Which pushrods?

[TeamBrian]

Not sure if this should be in technical or not but which pushrods do I need? I'm currently rebuilding my engine as a 1641, Scat25 cam etc, Scat 1:25 rockers, but I still need to do some more reading up on pushrods. Any advice please? Thanks.

 

[six]

You will need some cut to length. Best method, set up your valve geometry with an adjustable rod and measure it. HD Ali would be OK on that train or get some steel ones.

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[gvee]

Is it the ratio rockers that require a different pushrod length?

 

[six]

Yup. But once you start running diff cam etc to they all compound.

I've done a few builds now with 1.25:1 rockers and every time its been 5-6 mm shorter than stock length. But always mock up and measure

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[TeamBrian]

Thanks, Six.

 

[Alex VW Heritage]

The tool for measuring:

https://www.vwheritage.com/shop/AC000119/tool-adjustable-pushrod/" onclick="window.open(this.href);return false;

and the push rods themselves:

Chromoly are strongest:

https://www.vwheritage.com/shop/AC109433/push-rods-cut-to-length-chromoly-set-of-8/" onclick="window.open(this.href);return false;

Ali are lightest:

https://www.vwheritage.com/shop/AC1094054/push-rods-uncut-aluminium-scat-or-bugpack/" onclick="window.open(this.href);return false;

Unless your going for a high revving engine I would go for the chromoly over the Ali, they are cheaper too!

 

[K@rlos]

As it's a mild build ali would be fine. I have chromo rods in mine as it has a mean cam, dual valve springs and turns high rpm.

Downside with moly rods is they are noiser when the motors running...

 

[six]

Alex you are such a pimp. Lol what can we say.. Your gear is good though and good advice

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[TeamBrian]

What do you mean when you say the chromoly ones are noisier? Is it similar to noisy tappets?

 

[K@rlos]

What do you mean when you say the chromoly ones are noisier? Is it similar to noisy tappets?

Kind of, because moly is so hard they clatter a little bit, it isn't horrendous but noiser than a stock engine.

 

[TeamBrian]

Ah right...oh well, I can always turn the radio up! Any advice on setting valve geometry would be gratefully received.

 

[six]

Search on here. Its been done many times.

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[TeamBrian]

Will do. Cheers.

 

[Bay-low71]

The expansion rate of the chromoly ones are different to, which gives you the noise increase. Usually find the valve clearances are tighter with chromoly pushrods, I know a friend of mine sets his with no valve clearance. [FLUSHED FACE] the important bit is the tips as some of the cheaper after market ones have very poor tips. I bought an aluminium set from stateside tuning expensive but come with micro polished tips.


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[K@rlos]

The expansion rate of the chromoly ones are different to, which gives you the noise increase. Usually find the valve clearances are tighter with chromoly pushrods, I know a friend of mine sets his with no valve clearance. [FLUSHED FACE] the important bit is the tips as some of the cheaper after market ones have very poor tips. I bought an aluminium set from stateside tuning expensive but come with micro polished tips.


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I run zero lash on my motor

 

[TeamBrian]

What do you mean by zero lash?

 

[Bay-low71]

"Zero Lash" no clearance between the top of valve and the adjuster. Usually set to 0.006" when inlet and outlet valves are closed. I.e. "On the rock" [THUMBS UP SIGN][THUMBS UP SIGN]


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[TeamBrian]

Ah right....learning every day!

 

[Orange72]

Can't comment on the zero lash theory but if the valve gap ( noise is increasing ) as the engine is getting up to temp then run it up and re adjust to correct gap at full temp
I have built a few type 4 motors and always suffered with a bit of tappet noise with origional push rods, but on my last build 2270 I had to use chromoly rods but also used swivel foot adjusters
Quiet as a mouse, ish
But better than stock
I don't know if it's the better surface area of the swivel feet on the valve heads, but it makes sense
Ball top to socket on push rod end to rocker, flat surface from swivel foot to flat surface on valve head
Just a thought