340 dyno chart thoughts
That's what i just said. Advertisements used to be all over the place until a standard duration measurement was implemented. Now they all advertise at the standard. The standards came from SAE. you DO know what SAE is don't you?
I literally just said that. Thanks for repeating me?
Lustle, you need to get it through your skull that a camshaft's specs are determined long before you install that camshaft into an engine with valves. They design a camshaft using specs and they produce the camshaft using specs.
You mean like how I said valve events are ground into a cam? Camshaft specs are VALVE EVENTS. And yup, they are determined before the cam is ground. Just like I mentioned before. You do know what camshaft grinding is, right? You do know what they use to determine the grind, right? I've been mentioning this in my posts, are you sure you are reading them? Here it is again:
How do you calculate duration? You use valve events. How do you calculate valve events? By measuring the cam. How do you calculate LSA? You use valve events. How do you calculate valve events? Once again, by measuring the cam. Valve events are GROUND INTO THE CAM.
Here you are with that comprehension thing again:
One day if you ever care to look, you will find that duration is measured as a specified lift for a specified number of degrees and this is measured @ the lobe/lifter, NOT the valve.
You mean how I just mentioned that duration is determine by valve events as ground into the cam? I'm starting to notice a pattern here, I think it's with your comprehension. ONCE more now here:
LOOK AT THAT. I mention measuring the cam, before you did! Gee, repeating me again?
Think about that for a second. I'll just repeat it. Camshaft duration spec has nothing to do with the valve. It is simply measuring... the camshaft. you know.. the long bumpy thing? It actually still exists when it's not installed in an engine and can even be measured that way! Fancy that!
Are they bumpy for a reason? OH maybe it's because things are GROUND INTO THEM. And measuring the cam? What a radical... wait, you mean like I mentioned. Here it is again for you:
So now this.
View attachment 1715001683 View attachment 1715001684 View attachment 1715001685
Now, getting back to those SAE standards we talked about.
The standard for measuring duration on hydraulic cams is 0.006" of lift AT THE LOBE.
The standard for measuring duration on Solid cams is 0.020" lift AT THE LOBE.
I know that thinking isn't your strong point, I've explained the difference lash makes in how a solid cam's duration specs translates to actual valve timing TWICE now and still you don't get why you can't compare a hydraulic to a solid using the same 0.006" specs. So this time i drew you a picture, Good luck!
Awww, is someone getting frustrated cause they are wrong?
It's ok to admit when you are wrong frosty.
I understand lash. I understand how it takes up. I get all that. You seem to be the one with the comprehension problem here.
Also. I noticed how you forgot to quote a large part of my post. Is that perhaps cause you were wrong? Things like "can you determine duration without knowing valve events". BTW the answer is no. Easy to skip over stuff you got wrong, right?
This is the manufacturer's description of that cam?
Hughes Engines
Show me where it says IVC 64 ABDC on this page please.
All the values on this page are correct for the duration and lobe separation with 4 degrees advance.
To get IVC 64 ABDC you will need 11 degrees retard. good luck with that.
I notice something here. You once again leaving something out that you got wrong. Let's quote your original post again, shall we?
Where did you get these figures from?
The intake closing angle for a 250/254 - 108 LSA is 53 ATDC
The intake closing angle for 230/236 - 110 LSA is 45 ATDC.
So are we talking ABDC? OR ATDC? They are different. You, you do know that right? When I quoted the valve closing figures earlier, I said:
Hughes STL5054AS-8 250/254 -108ºLSA - Intake valve closing angle 64.
Comp XE274H - 230/236 - 110 LSA - Intake valve closing angle 63.
Now. I maybe made the "mistake" of not mentioning ABDC here. I assumed it was pretty clear what I was talking about. Considering the intake valve only closes ABDC. So I'll just assume you meant ABDC (even if you didn't. I did).
So I said. I got them from the manufacturer. You then say "hughes website doesn't say that". Completely forgetting about the Comp cams website. What did the Comp say? Oh that right. It said 63. Right from the manufacturer. How ever you came up with 45, you're wrong. By a lot. Once again easy to skip stuff that you were wrong about, isn't it?
Now lets look at your intake valve closing angle on the hughes. You insist it is 53 ABDC, right? So you are telling me. A cam shaft with 250/254 @.050 duration, .588/.600 lift, with a lash of only .010/.012. Closes the intake valve 10 degrees sooner than a cam with 230/236 @.050 duration, .488/.491 lift? Interesting.
One reason I like to use valve events. Is to calculate DCR. DCR calculators use seat to seat measurements. You know what seat to seat is, right? Is .020 seat? Hmm nope, but .006 is about as close as you can get. So. Lets punch that Hughes cam (as measured by you) into the DCR calculator. We will use my engine as an example. It's simple. 10:1 compression. .040 overbore/stock stroke. KB243 pistons. J heads with a valve job, minor cleanup, and some work on the turn. Pretty basic setup. Also I am at 3000 feet.
Now, DCR with the current XE274H cam:
Your dynamic compression ratio is 7.44:1 .
Your dynamic cranking pressure is 145.44 PSI.
And DCR with the hughes cam (again as measured by you):
Your dynamic compression ratio is 8.01:1 .
Your dynamic cranking pressure is 160.14 PSI.
So. If I put that hughes cam, with its 250/254 duration, and .588/600 lift. I will have MORE cranking pressure? And MORE DCR? Over a smaller cam?
Wow, maybe I should just stick the biggest cam I can in there. Obviously according to your calculations. It will work!
But hey, lets try my calculation of 64 degrees:
Your dynamic compression ratio is 7.38:1 .
Your dynamic cranking pressure is 143.90 PSI.
WHOA! The cam with MORE duration has LESS DCR and cranking pressure? That doesn't make sense. Does it? I mean, it's not much different, but 63 to 64 isn't huge. But obviously some of that is because of lash (yes I'm aware of what it is), LSA, and lobe design. I think we all (except maybe you frosty) know that LSA closes that intake a little sooner. Letting you get more cylinder pressure. And the XE274H is from what, 78? There have been numerous camshaft design improvements since then.
I hope you are realizing at this point, that your calculations are incorrect.
In the end. This is going to be my last hijack post on this thread. Obviously OP didn't intend for this conversation. If you wish to continue to be proven wrong frosty, please feel free to start another thread and I will feel free to debate further with you.
