Logo

After Engine Rebuild - Lack of power/Acceleration through entire range

I know it is supposed to be set @ 10°btdc but just would not start

BASE or Initial advance is only one small portion of Ignition timing.
We start up and idle on BASE, and that is it!

Other than the additional advance being built on top of BASE...... BASE contributes ZERO to any RPM above idle.
We need to be much more concerned about the progressive and total advance, AND the RPM at which each occurs!

The Progressive advance will increase as RPM increase.

Without this occurrence, LPCP would be completely out of whack!


.
 
Last edited:
So, the timing gear set was installed without any advance?

With advance it would not start

I believe that Chris is asking you if the camshaft was indexed in a 0 degree fashion, or if it was advanced or retarded.

I wonder if the camshaft is out of phase?
This would be easy to check if you have the full camshaft specs, a good degree wheel and a dial indicator.




By the way M and M...... no one here is chastising you or challenging your skills........... I think that we are all trying to help solve this issue.
 
Last edited:
.................................
Okay guys I have a few minutes here are the recorded measurements for Jay's engine.


Camshaft Style:Hydraulic flat tappet
RPM Range:1,000-5,000
Intake Duration at 050 inch Lift:212
Exhaust Duration at 050 inch Lift:218
Duration at 050 inch Lift:212 int./218 exh.
Valve Lift with Factory Rocker Arm Ratio:0.447 int./0.462 exh.
Lobe Separation (degrees):112
How were the hydraulic cam followers adjusted?
Did the mechanic use the 2 or 3 stop static procedure..... or did he use the much more accurate 8 stop static procedure?


Crankshaft
Journal Diameter
No. 1 2.4484
No. 2, 3, 4 2.4481
No. 5 2.4479
Taper .0002
Out of Round .0002

Main Bearing Clearance
No. 1 .0007
No. 2, 3, 4 .0022
No. 5 .00250
Crankshaft End Play .002
Connecting Rod Journals
Diameter 2.0978
Taper .0003
Out of Round.0003
Rod Bearing Clearance .0006
Rod Side Clearance .006

Deck height 6.358
The GM SBC 5.7L deck height should be 9.025"

Bore 4.00

Stroke 3.480

Dish pistons
Dished Pistons as in the GM Full Dished?
If so, the GM Full Dished piston should NEVER be used in the Marine version.
:mad:

Clearance. 0020
Volume +7.00cc

Ring clearance
Top .014
2nd.014
Oil .011

Valves 1.94 int/1.50exh.

Cylindar Head combustion chamber volume 64cc

Average compression 9.4:1

RPM curve is 346hp / 360ft,lbs @ 4800

Ingnition is GM (OEM) coil distributor and module.
Has anyone actually looked at the spark lead?
In other words, and with a properly marked off harmonic balancer, and with a known to be true #1 TDC......, has the progressive and TA been verified?


fuel pressure is 23.5 @ 3000 rpm.

Fuel system is stock dual pump w/separator

So as you can see this was a refresh build and rotating kit is OEM direct replacement
 
Yes, I think that we are all aware that this is an MPI, and that the ignition system is EST.

Questions:
Assuming that the harmonic balancer is properly marked off, and assuming that you are able to use a timing light in standard mode;

Where is the spark lead at idle rpm?
Where is this spark lead at 1,200 RPM?
at 1,500 RPM?
at 2,000 RPM?
at 2,500 RPM?
at 3,000 RPM?
at 3,200 RPM?
at 3,500 RPM?

Yes, we all know that the EST controller takes care of the progressive and TA..... but.... what if that system is malfunctioning???
 
Last edited:
Perhaps I'm not being understood.
I'm asking if you are able to provide the ignition advance numbers at the various RPM.
at idle RPM?
at 1,200 RPM?

at 1,500 RPM?
at 2,000 RPM?
at 2,500 RPM?
at 3,000 RPM?
at 3,200 RPM?
at 3,500 RPM?

If you were to see this data in graph form, it should look similar to this curve graph below.
This is an Example ONLY.
NOTE: the vertical scale will be minus BASE advance.
When doing the math, BASE must be added to the scale values.
When viewing dynamically, BASE will always be included.
 

Attachments

  • Ignition advance line graph VP 5.7L .jpg
    Ignition advance line graph VP 5.7L .jpg
    81 KB · Views: 56
Isnt there a jumper that locks the distributor at base timing? Is it a marine distributor? Base timing is not as important as all in or total spark advance. Like Ricardo says graph out the progressive spark advance and note the rpm the distributor stops advancing. Once your sure the engine is 100% then you adjust prop pitch for proper WOT rpm. Your probably close map out the advance curve on the water under a load?
 
If this is an MPI engine with the HVS (distributor with flat cap) Timing is not adjustable. You index the HVS and the ecm takes over. Two revolutions and the engine starts.
Since the timing chain is new and tight the timing should not need to be fine tuned. You can move the HVS slightly to improve the running condition with a slightly loose (Worn) timing chain. All timing is controlled by the ECM.

Make sure you are using the marine Cap and rotor. Napa parts will not work.....Ask me how I know.
 
Last edited:
I think we have established that the timing is not the problem.
I have had numerous mechanics suggest a prop change to increase rpm under load.
Problem there is we could essentially get rpm up but speed might still be shallow on plane.
Any ideas?
 
......................
If this is an MPI engine with the HVS (distributor with flat cap) Timing is not adjustable.
HVS = high voltage switching.
Chris, correct me if I am wrong..... this HVS is a form of EST (electronic spark timing).

You index the HVS and the ecm takes over.
Yes, I think that we all understand this.


Since the timing chain is new and tight, the timing (distributor indexing) should not need to be fine tuned.
Agreed!

You can move the HVS slightly to improve the running condition with a slightly loose (Worn) timing chain.

All Ignition Advance timing is controlled by the ECM.
Agreed!
In order to comprehend this, we must first understand that the Non-Mechanically Advancing distributor housing (such as EST) is initially indexed as to offer full advance.
Since the laws of physics do not allow a spark event (at the spark plugs) to occur any sooner than it is initiated by the triggering mechanism, the ECM creates an electrical event delay.

This delay is then varied by the ECM as per engine RPM.
Example: at let's say 1,200 RPM, the delay brings the actual spark event to 2* BTDC.
Now when we add the BASE of 10* BTDC, each cylinder now sees an actual spark event at 12* BTDC.

This delay continues to be varied (reduced) as RPM increase.
Example: at let's say 3,200 RPM, the reduced delay now brings the actual spark event to 22* BTDC.
Now when we add the BASE of 10*, each cylinder now sees 32* BTDC.



What makes a 5.7L SBC Marine engine w/ MPI perform properly?

..... a good solid cylinder block.
..... a good crankshaft w/ 3.480” stroke.
..... good connecting rods of the correct length for Marine use.
..... good bearing surfaces.
..... a good oiling and filtration system.
..... proper pistons with a quench surface that mirrors the quench surface of the cylinder head (no GM F/D pistons :mad:)
..... a proper piston/bore fit w/ good piston rings.
..... a proper quench dimension.
..... cylinder heads with good valves, valve seats and springs.
..... cylinder head gaskets that seal correctly.
..... a camshaft of the proper profile for marine use.
..... the camshaft must be correctly indexed to the crankshaft.
..... the hydraulic cam followers must be adjusted correctly (I prefer the 8 stop static procedure for more accuracy).
..... a good fuel delivery system, in this case multi port injection.
..... a good working ignition system that is correctly indexed to the crankshaft.
..... the ignition system must produce the correct BASE advance and a correct advancing spark lead as rpm increase.
..... the ignition system must produce an honest LPCP that will occur at 12* to 14* ATDC.


If each of the mechanical components have been selected and assembled correctly and are functioning as they should, yet the ignition system is malfunctioning...... performance will suffer greatly.
Likewise if the fuel delivery system is malfunctioning.

If the mechanical aspect of this engine is as it should be, then it is very likely that he has an issue with either the MPI or the Ignition advance.
Not just BASE advance.... I'm talking about what occurs past BASE and up to the Full In RPM.

In order to take "user" or "equipment" error out of the equation, I suggest;
....... using a harmonic balancer that is correctly marked off up to approx 35*.
....... stroke the timing marks using a standard timing light, or a digitally advancing light in standard mode.

This will allow us to check the Progressive Advance and the Total Advance while seeing it in Real Degrees in Real Time!

As for the MPI, I am not up to speed on the trouble-shooting techniques for this.
Chris would be much more informed.


 
..........
I think we have established that the timing is not the problem.
I have yet to see the actually ignition advance curve as per any testing.
Why not map it out in graph form so that we can look at it?



I have had numerous mechanics suggest a prop change to increase rpm under load.
Should this freshly rebuilt engine perform as well or better than the previous engine?
I would say yes.

If so, why would you want to change to a lower pitch prop ?
In other words, if the old engine pushed this hull along just fine with the existing propeller, why doesn't this fresh engine?

Problem there is we could essentially get rpm up but speed might still be shallow on plane.
Yes, anytime we prop down, we may gain WOT RPM, but the speed will be sacrificed.


.
 
Last edited:
Dyno says the performance is there without any power loss and have spoken with several other companies and have been told that people buying 383 strokes have similar experience.
With that said, the issue was resolved by changing prop pitch.
My points:
Engine fires up emediatly
Engine idles smooth
Engine exccelerates nicely without lag or miss.
Engine does not get hot
Engine does not backfire
Engine goes from idle to wot emediatly no delay
Engine under load is at full rpm wot
Under load still no delay miss or lag from idle to wot and back
No change in engine sound or performance getting up on plane but dies take a while to get up on plane.
If it had anything to do with it timing would the results not be different?
 
First off guys sorry for the multiple messages service is spotty where I live

Anyway I see Rick might be leaning towards the ecu not functioning correctly
However my question is this
If ecu is not functioning properly wouldn't it be effecting the engines ability to run no matter what the rpm is even causing pre detination @ idle?
 
Ayuh,..... Jumpin' in late, 'n haven't read every word of this thread, But,..... I got a Question,.......

What, Exactly, Killed the old motor in this hull,..??

The only difference in runnin' this motor on the Dyno, 'n runnin' this motor in the hull,.... Is the Fuel System,.....

If the ole motor died from detonation induced damage, I'd be tearin' into the hull's side of the fuel system to see why,......
 
Old motor died due to stress cracks and rust on Oil Pan which gave out and killed motor, not he hulls fuel system. I will deal with Volvo Penta on that after.
 
.......................
Dyno says the performance is there without any power loss and have spoken with several other companies and have been told that people buying 383 stroker have similar experience.
With that said, the issue was resolved by changing prop pitch.
If I was to pull out my two Q/E built 5.7L 280 HP SBC engines, and was to replace them with two identical Q/E built 5.7L 280 HP SBC engines, I would NOT need to change the prop pitch.
Can someone please explain to me why replacing one engine with a similar but more powerful engine, would require dropping down in prop pitch?

I fail to see the logic in that!

My points:
Engine fires up emediatly
Engine idles smooth
Engine exccelerates nicely without lag or miss.
Engine does not get hot
Engine does not backfire
Engine goes from idle to wot emediatly no delay
Engine under load is at full rpm wot
Under load still no delay miss or lag from idle to wot and back
No change in engine sound or performance getting up on plane but dies (I assume that you meant "does") take a while to get up on plane.
If it had anything to do with it timing would the results not be different?
Are you comparing actual previous engine to new engine "dead-stop-to-planing-attitude" elapsed times?

In other words engine is screaming to get boat up on plane

First off guys sorry for the multiple messages service is spotty where I live

Anyway I see Rick might be leaning towards the ecu not functioning correctly
However my question is this; If ecu is not functioning properly wouldn't it be affecting the engine's ability to run no matter what the rpm is, even causing pre detination @ idle?
All due respect, I know of no such thing as Pre-Detonation. However, I am very familiar with Pre-Ignition and Detonation.
Each of these are two entirely different phenomena.

,
 
Back
Top