searching for torque curve specs for '87 5.7... total timing advance?

I bought a used boat... since then Ive been having some WOT running issues with the engine not coming up to rpm under load, and so did the previous owner, who bought it from an estate without any background information on it other than it was "supposed" to run great...
what I know for sure is, its a stock 1987 5.7, all original. NOT a vortec.
distributor is the original prestolite IBM-7013C with an electronlc pickup module in it. the flyweights seem to be free and snappy

after the initial (and disappointing) trial runs, I have pumped the fuel tank dry, flushed it, and pumped it out again to get all the old gas out, and then refilled it with ethanol free gas... and I checked the initial timing (6BTDC), the engine starts easy and runs fine, but it had no power... so I kept looking for problems and found a couple more of them.
the secondaries in the carb were stuck closed, but a bit of WD40 and working them and they freed up nicely... and then I pulled the exhaust elbows and found one of the flappers in the exhaust was stuck closed.... so I replaced the flappers, manifolds and riser elbows with all new parts and installed iridium spark plugs.

then back to the lake.... we idled out past the slow buoys, and then slowly opened the throttle... it seemed to run great. it climbed on plane much quicker and easier and i could now hear the secondaries open.... the boat, which on previous trips would only make 14mph was now quickly up to 20mph and climbing.... but at 22mph i felt a slight loss of power, and we dropped back to 20mph. then within 45 seconds another loss of power which took us down to 16mph..... so I stopped the boat and the engine was misfiring. this all happened within about 3 minutes of when I opened the throttle.... the engine started easy and sounded good except for the misfire.

so we limped to an anchorage and let the engine cool down, then pulled the spark plugs.
#2 and #8 cylinders had the spark plugs melted down, no tips, no electrodes, just the threaded portion and the white ceramic left.... all the others looked fine but with yellow on them rather than the normal shades of brown, black, or gray.... maybe due to the ethanol free gas?

when we got the boat back home, I checked compression... 145-150 on all cylinders except #2@ 0psi and #8@ 75psi.... after the disassembly I found the intake valves on both cylinders were leaking badly, but the exhaust seemed to be fine.... the intake valve on cylinder #8 was badly dished and the stem was almost 3/8 of an inch higher than the rest of them...

I dont know what led to the melt down, but I want to check the maximum advance timing to see what the distributor is doing at the higher rpm...
I have searched for hours on the internet looking for a torque curve chart for a 350 marine engine without success... but there is a lot of gossip on different forums claiming a wide range of numbers and what rpm these numbers are supposed to be seen at, but there is nothing that shows any commonality.... AND, a lot of the forums have some smartass saying check the manufacture specs and set it to that....yep, thats such an obvious solution but it seems no one can find any "manufacture torque curve specs" for the 5.7/350 engines. and neither can I... what is so top secret about these charts?...

can someone share some good proven Total Advance Timing numbers for a 5.7 MARINE engine with me, and at what rpm should the timing be "all in"?
thanks for any help...

the secondaries in the carb were stuck closed, but a bit of WD40 and working them and they freed up nicely...

Click to expand...

Ayuh,.... Yer motor is sufferin' from fuel starvation,....
Which causes detonation, which burnt down yer cylinders,...

A carb Rebuild will be a step in the right direction,....

bondo said:

Ayuh,.... Yer motor is sufferin' from fuel starvation,....
Which causes detonation, which burnt down yer cylinders,...

A carb Rebuild will be a step in the right direction,....

Click to expand...

bondo, thanks for the reply...
I wont disagree, and its easy enough to disassemble the carb and drop it in the tank....
but according to the way it ran for the guy I bought it from, the secondaries havent been operational for the 6 years he had the boat, yet he used the boat a lot and without any problems, as he thought it was normal.... and according to the way it ran after I got them working, it didnt seem as if it was starving for fuel, AND the flo-scan meter went from a maximum peak of 15gph before freeing the secondaries, to nearly 27gph after getting them working... if it is in fact starving for fuel, im left wondering what kind of flow numbers I should expect at WOT...

along with the rebuilt heads and a carb cleaning, im installing a new fuel pump, as the one installed now is the original one that came with the boat nearly 30yrs ago, which is more likely the cause of any lean condition that may be happening...

but im still looking for the total advance timing numbers.... thanks.

From what I can find is you want between 22 and 26 degrees spark advance at 3700 rpm. For total advance add base timing for all in or total timing. So if you set base timing at 7 degrees BTDC at 3700 rpm you should be between 29 and 33 DBTDC. You can map the curve make a chart with rpm on bottom and timing on the side then put a mark for every 500 rpm at ignition timing. I found that curve from a mercruiser 5.7 but a GM is a GM pretty straight forward.

First thing to do is check for true TDC with a piston stop tool. You can buy one cheap or make one out of one of those cooked spark plugs. Bust the center out and thread it for a long bolt and then pull all the plugs and disconnect the battery. Turn the crank about 20 degrees after TDC and make a mark on the damper at the timing mark. Screw in the piston stop #1 cylinder and touch the piston with the bolt. Then turn the crank until the piston comes back up and touches the stop and make another mark. True TDC is half way between the two marks. Use that mark to check adjust base timing and total spark advance. You can probably just set the distributor at 32 degrees all in and be good just make sure the advance stops around 3700 rpm. For best fuel economy do not run WOT keep the RPM at total advance and it will extend the service life of the engine.

OK...... Marine cruiser gasoline engine ignition advance is extremely critical.
The 1987 5.7L SBC (if OEM) is fitted with the dreaded GM Full Dished pistons.
These pistons cannot possibly create a Quench Effect.
That is strike #1.

Your old Prestolite distributor may not be advancing correctly...... and the Pertronix kit certainly doesn't help any!
Since you set BASE advance only, you do not know what the progressive is doing (via the flyweight system)
If the progressive is excessive, you may have Detonated several cylinders.
If so....... you may have caused severe engine damage.
If so..... that would be strike #2.



Make sure that your outer harmonic balancer ring has not slipped, causing your OEM #1 TDC indexing to be incorrect!
If in doubt...... perform a PPS (positive piston stop) procedure as Kim suggested!
(I use a degree wheel and a temporary pointer)

With the stop in place, gently rotate the crankshaft until #1 piston is stopped.
Move the degree wheel and/or pointer to read approx 30* BTDC.
(a 30* +/- split in either direction ensures more accuracy, so you may need to increase or decrease the depth of the PPS)

Now rotate the crankshaft in the opposite direction until again the #1 piston is stopped.
Again, move the pointer to approx 30* BTDC.

You may need to repeat this several times...... but that is no big deal!

(do not bump the degree wheel or pointer while removing the PPS)
When the PPS is finally removed from the spark plug port, the half way point between these two degree angles is your True #1 TDC.
This is when you will verify the OEM TDC markings.

And by the way..... if the outer balancer ring has slipped, it will slip again.
Best to replace it.



For ignition advance, you will want to see approx 6 to 8 degrees BTDC @ idle speed.
You will want to see a progressive advance (in a linear fashion) of up to approx 26 degrees @ 3,200 RPM.
If the progressive steadily continues and limits itself to 30 degrees or so....... it will not be an issue.

If you must adjust the curve, keep in mind that a 2* or 4* change to BASE advance is also a 2* or 4* change to the Progressive and Total Advance.






.

regarding your original question about "torque curves"; you'll be hard pressed to find that data for a production gasoline marine engine.....biggest driver is the unknown loads the engine will see.....a small block could go into a 3000# hull with a 1.5:1 outdrive and not work hard at all.....the same engine could go into a 30+ft houseboat with a 2.5:1 reduction gear and be working hard most of its life.....diesels are different beasts altogether which is why you can find torque curves for them easily...

OK....... let's try this:

centerline said:

I bought a used boat... since then Ive been having some WOT running issues with the engine not coming up to rpm under load, and so did the previous owner, who bought it from an estate without any background information on it other than it was "supposed" to run great...
what I know for sure is, its a stock 1987 5.7, all original. NOT a vortec.
The Hull must be clean and free from any marine growth.
Likewise with the stern drive if equipped.
The propeller must be in near pristine condition and must be the correct pitch/diameter.
The final or over-all gear reduction must be correct for the engine.
Engine must be healthy and must be fully tuned to OEM specs (there is a reason for this).

Keep in mind that the WOT RPM is a test RPM ONLY..... and it is not to be sustained for any duration.


distributor is the original prestolite IBM-7013C with an electronlc pickup module in it. the flyweights seem to be free and snappy
See my previous post.
If in doubt, take it to shop who owns/operates an ole school Allen, Sun or King distributor machine and have it checked out.

after the initial (and disappointing) trial runs, I have pumped the fuel tank dry, flushed it, and pumped it out again to get all the old gas out, and then refilled it with ethanol free gas... and I checked the initial timing (6BTDC), the engine starts easy and runs fine, but it had no power... so I kept looking for problems and found a couple more of them.
BASE advance is BASE advance ONLY........ we fire up on BASE and we idle on BASE only!
BASE advance alone is not a meaningful indication of what's occurring at the higher RPM range.



#2 and #8 cylinders had the spark plugs melted down, no tips, no electrodes, just the threaded portion and the white ceramic left....
when we got the boat back home, I checked compression... 145-150 on all cylinders except #2@ 0psi and #8@ 75psi.... after the disassembly I found the intake valves on both cylinders were leaking badly, but the exhaust seemed to be fine.... the intake valve on cylinder #8 was badly dished and the stem was almost 3/8 of an inch higher than the rest of them...
Detonation can cause this.

I dont know what led to the melt down, but I want to check the maximum advance timing to see what the distributor is doing at the higher rpm...
Yes...... that is a MUST!

I have searched for hours on the internet looking for a torque curve chart for a 350 marine engine without success... but there is a lot of gossip on different forums claiming a wide range of numbers and what rpm these numbers are supposed to be seen at, but there is nothing that shows any commonality.... AND, a lot of the forums have some smartass saying check the manufacture specs and set it to that....yep, thats such an obvious solution
It is also the most safe suggestion to make to a person who is relying on Internet Boating Forums for their information.
Learn to trust your source.
Use the source information only upon being satisfied that the source knows what he is talking about.


but it seems no one can find any "manufacture torque curve specs" for the 5.7/350 engines. and neither can I... what is so top secret about these charts?...
Again....... the average GM SBC that makes it's way into a boat is fitted with the dreaded GM Full Dished pistons.
This = NO Quench!
No Quench means that the GM (and/or the boat builder) recommends a lazy ignition advance as to combat Marine Load Ignition Induced "Detonation"
A lazy ignition advance equates to an equally lazy LPCP.
(LPCP = Location of Peak Cylinder Pressure)
All reciprocating engines must have a reasonable LPCP ( best if @ 12* to 14* ATDC ) in order to produce MAX torque.

can someone share some good proven Total Advance Timing numbers for a 5.7 MARINE engine with me, and at what rpm should the timing be "all in"?
Perhaps another member would be willing to. I am reluctant to offer an exact number for this as to avoid any misunderstandings and/or misinterpretation.
Add to that any unkowns on behalf of the owner, and it mean trouble........ and expensive trouble to boot!

In my opinion, each owner should be able to reference his/her OEM service or work shop manual for this information.

I will suggest that a safe curve will bring the progressive advance up in a rather linear line, and it will limit out at approx 26* to 28* BTDC @ no earlier than 3.2K RPM.
That would be with the understanding that there is the correct fuel/air ratio being delivered, no over-temp issues, no excessive loads, the correct final drive reduction, and so on.

Click to expand...

.

RicardoMarine said:

OK...... Marine cruiser gasoline engine ignition advance is extremely critical.

The 1987 5.7L SBC (if OEM) is fitted with the dreaded GM Full Dished pistons.


Your old Prestolite distributor may not be advancing correctly...... and the Pertronix kit certainly doesn't help any!
Since you set BASE advance only, you do not know what the progressive is doing (via the flyweight system)

.

Click to expand...

"The 1987 5.7L SBC (if OEM) is fitted with the dreaded GM Full Dished pistons."
this is a reman engine from HI Tech Engines in Spokane, assembled in 2010... the piston part number is H423NCP .030, stock heads..


"Your old Prestolite distributor may not be advancing correctly...... and the Pertronix kit certainly doesn't help any!"
thru further research, I have found out the distributor is OEM, Prestolite IBM-7013C, BID system.... no pertronix

does this new information change things? do you know at what rpm these distributors are set to be "all in"?

BTW, I have pulled the engine as #4 and #8 were affected.... I had to put a new piston in #4, but #8 seemed good, but the top ring was sluggish in its groove, NOT stuck, but not quite right either.... cleaned the grooves and new rings on it.... all other cylinders are good and no signs of damage..

NOTE: the spark plugs were burning with a yellow color, instead of the usual shades of gray/brown/black... is this due to the high octane ethanol free fuel?

I didnt realize the damper/balancer could slip, but I am very familiar with how to index a crank or cam and have the tools for it, so I will check to make sure the timing mark is correct.

Thank you...

centerline said:

"The 1987 5.7L SBC (if OEM) is fitted with the dreaded GM Full Dished pistons."
this is a reman engine from HI Tech Engines in Spokane, assembled in 2010... the piston part number is H423NCP .030,
The Sealed Power H423NCP is a GM Full Dished style piston replacement. It offers a quench band ONLY..... NO Quench Surface!!!!!
https://www.summitracing.com/parts/stl-h423ncp
stock heads..Do you know what the cylinder head's combustion chamber volume is?

"Your old Prestolite distributor may not be advancing correctly...... and the Pertronix kit certainly doesn't help any!"
thru further research, I have found out the distributor is OEM, Prestolite IBM-7013C, BID system.... no pertronix
Whether or not a Hall Effect kit has been installed, my point was with regard to the old advancing system.
This is centrifugal flyweight cam and return spring controlled.
A rust compromised return spring may allow the system to advance early.
Early or excessive advance may cause DETONATION !!!!!!! does this new information change things?
No. The H423NCP pistons actually confirm my thoughts regarding being very conservative with the Ignition Advance.

do you know at what rpm these distributors are set to be "all in"?
Again, see your OEM specs.
Many systems will be Full In at approx 3.2K to 3.5K RPM.
The more important question is........ what will the advance be (in crankshaft degrees) at this RPM???


BTW, I have pulled the engine as #4 and #8 were affected.... I had to put a new piston in #4, but #8 seemed good, but the top ring was sluggish in its groove, NOT stuck, but not quite right either.... cleaned the grooves and new rings on it.... all other cylinders are good and no signs of damage..

NOTE: the spark plugs were burning with a yellow color, instead of the usual shades of gray/brown/black... is this due to the high octane ethanol free fuel?

I didnt realize the damper/balancer could slip,
Yes...... you'll notice that on the OEM balancer, the outer ring is rubber isolated.
You'll also notice that the TDC mark is in the outer ring.
As the isolation material ages, it can allow the outer ring to slip on the inner hub.

but I am very familiar with how to index a crank or cam and have the tools for it, so I will check to make sure the timing mark is correct.
That would be good.
My recommendation is to use 30* +/- as your split angle. (that is 30* +/- on either side of TDC).

Let's say that your split ends up being 27*.
When both directions give you a 27* stop, you will then remove the PPS and bring the crankshaft around to ZERO.
ZERO will be your True TDC.

Click to expand...

..........................

This is the Sealed Power H423NCP piston.


.

as I have the heads off, I used a dial indicator on the piston to find true top dead center, and it is dead on to the damper mark... the distributor isnt rusty or corroded inside, so hopefully the springs havent been compromised, but when I get it back together and run it, it will tell me.
I may take it down and have it run on a distributor machine and see what its actually doing before installing it....

..............................

centerline said:

as I have the heads off, I used a dial indicator on the piston to find true top dead center, and it is dead on to the damper mark...

For TRUE TDC, a degree wheel must be used in order to achieve a split angle.
We can use a dial indicator or we can use a PPS to determine where the crank will be on either side of the angle that will be "split".
Otherwise, you will get close ONLY!


the distributor isnt rusty or corroded inside, so hopefully the springs havent been compromised, but when I get it back together and run it, it will tell me.
Yes, if your harmonic balancer is marked off up to approximately 35* (in increments of 5*), you will be able to strobe the markings and watch what the advance is doing.

I may take it down and have it run on a distributor machine and see what its actually doing before installing it....
That would be the best.
However, these guys are typically AUTOMOTIVE and think in terms of automotive degrees of advance/curve, etc.......... so make sure that you take your OEM Marine Curve Graph with you!

Click to expand...

One thing that has not been mentioned regarding fuel starvation is the possibility of a clogged anti-siphon valve or clogged fuel pickup tube screen.

Now back to the folks who really know marine engines...