Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

Breaking in a new engine, bores vs camshafts

General Engine Building Discussion

Forum Posts



Tech Articles

Talk about engine building here. New products, tricky questions or showcase your work - If it's engine building related it's welcome here.

= Resolved threads


Hi all,

Whats your normal procedure when all the components are new. It will have fresh bores / rings / bearings , but it wall also have brand new camshafts.

I've read before that the break in procedure for new cams is to run them at a steady 2k rpm for some minutes, but I'm conscious that i don't want to start glazing the bores, or am i just overthinking it?

All opinions welcome, thanks !

Following :)

It depends on the cam you're running. The break in procedure you're referencing is required for a flat tappet style cam. It's relatively rare that you'd use such a cam in a performance application and with a roller cam it's not essential.

Evo X 4B11T run a flat tappet style cam.

Does this apply to this engine ? (Run in procedure)

The difference with the EVO X engine is that the valves are much smaller and much lighter than a typical 2 valve pushrod V8. This in turn means that the valve springs don't need to provide anywhere near the seat pressure so the loading between the lifter and the cam lobe isn't comparable. I've broken in many import DOHC engines that run a cam on bucket style of valve actuation with my normal run in procedure with perfect results.

I'm hijacking this thread a little because it's about the same topic:

I've changed the camshafts on my CA18DET to a new OEM one and one almost new OEM one. Both looked absolutely fine and all their measurements where perfect in spec. In that process I've ground the top surface of all OEM hydraulic lifters to a flat polished finish like how they are when new.

I have checked the oil after 500 and 1000 km of running in. And both times there was quite some very fine abrasion on the magnetic oil plug (picture).

I am wondering if that is normal with new cams.

magn. plug after cleaning

It's not uncommon to find some amount of magnetic sludge on the oil plug during the break in process. If you've only changed the cam(s) though, this wouldn't be normal. One potential issue if you've ground the surface of the buckets is that they are induction hardened and depending how much material you've removed, it is possible that you may have ground through the hardening. I'd definitely suggest you inspect the surface condition of the buckets and look for any sign of wear on them or the cam lobes.

To clarify, I think, by "flat tappet cam'" Andre means those used in pushrod engines, especially American V8 engines, where the camshaft is placed in the 'V' between the cylinder banks. These engines depend on oil slashed onto the cam' lobes and followers for their lubrication and by holding the rpm at a high idle there will be a lot more oil being splashed around/thrown off the crankshaft than at idle - this is also why it is CRITICAL that plenty of camshaft lubricant is used, although I have also used anti-scuff assembly lube with a high level of moly' without issues. With almost all modern overhead comshaft engines there is a supply of oil directed right to the high load areas, so there is no problem with lubrication although I would still recommend the cam'or anti-scuff be used. Where there is very ligh loading on the components, high lift and/or heavy springs, it is generally a good idea to do the initial bedding in with a single spring to reduce the loading on the surfaces and after theinitial bedding the full sprink kit can be used.

Silas, that was probably the single worst thing you could have done!

Even if you carefully ground them with a surface grinder, with few exceptions, bucket followers are manufactured with a slightly curved base (you can check this by putting two new OEM ones base to base) to compliment the very, very slight taper on the camshaft lobes - this is to cause the follower to rotate and wear evenly as the lobe and follower bed in to each other. Grinding them removed that as well as, as Andre mentioned, potentially removing the hardened surface of the follower and potentially introducing irregularities that will accelerate wear of the camshaft and follower.

I'd recommend you pull the camshafts and followers and very carefully inspect them and, if the camshafts check out OK (at least consistent on lifts with no apparent breaking up or damage) re-assemble with NEW OEM or REPUTABLE aftermarket followers with plenty of cam' lube or anti-scuff paste - DO NOT grind or otherwise **** around with them - and break them in as per a new camshaft.

I thought the turning of the valves and lifters is achieved by the lobes of the camshaft being sightly off center to the lifter surface.

I have inspected and measured all the cam lobes. Everything is exactly the same height as when I have measured them prior to the install (thank god I am fussy with this stuff and always measure and write down everything). Also the lifter surfaces are looking very good and all of them are clearly turning what I can see from the circular bed in marks. I am almost certain the abrasion didn't come from the valvetrain, but you make me have to question that once again with what you have said about the lifters being curved. When you say curved bucket do you mean curved upward or downward (the center of the bucket being higher or lower than the outer rim)?

Convex, as in raised in the middle. The follower/lifters in you engine may not use this practice, though it is common for V8 engines and at least some OHC ones. You can check by holding two new, genuine followers against each other as there will be a distinct 'rolling' feel. I do have some new OEM 'INA' followers in the shed for a KBA Cosworth, that I can check - if I remember and can find them...

If used, the curvature is very gentle - from what I recall the Chev' engines use a 6 foot (1.83m) radius - and it has also been mentioned that some 'reconditioned' followers were merely ground flat, and should be avoided. personally, I have seen some followers on Chev' engines that were so worn that they had a deep hollow worn in them.

A little concerned about your mention of "bed in marks" though, as they are evidence of actual contact between the components (or contamination of the oil supply allowing debris to get between the parts) and REALLY shouldn't be there.

Found and checked those cam' followers/buckets - definite slight 'roll' to them.

Doesn't mean yours had the same, though, doesn't mean they didn't.

Hi Gord. Then I'm sure now that the thing with the convex shaped Lifters isn't the case in my engine. All the Lifters that I have ground smooth where very very minor concave before. I am sure that just was the usual wear from its 190'000 km running. Nothing looked worn out, just bed in.

Also the new bed in marks I mentioned. I am sure that is normal. I have never seen lifters with an absolutely mirror-like surface after running in the engine.

The abrasion I found is most definitely from other origin. I have installed a NVCS (VCT) cam gear on a modified oem camshaft. It's either from the gear internals (lots of Nissan VCT rattle problems can be found on the internet), or from the cylinder bores somehow. I need the dig deeper to find out.

We usually reply within 12hrs (often sooner)

Need Help?

Need help choosing a course?

Experiencing website difficulties?

Or need to contact us for any other reason?