Lobe Intensity vs Durability

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CamKing
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Re: Lobe Intensity vs Durability

Post by CamKing »

skinny z wrote: Fri Oct 15, 2021 4:30 pm
CamKing wrote: Fri Oct 15, 2021 3:36 pm
Thanks for that Mike.
I can see it's a question of risk (being longevity) vs reward (more power!).
I suppose the question I have to ask myself is how much risk am I willing to take. I'm at a point where I probably won't rack up the mileage that I used to but that said this IS going to be driver. I have to get to the Nevada road race somehow. That's 1500 miles one way.
I'm basically at square one on the valve train again having lost a link bar , spinning a lifter and wiping out the cam. So new cam and lifters at a minimum.
Specifically to you CamKing, your EHR73360 lobe (duration at 284/238 and lift at .575 with 1.6 rockers is about ideal) would require what kind of spring pressures? I'm currently set up with COMPs 26918 conical spring and tool steel retainers.
Specs are:
1.800"/125 Lbs
372 lbs./in.
Is that sufficient for that lobe?
And if may ask, which of your lifters would you recommend for a retrofit Gen 1 SBC using that lobe?
Are any of those a reduced base circle?

Thanks again.
It depends on the RPM, and the weight of the valves.
For that profile up to 6,000rpm, we normally use a PAC 1218X, 140# on the seat, and 330# at max lift.

For what you are doing, you may be better off going to a mechanical roller cam, designed for endurance. That way, you can make sure you have enough spring pressure to control the valve train in the unlikely chance you over-rev the engine, without having to worry about how the added spring pressure effects the hydraulic unit on the lifters.
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skinny z
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Re: Lobe Intensity vs Durability

Post by skinny z »

CamKing wrote: Sat Oct 16, 2021 12:59 pm

Now that is something I hadn't considered.
Prior to finding the mangled lifter set, I was firmly in the hydraulic camp. Now you have me thinking.
But...

Now this is exactly why I asked this question in the first place.
Based on those insights, it may be that I dial back my objectives a little just to be easier on parts. That is to say, the lesser of those two profiles may be the way to go. This is an engine I don't intend to open up again after it's completed and I've learned that the valvetrain gets the most abuse. Stepping up is obviously going to make the situation less tenable from my personal point of view. Been there, done that and don't really care to do it again.

Nevada may never happen. But the drag strip is only 20 minutes down the road! That puts a different spin on the build direction.

Thanks.
Kevin
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Re: Lobe Intensity vs Durability

Post by rebelyell »

Lobe
durability is inversely proportional to intensity
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Re: Lobe Intensity vs Durability

Post by PackardV8 »

rebelyell wrote: Sat Oct 16, 2021 5:47 pm Lobe durability is inversely proportional to intensity
Might one also say valve spring, seat, keeper groove, valve face life is also inversely proportional to intensity?
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Re: Lobe Intensity vs Durability

Post by rebelyell »

PackardV8 wrote: Sat Oct 16, 2021 8:18 pm
rebelyell wrote: Sat Oct 16, 2021 5:47 pm Lobe durability is inversely proportional to intensity
Might one also say valve spring, seat, keeper groove, valve face life is also inversely proportional to intensity?
from one jack to another ... Yes; of course.
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Re: Lobe Intensity vs Durability

Post by skinny z »

It's fair to say that all of these components are getting stressed. Proportionally or otherwise.
It certainly giving me cause to reconsider my performance goals.
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Re: Lobe Intensity vs Durability

Post by Orr89rocz »

Just go milder and better heads. Get power and reliability. No reason a hyd roller cant be used here. But solid roller stuff is nice too, i love my new setup with conical springs. Low loads but still stable and no hydraulic concerns
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Re: Lobe Intensity vs Durability

Post by bob460 »

Orr89rocz wrote: Sun Oct 17, 2021 6:39 pm Just go milder and better heads. Get power and reliability. No reason a hyd roller cant be used here. But solid roller stuff is nice too, i love my new setup with conical springs. Low loads but still stable and no hydraulic concerns
What springs are you using and on what combo?
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Re: Lobe Intensity vs Durability

Post by Orr89rocz »

2.300” valved turbo big block. Mid .700” lift 7000 rpm with One of comp conicals, setup at 135 seat 500 open
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Re: Lobe Intensity vs Durability

Post by skinny z »

Orr89rocz wrote: Sun Oct 17, 2021 6:39 pm Just go milder and better heads.
Milder yes. But this whole thing is built around the heads I have so they're staying. And they're set up with COMP's conical springs already. Lightweight retainers too. It would be nice to salvage something out of the valve train.

I can see where I'll be stepping back to a lobe along the lines of the XE grind. Maybe the XFI. Interestingly, the XFI 284/234 lobe calls for the spring package I'm running now as well as a 1.6 rocker.
There might be something to that.
Kevin
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Re: Lobe Intensity vs Durability

Post by Orr89rocz »

If you have comp 26918 those are beehives not conicals. And if they have as many miles as those lifters and cam, might wanna replace them anyway
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Re: Lobe Intensity vs Durability

Post by skinny z »

I see there's a distinction between conical and beehive. Fair enough. And I have the 26918's.
As for mileage, these are a 2nd set and somewhat fresher.
It remains to be seen if they're still in spec though.
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Re: Lobe Intensity vs Durability

Post by agertz1 »

In case I missed, is this a symetrical lobe profile ? Closing ramp on hotter cam ok ?
Art.
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Re: Lobe Intensity vs Durability

Post by bob460 »

Orr89rocz wrote: Mon Oct 18, 2021 8:17 am 2.300” valved turbo big block. Mid .700” lift 7000 rpm with One of comp conicals, setup at 135 seat 500 open
Is that the dual conical...............how do you get 135/500?.....what's coil bind?
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Re: Lobe Intensity vs Durability

Post by skinny z »

agertz1 wrote: Mon Oct 18, 2021 7:05 pm In case I missed, is this a symetrical lobe profile ? Closing ramp on hotter cam ok ?
Art.
COMPs XR288HR. Pretty unextraordinary.
Once I get into the engine itself I'll have a better determination on what went sideways.
I'm still guessing thrust button.
Kevin
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