I think we can agree that
"The intake centerline is the point of highest lift on the intake lobe. It is expressed in crankshaft degrees after top dead center (ATDC)."

1) so when it is recommended that a slant six cam is degree'd to set the ICL at 100 to 98, is that recommendation made regardless of the cam having 4 or 6 degrees of advance or perhaps 2 degrees of retard ground into it?

2) does the 100 to 98 ICL recommendation hold regardless of the LSA?

thanks

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Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

This doesn't matter as you are setting the ICL to 100... the exhaust lobes are set at their fixed angle by the LSA... so if a cam was advertised at a 108 centerline... you ask them to ground it at 104 (4 degrees advanced) you can still put a bushing in for 4 more degrees to make the ICL 100... same happens the other way if it's ground retarded you can move it by teeth or bushings to get your desired centerline.
For most cams we run in NA this holds true... but it is recommended to use the DCR calculator as a subjective reference to see what fuel and timing changes you will have to make
when you run the engine... I know the following...

I know that running a wide LSA cam with a low lobe profile (like a TPI cam) with very low overlap with high compression will not allow this combination
to occur... (some novices will read a cam article and arrive at the recipe in error because: if you advance the cam it lowers the peak torque rpm and limit your
upper rpm limit on the engine, if you widen the LSA the cam will have a smooth idle....so you should get a nice peak torque build with Infinity like idle capabilities....
which if added to a lower SCR engine would allow a turbo to balance out the efficiency and power of the engine...but when used in a higher compression engine
would cause the cylinder pressures to spike and require the end user to bandaid the situation with race fuel or need to add a diesel pump and injectors...)

A similar situation exists where the same such article will also state that a narrow LSA will also increase torque... and to a certain extent it will, but it also increases
overlap and bleeds useable cylinder pressure... so if someone again, misinterprets the article... running a street SCR, narrow LSA, and moderate duration could have
and engine that bled down the cylinder pressure and lacked low end torque...which can be bandaided by advancing the cam heavily... but it will still act like a regular
engine with a retarded cam (lumpy, gutless, needs loads more timing to barely run).


IMHO

DI has got it.

On every NA cam I have run (10?), 100 works very well. Some of these cams, I have tried different CL's and 100 is best.

For a really small or low overlap cam (MP 0.436"), I have run up to 103-104 and it works well. For bigger NA cams, 104 just shifts the HP peak up above where any of us should be revving a 4.125" stroke engine...

What are your cam specs?

Lou

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Home of Slant6-powered fun machines since 1988

Not trying to hijack this post, just want to clarify some points made by DI & Dart 270.

Interesting as this very example aligns with my newly reground cam specs. (Oregon #346) The head-fog is slowly clearing, but I'm still a bit confused. I get the concept where retarding cam moves peak HP & TQ band up in rpm, conversely advancing brings it down in rpm.

DI: As I had previously written in my "post" questioning "engine rebuild timing" under "ENGINE"; using online DCR calculator based on 0.050" lift it gives 9.06:1 at 100 degrees. Page 3 of "this other post" DI said that "advertised duration" has to be used when calculating DCR, not @ 0.050", and he predicts my engine will run on mid grade. I belive!

How would one find "advertised duration" as it is not listed on my cam card as such; Oregon left the Advertised Duration line blank. However, "duration @ 0.008" lift is underlined on my card, would this be the allusive advertised duration?

If "0.008" is said advertised duration one would need to measure at that lift via degree wheel find those angles if one were to re-caculate DCR.

I should have studied ME not CE, concrete lab was fun, but not much help 45 years later understanding camshaft design theory with this old head.

Dad Truck, your post has been helpful.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

it is a single pattern cam mechanical
duration at .050 272 I and E
duration at .015 309 I and E
lift at the valve .549
lobe separation 110

from the cam card, with the cam installed at 110 ICL @ .050
INT Open 26 BTDC
Int Close 66 ABDC
Exh Open 66 BBDC
Exh Close 26 ATDC

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

I have a question related to wjajr's, if you are selecting a cam from OCG's grinds how do you input that into a DCR calculator? The cam cards may have duration @ .008 which sounds close enough to advertised to me but the website only lists duration @ .020 and .050.

Brandon

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https://www.flickr.com/photos/162600228@N03/

.008" lifter rise is used by Oregon Cam Grinding for the advertised duration numbers. This is useful to compare one cam to another, especially in concert with the .050" lift numbers, but it's not the best number for calculating dynamic compression ratio. Compression doesn't begin until the intake valve is closed. So when does the intake valve close? If the intake lash were .008" the advertised duration and running valve closing point would be the same, but the valve lash is usually greater so the valve closes somewhat sooner. To be as accurate as we can the intake valve closing point needs to be measured with the valve lash set. The difference however should be small and you can see the change in dynamic compression by changing the intake valve closing point by a few degrees.

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Joshua

Thanks Josh.

Cam card calls for 0.012" lash both intake and exhaust. 0.012" / 1.5 rocker ratio= 0.008". So my cam grind #346 theoretically intake closes at 0.008" lift, right? Whatever that translates into angular measurement that would be the number to plug into DCC..

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

My experience has been that going under 100 is a losing proposition, but that was with bigger cams.

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Official Cookie and Mater Tormentor.

That is another issue with picking a cam...if the cam is big enough you can't get the peak torque below 3000 no matter how much advance you dial in.
(and there is a push over point in the mid-90's where it will be over advanced, then you have a tractor engine).

Somehow I managed to put my Clifford 300 in at 91* once. To say it had no top end would be an understatement.

_________________
Official Cookie and Mater Tormentor.

That is a big cam, DadTruck. Why did you choose 110 LSA? Most 225 people have done tests use 104 - 108 for NA. I like 105-106. 105 is what Dave Vizard estimates for the 225s ratio of cylinder displacement vs. valve size. The bigger this ratio, the smaller the LSA. This is one reason why smallblock cams tend to have larger LSA and big blocks have smaller LSA.

I believe you want to use 0.050" duration for DCR. Some companies use 0.020" and some 0.008" for "advertised".

I ran my 64 Dart cam at 96, 100, and 104. It was not bad at 96, but it did noticeably start nosing over around 5000. 100 was great all around. 104 was noticeably worse down low.

Lou

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Home of Slant6-powered fun machines since 1988

I bought that cam from Dennis who got it from Mike J,,
the cam was custom ground by Comp Cam back in 2007
then sat unused in Mike J's garage for ten years.

I asked Mike why he never used it and he said he really does not
remember, other than back in that time frame he said he was going with bigger
and bigger cams and maybe that one just got by passed..

there are notes written in with pen on the cam card that indicate the
cam was going to be installed at 107 ICL which seems out of step
with everything I have read,,,who ever penned the notes even calculated
and wrote in the valve events at 107 ICL.
The Comp Cam card already had the valve events at 110 ICL printed on it.
That note to install at 107 ICL is the reason I started this thread.

The Comp Cam numbers for 110 ICL @ .050 are
Intake open at 26 BTDC
Intake close at 66 ABDC

The penned in numbers for 107 ICL are
intake open at 29 BTDC
intake close at 63 ABDC

and I agree 105 to 106 is what I would expect as a LSA for a slant six cam.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

It is 0ossible Mike was still spraying then. 107 or later would be in nitrous territory. Even N/A with a 4400 stall low end would not be high on the list of things he needed.

_________________
Official Cookie and Mater Tormentor.