Mopar Performance Purple Mechanical Camshaft - P4120653AE Cam Card

[AJ/FormS]

lean toward a single pattern

I see that as a big fat no-no, on the street. If you don't run a cam like that, at split overlap, you immediately start losing Effective overlap at any other ICL. It gives you ZERO adjustability, in the event you have to give up pressure. In the examples I gave, I set the split to 6degrees, the very least I would run. This gives you about a 4* window, to play with pressure and not sacrifice too much Effective overlap.

 

[AJ/FormS]

I'm thinking 8 * advance in at 104?

That's a wrong thought.lol.
If the cam is ground with 4* advance already in it and all things are perfect, then it will come in 4* advanced. If you add 4* to that, that would indeed get you 8* advance; but I don't know anybody that would do that on purpose, especially not with a 468 cuber.
Here is that cam in the way that I write cams;
279/279/112.
the maximum overlap is (279 +279)/2, less (112 x2) =55*
at split overlap, the Ica would be;
55/2 plus 360, less 279, less 180, and sign change =71.5. Now I can calculate the rest of your numbers, and I get;
279/108.5/108.5/279/55 with an Ica of 71.5
intake/compression/power/exhaust/Effective overlap.

With 468 cubes, in a streeter; Split overlap is as good a place as any, to start.
But with just 8.5/1 Scr, I'd be leaning towards at least 2* advance; which trades away 2* from power extraction to compression but loses double that in Effective overlap, so the new numbers are;
279/110.5/106.5/279/51
> 106.5 is still plenty of extraction.
>The plus 2* of compression might only make 4psi at most, tho.
>If you have log manifolds, then Effective overlap means as good as nothing.

 

[TT5.9mag]

That's a wrong thought.lol.
If the cam is ground with 4* advance already in it and all things are perfect, then it will come in 4* advanced. If you add 4* to that, that would indeed get you 8* advance; but I don't know anybody that would do that on purpose, especially not with a 468 cuber.
Here is that cam in the way that I write cams;
279/279/112.
the maximum overlap is (279 +279)/2, less (112 x2) =55*
at split overlap, the Ica would be;
55/2 plus 360, less 279, less 180, and sign change =71.5. Now I can calculate the rest of your numbers, and I get;
279/108.5/108.5/279/55 with an Ica of 71.5
intake/compression/power/exhaust/Effective overlap.

With 468 cubes, in a streeter; Split overlap is as good a place as any, to start.
But with just 8.5/1 Scr, I'd be leaning towards at least 2* advance; which trades away 2* from power extraction to compression but loses double that in Effective overlap, so the new numbers are;
279/110.5/106.5/279/51
> 106.5 is still plenty of extraction.
>The plus 2* of compression might only make 4psi at most, tho.
>If you have log manifolds, then Effective overlap means as good as nothing.

See @Mopar69gts, told ya.

 

[rumblefish360]

My thoughts at this time lean toward a single pattern 220@.50, .500ish lift ground on a 108 LSA

I see that as a big fat no-no, on the street.

Consistently, a single pattern cam (almost) always makes more low end torque over a split pattern. The split pattern was thought up and designed to help a weaker exhaust port which also helps extend the top end punch.

 

[512Stroker]

Consistently, a single pattern cam (almost) always makes more low end torque over a split pattern. The split pattern was thought up and designed to help a weaker exhaust port which also helps extend the top end punch.

If you look at the old MP cam grinds like the .528, .557, .590 they are all single pattern cams

 

[rumblefish360]

Yup, knew that. Only a few that aren’t.

 

[Mopar69gts]

See @Mopar69gts, told ya.

That you did...thanks

 

[Mopar69gts]

That's a wrong thought.lol.
If the cam is ground with 4* advance already in it and all things are perfect, then it will come in 4* advanced. If you add 4* to that, that would indeed get you 8* advance; but I don't know anybody that would do that on purpose, especially not with a 468 cuber.
Here is that cam in the way that I write cams;
279/279/112.
the maximum overlap is (279 +279)/2, less (112 x2) =55*
at split overlap, the Ica would be;
55/2 plus 360, less 279, less 180, and sign change =71.5. Now I can calculate the rest of your numbers, and I get;
279/108.5/108.5/279/55 with an Ica of 71.5
intake/compression/power/exhaust/Effective overlap.

With 468 cubes, in a streeter; Split overlap is as good a place as any, to start.
But with just 8.5/1 Scr, I'd be leaning towards at least 2* advance; which trades away 2* from power extraction to compression but loses double that in Effective overlap, so the new numbers are;
279/110.5/106.5/279/51
> 106.5 is still plenty of extraction.
>The plus 2* of compression might only make 4psi at most, tho.
>If you have log manifolds, then Effective overlap means as good as nothing.

Thank you AJ.
This is a Marine Engine
That has good Exhaust but will only be turning 5000 to 5500 rpm max.
With low compression I went single pattern camshaft to help cylinder pressure
And the main reason for my question
About the best installed degree to also help with cylinder pressure.
It also has a small block gear ratio in the outdrive so that will help bottom end as well.
kinda the same as a low rear gear in car.
I'll take your advice thanks again!!
Mike

 

[Bewy]

Yup, single pattern. Why dual pattern? As Isky cams explains in his Tech Tips, it is from habit. The factories often used DP cams. The most logical reason is that the cars had restrictive exh manifolds, restrictive small diam exh pipe sizes & restrictive mufflers. So the exhaust needed 'help'; enter, extra exh duration.
A performance build has free flowing headers, large diam exh pipes & mufflers [ if used ].
Mother Mopar has left a history trail for us with the 63-64 Max Wedge engines that had factory headers...& single pattern cams.

 

[512Stroker]

Yup, single pattern. Why dual pattern? As Isky cams explains in his Tech Tips, it is from habit. The factories often used DP cams. The most logical reason is that the cars had restrictive exh manifolds, restrictive small diam exh pipe sizes & restrictive mufflers. So the exhaust needed 'help'; enter, extra exh duration.
A performance build has free flowing headers, large diam exh pipes & mufflers [ if used ].
Mother Mopar has left a history trail for us with the 63-64 Max Wedge engines that had factory headers...& single pattern cams.

I would think that if you had done your homework on your exhaust system that a single pattern cam would be the way to go. It is all a lot to consider when trying to pick out the right cam for your application.
A few engine builders told me to keep my Comp XR274HR-10 and change out the hydraulic roller lifters for solid rollers and be done with it.
Food for thought

 

[AJ/FormS]

Here's a thought;
Lets say you have a 268/276/114 cam It has a maximum overlap of
(268 +276)/2 less (2 x114)= 44
So to use all of the available overlap, you would install it at split overlap which is
(268/2) less 44/2=112, and so you have 44* of effective overlap, same as what's built in to the cam..
Your Ica will be;
(360 +22) less 268, less 180 and sign-change =66*Ica
Install that into a 10.0 340, and the pressure is predicted to be 159.3 at sealevel. The events are;
268/114/106/276/44; and in at 112= Ica of 66*

Now put it in an 8/1 340, still at 112, the events are exactly the same. But the pressure is now predicted to be just 120psi@ sealevel.
So what are you gonna do?
Well one guy on here might suggest to advance it a bunch.
Ok lets advance to 8* which would be in at 106. The new events are
268/120/100/276/ E-overlap down to 32*/Ica of 60*
and this will bring the pressure up to 127 in that 8/1 340; yahoo
In my opinion, that's a waste of time.

But ok, lets make it a 268 single pattern. still at 112LSA and at split overlap, the events are;
268/112/112/268/E-overlap is 40/ and the Ica is 68*
In the 10:1 340, this might make 155.8psi ....... hold on a sec, back up the bus, didn't the split pattern make 159.3? Why yes AJ your math said so.So what's going on? Well, the single pattern cam only has 40* of maximum overlap, so installed at split-O, the Ica comes in 2* later; namely 68* versus 66.
Ok/Ok; unfair you say.
Well, I'm trying to make a point here which is the blanket statement put forth above, that single pattern cams (almost) always make more low-end torque........... Which is possibly/ probably true, but at what cost to the top end? Notice the single pattern cam gave up 4* of Effective overlap. And the single pattern has 112* of power extraction, which is great for fuel-economy, but is a dead weight number at peak-power, especially for a head that has trouble getting rid of exhaust...... like the factory iron Mopar LA heads do.

Ok so, Lets see if we can actually compare two cams, one a split and one a single.
Since the intake duration is what ballparks the powerpeak, to be fair,we have to set that first. I chose 268*. So this time, lets try keep the extraction the same and lets toss that 114LSa cuz nobody runs that on the street. Let the LSA be tighter
Ok so lets work on a single pattern 268/268/110/48overlap, installed straight up at 110, and the events are;
268/116/116/268/48E-overlap and in at 110, the Ica is 64*... why anybody would want power extraction of 116* is beyond me. That might come in handy cruising at 65mph but is a good waste of time at peak-power. and the overlap is just 48*. It might also come in handy with a 2000stall TC.
Ok so how close can we get with a dual-pattern?
Well we gotta keep the 268. And I like a 6* split to allow some adjustment of the ICL; so that makes an exhaust of 274. And since I'm trying to target that stinking 116 power extraction, I'm gonna put it on a 106LSA. so what I get is;
268/274/106 and the events are ;
268/121/116/274/59* E-overlap/in at 105 for an Ica of 58*
Ok here it comes;from above;
268/116/116/268/48* E-overlap/in at 110 for an Ica of 64*

The split pattern has Plus 5* compression so maybe plus8psi CCA
The split pattern has Plus 11* more Effective overlap, for more midrange to peak, power
The split pattern has Plus 6* more exhaust duration, for the LA head.
The split pattern has a huge tuning window of +/- 4 or 5 degrees before the E-overlap falls to 48*
If you advance the split pattern another 3*, to in at 102/(4* advanced) the compression will go to 124*,(Ica of 56*) and the extraction will fall to 113. While the Effective overlap will fall to 52*, still 4* better than the single pattern.

So, IDK about you guys, but I know which cam I am choosing for my streeter.

But here's the deal;
Lets talk about the compression degrees Plus the extraction; I'll call it C&E. In the Single-pattern;
116 +116=232 which is a very good street number.
In the Split-pattern it is 121 +116= 237* a better number with the 268 Intake duration.
If, and I say IF, you were to compare these TYPES of cams using this C&E technique, then you might see a different picture.
Lets make a split pattern cam of 232* C&E, on a 110, with 48* overlap; the events are, or could be;
264/120/112/272/48 *Effective/in at 108 for an Ica of 60; compare this to; the single pattern from above;
268/116/116/268/48* E-overlap/in at 110 for an Ica of 64*
notice the C&E is 120 +112=232, same as 116 +116 =232
and overlap is still 48, and the LSA is still 110.
The exhaust duration has increased 4* while the intake duration has decreased the same 4*..
So how will this affect your engine?
Well; the split at 272 less 264= 8* which IMO, is excessive, even for stock LA heads. Be that as it may, maybe you can run 2" pipes,lol.
The Compression is 120 less 116= Plus 4* so again about Plus 6psi CCP
Extraction is 116 less 112= Less 4* but 112 is still a good number.
But the loss of 4* of intake duration means the operating rpm has come down about 100rpm, so I'll guess a loss of say 10Hp, over the peak. IMO the the loss of peak power, will be made up for by the increase in pressure, so it's a crapshoot as to ET from zero to 60mph.

So IDK, I'm not sold on a single pattern for street.

 

[AJ/FormS]

Thank you AJ.
This is a Marine Engine
That has good Exhaust but will only be turning 5000 to 5500 rpm max.
With low compression I went single pattern camshaft to help cylinder pressure
And the main reason for my question
About the best installed degree to also help with cylinder pressure.
It also has a small block gear ratio in the outdrive so that will help bottom end as well.
kinda the same as a low rear gear in car.
I'll take your advice thanks again!!
Mike

I'll dig into this later, right now I got work to do......

 

[512Stroker]

Here's a thought;
Lets say you have a 268/276/114 cam It has a maximum overlap of
(268 +276)/2 less (2 x114)= 44
So to use all of the available overlap, you would install it at split overlap which is
(268/2) less 44/2=112, and so you have 44* of effective overlap, same as what's built in to the cam..
Your Ica will be;
(360 +22) less 268, less 180 and sign-change =66*Ica
Install that into a 10.0 340, and the pressure is predicted to be 159.3 at sealevel. The events are;
268/114/106/276/44; and in at 112= Ica of 66*

Now put it in an 8/1 340, still at 112, the events are exactly the same. But the pressure is now predicted to be just 120psi@ sealevel.
So what are you gonna do?
Well one guy on here might suggest to advance it a bunch.
Ok lets advance to 8* which would be in at 106. The new events are
268/120/100/276/ E-overlap down to 32*/Ica of 60*
and this will bring the pressure up to 127 in that 8/1 340; yahoo
In my opinion, that's a waste of time.

But ok, lets make it a 268 single pattern. still at 112LSA and at split overlap, the events are;
268/112/112/268/E-overlap is 40/ and the Ica is 68*
In the 10:1 340, this might make 155.8psi ....... hold on a sec, back up the bus, didn't the split pattern make 159.3? Why yes AJ your math said so.So what's going on? Well, the single pattern cam only has 40* of maximum overlap, so installed at split-O, the Ica comes in 2* later; namely 68* versus 66.
Ok/Ok; unfair you say.
Well, I'm trying to make a point here which is the blanket statement put forth above, that single pattern cams (almost) always make more low-end torque........... Which is possibly/ probably true, but at what cost to the top end? Notice the single pattern cam gave up 4* of Effective overlap. And the single pattern has 112* of power extraction, which is great for fuel-economy, but is a dead weight number at peak-power, especially for a head that has trouble getting rid of exhaust...... like the factory iron Mopar LA heads do.

Ok so, Lets see if we can actually compare two cams, one a split and one a single.
Since the intake duration is what ballparks the powerpeak, to be fair,we have to set that first. I chose 268*. So this time, lets try keep the extraction the same and lets toss that 114LSa cuz nobody runs that on the street. Let the LSA be tighter
Ok so lets work on a single pattern 268/268/110/48overlap, installed straight up at 110, and the events are;
268/116/116/268/48E-overlap and in at 110, the Ica is 64*... why anybody would want power extraction of 116* is beyond me. That might come in handy cruising at 65mph but is a good waste of time at peak-power. and the overlap is just 48*. It might also come in handy with a 2000stall TC.
Ok so how close can we get with a dual-pattern?
Well we gotta keep the 268. And I like a 6* split to allow some adjustment of the ICL; so that makes an exhaust of 274. And since I'm trying to target that stinking 116 power extraction, I'm gonna put it on a 106LSA. so what I get is;
268/274/106 and the events are ;
268/121/116/274/59* E-overlap/in at 105 for an Ica of 58*
Ok here it comes;from above;
268/116/116/268/48* E-overlap/in at 110 for an Ica of 64*

The split pattern has Plus 5* compression so maybe plus8psi CCA
The split pattern has Plus 11* more Effective overlap, for more midrange to peak, power
The split pattern has Plus 6* more exhaust duration, for the LA head.
The split pattern has a huge tuning window of +/- 4 or 5 degrees before the E-overlap falls to 48*
If you advance the split pattern another 3*, to in at 102/(4* advanced) the compression will go to 124*,(Ica of 56*) and the extraction will fall to 113. While the Effective overlap will fall to 52*, still 4* better than the single pattern.

So, IDK about you guys, but I know which cam I am choosing for my streeter.

But here's the deal;
Lets talk about the compression degrees Plus the extraction; I'll call it C&E. In the Single-pattern;
116 +116=232 which is a very good street number.
In the Split-pattern it is 121 +116= 237* a better number with the 268 Intake duration.
If, and I say IF, you were to compare these TYPES of cams using this C&E technique, then you might see a different picture.
Lets make a split pattern cam of 232* C&E, on a 110, with 48* overlap; the events are, or could be;
264/120/112/272/48 *Effective/in at 108 for an Ica of 60; compare this to; the single pattern from above;
268/116/116/268/48* E-overlap/in at 110 for an Ica of 64*
notice the C&E is 120 +112=232, same as 116 +116 =232
and overlap is still 48, and the LSA is still 110.
The exhaust duration has increased 4* while the intake duration has decreased the same 4*..
So how will this affect your engine?
Well; the split at 272 less 264= 8* which IMO, is excessive, even for stock LA heads. Be that as it may, maybe you can run 2" pipes,lol.
The Compression is 120 less 116= Plus 4* so again about Plus 6psi CCP
Extraction is 116 less 112= Less 4* but 112 is still a good number.
But the loss of 4* of intake duration means the operating rpm has come down about 100rpm, so I'll guess a loss of say 10Hp, over the peak. IMO the the loss of peak power, will be made up for by the increase in pressure, so it's a crapshoot as to ET from zero to 60mph.

So IDK, I'm not sold on a single pattern for street.

Dam when you lay it out the numbers dont lie dual pattern would win the race.
I am still waiting to here back from Racer Brown, their shop got flooded, not real bad but Jim said they have a lot of clean up to do.

 

[rumblefish360]

Dam when you lay it out the numbers dont lie dual pattern would win the race.
I am still waiting to here back from Racer Brown, their shop got flooded, not real bad but Jim said they have a lot of clean up to do.

And @AJ/FormS As well.

AJ, often, as in most every post, you often balk and dissuade certain things but here you clearly state “Well what about the top end” & other things like “There’s that speed limit” which is found often all to fast and good gravy the list goes on and on and on ….

@512Stroker
How often are you going to be in the top end to worry about it. Before you start believing and blindly running into fences on the math, remind me of something, are we racing the car?

Just wondering.

If AJ would get his *** out of the calculators, and into the dyno room, he would t be selling you a du pattern danm so quickly.

You all can work the numbers out but when the science fails, I told ya so…. As well as missing variables

Go low @ 108 in the street fun toy. It’ll produce more torque where your living in most of the time.

 

[rumblefish360]

@AJ/FormS Why did you through in the low compression 340?
This is like you live to hear yourself talk via typing.
WTF DUDE?!?!

 

[448Scamp]

Dam when you lay it out the numbers dont lie dual pattern would win the race.
I am still waiting to here back from Racer Brown, their shop got flooded, not real bad but Jim said they have a lot of clean up to do.

That’s the problem using numbers. You can’t ignore overlap and think it doesn’t matter. A good header and correct cam timing with a single pattern cam will beat up on a split pattern cam every time. When things like the LSA get opened up for idle quality and such the engine gets less responsive to exhaust changes, because you defeat overlap.

 

[512Stroker]

And @AJ/FormS As well.

AJ, often, as in most every post, you often balk and dissuade certain things but here you clearly state “Well what about the top end” & other things like “There’s that speed limit” which is found often all to fast and good gravy the list goes on and on and on ….

@512Stroker
How often are you going to be in the top end to worry about it. Before you start believing and blindly running into fences on the math, remind me of something, are we racing the car?

Just wondering.

If AJ would get his *** out of the calculators, and into the dyno room, he would t be selling you a du pattern danm so quickly.

You all can work the numbers out but when the science fails, I told ya so…. As well as missing variables

Go low @ 108 in the street fun toy. It’ll produce more torque where your living in most of the time.

Thanks for your input
Application is street only

 

[AJ/FormS]

Thank you AJ.
This is a Marine Engine
That has good Exhaust but will only be turning 5000 to 5500 rpm max.
With low compression I went single pattern camshaft to help cylinder pressure
And the main reason for my question
About the best installed degree to also help with cylinder pressure.
It also has a small block gear ratio in the outdrive so that will help bottom end as well.
kinda the same as a low rear gear in car.
I'll take your advice thanks again!!
Mike

Mike; I know almost nothing about marine applications. Just enough to mess you up,lol.
-------------
But; hang on a sec; on this part I think I might be helpful;
With low compression I went (want?) single pattern camshaft to help cylinder pressure
After the engine is built, it is the Ica that controls the pressure. Not the cam being a single or split, pattern.
You can have two cams installed in identical engines, with the same Icas; one a single, and the other a split; and with the same Icas, the CCP will be the same.
What the Split pattern does, with the extra exhaust duration, is steal degrees from power extraction, usually carrying it into the overlap.
------------
Try this on;
Here is a FTH, single pattern suitable for 5500 in a car; (NOT a boat)
268/268, but for use at a fixed rpm could be ground on a 106 for marine use at WOT, giving you a 268/268/106.
In straight up, the events will be;
268/120/120/268/56 overlap, and Ica of 180 less 120=60*
Now lets put that on a dual pattern with a typical 8* split, but keeping the Ica to 60* again, and keeping the 106LSA. Here are the numbers;
268/120/116/276/60 overlap, and Ica of 180 less 120=60* again. Notice I took 4* from power extraction and gave it to the exhaust, which rotated the exhaust duration 4*into the overlap, increasing it from 56Effective to 60 effective.
So in the switch I concede that you may lose some torque at low-rpm, but with headers you will gain some power at peak, by virtue of the more overlap.
In a typical marine application you would have water-cooled log manifolds so overlap is not gonna account for much if anything, unless the exhaust "back-pressure" backs up into the intake.
Now, lets advance the single-pattern cams to Plus 4*.
The single becomes.
268/124/116/268/48 Effective overlap, Ica of 180 less 124=56*now . compare that to the split pattern above;
268/120/116/276/60 overlap, in straight up.
notice the gain of 4* of compression. and
the loss of 12* of overlap! and
the same extraction now.

now, in an 8/1, 318 with an Ica of 56* the pressure is predicted to be 131.74 .
At Ica of 60*, the pressure is predicted to be 127.32; this is
a difference of 4.42 psi and maths to an increase of 3.47%...
Now, riddle me this; in a boat, what is your engine required to do?
That engine is doing one of three things; idling, cruising, or full speed ahead; am I right?
So when exactly is this 4.42psi pressure loss gonna be a problem? Certainly not at idle. Certainly not cruising; you just use a tiny bit more throttle. And at WOT, that 12* of overlap, with headers, will kill any thought of the missing 4.42 psi
I rest my case.

Now; if you do NOT have headers, as already said, the overlap won't mean much. In which case there is no good reason to run a split, nor to run a 106LSA. However, to run a 268 cam with a an early-closing intake, you sorta got to run a tight LSA anyway.

Like I said, IDK much about marine engines ............

BTW
at WOT,and at rpm;
your engine does not care much about any of the advertised numbers.
What is does care about, is the .050 numbers, and the lift, and being able to process massive amounts of cold air.
I used the 268 FTH numbers because this will get you about a 224@.050 cam, which usually has about a 5000 rpm power-peak. If you really need a power peak of 5500, then you might want about 244@ .050 which is a stinking big cam, and it will about kill your, already stated to be, low cylinder pressure.

 

[Mopar Tech]

Mike; I know almost nothing about marine applications. Just enough to mess you up,lol.
-------------
But; hang on a sec; on this part I think I might be helpful;
With low compression I went (want?) single pattern camshaft to help cylinder pressure
After the engine is built, it is the Ica that controls the pressure. Not the cam being a single or split, pattern.
You can have two cams installed in identical engines, with the same Icas; one a single, and the other a split; and with the same Icas, the CCP will be the same.
What the Split pattern does, with the extra exhaust duration, is steal degrees from power extraction, usually carrying it into the overlap.
------------
Try this on;
Here is a FTH, single pattern suitable for 5500 in a car; (NOT a boat)
268/268, but for use at a fixed rpm could be ground on a 106 for marine use at WOT, giving you a 268/268/106.
In straight up, the events will be;
268/120/120/268/56 overlap, and Ica of 180 less 120=60*
Now lets put that on a dual pattern with a typical 8* split, but keeping the Ica to 60* again, and keeping the 106LSA. Here are the numbers;
268/120/116/276/60 overlap, and Ica of 180 less 120=60* again. Notice I took 4* from power extraction and gave it to the exhaust, which rotated the exhaust duration 4*into the overlap, increasing it from 56Effective to 60 effective.
So in the switch I concede that you may lose some torque at low-rpm, but with headers you will gain some power at peak, by virtue of the more overlap.
In a typical marine application you would have water-cooled log manifolds so overlap is not gonna account for much if anything, unless the exhaust "back-pressure" backs up into the intake.
Now, lets advance the single-pattern cams to Plus 4*.
The single becomes.
268/124/116/268/48 Effective overlap, Ica of 180 less 124=56*now . compare that to the split pattern above;
268/120/116/276/60 overlap, in straight up.
notice the gain of 4* of compression. and
the loss of 12* of overlap! and
the same extraction now.

now, in an 8/1, 318 with an Ica of 56* the pressure is predicted to be 131.74 .
At Ica of 60*, the pressure is predicted to be 127.32; this is
a difference of 4.42 psi and maths to an increase of 3.47%...
Now, riddle me this; in a boat, what is your engine required to do?
That engine is doing one of three things; idling, cruising, or full speed ahead; am I right?
So when exactly is this 4.42psi pressure loss gonna be a problem? Certainly not at idle. Certainly not cruising; you just use a tiny bit more throttle. And at WOT, that 12* of overlap, with headers, will kill any thought of the missing 4.42 psi
I rest my case.

Now; if you do NOT have headers, as already said, the overlap won't mean much. In which case there is no good reason to run a split, nor to run a 106LSA. However, to run a 268 cam with a an early-closing intake, you sorta got to run a tight LSA anyway.

Like I said, IDK much about marine engines ............

BTW
at WOT,and at rpm;
your engine does not care much about any of the advertised numbers.
What is does care about, is the .050 numbers, and the lift, and being able to process massive amounts of cold air.
I used the 268 FTH numbers because this will get you about a 224@.050 cam, which usually has about a 5000 rpm power-peak. If you really need a power peak of 5500, then you might want about 244@ .050 which is a stinking big cam, and it will about kill your, already stated to be, low cylinder pressure.

Wow you made my brain hurt. Lol I worked for a few cam company's that do cams from street to top fuel. They don't spend the time figuring out how the numbers work like you do. Lol want to come straighten them all out? Lol

 

[Mopar Tech]

Sorry to mention this but its kinds funny. Aj you mention a couple of hyd cams that you like. You do realize the company's box they were on we not the designer? No ,I've sold them cams and they had nothing to do with the love design. Oh yeah another thing that strikes me as odd. I'm not picking on ya. Only to try and help because we should all be learning. Right? A 223 or 4 at .050 don't need to rev to 6200rpm much less above that. Not saying it wont,just it's out of juice without a killer head and small cubic in build. Your numbers still I just have to leave to you.

 

[Mopar Tech]

Sorry I guess spell checks trying to help.

 

[Mopar69gts]

Mike; I know almost nothing about marine applications. Just enough to mess you up,lol.
-------------
But; hang on a sec; on this part I think I might be helpful;
With low compression I went (want?) single pattern camshaft to help cylinder pressure
After the engine is built, it is the Ica that controls the pressure. Not the cam being a single or split, pattern.
You can have two cams installed in identical engines, with the same Icas; one a single, and the other a split; and with the same Icas, the CCP will be the same.
What the Split pattern does, with the extra exhaust duration, is steal degrees from power extraction, usually carrying it into the overlap.
------------
Try this on;
Here is a FTH, single pattern suitable for 5500 in a car; (NOT a boat)
268/268, but for use at a fixed rpm could be ground on a 106 for marine use at WOT, giving you a 268/268/106.
In straight up, the events will be;
268/120/120/268/56 overlap, and Ica of 180 less 120=60*
Now lets put that on a dual pattern with a typical 8* split, but keeping the Ica to 60* again, and keeping the 106LSA. Here are the numbers;
268/120/116/276/60 overlap, and Ica of 180 less 120=60* again. Notice I took 4* from power extraction and gave it to the exhaust, which rotated the exhaust duration 4*into the overlap, increasing it from 56Effective to 60 effective.
So in the switch I concede that you may lose some torque at low-rpm, but with headers you will gain some power at peak, by virtue of the more overlap.
In a typical marine application you would have water-cooled log manifolds so overlap is not gonna account for much if anything, unless the exhaust "back-pressure" backs up into the intake.
Now, lets advance the single-pattern cams to Plus 4*.
The single becomes.
268/124/116/268/48 Effective overlap, Ica of 180 less 124=56*now . compare that to the split pattern above;
268/120/116/276/60 overlap, in straight up.
notice the gain of 4* of compression. and
the loss of 12* of overlap! and
the same extraction now.

now, in an 8/1, 318 with an Ica of 56* the pressure is predicted to be 131.74 .
At Ica of 60*, the pressure is predicted to be 127.32; this is
a difference of 4.42 psi and maths to an increase of 3.47%...
Now, riddle me this; in a boat, what is your engine required to do?
That engine is doing one of three things; idling, cruising, or full speed ahead; am I right?
So when exactly is this 4.42psi pressure loss gonna be a problem? Certainly not at idle. Certainly not cruising; you just use a tiny bit more throttle. And at WOT, that 12* of overlap, with headers, will kill any thought of the missing 4.42 psi
I rest my case.

Now; if you do NOT have headers, as already said, the overlap won't mean much. In which case there is no good reason to run a split, nor to run a 106LSA. However, to run a 268 cam with a an early-closing intake, you sorta got to run a tight LSA anyway.

Like I said, IDK much about marine engines ............

BTW
at WOT,and at rpm;
your engine does not care much about any of the advertised numbers.
What is does care about, is the .050 numbers, and the lift, and being able to process massive amounts of cold air.
I used the 268 FTH numbers because this will get you about a 224@.050 cam, which usually has about a 5000 rpm power-peak. If you really need a power peak of 5500, then you might want about 244@ .050 which is a stinking big cam, and it will about kill your, already stated to be, low cylinder pressure.

Thank you AJ for taking the time to go over all that.
I appreciate it.
I'm gonna install it straight up
Degreed at 108*
The main reason Marine Engines
Have wide LSA is the possibility of reversion sucking water back into exhaust ports hydraulicing the Engine.
Mercruiser uses 114 to 118 LSA
Howard's said no less then 112
With water cooled manifolds or water injected headers.
Some guys will move where the water comes into the exhaust further down stream so they can run a tighter LSA.
Also most mercruiser cams are single pattern too.
Thanks again.
To the OP did you get your cam figured out?

 

[RustyRatRod]

AJ does try his best to fully explain & help so you understand. You can’t beat that.

The hardest thing (besides reading the ultra long post) is what he was saying. Finding a cam with the best theoretical valve timing points for the task at hand. Often, it is simply not made.

There was a time …. I would search for these things after I did the math. If the cam companies know this math, why are they not available? Hummmmmmm

These days, along with the hordes of people searching for a cam or a better one, it is difficult to find “THAT” cam. It’s made worse without a cam card or actual events. Like the MP cams. Through the experiences of others, we have all learned that advancing the cam (or retarding a cam) will produce certain results.

I have not seen this done or suggested in this thread though the results and it’s effects would probably not produce what the OP is looking for. Help some? Yea!
Help enough? Probably not. At least from reading this thread probably not.

I think he's fulla ****. That's my story and I'm stickin to it.

 

[512Stroker]

Thank you AJ for taking the time to go over all that.
I appreciate it.
I'm gonna install it straight up
Degreed at 108*
The main reason Marine Engines
Have wide LSA is the possibility of reversion sucking water back into exhaust ports hydraulicing the Engine.
Mercruiser uses 114 to 118 LSA
Howard's said no less then 112
With water cooled manifolds or water injected headers.
Some guys will move where the water comes into the exhaust further down stream so they can run a tighter LSA.
Also most mercruiser cams are single pattern too.
Thanks again.
To the OP did you get your cam figured out?

I have a general idea of my new cam spec.
Have not pulled the trigger yet.

 

[Mopar69gts]

I have a general idea of my new cam spec.
Have not pulled the trigger yet.

I have a general idea of my new cam spec.
Have not pulled the trigger yet.

Ok good
Your smart to do as much research as possible to get the results you want.
Btw. From what I've seen lately cam cores are scarce, Howards said a month or two
Hopefully.
Good luck on your build!