Rockers!

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Rockers!

Postby Marc Hilton » Mon Jul 06, 2015 9:43 pm

Hi guys

I'm in the market for a set of 1.5:1 ratio roller tip rockers, preferably the purple anodised Minispares item but I'll consider others. Also any pre-A+ drop gear sets at 1:1 ratio?
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Re: Rockers!

Postby streetsy » Tue Jul 07, 2015 5:06 am

Unless you are looking to rebuild your engine quite often 1.5 rockers are best avoided. They put excessive loads onto push rods, can and followers. The lifespan of the rollers is also questionable.
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Re: Rockers!

Postby Marc Hilton » Tue Jul 07, 2015 7:36 pm

Hmmm, not so sure about that. However, I'm quite sure the fact I have double valve springs, a Kent 286 camshaft and 1330cc instead of the standard items will put more stress onto the push rods than the roller rockers will, considering they're designed to reduce torsional loads within the rocker arms by reducing friction at the point of contact with the valve stems.
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Re: Rockers!

Postby Mtrike » Tue Jul 07, 2015 8:16 pm

I may have a second hand set available in the autumn. I need to replace the head gasket and I'll be changing the rockers to a standard set at the same time, for the reasons already stated. My engine is 1380 also with a 286, I doubt there will be any discernible difference but hopefully the cam will live longer as well as the push rods wear less. I understand the excess comes about because of the increased speed/acceleration of the rods rather than lateral loads.
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Re: Rockers!

Postby streetsy » Tue Jul 07, 2015 9:12 pm

The advice comes from renound a-series engine builder Mr A C Dodds at stoneleigh where he was guest speaker. Say a valve needs 100lbs of force to open in, standard rocker 1.18:1 ish, 118lbs on the rods, followers and cam. Up to 1.5:1 it's 150lbs. Static forces on the valves whilst stationary also increase by the same rate and as Mtrike says velocity is increased as the valve has to open further due to the increase in ratio but has the same amount of time to do it as the duration of the cam doesn't change thus the valve must move quicker, also wearing valve guides faster. Roller Bearings will collapse too.
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Re: Rockers!

Postby Marc Hilton » Sat Jul 11, 2015 9:54 am

This does make sense. Surely some manufacturing company, such as Kent or Piper, should invest in producing appropriately uprated push rods and valve guides to compensate for the increased forces and wear? Mtrike do you think you will see a drop in power/torque or response going back to standard rockers?
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Re: Rockers!

Postby Rich » Sat Jul 11, 2015 6:18 pm

I've got a Kent 266 in my 1330 and adding the 1.5 rollers took it to about as far as I would want for a road engine, they might just take your already relatively hairy 286 to a point where the car will be a pain to drive.
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Re: Rockers!

Postby Mtrike » Sat Jul 11, 2015 9:09 pm

Rich
You are not far wrong, the 286 will go too first time the engine is out. Apart from the lumpy fast idle the whole combo is too powerful for today's traffic, it's a boot it, brake it, boot it machine by the time the powers coming in in third you are already up to nearly 80 with a gear to go (not helped by a high final drive in my case). Can be fun but gets wearing, it's more suited for a circuit. What is good is the 1380 gives it reasonable torque at 3000 and means it cruises well.
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Re: Rockers!

Postby Crowmann » Sun Jul 22, 2018 11:30 am

Hmmm

New owners view of Mikes old ride (Blue Pastiche convertible) I put the car back on the street for a little shake down and IMO its peppy but easy enough to drive in what ever way you might wish.

Lumpy idle - sure but too fast … err no. It feels like a perky A series to me and little more and certainly not too fast for the road or anywhere else for that matter. Maybe I have become more accustomed to modern performance cars but I for one will not be looking to pick a Two Fast style show down with anything nippier than a 1.6 Mk1 MX5. Sorry.

In truth my expectations around this lump was that it would be unusable - as per previous posts. It is in reality fine and given its a low mileage type machine the wear issues should not really be a problem. The real concern might be why it keeps needing head gaskets as its on its second replacement in possibly 2000 miles or less.
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Re: Rockers!

Postby Mtrike » Fri Jul 27, 2018 10:19 pm

We’ll disagree about the drivability but as far as I know this is is the first head gasket failure. As I never lifted the head I don’t know what was used but I assume it was a stock head gasket that might explain the blow through.
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