help with cam shaft procedure

[Sammysmut]

hello fj owners i bought a 50 k mile fj that started but only ran choked for 500 bucks a while back. the compression is decent and one spark plugs is very oil fouled. i did the valve shims and and broke down the carbs leaving the bodies together and putting everything back where i found it. it ran great except it quickly developed a smokeing issue after decel and on start up. one spark plug is quite obviously oil fouled and after rechecking the compression im think valve stem seals. so.. ive never taking a 4 cylinder head apart and im not understanding the procedure in the cylmer manual fully. it says to put #1 at tdc then remove in order intake 3,1,4, and finally 2 cam caps. this means intake 2 is the last to be removed and is compressing the valve bucket until the bolts back out enough to allow the cap to lift. and then it says to remove exuahst caps in the same numerical order with 2 being the final cap to come off now lobe 3 is the one compressing its valve buckets cantilevering the entire cam shaft. this doesnt seem right and im afraid to damage something. does anyone know where i can find better instructions or am i just overthinking this and the cam shaft can withstand this tension

[Sammysmut]

scratch all that popped one  of the caps off and the barring surfaces are scored to shit.

[Old Rider]

You have to losen the capbolts in steps first a little on cap 3 then a little on 1 then a little on 4  and so on. Do you have pick of the scoring?

[ribbert]

scratch all that popped one  of the caps off and the barring surfaces are scored to shit.

"Scored to shit" is a relative term and 50k is not much for an FJ engine, perhaps post a photo, we have some very experienced members here.

Noel

[fj1289]

scratch all that popped one  of the caps off and the barring surfaces are scored to shit.

"Scored to shit" is a relative term and 50k is not much for an FJ engine, perhaps post a photo, we have some very experienced members here.

Noel

THIS!  It is amazing what these bikes will run with and run through. 

If you REALLY think it is too bad - it is possible to line bore the head - contact RPM for details on that.  Although any competent machine shop "should"  be able to do the job, sometimes it is nice to have a machine shop that is couched for that is familiar with the job!

[Pat Conlon]

Chris, rather than dealing the aluminum journal surfaces, is it possible to overbore so as to install replaceable bearings in the cam journals?

I've always wondered...

[fj1289]

Pat - I have no idea!  When my trailer was stolen way back when, I lost the cam caps for a ported big valve head I had.  Shipped it to Randy - he replaced the cam caps and had the entire assembly line bored to properly fit the new caps - they are originally machined to the head on assembly and have to be line bored for proper fit if replaced.  I would wonder if there would be enough material left in the caps to keep it all aligned at high temps and high loads (bigger cams, stouter springs, etc ) if you removed enough to add in some kind of bushing half?  I haven't heard of it on other overhead cam engines, but I'd bet it had been done at some time 

[ribbert]

Chris, rather than dealing the aluminum journal surfaces, is it possible to overbore so as to install replaceable bearings in the cam journals?

I've always wondered...

I asked my mechanic about this. He said, he sees no reason why you couldn't, but also no reason why you would, repairs are much more practical and replacement even more so with parts so plentiful. In practice the greatest difficulty would not be the machining, but sourcing a suitable bearing unless one had been made specifically for that application (they would need to be split).

In an era when labour was cheap and parts expensive, machining solutions were common and there were machine shops on just about every corner, now it's the other way round. These days, unless it was something special, rare, expensive or unavailable, you'd throw it over your shoulder and get another one, especially a 4 cylinder as most standard machining charges are on a per cylinder basis.

He says the most common fix was to machine a bit off the flats of the caps and head and then line bore them or if the damage was too great for that, build up the bearings (and line bore it).

The whole idea is really only of academic interest anyway because it's not a problem FJ's suffer from, there are 1000's of high mileage FJ's out there, many of which have done so on poor quality, infrequently changed oil and suffered all sort of other abuses without incident.

My mechanic is keen to see what the owner deems "scored to shit" I hope he posts a photo.

While my mechanic has never done this to cam bearings, he has done many "poured" to shell bearing conversions which is a similar operation.

Noel

[Pat Conlon]

Thanks Noel, thanks Chris