Is Quench Required?

[Newbomb Turk]

Is this the one? I'm failing to see how this is any different than the cam card. It also calls for a 106 ICL. Can you explain it for my dumbass?

View attachment 1716408695

On my phone it’s incredibly small. Hopefully it’s bigger so you can see it better.

Your overlap triangle is that triangle in the middle where the exhaust is closing and the intake is opening. That’s overlap. Both valves are off the seat at the same time.

Where the exhaust closing line crosses the intake opening line is always at max valve lift at overlap.

Think about this. Valves open more flow more. That’s basic. So how far off the seat at TDC the valves are and WHERE that occurs relative to TDC is critical.

If you blow it up and look at the TDC line you can see with your 110 LSA and 106 ICL the triangle is shifted to the left of TDC. That’s because the cam is advanced. And the intake valve will be open sooner and be further off the seat before TDC.

If the cam was “straight up” at say a 108 ICL both valves would be off the seat the same amount and that would occur at exactly TDC. And your overlap triangle would be centered over TDC.

This is generally where engines make the best power IF the headers are tuned and the LSA is ground where it should be.

If the cam was in at say a 110 ICL it would be retarded and the overlap triangle would be shifted to the right of TDC.

I’m just using those numbers as examples.

Right now you have the numbers at 110 LSA and 106 ICL and it’s advanced. That’s the 4 degrees you’ve entered where it says advance.

To move the overlap triangle just change that 4 degrees in the advance box to 3 degrees and you can see the overlap triangle either get centered over TDC or it will at least move to the right a slight amount.

Keep lowering the advance number by one until you see the overlap triangle centered over TDC and when you get that number that’s where I’d install the cam.

I’m not sure without doing it myself where that would be but just play with it and see what you get.

Edit: I just used your numbers and it looks like to center the overlap triangle you need to be on a 108 or a 109.

I can’t tell for sure because it’s so small on my phone I can’t see exactly where it is. But it’s either 108 (plus 2) or 109 (plus 1). Plus 4 is definitely advanced.

Play with it a bit and use different numbers and see how the overlap triangle moves around.

One interesting thing I’ve found is most off the shelf cams that call for a plus 4 install don’t center the overlap triangle.

The math I use always centers the overlap triangle regardless of what the LSA/ICL numbers are.

For example, the math might call for a 110 LSA and a 107 ICL but when you use MGI speedware even though the overlap triangle should be advanced it always comes out centered.

 

[autoxcuda]

Well, ****...

For comparison sake, I run iron heads on my 9.6:1 340 with a small cam with fast ramps (61* IVCA) and have never had an issue.

That aluminum vs iron vs compression ratio deal is a little overblown.

 

[autoxcuda]

What's advertised (seat) intake duration on the cam?

274/280

 

[mopowers]

On my phone it’s incredibly small. Hopefully it’s bigger so you can see it better.

Your overlap triangle is that triangle in the middle where the exhaust is closing and the intake is opening. That’s overlap. Both valves are off the seat at the same time.

Where the exhaust closing line crosses the intake opening line is always at max valve lift at overlap.

Think about this. Valves open more flow more. That’s basic. So how far off the seat at TDC the valves are and WHERE that occurs relative to TDC is critical.

If you blow it up and look at the TDC line you can see with your 110 LSA and 106 ICL the triangle is shifted to the left of TDC. That’s because the cam is advanced. And the intake valve will be open sooner and be further off the seat before TDC.

If the cam was “straight up” at say a 108 ICL both valves would be off the seat the same amount and that would occur at exactly TDC. And your overlap triangle would be centered over TDC.

This is generally where engines make the best power IF the headers are tuned and the LSA is ground where it should be.

If the cam was in at say a 110 ICL it would be retarded and the overlap triangle would be shifted to the right of TDC.

I’m just using those numbers as examples.

Right now you have the numbers at 110 LSA and 106 ICL and it’s advanced. That’s the 4 degrees you’ve entered where it says advance.

To move the overlap triangle just change that 4 degrees in the advance box to 3 degrees and you can see the overlap triangle either get centered over TDC or it will at least move to the right a slight amount.

Keep lowering the advance number by one until you see the overlap triangle centered over TDC and when you get that number that’s where I’d install the cam.

I’m not sure without doing it myself where that would be but just play with it and see what you get.

Edit: I just used your numbers and it looks like to center the overlap triangle you need to be on a 108 or a 109.

I can’t tell for sure because it’s so small on my phone I can’t see exactly where it is. But it’s either 108 (plus 2) or 109 (plus 1). Plus 4 is definitely advanced.

Play with it a bit and use different numbers and see how the overlap triangle moves around.

One interesting thing I’ve found is most off the shelf cams that call for a plus 4 install don’t center the overlap triangle.

The math I use always centers the overlap triangle regardless of what the LSA/ICL numbers are.

For example, the math might call for a 110 LSA and a 107 ICL but when you use MGI speedware even though the overlap triangle should be advanced it always comes out centered.

Thank you for the explanation. I fully understand the concept of overlap. I just didn't (and maybe still don't) quite get how the center of the overlap triangle wouldn't line up with where the cam card puts it. I'm okay with not understanding that though and will take you for your word.

Though I'm absolutely not looking for every ounce of power out of this combo - not even close - I actually wouldn't mind installing the cam a couple/few degrees retarded. That would lower my effective compression ratio couple tenths.

274/280

View attachment 1716408740

Thanks. Strange they list it at 0.015" valve lift. I added a couple degrees to compensate and looks like your dynamic compression ratio is in the 7.8 range. That's right around where I'm at with my iron headed 340 and I've never had an issue with detonation. I wonder if there is something else going with the tune or something.

 

[Newbomb Turk]

Thank you for the explanation. I fully understand the concept of overlap. I just didn't (and maybe still don't) quite get how the center of the overlap triangle wouldn't line up with where the cam card puts it. I'm okay with not understanding that though and will take you for your word.

Though I'm absolutely not looking for every ounce of power out of this combo - not even close - I actually wouldn't mind installing the cam a couple/few degrees retarded. That would lower my effective compression ratio couple tenths.


Thanks. Strange they list it at 0.015" valve lift. I added a couple degrees to compensate and looks like your dynamic compression ratio is in the 7.8 range. That's right around where I'm at with my iron headed 340 and I've never had an issue with detonation. I wonder if there is something else going with the tune or something.

It’s easy once you look at the graph a bit.

Maybe look at some other cams using the graph. You can use my numbers.

281/281 255/255 105/105 620/620

Put it at 0 advance and look at the overlap triangle. You’ll see it’s centered over TDC.

Then add 1 degree advance and watch it move the triangle to the left. That is advancing the cam. Keep adding a free of advance and watch it move further left.

That shows you where true “straight up” is for any cam you want to graph, regardless of what the cam card says.

The anomaly I’ve found is using the math I do to get cam timing.

Almost always it will call for the LSA and the ICL to be two different numbers. Like 110/107.

Using the numbers from the math I use on the graph you’d think that the 110/107 would show the triangle to the left of TDC (advanced) but it doesn’t. It centers the triangle.

Running your cam, the 110/106 advanced the cam so it’s technically straight up. It’s advanced.

I moved it 2 degrees (2 degrees retarded from the cam card) and it looked centered.

To me, that’s where I’d install the cam and not where Comp wants it.

At home I have an interview with Billy Godbold where he says to center the triangle.

The reason the card says to install it advanced is because Comp is betting (and probably betting correctly 90% of the time) that the end user picked a cam that’s too big. So the advance it.

There is a common misconception that big cams “bleed off” cylinder pressure. That’s not exactly what happens.

What’s really happening is you are moving the IVC point either earlier (advanced) or later (straight up or even regarded which moves the triangle to the right of TDC and there are some rare instances where you need to do that but you are likely not one of those cases) and what that does is it changes how soon you start to build cylinder pressure.

It may sound like tomato-tamoto but it’s a difference that matters.

If you think about it, until the intake valve closes you aren’t building any cylinder pressure. As soon as it closes you start making cylinder pressure. Follow me here. At that point you can now calculate your Effective Compression Ratio.

It is always the same, unlike dynamic compression ratio which is dynamic, meaning it changes with load/rpm/temperature and some other stuff I’ve forgotten.

That’s why I don’t use DCR and my cam math doesn’t either. It’s too hard to calculate where ECR is easily calculated and never changes.

So getting your cam straight up, which in your case looks like (on my phone) you’ll be 110/108. That centers the triangle. If you do 110/110 it’s 2 degrees retarded. 110/106 is 2 degrees advanced.

It will start making sense when you look at multiple cams on that graph.

 

[mopowers]

It’s easy once you look at the graph a bit.

Maybe look at some other cams using the graph. You can use my numbers.

281/281 255/255 105/105 620/620

Put it at 0 advance and look at the overlap triangle. You’ll see it’s centered over TDC.

Then add 1 degree advance and watch it move the triangle to the left. That is advancing the cam. Keep adding a free of advance and watch it move further left.

That shows you where true “straight up” is for any cam you want to graph, regardless of what the cam card says.

The anomaly I’ve found is using the math I do to get cam timing.

Almost always it will call for the LSA and the ICL to be two different numbers. Like 110/107.

Using the numbers from the math I use on the graph you’d think that the 110/107 would show the triangle to the left of TDC (advanced) but it doesn’t. It centers the triangle.

Running your cam, the 110/106 advanced the cam so it’s technically straight up. It’s advanced.

I moved it 2 degrees (2 degrees retarded from the cam card) and it looked centered.

To me, that’s where I’d install the cam and not where Comp wants it.

At home I have an interview with Billy Godbold where he says to center the triangle.

The reason the card says to install it advanced is because Comp is betting (and probably betting correctly 90% of the time) that the end user picked a cam that’s too big. So the advance it.

There is a common misconception that big cams “bleed off” cylinder pressure. That’s not exactly what happens.

What’s really happening is you are moving the IVC point either earlier (advanced) or later (straight up or even regarded which moves the triangle to the right of TDC and there are some rare instances where you need to do that but you are likely not one of those cases) and what that does is it changes how soon you start to build cylinder pressure.

It may sound like tomato-tamoto but it’s a difference that matters.

If you think about it, until the intake valve closes you aren’t building any cylinder pressure. As soon as it closes you start making cylinder pressure. Follow me here. At that point you can now calculate your Effective Compression Ratio.

It is always the same, unlike dynamic compression ratio which is dynamic, meaning it changes with load/rpm/temperature and some other stuff I’ve forgotten.

That’s why I don’t use DCR and my cam math doesn’t either. It’s too hard to calculate where ECR is easily calculated and never changes.

So getting your cam straight up, which in your case looks like (on my phone) you’ll be 110/108. That centers the triangle. If you do 110/110 it’s 2 degrees retarded. 110/106 is 2 degrees advanced.

It will start making sense when you look at multiple cams on that graph.

Thank you. It looks like you're right. In my case, it appears as though 1-2* is the sweet spot. I was thinking installing any cam "straight up" would center the overlap triangle, but I guess that's only the case for non- split duration cams. When the cam has a split duration, it's understandable that the overlap center would be skewed to one side at straight up. That is even more prevalent as the split in duration gets larger.

Seeing's how my timing set allows for 2* increments, I may opt to install the cam ICL at 110 (-4 from cam card spec). This is beyond splitting hairs in my case, but interesting none the less. At this point I'd rather err on the side of less effective compression to help with detonation resistance.

 

[RustyRatRod]

On my phone it’s incredibly small. Hopefully it’s bigger so you can see it better.

Your overlap triangle is that triangle in the middle where the exhaust is closing and the intake is opening. That’s overlap. Both valves are off the seat at the same time.

Where the exhaust closing line crosses the intake opening line is always at max valve lift at overlap.

Think about this. Valves open more flow more. That’s basic. So how far off the seat at TDC the valves are and WHERE that occurs relative to TDC is critical.

If you blow it up and look at the TDC line you can see with your 110 LSA and 106 ICL the triangle is shifted to the left of TDC. That’s because the cam is advanced. And the intake valve will be open sooner and be further off the seat before TDC.

If the cam was “straight up” at say a 108 ICL both valves would be off the seat the same amount and that would occur at exactly TDC. And your overlap triangle would be centered over TDC.

This is generally where engines make the best power IF the headers are tuned and the LSA is ground where it should be.

If the cam was in at say a 110 ICL it would be retarded and the overlap triangle would be shifted to the right of TDC.

I’m just using those numbers as examples.

Right now you have the numbers at 110 LSA and 106 ICL and it’s advanced. That’s the 4 degrees you’ve entered where it says advance.

To move the overlap triangle just change that 4 degrees in the advance box to 3 degrees and you can see the overlap triangle either get centered over TDC or it will at least move to the right a slight amount.

Keep lowering the advance number by one until you see the overlap triangle centered over TDC and when you get that number that’s where I’d install the cam.

I’m not sure without doing it myself where that would be but just play with it and see what you get.

Edit: I just used your numbers and it looks like to center the overlap triangle you need to be on a 108 or a 109.

I can’t tell for sure because it’s so small on my phone I can’t see exactly where it is. But it’s either 108 (plus 2) or 109 (plus 1). Plus 4 is definitely advanced.

Play with it a bit and use different numbers and see how the overlap triangle moves around.

One interesting thing I’ve found is most off the shelf cams that call for a plus 4 install don’t center the overlap triangle.

The math I use always centers the overlap triangle regardless of what the LSA/ICL numbers are.

For example, the math might call for a 110 LSA and a 107 ICL but when you use MGI speedware even though the overlap triangle should be advanced it always comes out centered.

So, you're talking about moving the ICL ONE degree. How much will power benefit from THAT?

 

[Newbomb Turk]

So, you're talking about moving the ICL ONE degree. How much will power benefit from THAT?

It would be 2 degrees and it’s not the ICL that matters.

It’s Intake Valve Closing and 2 degrees matters.

 

[mopowers]

In my case, 2* means going from 8.25 DCR to 8.12 DCR and 4* takes it to 7.98. That may make the difference in pinging or not. Any power difference means squat to me for this build.

 

[RustyRatRod]

It would be 2 degrees and it’s not the ICL that matters.

It’s Intake Valve Closing and 2 degrees matters.

Well I can tell you two crank degrees added or removed with the distributor makes a noticeable difference, so there's that.

 

[Newbomb Turk]

In my case, 2* means going from 8.25 DCR to 8.12 DCR and 4* takes it to 7.98. That may make the difference in pinging or not. Any power difference means squat to me for this build.

Ok, I’m back on my iPad so I can actually see something.

I just ran your numbers again and it looks like a 109 ICL is pretty close to centered up.

But…a 110 ICL moves the triangle so little to the retard side that I’m with you. I’d go in at 110 and send that mother.

Thats going to close the intake 4 degrees later which lowers you ECR and DCR (at whatever numbers that math is figuring DCR).

Graphing the cam timing and being able to move the timing around so I can see it visually makes it way easier for me to see what I really want.

 

[RustyRatRod]

Ok, I’m back on my iPad so I can actually see something.

I just ran your numbers again and it looks like a 109 ICL is pretty close to centered up.

But…a 110 ICL moves the triangle so little to the retard side that I’m with you. I’d go in at 110 and send that mother.

Thats going to close the intake 4 degrees later which lowers you ECR and DCR (at whatever numbers that math is figuring DCR).

Graphing the cam timing and being able to move the timing around so I can see it visually makes it way easier for me to see what I really want.

Can you cliff note the differences in DCR and ECR? Preferably for the learning impaired.

 

[Newbomb Turk]

Can you cliff note the differences in DCR and ECR? Preferably for the learning impaired.

Yeah, just give me a few hours. I just spent the last 15 hours at the ER with my mom.

I need to unscrew my head for a bit and catch a nap.

 

[RustyRatRod]

Yeah, just give me a few hours. I just spent the last 15 hours at the ER with my mom.

I need to unscrew my head for a bit and catch a nap.

Uh oh. Sendin prayers her way.

 

[273]

Can you cliff note the differences in DCR and ECR? Preferably for the learning impaired.

From what I've been getting from the DCR and ECR convo's is 99.99% when someone says DCR they really should be saying ECR and for it to be DCR you would have to figure rpm and mass under various different scenarios eg.. temp, altitude, throttle position, load etc..

 

[273]

Sending prayers.

 

[mopowers]

Ok, I’m back on my iPad so I can actually see something.

I just ran your numbers again and it looks like a 109 ICL is pretty close to centered up.

But…a 110 ICL moves the triangle so little to the retard side that I’m with you. I’d go in at 110 and send that mother.

Thats going to close the intake 4 degrees later which lowers you ECR and DCR (at whatever numbers that math is figuring DCR).

Graphing the cam timing and being able to move the timing around so I can see it visually makes it way easier for me to see what I really want.

Thank you for confirming. At this point, I'm prepared to take the block back to my machinist, zero-deck it and order up a 0.039" gasket. This will net a 10.46 static compression ratio, quite a bit more than I was shooting for but it'll have a decent 0.039" quench and aluminum heads with a good chamber design.

With my cam installed at 110* ICL, the IVCA will be at 71* (actually the .006" IVCA, so it may even be a degree past that) and net an effective CR of 7.98:1 (just 0.10 higher than my iron-headed 340 that runs great on 91 oct) and a calculated cranking pressure of 162.75. The calculator I use, calls it dynamic CR, but it's essentially effective CR. I've noticed those terms being used interchangeably when they all really mean effective CR. It's based on effective stroke which is calculated based on when the intake valve actually closes.

What's a tad worrisome is the fact that @autoxcuda 's combo had similar numbers and he seemly had detonation issues on the same fuel I'll be limited to. If mine ends up pinging and I can't tune it out, I'll replace the pistons or pop the heads off and go to town with a carbide. haha. I appreciate everyone's feedback.

@Newbomb Turk - Well-wishes to you and your mother. I hope she recovers swiftly.