Logo
FULL SITE MENU

RH 454 crusader timing

"I was thinking about just the

"I was thinking about just the pushrod side of the fulcrum which turns out to be in error. Turns out you can approximate the plunger travel by multiplying the TURNS * PITCH * (1+ RockerRatio). The exact form of the equation is very cumbersome and provides an answer that has no significant difference; i.e., the approximation is very accurate.

So, for a normal BBC rocker arm on a 7/16" stud, one turn would move the plunger down just under 0.080".

Formerly, multiplication and division are inverse operations, not forms of mathematics."
 
"Okay I got my new advance tim

"Okay I got my new advance timing light from snap-on.

It does battery volts, charging volts, dwell, tach and advance timing.

I'm going to use it for advance timing and I don't have the tape yet. I figure if I never read this thread I'd never even be concerned but now I will make some hard marks on the harmonic balancer (to prove the tool works as it should). Thanks


My question is; I will keep the acdelco distributor on run mode the whole time, even at idle to get the base or get base with jumper set to time mode?

Looking at the advance curve in the book I should expect a small advance even at idle, yes?

Second, if I have a better adjustment at 2800 where I cruse most of the time, I should just adjust it to what the book indicates it should be, yes?

Looking at the curve it is very steep from idle to 1100 rpm.

Thanks

Ps thinking hard marks could be at 5 degree spacing just to prove light is okay"
 
"Mark, I have not yet complete

"Mark, I have not yet completed this, I got terribly side tracked...., but one turn of a 7/16" 20 tpi equals 0.050" at the thread.
Now do the math pertaining to the ratio between valve stem and push rod (rocker ball swivel being the fulcrum) and that will equate to travel of the plunger.
Since this would not be on the multiplying side of the ratio, this may be less than .050" at the plunger for one full turn of the adjusting nut.

This would leave the plunger shy from the top of it's retainer by this amount!"
 
"Scott, you first need to be c

"Scott, you first need to be clear on the difference between BASE advance, and what TA is.
The advancing increments from BASE advance to Full-In "TA" will show you the curve (if plotted out in graph form).

As for your question re; advance at idle.... This is BASE spark lead (advance).... and yes, it is a spark lead.... as in advanced from where the piston is in relationship to TDC.
I believe that your particular ignition should be in BASE mode when setting this!

In addition to BASE, you now have ignition ADVANCE, which is on top of what BASE is.
(most all graphs will reflect this, and will not include BASE advance in the graph)
When checking this, the ignition will NOT be in BASE mode.

Additional ignition advance should never start below 1k rpm, IMO.
(again, do not confuse BASE lead/advance with mechanical or electronic advancing... these are two separate functions!)

NOTE: I do not know what a BB curve should be for YOUR engine, but you will want to look at this.

Yes, the hard marks are a good idea."
 
"Scott:

When I switched ove

"Scott:

When I switched over to the electronic stuff, I set mine to ensure full advance, per the spec, and let the timing at idle go wherever it was. So far, the module has performed within its spec limits. My total advance is 32 and 14 at idle. yes, the module only has 20 degrees of nominal advance. Make sure the spec you use reflects the engine's needs with that distributor.

Ricardo: That was the thought I had when I suggested dividing by the rocker ratio. If you draw the vector diagram, you'll see that the fulcrum point for the adjustment has to be the valve (if not, how does the valve stay closed?). Being the rocker is fixed in length, the movement at the pushrod end has to be more than that at the nut. I went thru the drawing with the mechanical guy at work and he started showing me all the corrections. That's were the complications started. They amounted to ~0.001" of vertical offset so I've deemed them negligible."
 
"Mark, I may shoot you an emai

"Mark, I may shoot you an email if you are open to the idea of discussing this further.... or you shoot me one!
I'm sort of stuck on this ratio thing when it comes to reversing the math.... I.E., Valve theoretically stationary and becoming the fulcrum point... and then calculating push rod travel per 1 nut rotation! The ratio in this direction is no longer mulitplying 1:1.5. I'm stuck in how to best explain this
uhoh.gif
although in my head, I understand it!
Fun topic, though!


Scott, be sure that you understand that what Mark is talking about (full advance) is a "full in" advance that only occurs at a prescribed RPM.
This is critical when doing this.... too much TA/too soon can cause damage!
IOW's, when you hear/read a unit of TA (in degrees), note that there is an RPM related to this number of degrees!
You should probably find an ignition curve graph for YOUR engine and use that data!
It will help you understand what's going on.... or better said, what should be going on!

Then with your marks on the balancer and timing light, you can verify if all is working as it should.

."
 
"The curve I said I was lookin

"The curve I said I was looking at is from the crusder manual that I order from this site (TECM596 R1-5/93) and is the Delco E.S.T. Distributor Spark-Advance Curve under the section Electrical Section 6-49.

Y axis is labled "degrees spark advance - crankshft"
X is labled Engine RPM.

It has a solid line and two broken lines where solid is mean and broken lines are limits.

The curve varies from 0 degrees to 20 degrees and 500 RPM to 4800 RPM.

I dont know how the delco est works, but my simple mind thoungt the curve was isolated function based on only the rpm input of the engine. is there any other input engine specific?

Am I missing a engine specific specs? I love getting totaly confused and then unconfussed as that means I should be either learning something or validating that I was on track. its all learning really...

PS the top of the curve completely flat at 4300 which is my WOT. Assuming that to be the "full in"
Thanks guys"
 
"Scott:

The curve is the ad

"Scott:

The curve is the advance of the EST module and excludes the initial timing. So add the spec'ed initial timing to the MAX of the Module = total advance. You want to be there at the "full in" RPM you mentioned, when the curve goes flat.

There is no other "input" to the advance function beyond RPM.

Ricardo: Here's a cartoon of the "lash" calculations <center><table border=1><tr><td>http://www.marineengine.com/discus/icons/mime_pdf.gif""" align=left alt=""application/pdf"">lash
[url=""][b]Valve lash.pdf[/b][/url] (10.2 k)</td></tr></table></center>. By all means, feel free to email if you find a significant error. Granted there are a few "simplifications" that have been made but they generate no significant error."
 
"No.... The rpm at which the a

"No.... The rpm at which the advance stops progressing is your "limit".
WOT is WOT, and for the sake of this conversation, has nothing to do with advance curve.
There is a continued rpm range where no additional spark lead will occur... and this will be right up to WOT and Red Line.... of which is not to be confused with WOT.
(WOT is an rpm that an engine should be capable of reaching given that: Engine is in full tune/prop is correct/ratio is correct/hull is clean, etc. It is used for this purpose ONLY.)

Also note that most.... I say MOST advance curves (shown in graph form) will not include BASE advance.

So when checking this with your timing light dynamically, one must consider that BASE must be added.
Somewhere shown in this curve graph, there may be a notation indicating that BASE is not included.
Double check this before proceding!

."
 
"Mark, we should have a phone

"Mark, we should have a phone call for the fun of it!
According to Z, the plunger travel "down" would be .7942"!
0.7942" is just over 3/4"!

The actual cam follower plunger/piston travel on average is only .080" to .100"!
The math appears to not work!

But the image is excellent! And with the correct formula, should explain what we are both trying to come up with.
What say yee?

ME.com and most all here are great.... and in many other forums, this would have turned into an arguement or heated debate! LOL"
 
"The formula is fine, I just d

"The formula is fine, I just dropped one of the zero's.

should be 0.0749.....in both places, not just one.

revised attachment
<center><table border=1><tr><td>http://www.marineengine.com/discus/icons/mime_pdf.gif""" align=left alt=""application/pdf"">BBClash
[url=""][b]Valve lash.pdf[/b][/url] (10.2 k)</td></tr></table></center>"
 
"OH oh. The next step is to c

"OH oh. The next step is to calculate the delta in linear expansion in the Z-direction of the head vs the push rod, due to unequal heating. Plus we might not get away with assuming the rod is normal to the axis of the rocker at rest. "
 
"Al:

Back in the olde days,

"Al:

Back in the olde days, Thomas Jefferson coined the phrase "intellectual intercourse"; try to interpret it in the context of the period. I view it as a byproduct of having an analytical mind and a desire to minimize my ignorance.

DD:

I think we all know the rod and the arm should NOT be orthogonal at rest. that said, it sure makes doing the cartoon easier. It wouldn't make any big difference as we are looking for the linear displacement due to a small angular change. Now you have a valid point with the thermal factors; since you can do the adjustment cold, does it matter? only during operation and that is accounted for in the rest of the design of the valve train."
 
question: what do you get whe

question: what do you get when you fill a room full of great boat mechanics that are also engineers...

answer: sometimes a thread like this but ALWAYS a stimuilating read...

thanks again to all you guys!!!!
 
"[b]Quote: "Where the heck

"Quote: "Where the heck do you guys come up with this "STUFF"?"

Simple..... We're all with Ram Dass over at Timothy Leary's house!
biggrin.gif


."
 
I adjusted the rockerarms and

I adjusted the rockerarms and running real smooth now without any chatter nice and quiet. It seemed like they still sould be tighter cause I can wiggle to rockerarms with abit of force just on the closed valves is this mormal? Real test on getting on plane tomarrow. Thanks for the help.
 
"if they don't go WHACK,

"if they don't go WHACK, WHACK when the engine is running, you should be ok. when the lifters bleed out (engine off) there may be a bit of play in the valve train. When the engine runs and the oil pressure returns, that "give" should go away."
 
Back
Top