what size magnet should i put on my filter

I use 25mm dia x 10mm thick.
1 each side, but 1 will do.
Similar to these- http://aussiemagnets.com.au/product/-20 ... th%29.html

These are `rare earth' magnets, not cheapo ferrite ones (which are too weak to do any good).

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

the ones I got some time ago are 10mm deep and a diameter or 20mm which is perfect

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Stop Licking the Dog...I Don't Care Who Started It

If you have a dead computer hard drive break it open and grab out the magnet. Those suckers are strong.

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"Investing my Super in a Cooper" &
"Re-living my Surfing Past in a Woody"

If any ferous material makes it this far (the filter) let the filter do it's job - that is filter.

If the filters you're using need magnets, buy better filters.

There is (or should be) after all a magent on your sump plug.

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The full flow filter passes anything smaller than about 50 micron.
I'd try this then cut a filter up before you knock it.. as I did.
You would not believe the fines a rare earth magnet picks up (and retains) in there.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I like to try different stuff as much as the next guy. I don't knock anything for the sake of knocking it

I did cut up and look through various filters some time ago now. Yes, it is an eye operner.

If your filter only does down to 50 micron then refer my earlier post.

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OK, please post us a list of spin-on filter brands, prices, and their filtering ability.

[edit] I paid $3.50 ea for my dozen Cooper filters, the magnets cost me $0 from work years ago and being reuseable, have paid for themselves many times over.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

These for one are better than 50 micron

http://www.knfilters.com/oilfilter.htm

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they look expensive.... I do the hard drive magnet thing

edit: evidence!!

my spider gears ground themselves into oblivion last year, it was very impressive how scored and ground out the oil pump was... but the crank bearings were just fine

OK.

But..........

Any magnet will only capture what passes within it's influence........

A half decent filter will capture so much more.......

I kinda look at like an insurance policy....

<EDIT> At the end of it, we fit filters to extend the life of the engine (and gearbox). The quality and grade of the oild has far more to contribute to this than filters and / or magnets.

What you found in your oil pump (spider gears?) - I have seen the same several times now, on engines that did not run magnets.

If it gives you a warm fuzzy feeling, fit them. I know that they won't help.

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Taken from http://people.msoe.edu/~yoderw/oilfilte ... study.html

"The SAE J1858 test provides both particle counting and gravimetric measurement to measure filter capacity and efficiency. Actual counts of contaminant particles by size are obtained every 10 minutes, both upstream (before the filter) and downstream (after the filter), for evaluation. From this data filtration ratio and efficiency for each contaminant particle size can be determined as well as dust capacity and pressure loss as a function of time. Typical numbers for paper element filters are 40% at 10 microns, 60% at 20 microns, 93% at 30 microns, and 97% at 40 microns".

Most filter makers I find don't tell you what the filtration efficiency is, or how long before the bypass valve opens.
As Simon says, I know the magnets work, with Cooper, Coopers, Delphi, and Ryco spin-on ones.
I might just buy a K&N and prove it works with them too.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I can't figure out what the K&N equivalent for a Z418 is... they don't list for a Rover, Leyland etc. and Ryco isn't in their cross reference

As I say, the magnets won't help.

I'll explain a little.

Particals cannot pass through the oil 'quickly' because it is a thick liquid. Therefore in the case of ferous materials they need to pass very close to the magnets (even rare earth magnets) to be captured and not 'swept' along with the flow of the oil. There are chemicals within the oil designed to do specifically that, it's part of the detergent action of the oil. And the oil does flow fairly quickly through here.

If you calculated the ratio of volume within the filter between the filter case and the upstream side of the filter medium and (being very generous) 100 microns around the internal surface of the filter case it is less than 0.5% of the oil volume that may be 'filtered' by the magnets. And that is being quite generous.

So when 99.5% of the oil is by-passing the magnets, what's the point? It's the proberbial pimple on the elephants backside. Clearly, whatever filter you are using works without the magnets.

On top of that, not all the oil does reach the filter head in any event. There is a portion of the oil that goes via the relief valve.

I have pulled down an engine that the owner used magnets on and I have pulled down many that did not. I found no evidence what so ever that the magnets did anything.

There are various kits about that fit to the oil pick-up pipe (externally). Some of these use magnets, some filters and some a combination of both. There is a magnet variety that I have seen that fits in to the back of the gearbox, where the cover plate is over the oil pick-up pipe. For 'Filtering' these do work well as there is only a very small area between the magnet and the surounding pipe.....BUT for this same reason, they restrict oil flow....and they are a PITA to get to to clean.

If it lets you sleep at night, fit the magnets.

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So in regards to your question Jimmy, Doc is on the money.

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Your silliness has been noted.