Steel Pushrods

[geodoc]

I've installed lash caps on a LM1 to get kind to the rocker faces & to keep the pushrod socket to rocker angular clearance as well as same geometry, the pushrods need to be a bit shorter. The trick seems to find a place that can provide metric spec rather and inch spec ball & socket ends.

Smith Brothers only has inch radius ends, but can provide aluminum rods. Manton can provide metric ends, but can't do it in aluminum, only steel:

http://www.mantonpushrods.com

So I'm thinking that Manton's would be the way to go of course, wanting the ends to fit the lifter and rocker ball. Problem is, if you run steel rods I would assume that you need to run a clearance that's appropriate to it's lower expansion rate, that is different that the stock aluminum clearance.

No experience here, but I seem to remember that some racing guys were (are) running steel pushrods. So what valve clearance do they run?

BTW: the price for Manton pushrods is $8.00 each. Not bad!

 

[Rosey]

George
I have used steel pushrods made by Raceco (USA) in a LM3 and the instructions say to set the clearance at 2 thou.
Worked well for me for 40,000 kms.
Brett

 

[geodoc]

Yeah, I'm getting a bit of information from Charley Cole and Guzziology too that say just that ...... .002"

Wonder what one earth would have caused the pushrods to bend in the 1st place. The spring pressure wouldn't seem to be an issue:

~ 105 lb static
~ 245 lb @ full lift

George
I have used steel pushrods made by Raceco (USA) in a LM3 and the instructions say to set the clearance at 2 thou.
Worked well for me for 40,000 kms.
Brett

 

[Penis Rotor]

We've got ChroMo pushrods in our race bike and use 2 thou cold. Other alternative would be to set 'em hot with the ability to pin the rod but little more1 2 hou cold will cause less pain though. I originally bought the steel rods for my little hot-rod that was running to ten grand so I was running high spring pressures and I was worried about collapsing the alloy rods. Thing is the ChroMo rods are substantially heavier from memory. Unless you're chasing really high RPM I tend to think they are a product whose benefits are offset by their disadvantages. What cam are you running?

Pete

 

[geodoc]

Heh Pete,

Running a Megacycle 620X10. The valves are black diamond (tips trimmed slightly for the lash caps) and springs are of unknown mfg. from Mike Rich. Rockers are stock.

This bike is strictly a street hot-rod and would not see more than 8000RPM. Main reason for the steel pushrods is that they can be had in a custom length and with metric radius ends.

They are available in .035" wall thickness which would seem adequate, though was planing to consult with Mike Rich on that before ordering a set.

We've got ChroMo pushrods in our race bike and use 2 thou cold. Other alternative would be to set 'em hot with the ability to pin the rod but little more1 2 hou cold will cause less pain though. I originally bought the steel rods for my little hot-rod that was running to ten grand so I was running high spring pressures and I was worried about collapsing the alloy rods. Thing is the ChroMo rods are substantially heavier from memory. Unless you're chasing really high RPM I tend to think they are a product whose benefits are offset by their disadvantages. What cam are you running?

Pete

 

[rolf j]

We've got ChroMo pushrods in our race bike and use 2 thou cold. Other alternative would be to set 'em hot with the ability to pin the rod but little more1 2 hou cold will cause less pain though. I originally bought the steel rods for my little hot-rod that was running to ten grand so I was running high spring pressures and I was worried about collapsing the alloy rods. Thing is the ChroMo rods are substantially heavier from memory. Unless you're chasing really high RPM I tend to think they are a product whose benefits are offset by their disadvantages. What cam are you running?

Pete

Still perhaps the steel is the way to go? I'm tempted myself even though I haven't had problems so far. The Guzzi crowd doing racing around here seem to have pushrods as a consumable article, a number of them have failed, even with rather mild cams. They seem to work perfectly for a while and then suddenly collapsing at the end, giving a sudden 5mm lash! Often one see a clean compression failure of the aluminium rather than the rods being bent. There is a tendency the guys around here go rather conservative on the lash, 7 to 9 thou. Could this perhaps be reduced even with alu pushrods to save the poor things from hammering?? (but perhaps at the cost of increased risks for the valves?? )

 

[Guzzistaracing]

I would go for a set of Titanium pushrods if I was racing anything with pushrods. Here is one link, one of several suppliers. Kind of expensive but if you want the best......?

http://www.paeco.com/Titanium Products.htm
http://www.paeco.com/Valve Train Equipment.htm

 

[geodoc]

a set of 8 arrived today from Manton (enough for 2 bikes with lash caps: .125" shorter effective length). Clearance set to a loose .002".

Fired up one bike with them installed and seems fine. Will test ride Monday (after Vashon Vintage bike bun-toss this Sunday).

They are A LOT heavier than stock. Mike Rich said could get away with .035 wall. Manton suggested .056 & that's what I went with.

8 pushrods: $65.

 

[rolf j]

a set of 8 arrived today from Manton (enough for 2 bikes with lash caps: .125" shorter effective length). Clearance set to a loose .002".

Fired up one bike with them installed and seems fine. Will test ride Monday (after Vashon Vintage bike bun-toss this Sunday).

They are A LOT heavier than stock. Mike Rich said could get away with .035 wall. Manton suggested .056 & that's what I went with.

8 pushrods: $65.

Very interested in hearing about your experinces.

I had contact with Paeco, got swift response, and will send a sample of my existing alu-rods and place order for a set of the titanium ones for testing. I suppose the 0.002" gap measured cold is the way to go for for titanium rods as well? (SCARY low value!)

rolf j

 

[geodoc]

Heh Rolf,

When I was ordering I mentioned titanium push rods to the guy at Manton just out of curiosity. He said that they have tried it out, but not satisfied with the reliability. He did say for certain installations where it could work (short lengths perhaps?), they have a certain alloy that seems to work better than others. Apparently an alloy that allows more flex than the more common ones which apparently have little flex and while hard, tend to be somewhat brittle.

Give them a call. Friendly folks.

FWIW, Tom here uses steel pushrods on his Bonneville Trident and spins it up to 9500 RPM with a very wild cam. He mentioned too that they are noticeably heavier than the stock aluminum ones.

GD

a set of 8 arrived today from Manton (enough for 2 bikes with lash caps: .125" shorter effective length). Clearance set to a loose .002".

Fired up one bike with them installed and seems fine. Will test ride Monday (after Vashon Vintage bike bun-toss this Sunday).

They are A LOT heavier than stock. Mike Rich said could get away with .035 wall. Manton suggested .056 & that's what I went with.

8 pushrods: $65.

Very interested in hearing about your experinces.

I had contact with Paeco, got swift response, and will send a sample of my existing alu-rods and place order for a set of the titanium ones for testing. I suppose the 0.002" gap measured cold is the way to go for for titanium rods as well? (SCARY low value!)

rolf j

 

[geodoc]

Learning by doing .......................

Installed the Manton steel pushrods spec'd 1/8" shorter to suit the lash caps. Set lash of .002" IN & .003" EXH at the loosest point in a complete rotation rather than TDC. Took it out to ride and had rough running at lower RPM w/ crap idle even when hot, but really bad when cold.

Back to the bench. Checked lash at TDC & found nil. Reset to same as above only at TDC this time. Check lash & found loosest point in rotation now measured ~.008" ! Talked to Mike Rich and he recommends setting lash at TDC. He also cautioned that with the MUCH heavier steel pushrods it will likely need heavier valve spring pressure.

Test-rode with lash set at TDC. Runs fine, though it clatters quite a bit.

Called up Megacycle to ask about having way more clearance elsewhere than TDC. The fellow there informs that this is normal for that cam and he would set clearances at the loosest point. But, he also said that with steel pushrods in aluminum cylinder air-cooled engines can cause a rough running problem due to their differing expansion rate. Some alu. cyl air-cooled race bikes he says need to pre-heat to operating temp. so that they will run at all when using steel push rods & appropriate lash set when cold. He mentioned that XR-750's ended up with aluminum ones for just this reason.

Megacycle guy also cautioned against running .002 / .003 at TDC and living with the looser clearances elsewhere in the rotation w/ steel PR's because it ends up with undesirably large clearances when it heats up and is really hard on the valves / seats / lifters / cam. This makes me recall that DR said Guzzi tried steel pushrods in the Sport 1100 and rejected them because of accelerated valve train wear. Maybe this is why they ended up sticking with aluminum though w/ a thicker wall than before.

So, maybe steel pushrods are not such a good idea for a street bike, or even an aluminum cylinder air-cooled race bike.

The Megacycle guy also mentioned that Kibblewhite is able to provide aluminum push rods in custom lengths. I called them and they do indeed and have the appropriate ends too.

Like I said, learning by doing ...................................

 

[rolf j]

Thanks geodoc for sharing your experience!
I found that Paeco actually supplies aluminium pushrods made from material with higher strength than "normal". They sell them for $12,- each(plus $6,-each if custom made as they state below).

This is what they write on their web site:
http://www.paeco.com/Valve%20Train%20Equipment.htm

"Aluminum pushrods, made from 2024-T3 alloy, are slightly lighter than the stock pushrods, and are approximately four times stronger than the stock ones. Because of this, they don't flex at high RPM as the stock pushrods do. To prevent undue wear at the ends, the tips are made of hard, durable bronze that are designed to "bed in" to the lifter and rocker ball for best possible fit. These are the best aluminum pushrods available anywhere in the world. These can be made up for you in non-standard lengths for an extra $6.00 per pushrod. Titanium pushrods are for racing engines and are extremely strong, plus being lighter than the aluminum pushrods. They are made to order, and there is no extra charge for special lengths."

Perhaps this alu alloy is the way to go? I.e. doing away with the expansion problems and hoping that a notch better alu-material will do the job?

After what you have said about your steel rod experience, the improved alloy is probably what I will test out....

rolf j

 

[geodoc]

I just sent my sample pushrod to Kibblewhite this morning. I wonder about the expansion rate issue with titanium. No idea about it's rate v aluminum. Same w/ carbon fiber. With either maybe there's the same valve clearance issue to deal with. Going to stick w/ aluminum.

I wonder if Kibblewhite can perhaps hardness test the original Guzzi pushrod to get an idea of what alloy it is. BTW, the Manton guy mentioned that you want a small amount of "springiness" in the push rod so it will help to cushion abrupt valve train loading a bit. This is another place where maybe steel (ti / carbon fiber?) is great for racing and not so good for 100,000 mi. + street bikes.

Yet more engineering trade-offs that lurk, eh?

Thanks geodoc for sharing your experience!
I found that Paeco actually supplies aluminium pushrods made from material with higher strength than "normal". They sell them for $12,- each(plus $6,-each if custom made as they state below).

This is what they write on their web site:
http://www.paeco.com/Valve%20Train%20Equipment.htm

"Aluminum pushrods, made from 2024-T3 alloy, are slightly lighter than the stock pushrods, and are approximately four times stronger than the stock ones. Because of this, they don't flex at high RPM as the stock pushrods do. To prevent undue wear at the ends, the tips are made of hard, durable bronze that are designed to "bed in" to the lifter and rocker ball for best possible fit. These are the best aluminum pushrods available anywhere in the world. These can be made up for you in non-standard lengths for an extra $6.00 per pushrod. Titanium pushrods are for racing engines and are extremely strong, plus being lighter than the aluminum pushrods. They are made to order, and there is no extra charge for special lengths."

Perhaps this alu alloy is the way to go? I.e. doing away with the expansion problems and hoping that a notch better alu-material will do the job?

After what you have said about your steel rod experience, the improved alloy is probably what I will test out....

rolf j

 

[rolf j]

Regarding thermal expansion coefficients, the various handbooks seem to differ a bit in the decimals, but the following should not be too far off:

Aluminuim: 23 micrometres per metre per degree (K)
Steel: 13 micrometres per metre per degree (K)
Titanium: 9 micrometres per metre per degree (K)

I.e. aluminium expands more than 2,5 times that of titanium and nearly 1,8 times that of steel.

It seems the safest option to avoid side effects that nobody understands is perhaps to use a decent aluminium that doesn't collapse under the load like the original ones..... the aluminium alloy of Paeco will be my choice I reckon, and we'll see next season if the strength is sufficient. The original ones are on the borderline as they seem to survive for quite a while even on the track, but eventually they all seem to give in under race conditions with race cams and harder springs....

rolf j

 

[geodoc]

I received a set of aluminum pushrods from Smith Bros - again .125" shorter to accommodate the lash caps, and installed with lash set per the fellow at Megacycle's recommendation: let at loosest point, or about where the opposite valve is full open more or less. Test run and seemed OK-ish. Then a conversation with Mike Rich and found out from him that the usual SAE ball ends as installed by SB, Manton, Kibblewhite, etc. while very close in radius to the Guzzi spec, are not exactly the same. Actually, he grinds off the very outside of the radius on SB pushrods for a more exact fit prior to installation. He did say though that it works fine and does not harm the lifters to just let then bed in by themselves which they do after 20-25 miles then re-adjust the clearances if necessary. He also re-emphasized his recommendation to not set the lash at the loosest point, but rather set at TDC as usual. He went on to explain his reasons for this regarding the profile of the acceleration ramps.

So armed with that information, I reset the lash (.006 & .008 @ TDC) with my now-bedded in ball ends and took it out on the road. Yep ...... there's a difference - better idle and it seems a tick smoother.

For info the Smith Bros. items are 3/8" dia. 2024-T3 w/ .096" wall and cost about $12 ea.

And BTW Rolf, thanks for the expansion rate info. Looks like if steel is problematic with air cooled engine expansion rates mismatch, the Ti would be even more so.

Regarding thermal expansion coefficients, the various handbooks seem to differ a bit in the decimals, but the following should not be too far off:

Aluminuim: 23 micrometres per metre per degree (K)
Steel: 13 micrometres per metre per degree (K)
Titanium: 9 micrometres per metre per degree (K)

I.e. aluminium expands more than 2,5 times that of titanium and nearly 1,8 times that of steel.

It seems the safest option to avoid side effects that nobody understands is perhaps to use a decent aluminium that doesn't collapse under the load like the original ones..... the aluminium alloy of Paeco will be my choice I reckon, and we'll see next season if the strength is sufficient. The original ones are on the borderline as they seem to survive for quite a while even on the track, but eventually they all seem to give in under race conditions with race cams and harder springs....

rolf j

 

[TINTIN]

Hi Rolf, Geodoc

Interresting topic, it's true, the original aluminium pushrods have really been a consumable among "our" Guzzi raceres here in Norway. BUT just in case you are not aware of it: The original aluminium pushrods were updated from the 1100 sport model and on according to Dave Richardson. They are interchangable with the older ones (and look the same but according to Dave, have thicker walls). I have myself used these in all my engines and never experienced any problems. Admittable, I haven't run my engines beyond 9K and haven't run the absolutly wildest cams either. But still, I have run wilder engines than many of the other guys with pushrod trubles, so it seem quite evident that the pushrods in fact was updated and that the new spec works.

 

[rolf j]

Thanks TINTIN for clearing the fog off this topic! I wasn't aware of any difference between the various production year. (Amazing how this useful information is sitting right here in the neighbouthood...!)

Perhaps you by chance also know what the magic of alloy 2024-T3 is all about? Perhaps it doesn't matter much when the Mandello guys just simply thickened up the wall and the problem was solved...voila!!

rolf j

 

[TINTIN]

There exists two wonderfull books: The racing motorcycle - A technical guide for constructors, volume 1&2 by John Bradley. Volume 1 is a general discusion of the fundamentals while volume 2 is more of a practical discusion. Chapter 3 in volume 2 is dedicated aluminium alloys. According to Bradley, the 2xxx-series alloys are all alloys having copper as the main alloying element. The old original Duraluminium was such an alloy. Similar modern alloys are the 2017A, 2014A and 2024. The T3 refer to the kind of heat treatment and means that it has been solution heat treated, coldworked immediatly afterwards and then left to age naturally.

It's only a fraction stronger though, than the very common 6082 T6 and not as strong as the 7075 T6 or T7 alloys. However, a pushrod most of all need to be fatigue resistent and since the 2024 T3 has quiet good elongation properties it is probably also quiet fatigue resistent. Likely too, since it has aircraft origin.

Obviously 2024 T3 pushrods are not bad but the claim that they are 4 times stronger than the original does nothing but discredit the manufacturer: Of course they are not 4 times stronger! btw, strength as such, is anyway not a technical term. In order to be quantified it has to be stated what kind of strength, under what conditions.

Heat may also be a factor in pushrod life. Some aluminium alloys are rather sensitive to heat and lose a substantial amount of strenght when heated. I don't know how hot a pushrod get under racing stress but it might be a reason for the failures we have seen. In that respect the 2024 alloy may be a good one: quality pistons are often made from an other alu-copper alloy, the 2618, and pistons live a very hard and hot life....

However, as for me, I would always use the OEM part whenever possible and whenever I'm not positive it will not work. In my oppinion, OEM Guzzi engine parts hold a very high level of quality: In order to make this arcaic construction work in a modern world they simply have to!

 

[Hudriwudri]

Hi there @ All

Its been quite some time since i posted last for multiple reasons.
Anyways as im currently finding slowly a lil more time to dwell on the guzzi theme i read this thread with avid interest.
Besides the initial ranting n babbling i'll "try" to keep it short now.

Personally i thought lenghty over the years on Ti pushrods but as the availability of Ti6Al v4 (the higher t-strength grade) tubing is basically nil as its basically just available and used in non tube stock i abandoned that idea pretty much. I also looked into Ti3Al2.5V as it is the widely (i.e. Ebay) alloy for ti tubing
but was not to impressed by the 0.2%stress (483n/mm2)among other
Things as i suspect ( never did the necessary buckling load calculations) that the so called buckling-resistance might be substantially lower on 3.5Al2.5 in comparison to 6al4.
So far i did not find the time to do the necessary calculations as i personally also thought it to be currently neglectable for following reasons that regard some of the facts mentioned by tin tin.
From what i got told and also read ( if memory doesnt trick me) the original pushrods were/are supposedly made out of ergal which would imply 7075 specs those should with the proper treatment be of considerable strength (comparable to ti3al2.5v with about 430-510N/mm2 @0.2% stress depending on T-state)
Anyways to cut it short im convinced that nicely made 7075 rods in slightly increased diameter should be well up to the job.
If some of you really wanna get top of the line stuff then i would recommend giving 3M a call since they are currently the only suppliers of metal matrix pushrods of amazing buckling resistance and a weight similar to aluminum.
I dont remember anymore too clearly the rod diameters but if memory doesnt trick me it was around 10mm's.
But one would need to call also for the cap issue. Price tag was unfortunately in the rather hefty range which can be explained though by the need for specialised machining processes, nevertheless hefty.
If one really longs for the best i would think that those 3M MMC puppies should
be the way to go as they are also being used by the
nascar guys with by far heftier spring values than usually found on guzzis.
Also i would be inclined to think that one could do a crude comparison test between pushrod types by means of a precise fish (pull type) scale and measuring the deflection.

Kind regards to all of you

Christian

 

[Chris R]

HI George,
You can forget about carbon fibre - the expansion rates are such that the lash has to be set so the valves are actually open when the engine is cold! Kind of like the briggs and stratton easy start scheme.

How do I know? I had a friend at the now defunct PRT who gave me a set. Carbon fibre looks great - light, strong, extremely stiff - but its failure mode is to turn into explode into dust!

Personally I think a thicker solid aluminum pushrod using a higher grade alloy is probably the best compromise. I suspect the only reason steel pushrods have been the go to mod for hot rods is that custom steel pushrods are cheap and easily available from the american V8 brigade. Of course the only way to tell weither they do any good at all is a proper A-B test on a dyno.

If you are going for new pushrods I guess you can save some money using FIAT 126 lifters and having them make appropriate ends?

Of course the other unexplored avenue with the guzzi is to use roller lifters given that valve to valve and piston to valve clearance is largely set :evil: .

Ta,

Chris

Ta,

Chris