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timing early 350/5.7

jclays

Regular Contributor
Good morning Ive seemed to have forgotten what the initial timing for earlier 350/5.7 carbureted, Prestolite electronic ignition. I think its around 6 degrees before top dead center.
Do I time the counter rotating engine the same or does it come up at after top dead center?
Thanks
Jim
 
Good morning Ive seemed to have forgotten what the initial timing for earlier 350/5.7 carbureted, Prestolite electronic ignition. I think its around 6 degrees before top dead center.
Do I time the counter rotating engine the same or does it come up at after top dead center?
Thanks
Jim

Jim, your concerns will be with 3 aspects of ignition advance.

1..... BASE or Initial, of which is the amount of degrees that the cylinders see at/near idle RPM.
We fire up on BASE, and we idle on BASE, and that's it.

2..... the progressive advance as RPM increase. This will typically be rather linear.

3..... the total advance at which each cylinder sees at the prescribed RPM.

Pay more attention to the progressive and total as per your OEM ignition advance curve.

You no doubt have a SBC built with the GM style Full Dished pistons, of which makes this engine more prone to Detonation.
DO NOT exceed the prescribed total advance at/around 3,200 RPM, and you will be OK.


As for the RH rotation engine, with exception to reading the strobe light on the opposite side of the harmonic balancer's TDC mark,
you will time it identically.



.


 
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Jim, your concerns will be with 3 aspects of ignition advance.

1..... BASE or Initial, of which is the amount of degrees that the cylinders see at/near idle RPM.
We fire up on BASE, and we idle on BASE, and that's it.

2..... the progressive advance as RPM increase. This will typically be rather linear.

3..... the total advance at which each cylinder sees at the prescribed RPM.

Pay more attention to the progressive and total as per your OEM ignition advance curve.

You no doubt have a SBC built with the GM style Full Dished pistons, of which makes this engine more prone to Detonation.
DO NOT exceed the prescribed total advance at/around 3,200 RPM, and you will be OK.


As for the RH rotation engine, with exception to reading the strobe light on the opposite side of the harmonic balancer's TDC mark,
you will time it identically.



.


so for the layman the after top dead center mark
 
if the reverse rotation engine has the SAME timing tab as the standard rotation engine, then you want to use the AFTER side to set the initial timing. The 'bad' part is that there usually aren't many graduations on that side.

As far as the value, I don't have anything from Crusader that goes back to your mid-60's vintage...the early 70's material I have covering marine GM's suggests 8 deg BTDC would be a good starting point.
 
Mark mentioned mid 60s.
FYI..... if these are mid 60s SBC engines, then they may not have the GM Full Dished pistons in them.


Here is an example ONLY of what you will be looking for.



fetch



Again..... example ONLY!


2009-08-17_155950_7.4firingorder+timingcurve.jpg



DO NOT use an Automotive curve!



Suggestion:

Adjust your BASE advance.
Increase RPM as you strobe the timing marks.
Plot this out on graph paper in increments of 500 RPM up to 3,200/3,500 RPM.
Post your results.


NOTE:
Your dynamic advance will be only as good as are your OEM TDC markings..... ( i.e., outer balancer ring has not slipped, tab is not bent, etc.)
If the TDC marks are off, so will your advance be off.






.
 
Rick, if you want to know what pistons are in there, jump to page 63. See, thirty seconds with a web search and there you go and no blue text was harmed in the making of this posting.
 
Thank you, O2!

Jim, O2batsea has found a Crusader Service Manual for you in PDF format.

According to PDF page 63, and if no one has changed pistons in your engine, your engine will be fitted with single valve relief Flat Top pistons (according to the manual).
This piston profile (for the 5.7L build) must be used with the 76cc cylinder head combustion chambers.
Smaller chambers = excessive CR.
Larger chambers = low CR.


Regarding ignition advance:

Like with many of these service or work shop manuals, they give us BASE or Initial advance only.
Unless we know (without any doubt) that the mechanical ignition advancing system is working perfectly, BASE and/or Initial advance values are rather meaningless!
In other words..... 10* BTDC is for BASE ONLY. It says ZERO for anything else!


Like said.... we fire up on BASE and we idle on BASE, and that's about it.

The much more important aspect will be the Progressive advance and Total advance and the RPM at which they occur.


Example for a mechanically advancing system:

Let's say that you set BASE @ 10* BTDC.
As your RPM increase, the advancing system increases the spark event timing.

Let's say that with this BASE value, the advancing system is shy by several degrees or more.
This means that at the Total Advance RPM, the engine will not produce it's potential power (i.e., makes for a lazy LPCP)

Let's now say that with this BASE value, the advancing system is strong by several degrees or more.
This means that at the Total Advance RPM, the engine is seeing too much ignition lead, of which will very likely lead to Detonation.



For the Marine Gasser, this is extremely important to know and understand!



.







 
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Rick, if the manual is to be believed, then the timing is set at 500 rpm and that's that.

View attachment 25869

That would be assuming (a dangerous word) that the mechanical advancing mechanism is working perfectly as per the OEM specs.
One rust compromised flyweight return spring (as in weak spring value), one broken flyweight return spring, one sticky flyweight, excessive shaft play, etc. ... and you'll have a progressive advance that is incorrect!
I'm not willing to make an assumption like that.




Ignition TA  Crusader BS.jpg
 
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As usual you are assuming things that are not in evidence. This is what the people who built the engines say to do. Calling it BS is just not a responsible thing as it goes against the recommendations of the manufaturer.
Unless the engines have been fit with something other than what the factory put on there, you should stick to the manual.
 
As usual you are assuming things that are not in evidence. This is what the people who built the engines say to do. Calling it BS is just not a responsible thing as it goes against the recommendations of the manufaturer.
Unless the engines have been fit with something other than what the factory put on there, you should stick to the manual.

You are incorrect!
I am in Pro-Active Damage Preventative mode.

Thread title: Timing early 350/5.7

Post #1: Prestolite electronic ignition

Being conservative, lets say that these are mid 70s to early 80s systems.... which I believe is prior to Crusader using EST.
That means that these have been in service for at least 40 years.
After 40 years of service, there is absolutely NO WAY that I would suggest that the advancing components are working perfectly!
That would be irresponsible of me.

I would be checking this out dynamically, of which apparently goes completely against the Crusader manual phrase that I drew the red outline around.


I know of NO true Marine mechanic who would set BASE advance only, and then walk away!



.
 
I don't think Crusader was saying, "Do not check the ignition system dynamic advance". When they say "power timing", my take is they are talking about the process some folks do where they adjust the timing only by ear. They rev up the engine a little and find the sweet spot where RPM is the highest and the engine is running the smoothest. Here's a guy advocating "power timing": https://forums.ihpartsamerica.com/threads/ignition-power-timing.2122/ (Just to be clear: I would never power time my engine.)

In the part Rick thinks is BS, Crusader was just saying, "Use a timing light and set the base timing to our spec".
 
As usual, there's the factory manual, then there's what Rick Says. Rick knows more about everything than anyone else on this forum, anyone who ever wrote a service manual, every engineer that ever worked for any marine manufacturer and anybody else you can name.
 
.................
I don't think Crusader was saying, "Do not check the ignition system dynamic advance".
DJR, I would certainly hope not.
We should always look at what the progressive advance is doing from idle RPM to the full-in RPM.

When they say "power timing", my take is they are talking about the process some folks do where they adjust the timing only by ear. They rev up the engine a little and find the sweet spot where RPM is the highest and the engine is running the smoothest. Here's a guy advocating "power timing": https://forums.ihpartsamerica.com/threads/ignition-power-timing.2122/
(Just to be clear: I would never power time my engine.)
Nor would I.
And DJR, you are correct! If Crusader is saying "DO NOT power time this engine" as though lifting the hatch and playing around with the distributor while under way and under a load......... I would completely agree with them.
Doing that is just plain stupid, and it's a recipe for engine damage.


In the part Rick thinks is BS, Crusader was just saying, "Use a timing light and set the base timing to our spec".
Actually, I'm suggesting that we set BASE advance, but that we DO NOT stop there.

I'm suggesting that we continue and look at the progressive advance (as RPM increase) and look the total advance at the RPM at which it occurs.
That is the only way that we will know if the old and worn mechanical distributor is doing what it's suppose to be doing.


Please ignore post 16. There is no value there.
 
The link to the manual posted by o2 is a real find. I have downloaded it into my computer so it will not go away when the offering site goes out of business. Lots of good hints that are still useful on my more modern 5.7s, and also many memories there that remind me of my old Chevies in high school. Been a few years since I worried about points and dwell. Can you believe they discussed disassembly/cleaning of hydraulic lifters? Modern lifters have tolerances that exceed the ability to machine (7 millionths of an inch) so parts are machined and then size matched. You don't want to throw those pieces in a bucket!

As for the timing, I think that the point of the writer is that the only thing you should adjust is base timing as there is no other adjustment you can/should make. He also suggests "checking" the advance mechanism by manually advancing the rotor and seeing if the springs snap it back. All good old time advice and that should detect most problems in the old mechanical advance. I imagine even back then real pros went further and then were perhaps faced with the dilemma of adjusting the total advance to spec (and being off on the base advance) or rebuilding or replacing the advance mechanism. Clearly beyond the scope of this manual.

Never heard of "power timing". Neat stuff. Wish I would have tried it back then before learning (now) it is a bad idea.
 
Back then you couldn't swing a dead cat without hitting a shop that had a distributor testing machine. You could have had it put on the tester and checked if it was in spec or what. Those were the days.
I suppose it was assumed that your distributor was in good order since it would have been new at the time. That's why there was no further mention of it in the manual perhaps.
 
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