Burning smell/smoke after fresh top end???

[Nrgy]

This is for a 300ex, but figured I'd post here for the higher traffic.

I just finished installing a 330 big bore, fresh gaskets, new piston/rings, new ported & polished head with new guides and seals. I put in fresh new Honda 10W-40 oil, and changed the jetting.

To my surprise (being my first engine tear down), it started right up the first try. Everything sounded normal, but after around 1-2 min of letting it idle, I could smell some sort of burning smell. Then smoke started coming off the surface of the engine and the header. At first I thought this might be steam since I rinsed the engine down with water, but it kept doing this for another minute or so. I shut it down since I'm just not sure what is causing this?

Is this normal for a fresh top end to have a burning smell? Is this just all the gaskets and such breaking in? What about the white smoke coming off the header and around the head? Thanks for any help.

[Stickman400]

Yea, that is the gaskets curing and all the oils and water burning off that got collected on the motor while it was torn apart sitting on the floor/workbench. Mine did that same thing for a couple minutes after I rebuilt my 400. It should stop after a few minutes, but if it doesn't I wouldn't worry too much, as long as you know everything is correctly assembled and you didn't overlook something ovbious you should be fine.

[on the rocks]

from the sounds of it you just screwed your self on seating the rings in it.

[Stickman400]

Well when you first start the engine after a rebuild you want to let it sit and idle for 5 minutes or so to get up to operating temp. and check for leaks, then run the piss out of it to break in the rings. So as long as he didn't let it sit and idle for more than 5 minutes he should be fine.

[Nrgy]

Ok cool. Thanks for the feedback. No I didn't let it idle for more than 5 minutes so hopefully I didn't screw up the break-in.

I'll start it up again today, let it warm up, and do a proper break-in now that I know the burning smells and smoke is normal :)

I kinda thought it might be since the engine did sit apart for about a month, and I'm sure some oils and moisture did collect in and on the various parts. So hopefully that will all burn off soon so I don't have to freak out haha. Thanks for confirming that!

[Nrgy]

Well just to update...I started it up again this evening and I didn't notice any smoke so it looks like it was just burning off some oils before. The cylinder was brand new as well so maybe some residue was left from the casting process, as most of the burning smell has gone away as well.

Now if nothing unusal happens in the next hour or so of runtime I think I can call it a success!