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After 6 months of procrastinating, I just swapped my L cams for H and swapped the H model cam tops along with it as I buggered my L's ones (I could repair them at one of the local machining specialists, but figured I'd get some undamaged goods and as close to SP cams as I could afford). Used all the right lubes as the manual says. Started her up and she runs fine, sounds a little gruntier (as I expected); goes fine when I took it around the block...blah blah, have done about 5 kilometers so far on these things without revving past 9,000rpm (there doesn't seem to be a noticable powerband at 4k rpm; I think it moved to 2000 rpm, and there is slightly higer compression than I remembered; but that could be because I gaped the spark plugs, am running a mixture of old petrol with newer put lower octane petrol and I haven't ridden it in a while).

Now here's my dilemma: I just spoke with another fellow who says that I should have line bored the whole thing before assembly. I don't doubt his background (worked constructing heads for Chevrolet in the US) but his concern lies with bearing squish upon tightening the caps, thus miss-aligning the setup, destroying the bearings and overheating the head. Being that the 400's head hasn't any bearings, should I be concerned about line boring the head?

I'm a little concerned about there being different wear patterens on the cam support journals in the head; but that's all so far. If the Cam was warped I think the Mechanic I got to inspect the rig would have saw it. What's the lieklyhood of the cam not fitting properly, and what should I listen for and expect if it doesn't? Are any of these concerns worth worrying about?

the manual doesn't make note of line boring when swapping cams in the H model Top-End section (I don't see why it would either); but let me know your thoughts with regard to my brand-spanking-used cams.

Cheers

actually it is mentioned in the manual, where it tells you to replace the cam caps in the same locations they were in on disassembly because they are machined in one with the head and will be misaligned if not replaced exactly..

its something i've been wary of every time i've rebuilt an engine, although i have heard of several folk snapping a cam cap and just swapping in a used one from another engine.. how long the engine will last like this i dont know, and wouldnt like to guess.

most i've ever done is polish the bearing surface of the cam caps and head if i've noticed any scoring on disassembly, it aint perfect, but i figure its safer than a cap off another engine.

If i HAD to use a different cap, i'd torque it down to the head without the cam installed and visually check the state of alignment before going any further.

swapping cams over shouldnt be a problem providing they are not scored, its keeping the head and caps matched that's the important bit.

best/correct option is to strip head right down, and take it to a machine shop to be sorted properly i guess.

As for symptoms.. at a guess.. extra friction, rapid camchain wear...

well damn, I guess I'll have to rebuild the original L caps or rebuild the H head I've got and swap heads.

Does anyone have any thoughts on making sure the caps are compatible, or is it a full loss? What are my options in this situation?

you may be ok, im rather cautious.

Cheers mate,

I've found enough cautious web pages to make me think I should look into it more. I've currently got the thing apart again and having a look around; so if there are any ideas as to what to look for or do, now is about the time I'll be looking into it.

The caps and head are machined together and are "matched"

Changing the caps or the cams could lead to problems...........if for example there is not enough clearance between the camshaft and the cap/head then it will not get enough or any oil.........excesssive wear will soon be apparent.

Also if the clearance is too great the camshaft will be able to move around too much................leading to excessive wear...


If I were you I'd rebuild and check the oil clearance at every bearing surface using Plastigauge................you might just be lucky.
Plastigauge is expensive but is much cheaper than a fecked head or fecked camshafts............


You can get Plastigage............... or............ Plastiguage on ebay search for both spellings...........or google it