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Clatter
Samba Member
Joined: September 24, 2003
Posts: 7537
Location: Santa Cruz
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 Posted: Wed Jan 25, 2023 8:59 am Post subject: Re: Aluminum or steel pushrods? |
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Handbags, ladies... 
I've been involved in the hobby for 45 years!
Does that make me smart?
Not at all.
In a modern world, even stupid people can live to old age.
As for flywheels and carbs adding to the possibility of valve float,
Here's something from Berg:
http://www.geneberg.com/cat.php?cPath=6_150_2763
A big contributor to valve float can be low gearing, as in an early Bus.
Rapid -change- in RPM, acceleration, can cause float to come in earlier.
Think of the cam 'flinging' the lifter off the nose, if you will.
BITD, when there were speed shops, there were two types of springs hanging on the wall.
"Singles" and "duals".
"Singles" were all pretty much the same regardless of what color blister pack they came in - Scat, Bugpack, Empi, didn't matter.
They were often the same spring in different packaging.
"Duals" were the same springs with an inner added.
Sure, there are "Chevy" "K-800s" "triples" "650s" yadda yadda,
But for regular street springs, it's singles or duals.
The convention continues to this day, and why not?
Most street cars aren't built to these exacting standards,
Especially before the Samba came along..
"shimming the rockers to zero clearance" is a term thrown around.
And it's a good one.
I guess you should say "loose zero" like we do with steel pushrods.
Because ACVWs are fed a meager bit of pressurized oil to lube the shafts,
We try and contain as much as we can.
The closer you get to zero side-play without binding the better to contain lubrication.
Zero isn't possible because of the shims available, but it's the goal.
So, for our OP,
He needs a set of singles with shafts shimmed to zero.
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Bus Motor Build
What’s That Noise?!? |
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12714
Location: Western Canada
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| Posted: Wed Jan 25, 2023 9:10 am Post subject: Re: Aluminum or steel pushrods? |
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| Nightshift wrote: |
| oprn wrote: |
| Nightshift wrote: |
| What does stock or aftermarket crank have to do with valve springs??? |
Valve float is RPM related, correct? Stock cranks are RPM limited.
| Nightshift wrote: |
| Zero side play?? How does the oil get in. ?? Come on! That’s very bad advice! |
The rocker arms are fed oil by the pushrods. The rockers are then drilled to feed the rocker shafts. The oil then goes up the valve side of the rocker arm and out to feed the end of the valve stems. Any access oil also squeezes out between the rocker shims.
The rocker shafts are not splash lubricated if that is what you are thinking so no the oil does not get in, it gets out. |
And this has to do with zero play on the rockers how?????? Lol |
I tried to explain to you how the rockers are oiled but I am not sure that you get that even now!
This advice by the way is not my invention, I got it from some knowledgeable people on this site. It parallels the advice given for zero valve lash for steel push rods, how do the valve tips get oiled there? . And if you think about it, that is how VW set them up with the wavy washers. Why wasn't that a problem too?
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vwracerdave
Samba Member
Joined: November 11, 2004
Posts: 15303
Location: Deep in the 405
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| Posted: Wed Jan 25, 2023 10:08 am Post subject: Re: Aluminum or steel pushrods? |
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| modok wrote: |
Sometimes yes the flywheel makes a difference.
For two reasons. One being the instantaneous rpm, the other being that if the engine accelerates very fast "modes can stack"
He swung on that one but missed, we all miss a few |
Some people just don't understand valve float happens from how fast you rev not just how high you rev. You can have valve float at 3000 RPM.
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2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK
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Watch my racing video's http://www.youtube.com/user/okvwracer/videos |
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jpaull
Samba Member
Joined: February 22, 2005
Posts: 3462
Location: Paradise, Ca
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| Posted: Wed Jan 25, 2023 10:56 am Post subject: Re: Aluminum or steel pushrods? |
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| vwracerdave wrote: |
| modok wrote: |
Sometimes yes the flywheel makes a difference.
For two reasons. One being the instantaneous rpm, the other being that if the engine accelerates very fast "modes can stack"
He swung on that one but missed, we all miss a few |
Some people just don't understand valve float happens from how fast you rev not just how high you rev. You can have valve float at 3000 RPM. |
If a person sized their valve springs so light that they need to account for lightened flywheel or not, they are waaaaaayyyyy to light on spring pressure.
I have a 10lb flywheel, 10.4:1 compression, with single beehive springs that only have 110lbs on the seat and 250lbs fully open. It revs really fast, and with the belt off its insanely fast revving. No valve float ever. A person would to size a spring insanely too light to need to calculate flywheel weight into the equation. If they are at that point, the spring is tooooooo light, there is no room for other factors that will need more spring tension to follow the cam lobes without float. |
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12714
Location: Western Canada
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| Posted: Wed Jan 25, 2023 11:43 am Post subject: Re: Aluminum or steel pushrods? |
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| vwracerdave wrote: |
| modok wrote: |
Sometimes yes the flywheel makes a difference.
For two reasons. One being the instantaneous rpm, the other being that if the engine accelerates very fast "modes can stack"
He swung on that one but missed, we all miss a few |
Some people just don't understand valve float happens from how fast you rev not just how high you rev. You can have valve float at 3000 RPM. |
Food for thought... maybe so... same principle as ramp speed.
Should really only happen with a loss of traction or a missed shift I think... maybe in 1st gear too.
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Dan Ruddock
Samba Member
Joined: October 25, 2012
Posts: 3594
Location: Sarasota, in my adopted state of Florida
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| Posted: Wed Jan 25, 2023 12:39 pm Post subject: Re: Aluminum or steel pushrods? |
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Aluminum or steel pushrods?? I like aluminum for street use.
How much hot valve clearance and the cam design determines how much noise or lack of any noise you will have. Even with adjusting the steel pushrods to loose zero they will still have more hot clearance than aluminum adjust to .005"
Of coarse this is head temp dependent. My measurements on this was not an overheated head.
The only reason steel pushrods are noisier is the larger hot valve clearance.
The cam design also plays a big roll in this, if the cams lash ramp is slow and long enough both aluminum and steel will be quiet but most all VW cams are not like this.
If the valve train has enough slop in it you will miss the slow/gentile part of the cams profile, the valve will be slapped open and slammed closed, This is what makes the noise.
Yes rocker side play is also a factor. Loose zero is better for semantics and avoids stupid arguments. VW used wavy washer to solve tolerance/fit issues and with the weak valve springs it worked.
I never use stock rockers anymore so I don't care about having to sliding a feeler gauge under a elephant foot.
Most aluminum pushrods on the market are not ridged/strong enough for a good HP engine. |
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