340 dyno chart thoughts
Jesus Christ, really? 255 at .050 is small? On 340 inches? Get real. You'd argue with a stop sign.
At some point, when you grow up, you'll figure out you are wrong and admit it.
So let's play your silly game. A 292/.509 MP cam is 248 at .050. Most guys say it won't make vacuum, all that ****. My cam is 11 degrees SMALLER on the seat yet it's 8 degrees BIGGER at .050. What part of that don't you get?
You and your mixed up understanding of camshaft and induction screws people up if they listen to you. You cause those who listen to you to produce underachievers. If you are an engine builder, it's sickening to watch the same old lies and mistakes get repeated for DECADES. It's time to stop the ****.
By the way, my LSA is 105 and it's installed on a 105 ICL. By your understanding, it still won't idle.
It doesn't matter what I say or do, it's like people stuck in Scientology. They never want to admit what they knew or did for a lifetime was wrong.
It has to stop.
I NEVER said 255 is small on a 340. I said 10" of vacuum is unusually high unless it's a solid cam with lash. then you said it WAS a solid cam with lash after all. so where exactly was i wrong, genius?
What I am saying is that 255 lobe duration in a solid cam is going to behave more like a 243 duration hydraulic cam. This is why your 255 solid cam has about the same idle vacuum as the 241 mp cam you recommended earlier.
Do yourself a favor and picture it in your head. The cam is turning, the lifter rises in it's bore. but the lash has to be taken up so the valve doesn't begin to move until the lifter has raised 0.014" on the intake and 0.016" on the exhaust. if you were to check this with a degree wheel how many crank degrees do you think this would take off the opening and closing sides? I guarantee you it would be at AT LEAST 10 degrees when combined.
That's why you're getting a good amount of vacuum, your duration and overlap is being eaten by lash. It isn't your super duper magical tuning skills, There's nothing difficult about tuning an idle. You act like you're the only one who knows how to do it.
I run a 254/254 on 108 in my 318 and it gets 10-11" vacuum too, And so it should, not because of any super duper fast rate ramp rate on the lobes, Nor because of any fancy black magic tuning skills. It's just an ancient isky Z35 with some lash.
Solid cams need to be bigger by 0.050" spec to have the same torque curve as a much smaller hydraulic grind, the more lash, the more duration is needed to compensate. If you're going to start trying to compare solids to hydraulics in a thread where everyone else is only talking about hydraulics, you probably should state what you're talking about from the get-go instead of waiting to be questioned about it.
I explained above why seat duration is virtually irrelevant to overlap specs. they're measured at 0.006" which is a lift value where a valve is barely functioning. If you have a fast ramp rate on your lobes that's great and it will help..."slightly", 0.050" specs are popular for a reason.. they're actually useful!
All your rantings and anecdotes still don't change the fact that if you keep everything else equal (no more comparing solid cams to hydraulics, wtf were you thinking?) having longer duration lobes as measured by 0.050" specs and/or a narrower lobe separation angle WILL have a higher more overlap and WILL effect idle vacuum.
Seriously, you're the one who's screwing people up by saying higher overlap @ 0.050" won't affect idle, or that you can switch from a 231/231 on 110 to 241/241 on 106 without losing any vacuum or drivability, or that saying lobe separation angle is just a function of valve events etc.
You're the one screwing people up by talking about how you ran a bigger cam and a smaller cam with the same resulting idle vacuum but neglecting to mention that one of them was a solid cam with lash and the other was hydraulic. You seem to think this doesn't make a difference, If that's the case. you're flat-out wrong.
Like i said from the start. OP's cam has 11 degrees overlap at 0.050". the cam you recommended has 29 degrees overlap @ 0.050"!
How can you possibly justify your claim that this will make no difference to idle vacuum? I'm listening.. you have my attention!
IF right at the start you had said you can change from a 231/231 on 110 hydraulic to a 241/241 on 106 SOLID without losing vacuum, then i probably would have agreed with you. But you didn't you were talking about two hydraulics.