Alu push rods vs spring preassure

[Jon]

You are right , it is a bus engine which is built for no high rpms ...
I would look for the fast engines ... this is what i do since 30 years now and still it is ok . the us guys are the fastest and they will continue like that .

Udo

Well Skinne is running aluminium dual tapers, that he makes and sell....  but he is not the fastest in the world.

[Udo]

a aluminum push rodded engine just won the unlimited street event at Las Vegas

i think Ollie Frey build that engine ??

Udo

[Shag55]

I think Eric and Scott built his engine. He is using BeeHeive springs also but that motor does not turn over 6500rpm either.

[Udo]

This is what i thought too . it is a big cc turbo engine with lower rpms

what about those N/A engines like super street pro stock or super stock , what do those use ?  I saw big chrom molly push rods like more than 12 mm

Udo

[Shag55]

Most guys are using Manton dbl tapered. I will try a set of Johns dbl tapered 7075s on the street car. I only have 180seat and 430 otn pressure on it. On my AC motor I have 650 OTN pressure so no alloy there. I would like some tai ones but the ones I find have no through hole.

[andy198712]

I though ti is tricky due to its properties, expansions or ....?

Beehives seem to be a good peice of the puzzle, I'd love to try some!

[Fiatdude]

a aluminum push rodded engine just won the unlimited street event at Las Vegas

i think Ollie Frey build that engine ??

Udo

Nope, it was a Red Baron product

[John Maher]

Digging a little deeper into the detrimental effects of running excessive valve clearance, I've run off some data and graphs from a Cam Pro Plus test on an Engle FK89. The graphs I've posted here are based on lift at the cam in 1 degree increments. This method reveals a whole lot more info than the basic snapshot provided on the cam card.

First of all, lift profile for the intake (blue) and exhaust (red):



Here's a selection of the data generated. To keep things to a minimum I'm only listing figures concerned with the valve lash area i.e. from .001" to .040" of lifter movement. The figures below are for the intake lobe on no1 cylinder. From left to right...
Column 1: degrees BTDC
Column 2: lift in thousandths of an inch
Column 3: lifter velocity (lift per degree) i.e. the change in lift per degree
Column 4: lifter acceleration (lift per degree per degree) i.e. the change in velocity per degree

    Deg         Lift            Vel                 Acc

   -58    0.001020     0.0000064     0.0000009
   -57    0.001024     0.0000644     0.0000088
   -56    0.001068     0.0000734     0.0000091
   -55    0.001146     0.0000826     0.0000093
   -54    0.001225     0.0000920     0.0000094
   -53    0.001308     0.0001014     0.0000095
   -52    0.001434     0.0001109     0.0000095
   -51    0.001623     0.0001204     0.0000096
   -50    0.001745     0.0001301     0.0000098
   -49    0.001906     0.0001401     0.0000103
   -48    0.002103     0.0001507     0.0000111
   -47    0.002304     0.0001623     0.0000123
   -46    0.002540     0.0001753     0.0000140
   -45    0.002780     0.0001903     0.0000164
   -44    0.003060     0.0002081     0.0000196
   -43    0.003379     0.0002295     0.0000236
   -42    0.003737     0.0002554     0.0000287
   -41    0.004131     0.0002868     0.0000347
   -40    0.004528     0.0003249     0.0000419
   -39    0.004966     0.0003707     0.0000502
   -38    0.005438     0.0004254     0.0000597
   -37    0.005918     0.0004901     0.0000703
   -36    0.006466     0.0005660     0.0000820
   -35    0.006989     0.0006541     0.0000946
   -34    0.007631     0.0007552     0.0001081
   -33    0.008375     0.0008702     0.0001222
   -32    0.009099     0.0009997     0.0001369
   -31    0.009966     0.0011440     0.0001518
   -30    0.010863     0.0013033     0.0001668
   -29    0.012088     0.0014776     0.0001815
   -28    0.013674     0.0016664     0.0001959
   -27    0.015013     0.0018693     0.0002095
   -26    0.016399     0.0020853     0.0002221
   -25    0.018257     0.0023135     0.0002335
   -24    0.020569     0.0025524     0.0002436
   -23    0.023159     0.0028007     0.0002521
   -22    0.026081     0.0030565     0.0002588
   -21    0.029435     0.0033182     0.0002636
   -20    0.032912     0.0035838     0.0002666
   -19    0.036837     0.0038514     0.0002675
   -18    0.040703     0.0041189     0.0002665

For the sake of making the mathematics easier, assume a rocker ratio of 1.5:1
With a cold lash setting of zero with cast iron cylinders and aluminium pushrods, you might achieve a hot lash figure .006", which translates into .004" lifter motion (.004" x 1.5 rocker ratio = .006" @ the valve). This also happens to be the lash figure Engle print on their FK89 cam card. Checking this against the Cam Pro Plus figures above, lifter velocity @ .006" valve lift (.004" @ the lifter) is ~0.0002869"/deg/deg.

Substitute a chromoly pushrod and hot running valve lash will be in the region of .015" (.010" at the lifter), i.e. lifter velocity at the point the valve is lifted off the seat will be ~0.0011440"/deg/deg. That's a lifter velocity four times greater than with .006" lash.
(lift in thousandths of an inch on the X axis, velocity in inches/degree/degree on the Y axis)



[The CPP software uses the same colour for both curves (lift and velocity), which might make things look a little confusing. I've added the red vertical line to denote the lift increment being discussed. The red horizontal line shows the point on the velocity curve at which that figure occurs]

Now the worst case scenario: aluminium cylinders and chromoly pushrods. This is likely to result in a hot valve clearance figure of approx .040" (1mm). Being on the generous side, lets assume a hot lash figure of .030" (.020" @ the lifter). Lifter velocity is now ~0.0033182"/deg/deg.... an increase of more than one thousand percent! over the iron cylinder, aluminium pushrod combo:



In summary, the greater the differential between cold and hot lash settings, the harder you're hitting the valve train.... unless the cam has extended clearance ramps designed to keep lifter velocity relatively low at your widest lash setting but the majority of camshaft manufacturers are unlikely to have taken into account the metallurgy of your cylinders and pushrods when designing their clearance ramps and lift profiles.

This is a very deep subject. It's difficult to convey what's going on with a few graphs and one snippet of data but hopefully some of this makes at least a little sense?
I need to point out that the data I've presented here is related to the FK89 only. Other cam manufacturers can (and do) take a different approach to clearance ramp design.... but that's a whole different can of worms ;-)

[Wheelhop]

Thank you for posting this.
I have always found Mr Mahers writings most interesting and useful.

[Jon]

the majority of camshaft manufacturers are unlikely to have taken into account the metallurgy of your cylinders and pushrods when designing their clearance ramps and lift profiles.

Many of the cam profiles have been sold since the seventies, how can they not have addresses this before?
I would think that the super wide engines of today is bound to grow more, and that might exaggerate the problem?

the data I've presented here is related to the FK89 only. Other cam manufacturers can (and do) take a different approach to clearance ramp design.... but that's a whole different can of worms ;-)

As cam profiles go, isn't the FK89 a relatively friendly cam when it comes to rate of acceleration?

It seems that this is a negative spiral, with a lot of sudden force you have to beef up everything, and then you need the chromoly to take the beating.

Thanks for contributing John!!

[Jeff68]

There seems to be so many variables to consider with this. There doesn’t seem to be an easy answer. The most common theme is that (as always) you have to consider all of the components of the valvetrain (weight!) the cam lobe design, top rpm the valvetrain / engine will see and make power, the rate at which the engine achieves top rpm, and finally how hot the engine gets. Did I leave anything out? I only drive a street car with a 2110, fk10 cam, 1:45:1 Berg rockers, ported heads, 48 IDA’s, with chromoly pushrods etc.  I have been contemplating trying aluminum pushrods as when I have read about them there seems to be advantages to using them, lower weight, less noise, possibly less wear, better performance. My problem is I don’t have a lot of money to experiment and possibly do damage to the engine if the aluminum pushrods didn’t work as I thought they would. The engine runs well but like most of us, I want the best running engine I can get.  Even though I try to use my own knowledge and reasoning to decide what is best, I think it’s smartest to take the advice of the people that have a lot of success and experience with certain combinations (in this case valve train components).

So I would like to hear opinions from experienced engine builders on for a street engine like mine what valvetrain components choice would work best?  Lifters, pushrods, valve springs, retainers, ect? Thanks for sharing all of the information in this thread!!
Jeff

[John Maher]

There seems to be so many variables to consider with this. There doesn’t seem to be an easy answer. The most common theme is that (as always) you have to consider all of the components of the valvetrain (weight!) the cam lobe design, top rpm the valvetrain / engine will see and make power, the rate at which the engine achieves top rpm, and finally how hot the engine gets. Did I leave anything out? I only drive a street car with a 2110, fk10 cam, 1:45:1 Berg rockers, ported heads, 48 IDA’s, with chromoly pushrods etc.  I have been contemplating trying aluminum pushrods as when I have read about them there seems to be advantages to using them, lower weight, less noise, possibly less wear, better performance. My problem is I don’t have a lot of money to experiment and possibly do damage to the engine if the aluminum pushrods didn’t work as I thought they would. The engine runs well but like most of us, I want the best running engine I can get.  Even though I try to use my own knowledge and reasoning to decide what is best, I think it’s smartest to take the advice of the people that have a lot of success and experience with certain combinations (in this case valve train components).

So I would like to hear opinions from experienced engine builders on for a street engine like mine what valvetrain components choice would work best?  Lifters, pushrods, valve springs, retainers, ect? Thanks for sharing all of the information in this thread!!
Jeff

I'm probably coming across in this thread like a total aluminium pushrod advocate. The truth is the vast majority of my engines go out the door with chromoly pushrods. That's probably in part due to the fact I've been using them in race and street motors for over 25 years. They're tried and tested. In the main they're reliable and there's a natural tendency to 'stick with what you know'. Plus there's a cost factor.... quality aluminium pushrods are significantly more expensive than chromoly.

With an engine like yours, I don't see any major downside to using chromoly pushrods. Your combination is very similar to many engines I've built over the years and I've got no major valvetrain disasters to report as a result of running chromoly pushrods. It's hard to say exactly what difference you would see if doing a back to back test with chromoly vs aluminium pushrods. It's a dead cert valve lash would be less at full operating temperature - that has to be a 'good' thing. You should see a small increase in rpm before valve float but your driving style and head/cam combination may not need to go there anyway i.e you might decide the cost-benefit ratio isn't worth it.

Continuing the cost-benfit theme as applied to a perfromance street engine's valvetrain, I personally have never seen the need to use anything other than chilled cast iron lifters. There are plenty of advocates for tool steel lifters, particularly amongst those who've had bad experiences with pitted lifters and worn cams. Most of my street enginesare fitted with Scat lube-a-lobes at approx one sixth the cost of tool steel.

It's still possible to build a high performance motor without having to resort to the more exotic (read 'expensive') stuff. A well built engine based on 'regular' performance parts can outperform a poorly built hi-tech engine featuring all the latest unobtanium valvetrain gizmos but build the hi-tech engine properly and it should definitely have the edge. Depends how important that extra performance is to you - and whether you can afford it or not.

As far as making advances in valvetrain technology for the aircooled VW is concerned, I've got to give JP Motorsport a plug yet again. There's no doubt in my mind the work Johannes has done with cam design allows an engine to make more power, achieve higher rpm before valve float and produce less friction at the lobe to lifter interface, while at the same time taking less spring force to keep everything under control. Exactly the areas I'd be looking for improvements in if building a maximum effort, high rpm engine. I've seen it for myself! If your build budget covers the extra premium those componets cost over more conventional (traditional) parts, go for it and reap the benefits but understand they only allow you to better exploit the potential of other parts in the system i.e. if your cylinder heads are crap and the intake system isn't sized or jetted correctly, a high quality valvetrain can't make up the difference.

[Udo]

There seems to be so many variables to consider with this. There doesn’t seem to be an easy answer. The most common theme is that (as always) you have to consider all of the components of the valvetrain (weight!) the cam lobe design, top rpm the valvetrain / engine will see and make power, the rate at which the engine achieves top rpm, and finally how hot the engine gets. Did I leave anything out? I only drive a street car with a 2110, fk10 cam, 1:45:1 Berg rockers, ported heads, 48 IDA’s, with chromoly pushrods etc.  I have been contemplating trying aluminum pushrods as when I have read about them there seems to be advantages to using them, lower weight, less noise, possibly less wear, better performance. My problem is I don’t have a lot of money to experiment and possibly do damage to the engine if the aluminum pushrods didn’t work as I thought they would. The engine runs well but like most of us, I want the best running engine I can get.  Even though I try to use my own knowledge and reasoning to decide what is best, I think it’s smartest to take the advice of the people that have a lot of success and experience with certain combinations (in this case valve train components).

So I would like to hear opinions from experienced engine builders on for a street engine like mine what valvetrain components choice would work best?  Lifters, pushrods, valve springs, retainers, ect? Thanks for sharing all of the information in this thread!!
Jeff

For this combo JPM alu pushrods with double springs should work. The K10 like the fk 87 does not need that much pressure

Udo

[Jeff68]

Thanks John for your reply! I was going to say I used chromoly pushrods because they are "tried and true". The parts in the valavetrain were selected from the engine parts supplier I bought my parts from (Bergs). We discussed my engine configuration and that's what they recomended.

I agree on your Johannes opinion. From what I've read on this forum Johannes at JPM has developed great new products! If I had the money I would really like to get a set of his heads, pistons, raptor cam, springs and pushrods and swap my current parts. I would compare the two different configurations to see the differences / improvements. A very expensive comparison! But I'm sure i would learn a lot.

Thanks Udo for your reccomendation as well. I'll keep it in mind.
Jeff

[Taylor]

Has anyone ever tried jamming a 7/16 aluminum Pushrod in there?

[dirk zeyen]

From Aircooled.net : Valve lash is critical on aluminum pushrods. It is possible to have a pushrod failure even though you haven't exceeded our RPM or spring pressure limits, and this is always due to excessive valve lash. If your valve lash gets over .010", the tips of the pushrods WILL get pounded into the pushrod. This is not a problem if your valve clearance is the way it's supposed to be, but a swivel foot failure, or loose valve adjusting screw, can cause excessive lash which can ruin these pushrods quickly.

[Ragtop]

I run Logmech aluminium pushrods, Raptor camshaft, JPM 230 heads and k800 I have reved it over 8 000 rpms without any problems. Last run I had 7600 rpm over the finishline with 2.4 bars of pressure. I think the engine is more quiet and responds quicker on the throttle.

[DWL_Puavo]

In this conversation the main point has been tighter valve lash with alu pushrods when the engine is warm. With alu rods the valve lash stays more stable when engine heats, with cromoly rods the valve lash increases as the engine heats up. This is quite clear and promotes alu rods.

When I looked at John's excellent post and graphs about FK-89 I noticed that lifter acceleration increases for a very long time, and the acceleration didn't slow down almost until the final degrees before full lift. This acceleration part is the thing that worries me, as the acceleration continues to increase at the same time that valve springs tension also increases. My main point here is that the most part of the acceleration happens in the same time that all the other forces in the valve train are also in/near their maximum.

I could imagine the more modern cam curve is modified so that the cam lift starts easy but increases rapidly in the beginning as there's not that much valve pressure at first. Then as the valve pressure increases, there's slow deceleration on the ramp, and then the achieved kinetic energy of every valve train part nicely competes against increasing valve spring tension. Thus the needed maximum force for the different parts could be reduced. So I'm imagining something like this:

- Slow easy start of the lift, also to take the lash away
- Rapid lift acceleration just after the slow start
- Slow easing off near the full lift / extended near-full-open period
- Rapid closing of the valve
- Slow and long ease-off to dampen the shock and possible bounce of the valve from the lash

When side-to-side comparing visually FK-46 and Webcam 86c, I noticed that 86c is way more "fat" on it's profile even if the number specs of the cams are quite like the same. Maybe this has something to do with this?

[Elnef]

I run Logmech aluminium pushrods, Raptor camshaft, JPM 230 heads and k800 I have reved it over 8 000 rpms without any problems. Last run I had 7600 rpm over the finishline with 2.4 bars of pressure. I think the engine is more quiet and responds quicker on the throttle.

Great info can you renember what install pres you have on youre k800 ?

Johannes told me I need around 190 in install preasure with the cam he has made for my engine but if I set them at 190 I will get around 500 on the nose and that is maybe to much for alu push rods ?

John

[Ragtop]

I run Logmech aluminium pushrods, Raptor camshaft, JPM 230 heads and k800 I have reved it over 8 000 rpms without any problems. Last run I had 7600 rpm over the finishline with 2.4 bars of pressure. I think the engine is more quiet and responds quicker on the throttle.

Great info can you renember what install pres you have on youre k800 ?

Johannes told me I need around 190 in install preasure with the cam he has made for my engine but if I set them at 190 I will get around 500 on the nose and that is maybe to much for alu push rods ?

John

I guess that is pounds right? I have around 180 on my setup. I have different ratio on in and out rockers.

[Elnef]

Yes its psi
I got 1,6 rockers and around 17mm lift on valve 

[BeetleBug]

Yes its psi
I got 1,6 rockers and around 17mm lift on valve 

NICE!

[Airspeed]

Interesting data from your cam profiler John!

Now the worst case scenario: aluminium cylinders and chromoly pushrods. This is likely to result in a hot valve clearance figure of approx .040" (1mm). Being on the generous side, lets assume a hot lash figure of .030" (.020" @ the lifter).

While the general conclusion is as valid as a bit of an open door - a lot of valve lash is bad for valve control -, how the heck did you came up with the above numbers for hot valve lash with alu cylinders?
Assumption from general alu expansion data?

I have ran several different alu cylinders and used alu pushrods and chro-moly push rods on those alu cylinders and your hot lash figures stated above don't even come anywhere close to reality. I could not even measure any different hot valve lash between cast iron and alu cylinders at all.

In fact, due to the problems some alu push rods had with withstanding some sorts of ecu rpm-limiters, I went back to chr-mo ones and ran up to 8K rpm on 26psi boost. Yes, with alu cylinders and chro-mo pushrods using VW style double springs. No clack-y-di-clack of 0.040 (1.0mm) or 0.030" (0.75mm) hot valve lash at all!

I think it would be best just to keep the topic confined to comparing alu pr's to chr-mo ones with actual measured hot valve lash figures in both cases, which is difficult enough to do as a hot engine really is...hot! 

[John Maher]

Interesting data from your cam profiler John!

Now the worst case scenario: aluminium cylinders and chromoly pushrods. This is likely to result in a hot valve clearance figure of approx .040" (1mm). Being on the generous side, lets assume a hot lash figure of .030" (.020" @ the lifter).

how the heck did you came up with the above numbers for hot valve lash with alu cylinders?
Assumption from general alu expansion data?

My .030"+ figure was measured on a Type 4 engine I built many years ago, fitted with a well known brand of aluminium cylinders - so the numbers I posted are not based on assumption alone (chromoly pushrods).

As for general expansion data - this shows aluminium expansion rate is approx double that of cast iron. There are many factors that might make the total expansion figure on one engine different to another. It's good you have a combination that avoids the extreme end of the spectrum I wrote about.

In 20+ years I've only used two sets of aluminium cylinders, both from highly regarded manufacturers (i.e. very expensive!). I'm not getting drawn into naming brands because I've no need to favour one over the other.... as of the last alu cylinder engine I built, I will never use aluminium cylinders again on a single cam, flat four, pushrod operated, aircooled engine.

IMHO... the 'pros' of aluminium cylinders (e.g. improved heat dissipation, lightweight) as compared to good quality cast iron, aren't enough to offset the 'cons'.

[richie]

    For the sake of making the mathematics easier, assume a rocker ratio of 1.5:1
With a cold lash setting of zero with cast iron cylinders and aluminium pushrods, you might achieve a hot lash figure .006", which translates into .004" lifter motion (.004" x 1.5 rocker ratio = .006" @ the valve). This also happens to be the lash figure Engle print on their FK89 cam card. Checking this against the Cam Pro Plus figures above, lifter velocity @ .006" valve lift (.004" @ the lifter) is ~0.0002869"/deg/deg.

i

My .030"+ figure was measured on a Type 4 engine I built many years ago, fitted with a well known brand of aluminium cylinders - so the numbers I posted are not based on assumption alone (chromoly pushrods).

As for general expansion data - this shows aluminium expansion rate is approx double that of cast iron.

John

so what am i missing here? when version one gives 006thou lash with alluminium pushrods and cast iron cylinders hot set at zero cold, then you state alluminium expansion is almost double that of cast iron, why doesnt the lash tighten up?      the ally pushrod expands more than the cast iron cylinder which is surely why you set lash at 006 on a standard vw engine[ally push rods,cast iron cylinders] so you dont end up holding open a valve and damaging it.

I want to try ally pushrods in a couple of engines but am not really seeing enough gain here yet to justify the expence?

cheers richie

[John Maher]

John

so what am i missing here? when version one gives 006thou lash with alluminium pushrods and cast iron cylinders hot set at zero cold, then you state alluminium expansion is almost double that of cast iron, why doesnt the lash tighten up?      the ally pushrod expands more than the cast iron cylinder which is surely why you set lash at 006 on a standard vw engine[ally push rods,cast iron cylinders] so you dont end up holding open a valve and damaging it.

I want to try ally pushrods in a couple of engines but am not really seeing enough gain here yet to justify the expence?

cheers richie

Cylinders heat up rapidly because they're subject to combustion temps.
Pushrods are primarily heated by the oil flowing through their middle.
When you start an engine from cold, head and cylinder temps rise quickly but pushrod expansion is down to engine oil temp, which takes a whole lot longer to rise than heads and cylinders.
The temp differential between the two is huge, so even if you were running aluminium cylinders and aluminium pushrods, the two won't expand by the same amount, at the same time.

Eg, a turbo drag motor with large capacity wet sump will go through the finish line with very high chamber and cylinder temps, but engine oil temp will be relatively low - unless you've pre-heated it before the pass. In that situation, aluminium pushrods can't expand to their max.

With a street engine, oil spends more time at it's recommended (higher) operating temp, so valve lash will be less, and more consistent.

[Airspeed]

As for general expansion data - this shows aluminium expansion rate is approx double that of cast iron. There are many factors that might make the total expansion figure on one engine different to another. It's good you have a combination that avoids the extreme end of the spectrum I wrote about.

Cheers John,
Yeah, I think it worked so well for me (and many others) is that the alu cylinders also only get half as hot as regular cast iron cylinders, outweighing the twice expansion rate?
Not kidding: my alu cylinders stay so cool, they draw heat from the heads, helping to cool them! Not the other way round as with iron cylinders.

Its a real pity you had such bad luck with your two builds, totally the opposite to my experience.
Amazing things are possible with alu cylinders. To me there are no cons whatsoever, well, only costs I suppose...

As with anything, many ways to skin a cat.

[richie]

Cylinders heat up rapidly because they're subject to combustion temps.
Pushrods are primarily heated by the oil flowing through their middle.
When you start an engine from cold, head and cylinder temps rise quickly but pushrod expansion is down to engine oil temp, which takes a whole lot longer to rise than heads and cylinders.
The temp differential between the two is huge, so even if you were running aluminium cylinders and aluminium pushrods, the two won't expand by the same amount, at the same time.

Eg, a turbo drag motor with large capacity wet sump will go through the finish line with very high chamber and cylinder temps, but engine oil temp will be relatively low - unless you've pre-heated it before the pass. In that situation, aluminium pushrods can't expand to their max.

With a street engine, oil spends more time at it's recommended (higher) operating temp, so valve lash will be less, and more consistent.

  Ok that sounds logical, I would expect the oil running back down the pushrod tubes that has been heated by the surface of the heads to have more of an effect on pushrod temperature,if the valve cover is already full at 3000rpm then there must surely be some heat transfer?  being that a FK89 is now a "street cam" I thought we were talking about the benifits on a street engine .
My main question has to be,how much "lift" do you expect to gain by running ally pushrods instead of chromoly at the drag strip? how much lift wont you loose by expansion? I have measured 0.030+ lash on a version of my turbo engine after a pass running alcohol  with 180f oil temp which is alot of lift to loose,if I can find a way to gain some of that back I will


cheers Richie

[Airspeed]

Richie,

I thought the huge acceleration figures (and thus with valve control loss becoming 'eminent', as discussed above) that that much lash results in, far outweigh the relative small loss in lift?

If you don't have valve control anymore, a little missed valve lift becomes a moot point right?

BTW, 0.030" lash is 0.76mm!! Being that an alu pr expands more then chro-mo, how much cold valve lash would this mean for an alu pr in that same engine? 0.060"?
Those are bizar numbers. The oil must get extremely hot in that engine for chro-mo pr's to expand that much. Probably extreme valve spring pressures? I found a very high correlation of spring pressure to oil temp... that combined with very hot heads might give the high enough oil temp to cuase this.
I am still dazzled by your numbers though. Interesting at the same time too!

Cheers for sharing,
Walter

[richie]

Richie,

I thought the huge acceleration figures (and thus with valve control loss becoming 'eminent', as discussed above) that that much lash results in, far outweigh the relative small loss in lift?

If you don't have valve control anymore, a little missed valve lift becomes a moot point right?

BTW, 0.030" lash is 0.76mm!! Being that an alu pr expands more then chro-mo, how much cold valve lash would this mean for an alu pr in that same engine? 0.060"?
Those are bizar numbers. The oil must get extremely hot in that engine for chro-mo pr's to expand that much. Probably extreme valve spring pressures? I found a very high correlation of spring pressure to oil temp... that combined with very hot heads might give the high enough oil temp to cuase this.
I am still dazzled by your numbers though. Interesting at the same time too!

Cheers for sharing,
Walter

walter

Now I am even more confused, my point was a relatively cold engine[alcohol fuel] with good oil temp and I still have enough cylinder expansion[steel cylinders,not cast] to gain 0.030 thou lash from cold,I am hoping ally pushords would gain some of this back by expanding more than the chromoly I used, I think that 0.030 thou lift lost is alot

cheers richie