday and he suggested starting with the springs, as I'm getting a frustrating hesitation when initially pulling up a skier. Switching those over tonight. Also replacing the knock sensor for the heck of it. Pulled the old one out and the tip is badly corroded. The fitting it was screwed into was blocked up with some chunks of rust as well.

I'm typically over on Pleasant Lake in New London, NH. Sometimes on Sunapee.

Thanks again.

 

[NHGuy]

So, I just took a look in the tech book on the Webers, which the Edelbrocks are cloned from. And your out of box jetting is a bit richer than Mercruiser. So you are good. Try a softer spring first, then a heavier one. Go back and forth til you are happy with the acceleration. What hole is the accelerator pump on? They can be moved to change the pump shot.

 

[achris]

I may be burying my head in the sand, but I'm assuming that 4,400 may be it for this motor. We only ski and cruise around the lake (Malibu Response), so I'm not too bothered by the 43 mph top speed. Of course I would like to know that I was getting everything out of it that I should.....

Skiing is the one activity that imposes the highest load on the engine. Having it propped to the very top of the rev range is critically important, especially when skiing. Most engine manufacturers actually recommending droppping another pitch down when pulling skiers. You need to change the prop to get those revs up.

TB-V. As someone already mentioned, it's a bit of a smart system. Just set the timing to the correct initial, in 'Base timing mode' and the module will deal with the total timing. If the fuel's a bit dodgy or the air a bit thin (high altitude) the module will retard the timing (via input from the knock sensor) to save the engine from detonation. If you set the intial timing too far advanced, the module may not have enough retard too achieve that. Set it to far retarded initially and the module won't be able to advance the timing to give you that kick of acceleration needed to get a 'bigger' skier off his bum.

Chris.......

 

[Scott Danforth]

if your running 93 octane with vortec heads, you can stay at the 14 degree base, however your loosing some power because the higher octane fuels have lower BTU capacity.

I suggest dropping back to about 12 degrees, drop down to 91 octane (or drop down to 10 degrees with 89 octane) and get the correct prop.

 

[powbmps]

if your running 93 octane with vortec heads, you can stay at the 14 degree base, however your loosing some power because the higher octane fuels have lower BTU capacity.

I suggest dropping back to about 12 degrees, drop down to 91 octane (or drop down to 10 degrees with 89 octane) and get the correct prop.

Interesting. I always assumed 93 was the best choice. The gas stations around here typically have 87, 89 and either 93 or 91. I'll run 89 at 10 degrees for a bit.

 

[Scott Danforth]

93 is a good choice if you need the octane as detonation mitigation (usually recommended by the OEM). I believe Mercruiser only requires 89 octane. in the midwest, the higher octain (premium) is also usually ethanol free. I ran 91 or 93 (and even 106 LL aviation fuel) in my SBC initially because I didnt want ethanol, however I played with cam choices, heads, ignition advance and a bunch of other factors to utilize the higher octane which forced me to run on 91 or higher.

now Im building a stroker BBC to run on 89 pump gas that will be stuffed into the bilge