cam bearings
Turbo Mini Forums

when you fit a new cam and bearings, what do you have to do to run them in eg the same as if you were running in the mains and big ends or do the 3000 rpm for 15 mins thing, do the bearings need to be run in for longer then the cam does

"Can I legally marry people now that I am ordained in the Church of the SubGenius?" aka i know jack sh"t

i also make things

i love coming home to chrome

have you had them done yet ? as i believe they have to be pressed in with a machine ?

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LEGENDS
MikeRace, Mini13

not done yet but will be getteing them done as rebuilding engine and putting in different cam, engine was rebuilt last year and run in so only done 2000 miles on it and now putting in new cam and geting cam bearings done at same time as getting block done eg decked and cleaned

"Can I legally marry people now that I am ordained in the Church of the SubGenius?" aka i know jack sh"t

i also make things

i love coming home to chrome

treat these cam bearings like the mains & big ends! exactley the same.

The cam does not load its bearings anywhere near as much as the crank. As long as you use plenty of assembly lube, and make sure you have oil pressure before you let the engine fire, they will be fine.
The 3000rpm for 20 mins thing, is called knocking the cam in, and is for the cam lobes and followers, essentially to take any high spots off both parts, but at a higher speed, so as not to cause micro-welding. All this might sound a bit extreme but make sure you do it, I have seen brand new builds destroy expensive race camshaft profiles in a matter of minutes, as a brand new engine was allowed to idle.

Not sure about this (Cam doesn't load it's bearings as much as the crank statement) but have a read of this and make up your own mind.

http://www.pumaracing.co.uk/cam1.htm

Having used a lot of roller cams in SB and BB Chevys in the past i always used ample amounts of cam lube and ran them at no less than 2500rpm while setting the carb floats and checking the timing so i guess around 15 mins tops. After that they were on their own to come up with the goods.
BUT always replace the followers on a new cam and you can knock out the old and knock in new cam bearings with the right tool.

Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe.

The loads on the cam are huge on the lobes themselves, but taking into account the power strokes being emitted by the ignition of the mixture in the combustion chamber, and the leverage against the crank caused by the stroke, I still stand by my statement that the crank bearings are loaded more than the cam bearings.

After all, in the real world, how many A series engines have you seen with crankshaft bearing failure? And then how many with camshaft bearing failure?

i would have to agree with Tom, i have never even considered a cam bearing change before (maybe iam wrong to have done this)
Due to the sheer loads put on the crank , so much so that the load can cause a crank to flex.
(why we put center main straps on )
This end therefore in my opinion has greater loads than that of the cam bearings.... however IMHO you are likely to blow out your big ends before crankshaft mains..............am i on the same page here ?....like Tom says i have never heard of camshaft bearing failure, but have seen many cases of big ends, crank mains being demolished.

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LEGENDS
MikeRace, Mini13

Personally I have never had a problem with cam bearings, and even have never heard of anyone that has (on A series engines).

However, considering that the new set of cam bearings are quite cheap at around £10-15, I have always changed them as a matter of course.

I see what you are saying Tom about the load being on the lobes.

But the force that is appied down onto the lobes is repeated into the bottom of the bearings as the camshaft is effectivly pushed down. I dont belive that that is greater than combustion pressures combined with the speed that crankshafts rotate.

For the sake of a few quid change the bearings!

So if i turn up the right sized drifts on the lathe at work i could then press in and out the bearings, but i hear they have to be reamed or honed to size, does this involve buying a special cam bearing-sized tool ?

They need to installed with a proper tool. It's a bitch, because they are so soft.

NOT DIY.

Excellent excavating again. Crap, I feel my position threatened..

years ago, someone on another forum said they mod'd a camshaft to use to fit new bearings, cant remember the specifics though

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

thats an interesting idea,

I made up my own fitting tool, there is info on the APT website. I've fitted a few sets now with this an it works a treat.

Did you use a press to fit them?
Because im thinking i can make up 3 appropriately sized drifts to fit into the press of the local engineering shop to save on labour for them to make them up.
Or make said drifts and 'drift' them in ghetto style..

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

no press,

just a peice of M10 threaded rod or studing and a couple of nuts. I also have a bearing race that sits under the nut so its nice and smooth.

if you need to use much force then theres somthing wrong and you ma distort the bearing.

LOL,

there are dimensions for the drifts on this site,

http://www.aptfast.com/

click the site contents and its about 1/3 of the way down.

in in addition to the 3 drifts i also made an extra one that fits in the largest one eithe with or without the bearing in place (has a step) and keeps the studding centralised so they pull in easier.

the trickiest bit is getting them started, the bearings have a generous taper on the outside edges though. A bit of WD40 and they normally pop past the first bit with a litle bit of spanner tightening then pull in easy as you like. just make sure you get the oil ways lined up.

Although i havent bothered to try it yet its probably worth a run round the edge of the bearing and hole in the block with a fine file just to ease things.

Maybe i'll do a how to and puller dimensions next time i fit a set.

Cam bearings officially drifted in, and sucessfully! I turned 3 drifts on the work lathe and a plug for the end wheere the nut seats. They definately need reaming to size though, so i have to buy 3 diff. sized reamers or is there a trick to this? My cam Definately doesnt fit into its bearings atm :(

That's why you use a cam bearing tool, as this get's it all lined up.
You CANNOT ream cam bearings as they are stupidly soft.

Take some emery cloth(?) and remove any high spots.

It may be that you have just raised a burr on the three ends that your "drifts" pressed against in which case, as V says, just remove the high spots (I would use wet and dry paper soaked in paraffin).

If they are undersize, you would never get them parallel using three seperate reamers - the "trick" is to take and old scrap camshaft and machine a short slight taper on the leading edge of all three bearing journals, then grind a few shallow slots across the journals. The slots need to have sharp corners but no raised burrs. Basically a homemade three diameter reamer. Use plenty of lubricant...

Schrödinger's cat - so which one am I ???

This sort of advice you can only get from someone who has done it,based on a lot of experience and a need to improvise where necessary.I like your style , sir !.

like all shells they dont actually need running in as they are seperated buy a film of pressurised oil, if the clearances are right of cause.

always looking for them bigger bunches of bannanas

drifted in? as with kinetic energy?

or pulled in with a length of studding?