Pushrods and the eternal search for cheap speed

[andrewlandon67]

So some buddies and I have been discussing ways to drop weight from various project vehicles lately, which has got me thinking about ways that weight loss can improve performance, aside from just having a lighter car. First though, here's some back story. When putting together my current 1915 about 5 years ago, I'd just come from a motor that ate pushrods every 1,500 miles or so due to some ruined lifter bores that I wasn't clever enough to diagnose until it was too late. While having somewhat learned my lesson about paying attention to what the car's trying to tell me, I still decided that my new motor would be better off with some massive .058" wall chromoly pushrods from CB Performance as the new motor's cam was even bigger and I'd be running it against some dual springs.

Five years of reliable service and surprising power later, this discussion about cleverly applied lightness has brought me back to those monster pushrods. While my FK-8 might have over .530" lift and the dual springs on my heads would still pretzel a set of stock pushrods long before they saw the fun side of 5,000 RPM, I've had a niggling thought in the back of my mind that some lighter pushrods might suit my engine better. The discussion of lightness brought that bit of doubt to the front of my mind, and before long I had seen that aircooled.net not only sells very highly reviewed HD Aluminum pushrods, but they claim a weight savings of over 50 grams PER VALVE over similar pushrods to what I'm currently running. Keeping in mind that my valve springs have now seen five years of fairly heavy service on both street and strip, and are now due for a good checkup/replacement that I plan on doing later this fall, when time and money are more available, I have found myself pondering what nearly a full Imperial pound of weight loss from my valvetrain might do for a revitalized engine with fresh springs and some Berg grooved venturis in the IDFs above.

My question now is this: would removing a considerable amount of weight from the valvetrain of a tried-and-true engine cause any negative effects? My main concerns are with the cam/lifters, if there might be some way that the lost weight might now give them too much wiggle room to cause trouble deep inside the case, or if there's anything else anyone would suggest watching out for or would make them hesitate before making such a large change to the valvetrain.

Let me know what you all think, I appreciate any advice on this!

[andrewlandon67]

No thoughts? Anyone even in here?

[richie]

I read it when you initially posted, and started to reply, but stopped as stuff like this is so personally opinionated & views vary so much what is right for me probably isn't for others, as an example I think your pushrods are far from the massive/monster etc you describe them as & maybe even to thin   As its been so reliable for 5 years are you changing things just for sake of it?

cheers Richie 

[andrewlandon67]

I read it when you initially posted, and started to reply, but stopped as stuff like this is so personally opinionated & views vary so much what is right for me probably isn't for others, as an example I think your pushrods are far from the massive/monster etc you describe them as & maybe even to thin   As its been so reliable for 5 years are you changing things just for sake of it?

cheers Richie 

I think I mentioned in the original post, this line of thinking kind of spurred from a discussion some buddies and I had been having about home-made carbon fiber moped parts and I just started to mentally go through what weight my bug could probably stand to lose, so I guess I am just thinking about changing things just for the sake of it. Some of the pushrod/valvetrain weight loss though is rooted more in an annoyance with how loud my valvetrain is as well as concern for my valves/springs as those .058" wall pushrods are certainly carrying some momentum at high RPMs which might be restricting the engine from reaching even higher, and possibly running cooler (more weight to move=more energy lost moving it=more heat.)

In the end, it's just a bit of fun thought to keep me from burning out too hard between work and school, though when I do get the chance to rebuild this motor, it'll definitely get the lightweight treatment in the spots that count.

[PPRMicke]

If we play with the idea
If the lifter weighs 25 grams, you can go over 8000rpm with standard springs with a 40mm valve

If you were to investigate what kind of material you have for alu in std vw as a stock, you would be surprised what quality it is in them

A light lifter is always better than a heavy one So T-P in tool steel is good stuff (55 grams)

We who play with Na engines in Sweden have an alu quality called 7075 and the push rod is conical from both sides
But would not think you drive the engine over 9000 rpm and have a lift height of around 18 mm on the valve

But one of the most important things is that you have the right pressure on the springs to the intended speed on the machine. It is often too high a pressure where the push rod fails or it wears out at the ends.

[j-f]

If we play with the idea
If the lifter weighs 25 grams, you can go over 8000rpm with standard springs with a 40mm valve

If you were to investigate what kind of material you have for alu in std vw as a stock, you would be surprised what quality it is in them

A light lifter is always better than a heavy one So T-P in tool steel is good stuff (55 grams)

We who play with Na engines in Sweden have an alu quality called 7075 and the push rod is conical from both sides
But would not think you drive the engine over 9000 rpm and have a lift height of around 18 mm on the valve

But one of the most important things is that you have the right pressure on the springs to the intended speed on the machine. It is often too high a pressure where the push rod fails or it wears out at the ends.

Speaking of springs pressure, how to find the correct one?
A w120 with chromoly pushrods and Engle lifters will not have the same needs than the same w120 cam with alu pushrods and CB lightweigth lifters, all the rest of the engine being equal?
I saw on the csp website, a nice chart with spring pressure. Berg being the softer ones.

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[Glauco]

Speaking of springs pressure, how to find the correct one?
A w120 with chromoly pushrods and Engle lifters will not have the same needs than the same w120 cam with alu pushrods and CB lightweigth lifters, all the rest of the engine being equal?
I saw on the csp website, a nice chart with spring pressure. Berg being the softer ones.

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[/quote]

good question, how do you determine optimal spring pressure? When I switched from scat chromoly pushrods to some stateside heavy duty aluminum ones I also switched to titanium retainers and saved something like 27gr . (12gr vs 22gr for 1 retainer and 48gr vs 65gr for the pushrods)
Goran from logmech advised me to use there lightest spring set witch gave me a little more pressure over the HD single scat's at full lift. it was to compromise for the higher RPM potential. my FK-65 won't allow me to rev higher, but at least it's possible 
If I ever get to my bigger engine I'll probably go for lighter lifters as well..

Glauco

[andrewlandon67]

Well now I've really opened the can of worms... This is all good stuff to know/think about, and a good reminder that there is never a truly easy way out with these engines!

[j-f]

Well now I've really opened the can of worms... This is all good stuff to know/think about, and a good reminder that there is never a truly easy way out with these engines!

Don't even dare to ask about which oil to use! 

[andrewlandon67]

Well now I've really opened the can of worms... This is all good stuff to know/think about, and a good reminder that there is never a truly easy way out with these engines!

Don't even dare to ask about which oil to use!  

Oh I definitely know to avoid that line of questioning...

Still, my question still stands. Would there be any gain from dropping nearly 500 grams of weight from my valvetrain, or should I just keep good, fresh springs in the heads and let the pushrods take the punishment?

For what it's worth, the lifters are Engle and the springs/retainers are the originals that came with the Empi heads, chromoly retainers and what I assume are similar to the old Bugpack dual springs. I'm not looking at splitting the case just yet, and this is a mostly street-driven motor in a full weight '67 with stock gears, so let's keep things realistic.

Also, I've read some (very) old posts on here saying that part of the advantage of aluminum pushrods is that since they expand with the rest of the engine, there's less loss of lift at normal operating temps, which has the dual effect of running stronger when up to temp as well as not beating up the valvetrain with excessive lash. Does that all check out, or should I just suck it up and go burn my fingers checking lash on a hot motor?

[ibg]

I see no down sides for a street motor, I have used the air-cooled.net straight ali pushrods with CB650 springs and and 86B with good results. I didn't really need the CB650 spring pressure, but I did need the lift they offer before coil bind.  The push rods were quiet and didn't mushroom under the tips.
the only down side to consider for a race motor is how much they might flex, loosing a bit of lift or introducing some more harmonics into the valve train. 

[andrewlandon67]

I see no down sides for a street motor, I have used the air-cooled.net straight ali pushrods with CB650 springs and and 86B with good results. I didn't really need the CB650 spring pressure, but I did need the lift they offer before coil bind.  The push rods were quiet and didn't mushroom under the tips.
the only down side to consider for a race motor is how much they might flex, loosing a bit of lift or introducing some more harmonics into the valve train. 

That's more the complexity I was asking for! My springs certainly aren't as heavy as the CB650s, which is a good sign, and the 86B is awfully similar to my FK-8. My only question at this point is: how many miles have you run them like that for?

[PPRMicke]

There is a very interesting How many weigh an aftermarket lifter A German VW from 1971 weighed 88 grams O many of today are around 95 grams Ps a lifter from a 34hp machine (1961-62) was around 80-84 grams 
/// Micke

[ibg]

I ran them for 5,000 miles and have pulled the motor down for new heads (JPM230) and cam and now going to use the JMP tapered ali push rods.
I have tried to make the valve train as light as possible, Ti retainers, ali push rods and schubeck lifters (52g)
you can get lighter 356 lifters that are under 50 grams 

[andrewlandon67]

I ran them for 5,000 miles and have pulled the motor down for new heads (JPM230) and cam and now going to use the JMP tapered ali push rods.
I have tried to make the valve train as light as possible, Ti retainers, ali push rods and schubeck lifters (52g)
you can get lighter 356 lifters that are under 50 grams 

Good to know! Would you think all of that lightweight valvetrain is worth the money/effort?

[ibg]

I haven't built enough motors to know, I'm thinking probably not really worth it    in a hp sense, but I hope it will lead to reasonable life for the valve train that will see 7,500 rpm.
I enjoy pushing the old platform and seeing what can be done.

[andrewlandon67]

I haven't built enough motors to know, I'm thinking probably not really worth it    in a hp sense, but I hope it will lead to reasonable life for the valve train that will see 7,500 rpm.
I enjoy pushing the old platform and seeing what can be done.

Yeah, I'm sure the real HP gains are only a handful at most, but I do like the idea of something a bit quieter and with less reciprocating mass moving back and forth all the time.

[brewsy]

Andrew,
See if you can find Peter Shattocks build thread and stuff. He and JP (of JPM) worked hard to ensure that mouse motor revs to well past 8K and Im pretty positive that they worked hard to keep valve train weight to a minimum.
FWIW I also think that, within reason, a lighter assembly will be better for longevity of parts and if you keep a sensible rev limit 'might' offer a longer service life.

Its something Im going to pursue when I ever get to building my motor.... 

Cheers
Marc

[andrewlandon67]

Andrew,
See if you can find Peter Shattocks build thread and stuff. He and JP (of JPM) worked hard to ensure that mouse motor revs to well past 8K and Im pretty positive that they worked hard to keep valve train weight to a minimum.
FWIW I also think that, within reason, a lighter assembly will be better for longevity of parts and if you keep a sensible rev limit 'might' offer a longer service life.

Its something Im going to pursue when I ever get to building my motor.... 

Cheers
Marc

Oh yeah, I forgot about that thread! That's a good one to look through though, thanks for the recommendation!

[Martin S.]

The discussion of lightness brought that bit of doubt to the front of my mind, and before long I had seen that aircooled.net not only sells very highly reviewed HD Aluminum pushrods,

I don't know if you remember my engine build but it's a 2332 turbo with huge valve lift and big valve 044 heads. It's been on the road every season since 2009 and hasn't been apart yet!
I used the the (straight) HD Al pushrods from Aircooled.net (smith brothers) mainly for quieter running, rather than weight but yeah sure, lighter! The engine rarely needs valve adjustment and is still running as strong as ever!

[andrewlandon67]

The discussion of lightness brought that bit of doubt to the front of my mind, and before long I had seen that aircooled.net not only sells very highly reviewed HD Aluminum pushrods,

I don't know if you remember my engine build but it's a 2332 turbo with huge valve lift and big valve 044 heads. It's been on the road every season since 2009 and hasn't been apart yet!
I used the the (straight) HD Al pushrods from Aircooled.net (smith brothers) mainly for quieter running, rather than weight but yeah sure, lighter! The engine rarely needs valve adjustment and is still running as strong as ever!

Just out of curiosity, what kind of lift are you talking? I don't have much interest in going beyond .550" with 1.4 rockers, and my current 1915 runs out of steam at around 6800 RPM so it's not like I'm trying to rev like a superbike, so I think they'd be more than up to the job. Slightly less noise would also be nice, but it's really hard to ignore the potential of a full US pound of weight taken from the valvetrain for me, plus keeping stock heat expansion rates means less lift loss when the engine is up to temp.

[Martin S.]

The discussion of lightness brought that bit of doubt to the front of my mind, and before long I had seen that aircooled.net not only sells very highly reviewed HD Aluminum pushrods,

I don't know if you remember my engine build but it's a 2332 turbo with huge valve lift and big valve 044 heads. It's been on the road every season since 2009 and hasn't been apart yet!
I used the the (straight) HD Al pushrods from Aircooled.net (smith brothers) mainly for quieter running, rather than weight but yeah sure, lighter! The engine rarely needs valve adjustment and is still running as strong as ever!

Just out of curiosity, what kind of lift are you talking? I don't have much interest in going beyond .550" with 1.4 rockers, and my current 1915 runs out of steam at around 6800 RPM so it's not like I'm trying to rev like a superbike, so I think they'd be more than up to the job. Slightly less noise would also be nice, but it's really hard to ignore the potential of a full US pound of weight taken from the valvetrain for me, plus keeping stock heat expansion rates means less lift loss when the engine is up to temp.

Here's a YouTube of when Steve was assembling the engine way back when, now having 70K views!
https://youtu.be/xX3iaHUI-SA

[andrewlandon67]

The discussion of lightness brought that bit of doubt to the front of my mind, and before long I had seen that aircooled.net not only sells very highly reviewed HD Aluminum pushrods,

I don't know if you remember my engine build but it's a 2332 turbo with huge valve lift and big valve 044 heads. It's been on the road every season since 2009 and hasn't been apart yet!
I used the the (straight) HD Al pushrods from Aircooled.net (smith brothers) mainly for quieter running, rather than weight but yeah sure, lighter! The engine rarely needs valve adjustment and is still running as strong as ever!

Just out of curiosity, what kind of lift are you talking? I don't have much interest in going beyond .550" with 1.4 rockers, and my current 1915 runs out of steam at around 6800 RPM so it's not like I'm trying to rev like a superbike, so I think they'd be more than up to the job. Slightly less noise would also be nice, but it's really hard to ignore the potential of a full US pound of weight taken from the valvetrain for me, plus keeping stock heat expansion rates means less lift loss when the engine is up to temp.

Here's a YouTube of when Steve was assembling the engine way back when, now having 70K views!
https://youtu.be/xX3iaHUI-SA

That's considerably more than I'm considering running at any point in the forseeable future, so if those HD Al pushrods can handle that, I'm sure they'll do just fine with my little old FK-8 on 1.4 rockers.

[Martin S.]

I was a bit concerned that I should have sprung for the pricier tapered versions, but I suppose at some point I need to realize that since this engine has been an amazing performer over the years, I don't have to worry about these straight pushrods. Steve said that they have been ground straight, which is the trick for making them last since any slightest wonkiness will cause even the tiniest flex, compound over time and eventually cause a failure.
Steve was one of those people that didn't need to listen to others internet advice and maintained that engine problems were almost always the fault of improper building. That includes flat-cam syndrome, running synthetic oil, buying too-expensive head studs, pistons, etc., etc. You can hear that in the video: "People will tell you that's too much lift... it's not" classic Steve!