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Alu push rods vs spring preassure
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Topic: Alu push rods vs spring preassure (Read 44960 times)
Elnef
Hero Member
Posts: 566
Alu push rods vs spring preassure
«
on:
November 22, 2012, 19:03:59 pm »
Hi
How much valve spring preassure on a alu push rods is it possible to run with
(dual tappered 7075 alu)
John
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BeetleBug
Hero Member
Posts: 2836
Snabba grabben...
Re: Alu push rods vs spring preassure
«
Reply #1 on:
November 22, 2012, 19:19:54 pm »
Quote from: Elnef on November 22, 2012, 19:03:59 pm
Hi
How much valve spring preassure on a alu push rods is it possible to run with
(dual tappered 7075 alu)
John
You`re asking the wrong question John. What you should ask is how LITTLE spring pressure you can run. I went down from K800 to a so called Chevy spring then to a single Chevy spring on my 2332 with a FK87. No problems at all. Revs to 8700 rpms.
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Jesse/DVK
Hero Member
Posts: 817
'64 2176cc
Re: Alu push rods vs spring preassure
«
Reply #2 on:
November 22, 2012, 19:37:52 pm »
What else did you change BB? Also looking into getting my valve train light already got 55 grams lifters.
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Der Vollgas Kreuzers
Elnef
Hero Member
Posts: 566
Re: Alu push rods vs spring preassure
«
Reply #3 on:
November 22, 2012, 20:25:06 pm »
Quote from: BeetleBug on November 22, 2012, 19:19:54 pm
Quote from: Elnef on November 22, 2012, 19:03:59 pm
Hi
How much valve spring preassure on a alu push rods is it possible to run with
(dual tappered 7075 alu)
John
You`re asking the wrong question John. What you should ask is how LITTLE spring pressure you can run. I went down from K800 to a so called Chevy spring then to a single Chevy spring on my 2332 with a FK87. No problems at all. Revs to 8700 rpms.
Hi Kalle
I belive I ask the right question I would like to know what people run with with "a lot" of cam and big valve 53/42 titanium
Do you know the weight on youre parts valve and lifter and maybe what spring preassure
John
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BeetleBug
Hero Member
Posts: 2836
Snabba grabben...
Re: Alu push rods vs spring preassure
«
Reply #4 on:
November 22, 2012, 20:35:18 pm »
Quote from: Jesse/DVK on November 22, 2012, 19:37:52 pm
What else did you change BB? Also looking into getting my valve train light already got 55 grams lifters.
Nothing. What happened was that I bent a Manton Pushrod at high rpm going of the throttle at high boost (on dyna packs) I changed the pushrods (and tubes) to the JPM alu ones and started out with the same K800 springs. After a little while I changed to the Chevy ones (if I remember correctly I had 390lbs at max lift with them compared to 420lbs with the K800`s) and later the same season I removed the inner chevy spring. Cam is a FK87 matched with 94g UDO lifters. Comp Eliminator heads with big, heavy valves.
-BB-
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10.41 - 100ci - 1641ccm - 400hp
Elnef
Hero Member
Posts: 566
Re: Alu push rods vs spring preassure
«
Reply #5 on:
November 22, 2012, 21:18:31 pm »
Thanks Kalle
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Tekken
Sr. Member
Posts: 307
www.proturbovw.com
Re: Alu push rods vs spring preassure
«
Reply #6 on:
November 22, 2012, 22:36:32 pm »
Kalle, what type of Manton pushrod did you bend-dual tapered?
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richie
Hero Member
Posts: 5687
Re: Alu push rods vs spring preassure
«
Reply #7 on:
November 22, 2012, 22:49:06 pm »
Quote from: BeetleBug on November 22, 2012, 20:35:18 pm
Quote from: Jesse/DVK on November 22, 2012, 19:37:52 pm
What else did you change BB? Also looking into getting my valve train light already got 55 grams lifters.
Nothing. What happened was that I bent a Manton Pushrod at high rpm going of the throttle at high boost (on dyna packs) I changed the pushrods (and tubes) to the JPM alu ones and started out with the same K800 springs. After a little while I changed to the Chevy ones (if I remember correctly I had 390lbs at max lift with them compared to 420lbs with the K800`s) and later the same season I removed the inner chevy spring. Cam is a FK87 matched with 94g UDO lifters. Comp Eliminator heads with big, heavy valves.
-BB-
So what you are really saying is you spent all your money on really expensive pushrods so couldn't afford new valve springs and just used what you had already lying around
Does amaze me that the weight saving of an ally pushrod makes that much difference to allow so much lighter spring pressure, I really need to try some myself and gain those benifits,I have not had a flat tappet VW engine that would spin that high rpm
cheers richie
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Good parts might be expensive but good advice is priceless
BeetleBug
Hero Member
Posts: 2836
Snabba grabben...
Re: Alu push rods vs spring preassure
«
Reply #8 on:
November 23, 2012, 08:36:05 am »
Quote from: Tekken on November 22, 2012, 22:36:32 pm
Kalle, what type of Manton pushrod did you bend-dual tapered?
No, I used the HD straight ones: Manton 3/8" Chromoly Pushrods, Straight, .058" Wall Thickness.
Quote from: richie on November 22, 2012, 22:49:06 pm
So what you are really saying is you spent all your money on really expensive pushrods so couldn't afford new valve springs and just used what you had already lying around
cheers richie
At that time I attended classes at a old school. The teachers told me that it was better with too much spring pressure than not enough. I tried several times to ask what was considered enough but could never get a straight answer.
I changed school and will never go back.
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10.41 - 100ci - 1641ccm - 400hp
Udo
Hero Member
Posts: 2077
Re: Alu push rods vs spring preassure
«
Reply #9 on:
November 23, 2012, 12:34:38 pm »
It is a question of what you have , FK 87 does not need that much spring pressure . i think elnef needs K800 with Jay Cee chrom molly pushrods
Udo
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www.Udobeckertuning.de
John Maher
Full Member
Posts: 140
Re: Alu push rods vs spring preassure
«
Reply #10 on:
November 23, 2012, 15:49:36 pm »
The valve spring and pushrod combo that works in one engine might not work in another, even if the cams have similar duration and lift.
Cams that take up initial lash more gently are kinder to the valvetrain - if you're not hitting the valve hard to lift it off the seat and then place it back on the seat in a more controlled manner, you can generally get away with less spring pressure.
Engine expansion plays a big part in the equation. If lash is set to zero when cold, what is it when the engine is at operating temperature? In many instances lash increases beyond the point at which the cam manufacturers designed in take-up ramp is intended to work i.e. the valve takes a hard hit on initial opening.
It isn't the lighter weight of an aluminium pushrod that allows you to run less spring pressure.... it's more related to the fact aluminium pushrods have a greater rate of expansion than chromoly, therefore valve clearances on a hot motor are smaller, which in turn makes the initial take up ramp on the cam work more effectively, resulting in a less stressed valvetrain.
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John Maher
Jesse/DVK
Hero Member
Posts: 817
'64 2176cc
Re: Alu push rods vs spring preassure
«
Reply #11 on:
November 23, 2012, 16:50:20 pm »
Than there is the next questions for a newbie like me. Is it possible to calculate the pressure needed? Or is it trial and error? Possible to hear valves float?
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Der Vollgas Kreuzers
BeetleBug
Hero Member
Posts: 2836
Snabba grabben...
Re: Alu push rods vs spring preassure
«
Reply #12 on:
November 23, 2012, 17:14:21 pm »
Quote from: Jesse/DVK on November 23, 2012, 16:50:20 pm
Is it Possible to hear valves float?
Yes indeed, you will notice valve float but then it is of course too late.
On a sidenote; next time you`re at a VW meeting I advice you to listen carefully to all the cars arriving and ask yourselves why they all have such a noisy valve train. Then read the post again from John Maher.
If you buy a camshaft from a serious company they will give you all the info needed.
-BB-
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Udo
Hero Member
Posts: 2077
Re: Alu push rods vs spring preassure
«
Reply #13 on:
November 23, 2012, 17:48:09 pm »
If you messure the cam on a cam doctor for example and have all the weights of the valve train you can calculate it . but it is better you have one that can tell you the experiance ...
Udo
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www.Udobeckertuning.de
John Maher
Full Member
Posts: 140
Re: Alu push rods vs spring preassure
«
Reply #14 on:
November 23, 2012, 18:13:40 pm »
Quote from: Jesse/DVK on November 23, 2012, 16:50:20 pm
Than there is the next questions for a newbie like me. Is it possible to calculate the pressure needed? Or is it trial and error? Possible to hear valves float?
Some of the better quality (ie expensive!) engine simulation software programmes will calculate spring rate and pressures if you've input complete cam data but you still have to test it on a
real
engine to see if the predicted results work in the real world.
There are things about your engine you may consider as
not
being directly related to the valvetrain but can still play a part in whether you float the valves or not.........
Regarding engine expansion (as mentioned in my previous post when talking about aluminium pushrods), an interesting point came up in conversation with Johannes from JPM the other day.... aluminium cylinders expand approx twice as much as cast iron. Zero cold lash becomes as much as 1mm (.040") when the engine is hot. All camshafts feature relatively gentle opening and closing ramps, designed to smoothly take up slack in the valvetrain (valve lash) before applying rapid acceleration to lift the valve off the seat. Most aftermarket cams feature an opening ramp on the assumption hot lash is approx .006" to .008". But with 1mm (.040") hot lash, the cam is well into its acceleration phase while the valve is still on the seat. WHACK!!
Same thing happens on valve closing.... instead of being decelerated in a controlled manner, the valve smacks into the seat before the lifter has made it on to the closing ramp of the cam. In this situation, regardless of what valve springs you're using, the valvetrain can never work as intended, except for the first few seconds after you set valve lash.
Just another example of how seemingly unrelated components can affect the end result and why it's often impossible to make a specific recommendation without taking a whole lot of stuff into account.
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John Maher
jaqo
Full Member
Posts: 168
Bugster Team
Re: Alu push rods vs spring preassure
«
Reply #15 on:
November 24, 2012, 01:43:30 am »
That's interesting. So what should be done when you're building an engine with aluminium cylinders and steel pushrods?
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Fiatdude
Hero Member
Posts: 1823
Re: Alu push rods vs spring preassure
«
Reply #16 on:
November 24, 2012, 06:15:49 am »
Quote from: jaqo on November 24, 2012, 01:43:30 am
That's interesting. So what should be done when you're building an engine with aluminium cylinders and steel pushrods?
Get dual taper aluminum ones -- my 2919 blows up, size wise, as it heats up -- and I just hated my steel PR
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John Maher
Full Member
Posts: 140
Re: Alu push rods vs spring preassure
«
Reply #17 on:
November 24, 2012, 11:28:48 am »
Quote from: jaqo on November 24, 2012, 01:43:30 am
That's interesting. So what should be done when you're building an engine with aluminium cylinders and steel pushrods?
Lower your rpm expectations.
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John Maher
jaqo
Full Member
Posts: 168
Bugster Team
Re: Alu push rods vs spring preassure
«
Reply #18 on:
November 24, 2012, 11:30:59 am »
Can't be done in this combo,i guess we'll have to buy some pushrods;)
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andy198712
Hero Member
Posts: 1063
Re: Alu push rods vs spring preassure
«
Reply #19 on:
November 24, 2012, 17:06:41 pm »
this all begs the question, is there a better way to set lash, ie when warm/hot?
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viNce
Jr. Member
Posts: 86
Re: Alu push rods vs spring preassure
«
Reply #20 on:
November 24, 2012, 18:19:35 pm »
If you set your valve lash hot with steel pushrods, you may have tight valves when cold
With Alu pushrods, setting lash to 0 when engine is hot could be a great solution, then you let the engine cool down and you look at the lash when cold. Now you know how to set your lash when cold for future settings.
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ALB
Newbie
Posts: 36
Re: Alu push rods vs spring preassure
«
Reply #21 on:
November 24, 2012, 18:31:41 pm »
Quote from: John Maher on November 23, 2012, 18:13:40 pm
There are things about your engine you may consider as
not
being directly related to the valvetrain but can still play a part in whether you float the valves or not.........
Regarding engine expansion (as mentioned in my previous post when talking about aluminium pushrods), an interesting point came up in conversation with Johannes from JPM the other day.... aluminium cylinders expand approx twice as much as cast iron. Zero cold lash becomes as much as 1mm (.040") when the engine is hot. All camshafts feature relatively gentle opening and closing ramps, designed to smoothly take up slack in the valvetrain (valve lash) before applying rapid acceleration to lift the valve off the seat. Most aftermarket cams feature an opening ramp on the assumption hot lash is approx .006" to .008". But with 1mm (.040") hot lash, the cam is well into its acceleration phase while the valve is still on the seat. WHACK!!
Same thing happens on valve closing.... instead of being decelerated in a controlled manner, the valve smacks into the seat before the lifter has made it on to the closing ramp of the cam. In this situation, regardless of what valve springs you're using, the valvetrain can never work as intended, except for the first few seconds after you set valve lash.
Just another example of how seemingly unrelated components can affect the end result and why it's often impossible to make a specific recommendation without taking a whole lot of stuff into account.
Does any one make cams with really soft initial ramps that would work better with aluminum cylinders? I'm thinking something that goes to 6500...
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reijo5
Jr. Member
Posts: 57
Re: Alu push rods vs spring preassure
«
Reply #22 on:
November 24, 2012, 20:01:14 pm »
I ve been thinking of switching to aluminium push rods , whos do you guys uses/ recomend ?
cheers
Jamie
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Fiatdude
Hero Member
Posts: 1823
Re: Alu push rods vs spring preassure
«
Reply #23 on:
November 24, 2012, 23:27:10 pm »
aircooled.net -- dual tapper
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Ovalholio -- GONE
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Get lost for an evening or two --
http://selvedgeyard.com/
Remember, as you travel the highway of life,
For every mile of road, there is 2 miles of ditch
dangerous
Sr. Member
Posts: 270
Re: Alu push rods vs spring preassure
«
Reply #24 on:
November 25, 2012, 01:33:17 am »
These are some interesting experiences.
The only experience I have, is with an engine I built using the LN cylinders,
and despite expecting to have to use aluminium PR due to expansion,
we tried some light cromoly ones set at zero lash, and it is very quiet.
Mind you the oil temp never goes over 100C, which would help.
I am "all for" aluminium pushrods if the flex can be reduced to acceptable levels,
but this would be a balancing act with the spring load, pushrod design and material(7075 or 2024),
and of course the ramp rate and other numerous details of the profile used.
For my own engine with a roller cam profile that has a fast ramp rate, but stable profile,
titanium valve, retainer and collet,
I have not found, or made an aluminium pushrod,(3/4"!) that does not lose lift through flex,
unless I get below about 400 nose pressure.
I think that it CAN be made to work, but will require a lot of spintron time.
At this stage, I think I can make it work with some of the large base(1.58") beehives, but these are not rated to .800", only .750"
To respond to the fellow's original question,
I would imagine the JPM taper deals made from 7075 should work ok
if using less than 450lbs and 1.5 rocker,
provided the lobe profile is not some wierd spring killer profile.
..which should be more than just about any flat tappet profile should ever need.
But as others have suggested, a simple question does not mean a simple answer, especially when it comes to valve train!
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Jyrki
Full Member
Posts: 221
8.88 & 251
Re: Alu push rods vs spring preassure
«
Reply #25 on:
November 25, 2012, 08:59:00 am »
Quote from: BeetleBug on November 23, 2012, 08:36:05 am
At that time I attended classes at a old school. The teachers told me that it was better with too much spring pressure than not enough. I tried several times to ask what was considered enough but could never get a straight answer.
I changed school and will never go back.
BR,
'one of the teachers?'
ps. still running 700lbs at full lift
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Udo
Hero Member
Posts: 2077
Re: Alu push rods vs spring preassure
«
Reply #26 on:
November 25, 2012, 09:21:00 am »
Alu pushrods on a race engine is more like female
Udo
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www.Udobeckertuning.de
Elnef
Hero Member
Posts: 566
Re: Alu push rods vs spring preassure
«
Reply #27 on:
November 25, 2012, 11:48:00 am »
Quote from: Udo on November 25, 2012, 09:21:00 am
Alu pushrods on a race engine is more like female
Udo
Hmm At least its not a type1 engine I am building
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Udo
Hero Member
Posts: 2077
Re: Alu push rods vs spring preassure
«
Reply #28 on:
November 25, 2012, 13:03:38 pm »
You are right , it is a bus engine which is built for no high rpms ...
I would look for the fast engines ... this is what i do since 30 years now and still it is ok . the us guys are the fastest and they will continue like that .
Udo
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Fiatdude
Hero Member
Posts: 1823
Re: Alu push rods vs spring preassure
«
Reply #29 on:
November 25, 2012, 18:18:19 pm »
a aluminum push rodded engine just won the unlimited street event at Las Vegas
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Ovalholio -- GONE
Ghia -- -- It's going
Get lost for an evening or two --
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Remember, as you travel the highway of life,
For every mile of road, there is 2 miles of ditch
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