Preparing block for new head

[Adammcf]

My new head came today and apart from scraping all the crap from the old head gasket away is there anything which needs to be done to the surface of the block so its ready for the new head?

Whats the best way of removing small bits of dirt and dust which has fallen into the combustion chambers as well? Just hoover it out and then wipe it clean?

[ian332isport]

My new head came today and apart from scraping all the crap from the old head gasket away is there anything which needs to be done to the surface of the block so its ready for the new head?

Whats the best way of removing small bits of dirt and dust which has fallen into the combustion chambers as well? Just hoover it out and then wipe it clean?

Adam,

Yeah, you need to remove all traces of old gasket from the surface of the block. I then give the whole surface a good going over with an abrasive pad (Scothbrite). This really gives it a good clean. Ideally you want it to be nice clean bare metal.

As for the crap in the bores, give it a good hoover to get the worst of it out. I then run some engine oil around the edges of the pistons (so it runs down between the piston and the bore), and turn the engine over by hand several times. As the piston drops back down, it will leave a ring of oil, and any gunk at the top of the bore that was sitting on top of the rings. Wipe the gunk/oil away and repeat. Keep doing this until there is little or no gunk left. You will see what I'm on about if you try it.

Also make sure there is NO oil or water in the holes the head bolts screw into. If you leave liquid in these, you will probably crack the block when you bolt the head on.

Finally, before you are about to fit the head/gasket, de-grease the head and block sealing faces. These need to be dry as a bone, and totally grease free. Use a solvent that leaves no residue like paint thinners or isopropyl alchahol. Petrol or white spirit tend to leave an oily film.

Cheers,

Ian.

[Andy_magic]

I usually put some grease down the bores to catch all the dust, old gasket etc and then clean it all up as mentioned above.

Oil in the threaded holes can also lead to incorrect torque on the bolts so they need to be really clean too.

[Adammcf]

Cheers for the advice guys. All makes sense. I didnt want to clean the block surface too hard incase I left little scores which might affect the seal.

Is it worth putting on any kind of gasket sealant when putting on the new head gasket or will it be fine just on its on and torqued up properly?

[ian332isport]

Is it worth putting on any kind of gasket sealant when putting on the new head gasket or will it be fine just on its on and torqued up properly?

You should not need any sort of gasket sealant on the head gasket.

If you look at the gasket, it usually has lines of sealer already on the surface (usually around the bolt holes, oil ways, water ways etc). These will form a good seal when it's all torqued down correctly.

Ian.

[Jos]

I normally use a straight block of very hard metal (high cobalt tool steel) and scrape the top of the block with that, it won't mark the block as long as you keep it flat but it does remove the old gasket a treat.

[Adammcf]

I used a wide flat screw driver last night to go over the surface and scraped as much off as I could. Its smooth to the touch but still looks stained etc. Maybe all it needs now is a good rub down with something like mentioned above.

[psychochild187]

cool, all the stuff i was going to ask!