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Pushrod Recommendations?


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#16 MIGLIACARS

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Posted 20 September 2017 - 05:49 PM

The one thing I always laugh about for Mini road cars is rear disc brakes.

They are completely unnecessary in a light car like a Mini and do virtually nothing. Still, I guess they make a profit for the vendors.

Even on race minis there is no need there so light, have you ever lifted the back of a miglia spec car. My brothers drunken party trick at race meetings  years ago was to lift it to his chest.



#17 Cooperman

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Posted 20 September 2017 - 07:46 PM

I do recall my old friend Mo Mendham who had what must have been the lightest race Mini at the time. I did lift the rear end once whilst he shoved the axle stands under it. But that was in the late 1960's!

#18 racingbob

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Posted 21 September 2017 - 08:21 AM

Fine in my historic mini reved 8000

#19 tiger99

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Posted 22 September 2017 - 08:24 PM

I have never heard of an alloy cored push rod, Utterly pointless, the tubular variety will be as stiff, and lighter. But there are many spivs, profiteers  and wasters who have nothing better to do than push ali upon unsuspecting customers, when it is often, but not always, one of the most inappropriate materials for the job. Anyone for an alloy crankshaft? Rods? 100000 mile warranty on them? 100 miles warranty? 1 mile warranty? (Enough for one drag race, maybe.) And the stiffness of a rod or tube is concentrated towards the outside, so drilling a hole down the middle makes hardly any difference. If I remember correctly, the stiffness is proportional to R4-r4 while the weight and tensile strength are proportional to R2-r2 where R is the outer radius and r is the inner radius. Compressive (buckling) strength gets a bit more complicated, but the straightness, related to quality of manufacture, helps. Ever looked at the diameter of the anti-roll bar drop links on a Mk 1 Ford Focus, which, as it is a very heavy bar, carry rather large peak compressive loads during hard cornering? Careful manufacture and the correct choice of material mean a lot.

 

I don't think that the Mini pushrod tunnels are large enough to take them, but in general the best material for pushrods would be tubular carbon fibre. But if you (a hypothetical "you", not any person on this forum) are obsessed about valve train mass to that degree you really need an overhead cam, and you do away with the pushrod tunnels to get more space for inlet and exhaust ports, then you realise that the layout is still restricting breathing, so it has to be crossflow, and then you will be wanting 4 vales per cylinder, so go down to the scrappy and find an entirely different modern engine.

 

All very well, but I have seriously over-revved several Mini engines, admittedly all 998 where the safe rev limit is higher than most other sizes, and nothing broke, certainly not the standard pushrods or pressed steel rockers. But I did keep my valve springs in good order, always replacing them at every major engine overhaul, which helps to avoid valve bounce, the cause of premature death of various valve train components.



#20 Cooperman

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Posted 22 September 2017 - 08:42 PM

From memory the only Mini engine where valve train mass, and hence inertia, was an issue was on the full-race 970 'S' which wold rev to a very high figure. 

The solution was to lighten the cam followers and to remove metal from the 'S' forged rockers, or fit pressed steel rockers with a line of weld to prevent 'spreading', together with fitting alloy valve caps. I don't think the push rods were altered, probably because the inlet tracts in the head had been opened up and there was not a lot of metal between the tract walls and the push rod holes.

If the tract wall was broken through into the push rod holes, the solution was to bore out a bit more and push fit a piece of thin-wall steel tube. But the I/D of the thin-wall tube would not have permitted larger diameter push rods.



#21 nicklouse

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Posted 22 September 2017 - 09:23 PM

i remember the first carbon fiber pushrods with alloy ends  they kept failing as they rubbed on the castings causing the fibers to separate in the ends. this must have been in the early 90s.



#22 Spider

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Posted 23 September 2017 - 12:03 AM

i remember the first carbon fiber pushrods with alloy ends  they kept failing as they rubbed on the castings causing the fibers to separate in the ends. this must have been in the early 90s.

 

Yeah, I remember those, they wouldn't take much abuse at all. They were too thick for the push rod holes, more often than not, they'd rub, then it was all over in short time.



#23 ACDodd

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Posted 23 September 2017 - 08:31 AM

I too use stock pushrods but in high revving engines with high valve lifts I shorten the effective unsupported length of the rod by shortening then adding a hardened steel foot on the end. This way the pushrod can be made longer or shorter as required, maximising geometry and increasing rigidity at the same time.

Ac

Edited by ACDodd, 23 September 2017 - 08:32 AM.


#24 Cooperman

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Posted 23 September 2017 - 09:56 AM

I guess it depends on what one thinks of as 'high revving'. A lot of those on here seem to think 6000 rpm is 'high', but i would think of over 8000 as high, whilst a 970 'S', properly prepared, would go to well over 9000.

 

The issue raised by this post is the selling of unnecessary so-called 'performance' parts to owners who have absolutely no need of them for their uses. The sales material will indicate that such parts are for 'fast driving' without defining what 'fast driving' actually is. The same as 'high revving'.

 

Those of us who have driven in real competition know what fast driving is and can make a judgement as to what improvements are needed for specific uses. 

 

For virtually all road use standard components are quite adequate, so long as good quality stuff is used, such as good brand brake pads and top quality standard discs. It might be supposed that if an owner buys a 'cheap' part and it fails early then he/she might be incorrectly convinced that a 'performance modified ' part should be used.

 

Those making a profit from such unnecessary sales will then make a 'nice little earner'.

 

A long time ago I listed on here some of the unnecessary parts which the vendors had on offer. Then some posted, typically, that such parts were 'vital for their "fast road" 998' which showed how well the sales 'puff' was working (for the vendors bottom lines, of course ;D ). Another example is; if a 'works' Cooper 'S' can win international rallies and races with standard 7.5" discs and race pads, why on earth would a road-going Mini ever need vented discs and 4-pot calipers. But it makes a profit for the vendors and that's what matters to them. I recently saw a 'front sub-frame reinforcing kit' which is not needed on a road Mini, or any sort of Mini really, In fact needed about as much as chimney is needed on a house without a fireplace.

 

I'm sorry if this sounds cynical, but many proud owners are not rich and do their best to make their Minis as good as possible. Then they read the adverts and articles in the two 'Comics' and decide that they really do need these unnecessary parts and spend their 'hard earned' on stuff they don't need.



#25 Spider

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Posted 23 September 2017 - 10:07 AM

I guess it depends on what one thinks of as 'high revving'. A lot of those on here seem to think 6000 rpm is 'high', but i would think of over 8000 as high, whilst a 970 'S', properly prepared, would go to well over 9000.

 

The issue raised by this post is the selling of unnecessary so-called 'performance' parts to owners who have absolutely no need of them for their uses. The sales material will indicate that such parts are for 'fast driving' without defining what 'fast driving' actually is. The same as 'high revving'.

 

Those of us who have driven in real competition know what fast driving is and can make a judgement as to what improvements are needed for specific uses. 

 

For virtually all road use standard components are quite adequate, so long as good quality stuff is used, such as good brand brake pads and top quality standard discs. It might be supposed that if an owner buys a 'cheap' part and it fails early then he/she might be incorrectly convinced that a 'performance modified ' part should be used.

 

Those making a profit from such unnecessary sales will then make a 'nice little earner'.

 

A long time ago I listed on here some of the unnecessary parts which the vendors had on offer. Then some posted, typically, that such parts were 'vital for their "fast road" 998' which showed how well the sales 'puff' was working (for the vendors bottom lines, of course ;D ). Another example is; if a 'works' Cooper 'S' can win international rallies and races with standard 7.5" discs and race pads, why on earth would a road-going Mini ever need vented discs and 4-pot calipers. But it makes a profit for the vendors and that's what matters to them. I recently saw a 'front sub-frame reinforcing kit' which is not needed on a road Mini, or any sort of Mini really, In fact needed about as much as chimney is needed on a house without a fireplace.

 

I'm sorry if this sounds cynical, but many proud owners are not rich and do their best to make their Minis as good as possible. Then they read the adverts and articles in the two 'Comics' and decide that they really do need these unnecessary parts and spend their 'hard earned' on stuff they don't need.

 

I recall none other than David Vizard using the term 'Snake Oil Salesman' at one of his talks a few years back and he was referring to a loud mouth (somewhat well known) coff coff tuner who was sitting in the front row.

 

It was actually the first time I'd heard that term.



#26 Ethel

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Posted 23 September 2017 - 11:00 AM

It's easy to make things out of tube and rod with just a lathe.



#27 tiger99

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Posted 23 September 2017 - 12:28 PM

Indeed! A lathe and mill are in my future plans. One item that comes to mind is when the regular questions about using rocker pillar shims come up, when the correct answer, to keep the rocker geometry correct, is to use pushrods of the correct length. A medium sized lathe, with CNC, which is very common these days, is big enough to turn them from solid, thick, radiused bottom end included. It would need a form tool for the rocker screw cup, plus at least a light grind or polish, then hardening, but it is not beyond the limit of possibility to do them at home. But I would make them tubular and just use the lathe to do the ends, which might be adapted from standard push rods to save time..

 

I saw some useful tubing the other week, as I was leaving Delphi, in the rubbish bin. Straight lengths of very high pressure (3000 Bar) diesel fuel injection tube. I wish I had grabbed it.. That stuff is used on large common rail direct injection diesel engines, and is carrying full pressure, plus some pulsation, all the time the engine is running, so it is well finished with no stress raisers. The (small!) central bore would help to align the machined ends, which could be tightly press fitted, brazed or TIG welded.

 

And think what else you can do with a lathe!



#28 Cooperman

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Posted 23 September 2017 - 03:24 PM

Unless the classic car in question is being used for real competition it is hard to see the need for most of the so-called performance parts which are currently on sale at the various vendors.

 

The various vendors make spurious claims about a couple of bhp here, or a few ft.lbs there as if it matters on a car used only on the public roads. It makes virtually no difference. It's like offset boring a block to 1380, then buying expensive pistons, etc., etc, and when using the car on the road it will perform, overall, no better than a nicely built 1275. Of course, there is the 'bar-room bu*****t' aspect, but most would rather have the cash in the bank.

 

A personal view is that the best and most important areas to improve a classic Mini are first of all to fit standard brake discs/drums of top quality then fit top brand pads and linings. That takes care of all the stopping. After that set the suspension up very accurately, using adjustable tie-bars up front with 1.5 deg neg camber lower arms (not with 13" wheels!) and the special lower arm offset bushes to enable the tolerances to be dialled out accurately. Set the rear as has been explained on here many times and have the suspension at standard ride height for best road-holding and optimum handling. Have top quality tyres.

 

After that just set the engine up to drive well and if modifying for more performance concentrate on getting the best torque rather than max BHP.

 

Once that is all done your Mini will give true 1960's retro feel and driving experience and all at a sensible cost with most of it being DIY type work.

 

But that's just my take on classic Mini owning and driving. One of the absolute nicest Minis I ever owned was the 1973 Innocenti 1300 Cooper Export which had a virtually standard engine and transmission. The head was lightly flowed and the CR was increased to 10:1. The suspension was accurately set up and the 10" wheels had good tyres. It really was like old-style driving and was very smooth. 



#29 MIGLIACARS

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Posted 23 September 2017 - 07:38 PM

The various vendors make spurious claims about a couple of bhp here, or a few ft.lbs there as if it matters on a car used only on the public roads. It makes virtually no difference. It's like offset boring a block to 1380, then buying expensive pistons, etc., etc, and when using the car on the road it will perform, overall, no better than a nicely built 1275. Of course, there is the 'bar-room bu*****t' aspect, but most would rather have the cash in the bank.

 

 

 

I do try and explain this to folk but it just ricochets off before entering the ear!

 

also 

 

If all the claims of an extra 2-3 bhp were true on every new item that came onto the market the power increase from my first race in 2003 to my last in 2017 would be something like 50 bhp.

but we all know that the engines built today are delivering no more power now than in 2001.

The lap times of the miglia cars prove this....  But I suppose it keeps some people in business..



#30 gazza82

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Posted 23 September 2017 - 08:22 PM

What about shortened rod with a heavily skimmed head to retain the rocker angle? Thoughts?

Only asking as I was given a set with my 1330 engine but won't be using them as I'll fit a stock 12G940 head.




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