TheSamba.com :: View topic

Wed Oct 19, 2016 7:43 pm

If I do nothing but replace my pushrods to chromoly, can I set my lash to zero and reduce my tapet noise? Are there other benefits? Performance? Wear?

Wed Oct 19, 2016 7:55 pm

Typically stock pushrods run quieter than steel/chromoly, is the engine getting up to temp? and what are you setting the lash at?

Wed Oct 19, 2016 8:31 pm

66brm wrote: Typically stock pushrods run quieter than steel/chromoly, is the engine getting up to temp? and what are you setting the lash at? .006 the standard gap

Wed Oct 19, 2016 10:50 pm

Chromoly is significantly heavier than aluminum, so if the upgrade in strength isn't needed stay with stock pushrods. If anything, performance may suffer with the heavier units.

Wed Oct 19, 2016 11:13 pm

ALB wrote: Chromoly is significantly heavier than aluminum, so if the upgrade in strength isn't needed stay with stock pushrods. If anything, performance may suffer with the heavier units.
Good to know. I was led to believe it was a performance upgrade. I was also led to believe that it would quiet the engine down by reducing tapet noise because you can set the lash to 0.

Thu Oct 20, 2016 7:30 am

ALB wrote: Chromoly is significantly heavier than aluminum, so if the upgrade in strength isn't needed stay with stock pushrods. If anything, performance may suffer with the heavier units.

No...its not. For sure yes....if for instance you are weighing a 1"X1" cube of each metal....sure its heavier.

However its also a LOT stronger. Depending on whose pushrods......most chromoly PRs have much less wall thickness and metalcthan most similar strength aluminum pushrods.

For example....my stock type 4 aluminum pushrods are about 35% heavier than my Chromoly pushrods from the type 4 store (manton).

I posted exact weights of the two pushrods in a another thread earlier in the year. Ray

Thu Oct 20, 2016 1:58 pm

raygreenwood wrote: ALB wrote: Chromoly is significantly heavier than aluminum, so if the upgrade in strength isn't needed stay with stock pushrods. If anything, performance may suffer with the heavier units.

No...its not. For sure yes....if for instance you are weighing a 1"X1" cube of each metal....sure its heavier.

However its also a LOT stronger. Depending on whose pushrods......most chromoly PRs have much less wall thickness and metalcthan most similar strength aluminum pushrods.

For example....my stock type 4 aluminum pushrods are about 35% heavier than my Chromoly pushrods from the type 4 store (manton).

I posted exact weights of the two pushrods in a another thread earlier in the year. Ray bingo!!
as for the oe poster. how you adjust and what all you have and what has been done also factors in as to how quiet or noisey it is/will be.

Thu Oct 20, 2016 3:38 pm

And....as a correction looking back.......my aluminum pushrod was about 8-9 grams heavier than the chromoly PR. So it was like 12-13% lighter for the chromoly.

The aluminum PRs .....the thick walled ones like type 4....are just wbout as tough in load carrying capacity.....but just are not as stiff with reference to flexing.....as chromoly. Ray

Thu Oct 20, 2016 3:54 pm

raygreenwood wrote: ALB wrote: Chromoly is significantly heavier than aluminum, so if the upgrade in strength isn't needed stay with stock pushrods. If anything, performance may suffer with the heavier units.

No...its not. For sure yes....if for instance you are weighing a 1"X1" cube of each metal....sure its heavier.

However its also a LOT stronger. Depending on whose pushrods......most chromoly PRs have much less wall thickness and metalcthan most similar strength aluminum pushrods.

For example....my stock type 4 aluminum pushrods are about 35% heavier than my Chromoly pushrods from the type 4 store (manton).

I posted exact weights of the two pushrods in a another thread earlier in the year. Ray

I'm the first to admit that I haven't personally compared the 2, but everything I've read (including manufacturers/vendors material and other people's info) states that (for type 1) properly made hd aluminum pushrods weigh significantly less than chromoly. Since the hd aluminum is more than adequate for most street engines and weight matters, it gets my vote.

This from Aircooled.net-
WEIGHT: For reference, in a 11.600" length, the weight of a stock pushrod is 39.1g, ACN HD Aluminum are 47.8g, ACN Dual Tapered HD Aluminum is 55.8g, Manton Chromoly Straight are 90.2g, and Manton DT Chromoly are 100.5g.

With hd aluminum (of the proper material and heat treat so they actually work and survive) being almost half the weight of comparable chromoly I don't see any reason to use the heavier pushrods in 90 or 95% of the street engines built, but that's just my opinion. Al

Thu Oct 20, 2016 4:06 pm

yes if you can afford the trick aluminum pushrods thats the way to go. the .035 ones sold by everybody still flex, but take a lot more than the oe aluminm ones. the .058 cromo's are a better choice Imho.also Ive see just toomany of the .035 cromo's with loose tips...it's not the thin tubing fault but rather it's the crap tips that are machined like poop and varry in size vastly. Im leaning toward making some titanium ones. we made them for our small blocks years ago, but that was with roller cams&9500+ rpm and....never had a failure but, we stoped using them due to the way titanium can splinter/shatter. I wont be spining my vw's up that high and also I may use them in my hyd roller cam motor.....if I ever finish it. it seems all my pokers in the fire have melted handles, kinda hard to grab at the moment.
and the aluminum that expands more should also add some hot duration to the cam....but Im not sure about that. I havent checked any good ones I did check oe ones and they loose about 6.5 degrees of @.050 duration just spining the motor cold(ever so slight flex&compression is all I can figure. the good ones may not or may be less. I wonder what the lash is on the good ones when hot vs chromo's hot. I personaly have no noise issues with my chromozones the way im set up. :shock:

Thu Oct 20, 2016 5:46 pm

Also one should look at the particular aluminum alloy used on any given PR. Just comparing wall thickness and weight.....is not the only measure of a PR.

Yes.....I know that I am speaking primarily from a type 4 point of view...and type 4 stock pushrods are massive compared to type 1.....but the only time I have ever used an aluminum PR other than factory PR on a type 4 with single HD springs (they sere basically type 1 PRs with a custom cut length)......I bent two of them 10 miles into it at a shift point of 4200 rpm. That was fun.

There is also more to all or this when selecting PRs....other than just weight.

For example and this is just stock.....for a type 3 (close enough to type 1).....the spring installed height is 31mm with qn at rest load of of 116-134 lbs.

Type 4 uses very wimilar if not exact same springs.....at an installed height of 29mm and 176 lbs.

Add into that information......whatever your full lift might be and fjnal on the nose sprijg pressure....and the valve weight/inertia this whole rig may be lifting at high speed.....and any potential insanity there may be to your particular cam grind profile.........and what may seem "stiff" enough.....may easily not be.

I am not telling you that you "should" be using Chromoly PRs. I dont have enough experience with a super wide range of ACVW build types to be able to do so. But.....lay out your build in front of a lot of other people here...including the driving and shifting style...valve train specs etc......and give some heed to the specs.

In reality when chromoly PR's are NECESSARY.....the 10 grams or so of extra weight on such a light part.....for what it delivers back in stiffness......is not worth considering. Ray

Thu Oct 20, 2016 5:56 pm

It'll be quieter cold but louder when hot. Steel should be louder, but not a lot.
Lash changes as the engine warms up.

IMO, it's best when the actual lash matches the lash ramp on the cam, which means, not all cams will want the same!

Thu Oct 20, 2016 6:06 pm

From the Manton website

"Do not be overly concerned about pushrod weight. The pushrod is on the slow moving side of the valve train. The additional weight of a heavy wall pushrod usually provides a much needed increase in valve train stability."

I've run the AC.net pushrods and drank the koolaid if you will. I'm a huge fan of AC.net so don't think this is a strike at them. I don't think they can handle dual springs with any significant RPM (6500rpm). Mine were flexing and rubbing on the pushrod tubes. I switched to Jaycee ~.080" wall, rock solid.

If your not approching cam flattening spring forces (400-450lbs+),and you are not seeing enough rpm for float (needing to lighten your valve train), you are better off with chromoly.

Thu Oct 20, 2016 6:17 pm

it's on the slow side? not with a 1.1 or 1-1 rocker

The higher ratio the rocker, the heavier your pushrod can be, and needs to be. Also gives you MORE lash variation at the valve. Aluminum and steel are basically the same for strength to weight, but steel is simpler and more compact, and the being more compact matters a lot in some engines, and alsways handy at least. Type-4 has the darn exhaust go through the pushrods so why do they use the largest ones?? Because, as we all know, the engineers who built it were messed up in the head :P

Thu Oct 20, 2016 6:58 pm

modok wrote: it's on the slow side? not with a 1.1 or 1-1 rocker

The higher ratio the rocker, the heavier your pushrod can be, and needs to be. Also gives you MORE lash variation at the valve. Aluminum and steel are basically the same for strength to weight, but steel is simpler and more compact, and the being more compact matters a lot in some engines, and alsways handy at least. Type-4 has the darn exhaust go through the pushrods so why do they use the largest ones?? Because, as we all know, the engineers who built it were messed up in the head :P

That and the stock rocker ratio is 1.3:1 on type 4. Ray

Thu Oct 20, 2016 9:44 pm

Pretty soon, we'll be able to buy carbon composite pushrods from JPM or CSP. Harder than steel; almost diamond-hard, and lighter than any pushrod, ever. Johannes seems to think that pushrod weight is a big deal. He also requires a sturdy valvetrain to achieve higher and higher RPM. Maybe that's why they only sell steel pushrods right now. Carbon composites would be the best of both worlds.

Thu Oct 20, 2016 10:28 pm

I've run Manton chromoly pushrods for several years, both the 0.035" and 0.058" wall thickness. They have to be set at zero cold lash and will start getting noisy when the engine warms up. I've checked the warm lash many times and it's usually 0.010-0.014"...not ideal.

Now I'm running the Logmech dual-tapered 7075 aluminum pushrods and enjoy the quieter running engine. JPM also makes a similar aluminum tapered pushrod, and a couple other vendors sell the Smith Brothers version:

Thu Oct 20, 2016 11:28 pm

There are lots of choices for aluminum pushrods now: Smith Brothers (pushrods.net), Aircooled.net, JPM, CB Performance, the ones Neil uses...

Saving weight on the valve train is always good to do.

Fri Oct 21, 2016 6:55 am

neil68 wrote: I've run Manton chromoly pushrods for several years, both the 0.035" and 0.058" wall thickness. They have to be set at zero cold lash and will start getting noisy when the engine warms up. I've checked the warm lash many times and it's usually 0.010-0.014"...not ideal.

Now I'm running the Logmech dual-tapered 7075 aluminum pushrods and enjoy the quieter running engine. JPM also makes a similar aluminum tapered pushrod, and a couple other vendors sell the Smith Brothers version:

Are you sure you do not have a decimal point error in your post?

While no expert and knly having worked in about a half dozen air cooled engines with chromoly rods.....I have never seen the lash grow from a tight moveable "0" to more than about .003" to .005".

I can guarantee you that with the ball and cup radius of the stockish type 4's....a valve lash of .014" greatly risks dropping the PR ball out of the cup and lots of wear in the whole valve train. I have just not seen that.
Also.....if you are getting lash gaps like that....you are not adjusting far enough down the base circle of the cam.

This is already an issue with stockish cams. For instance....on a stock type 4 cam.....and type 1s have a lot or this as well......setting the stock PRs at .006" lash at EXACT TDC by the crank pulley and distributor rotor position......and then further rotating the crank....will open the lash up to about .010". This is because stock EXACT TDC is not at the exact BDC of the base circle of the cam. Its found a slight amount up the ramp of the cam lobe.

While one can probably correctly assume that the factory actually wanted this much REAL lash....and knew exactly where they were telling mechanics to set the lash (.006" at crank position indicated TDC)....and decided to use the crank indicated TDC method because its the simplest way to train virtually anyone to set all four cylinders exactly the same........
.........you cant.....or at least shouldn't...... use the exact factory method to to adjust valve lash with chromoly PRs.....because they do not expand at the same rate as stock PRs.

You should ...in my opinion and limited experience......find the very start of the actual base circle or BDC of the cam lobe to adjust valve lash. Ray

Fri Oct 21, 2016 7:04 am

Ray, I thought I had saved a link on adjusting lash this way, but I can't find it...could you post a link to it?
Thanks