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CVO Technical => Twin Cam => Topic started by: MCE on September 19, 2018, 10:12:14 AM
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Looking for opinions from other cylinder head guys;
I used Kibblewhite's 660 spring on a set of 103 heads and the seat pressure ended up at 175. (360 open).
The cam is a Tman 585.
I got some guff from the customer telling me that the seat pressure is too high and it's going to "wear out
the lifters". HUH? He said it should be 150# on the seat.
So, I was looking for some input from some of you other head guys. (IME, a little extra seat pressure is
good insurance to keep the lifter on the lobe)
What say you?
PS: Tman's street head specs call out 175# on the seat too
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Guys started crying about seat pressure after HD came out with beehive springs. Before that all your aftermarket springs were 170+ on the seat & you weren’t having any problems. I ran 180# on the seat with aluminum retainers on my Evo for years. If they had forums back then everybody would be telling me how bad they were. If HD was using a better lifter everybody would want a stiffer spring. New springs & new lifters no problem.
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I appreciate the input Larry, thank-you.
Everybody wants to tell you how to do your f--king job, AFTER YOU'RE DONE doing it!
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On AV&V's site, their lowest pressure beehive spring is 165# on the seat.
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But that is just one number, what about the spring rate?
And doesn't the weight of the springs and valves matter and should be part if the decision?
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But that is just one number, what about the spring rate?
And doesn't the weight of the springs and valves matter and should be part if the decision?
what are you talking about? it's pretty easy to calculate the rate using two data points (open & closed).
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Yes and it matters. What spring rate and pressures are required? It is not a single answer, one size fits all, despite adequate travel for the lift.
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The subject at hand was seat pressure. I understand what spring rate is, valve train weight, ramp speeds, (acceleration) and so fourth. That wasn't my question (Larry answered it already). But thanks for enlightening us with your infinite wisdom.
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The point of contention is some customer is questioning the seat pressure (he wanted it to be 150).
I don't know of a beehive spring that's 150# at 1.850ish.
Sorry for being snappy, but these people piss me off.
PS: He didn't tell me that s--t until I finished them, (That's what really got me going)
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Matt, makes one wonder if he’s so smart why did he have you do his heads! I have you do mine cause you know a helluva more than I do!!!
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With me, it depends on the cam, and the valve size being used. I like to be @ 160 on the seat with the cams I frequently use. I know, from the amount of heads I do, where I have to be for valve protrusion vs. installed height. Aggressive cams, 2.100" + valves = more pressure. ;)
John
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With me, it depends on the cam, and the valve size being used. I like to be @ 160 on the seat with the cams I frequently use. I know, from the amount of heads I do, where I have to be for valve protrusion vs. installed height. Aggressive cams, 2.100" + valves = more pressure. ;)
John
Thanks John, That's pretty much what I do as well. How they ride also influences my decision and if it's a light Dyna vs. big heavy bagger. Bottom line is, 175 on the seat aint gonna hurt a darn thing. And that particular guy likes to ride it hard.
This is one of the 110 conversions I did that puts out a solid 130/130. It broke a factory spring so they were in for a freshen up and repair. So I used the premium KW springs with the 9* locks.
On a positive note: I just got a call from a guy that's ecstatic with how his runs, so there's that. (Those types of calls cancel
out the dumb sh!t and make me want to keep doing this).
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Matt, makes one wonder if he’s so smart why did he have you do his heads! I have you do mine cause you know a helluva more than I do!!!
It's a 103->110 conversion that puts down 130/130. That's why! LOL
(he a nice guy, but questions and second-guesses everything I do)
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Ok so I am confused Matt. I have heard you on this forum and on others say the stick on beehives at 140# works great, why go up to 180?
On another but related note, years ago I did testing to actually get the valves in a similar head bike to lift. Another shops heads, 1.9 x 1.61 8mm valves. Tw6hg and 570g. Went from 120 up in 4 steps to see if lofting would occur and what pressure was needed to actually control the valves up to 6200. 120 was a full failure either cam. At 140 the 570 started to behave, at 150 the 6h was ok. Worse case they would not even run down the road in the midrange.
Currently on the CVO heads I am running a Manley or AV&V double with TI retainers. Both when installed at 1.880 come in at ~155#. I also am using conicals (not beehive) at 140# 1.800 instead height for certain applications. Regarding lifter life..if you hear the valves clattering the lifters are being pounded by skipping the roller on the lobe momentarily. The stock 110 and 103 CVOs both experience this regardless of the lifters used.
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I don't know of any after market beehive spring that's under 160# at 1.850 (ish).
You can get close with the (used) factory spring, but after having one break I'm
a little gun shy about re-using those things.
If you have a spring in mind, feel free to share the part number. thanks
(S&S has one that's got 135 at 1.850, but he didn't want S&S springs in his motor.)
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Pick up a pac or Manley catalog
Or lunati or comp for that matter
Plenty of springs to be sourced and retainers,seats,locks to go with them
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Exactly
And now we are back to the same place we were at in the last beehive discussion. Matt the point I was trying to make about rate is seat pressure is not the whole picture and when the rate is too low despite a lot of preload, the seat pressure, the beehives are not necessarily going to control the valve that well. Especially with the lack of rigid pushrods. Think pole vault. This is another reason I have changed away from beehives springs, for a higher rate. Nothing you don't understand I'm sure just may not agree with.
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I'm not disagreeing at all. Spring rate is super easy to measure/calculate. It's a simple linear equation (9th or 10th grade math).
I'm going to continue using beehives, for a variety of reasons that I don't feel like litigating here.
-Cheers
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Beehive springs/retainers have less mass, (one of their advantages). That alone will minimize pushrod deflection
(pole vaulting as you call it) during an aggressive valve opening event. TI retainers help, but a
double spring is still going to have more mass than the beehive. F=MA
Then there's the issue of spring harmonics, beehives don't have a single resonant frequency, it's spread out over
a wide range to minimize harmonic "ringing". Probably not an issue on these engines, but IDK for sure.
I'm not here to convince anyone or change people's minds. Use whatever you feel comfortable with!
-MC
PS: I'm going to run it by Darin Morgan when I see him next week.