Cleaning block deck and head face - what do you do?

richiep

Club Member
Here's one for the engine builders: what process/products do you use for cleaning up a block deck and head face during a head gasket change?

I'm part way through addressing the seeping gasket issue I've had for years and head is now off. I've got plenty of products and tools on the go but wanted to see if anyone had any particular tricks or approaches that work for them to get to nice clean gasket-friendly surfaces?

FYI, it's been quite illuminating. Although the coolant seepage down the RHD side of the block has been minimal (usually when cold), the evidence of a growing internal threat was there once the head was removed. There was some evidence of coolant on the head bolts and in their threaded holes into the block. A small amount of mingling of water and oil was occurring around the outer reaches of the gasket in those areas. Thankfully nothing near the bores though. There's a terrible amount of scraping and cleaning required though (this on an engine with only about 10k miles on it). Looks like ****! Pistons wiped off very easily though.

Head is being stripped over the next few days and then will be checked for warpage. There isn't much room to skim though, given if I remember correctly it's had 2mm off already; hopefully minimal to no warpage... :unsure:
 

jonbills

Membership Secretary
Site Administrator
I just use a scraper to remove the old gasket and cellulose thinners to de-grease it.
 

uk66fastback

Club Member
Is that right? 2mm off already - blimey! Must have been badly warped previously at some stage then?

I think my dad used to just use petrol to clean stuff down - in the days when there was nothing else really .. anything that degreases it will do - there'll be a line of products at your local motor factors to do the job?
 

richiep

Club Member
I'd still give it micro skim.... The only way to ensure it's got a clean flat surface

That's what I have in mind for the head. The less the better, just to clean it up and check for consistency.

2mm is what I was told when I acquired it back in the day. I'd have to measure to confirm though (that was in the days before I dared get stuck in inside the engine - Mark Rayner did the long block build). It required a good few tower shims though to compensate. The factory dimples in the casting to show max skim depth are bottomed out, so however deep they are gives you the answer. The head is an N42.
 

jonbills

Membership Secretary
Site Administrator
On an L24, that's probably something like 10.5:1 CR

... Correction: more like 11.5:1. But of course it depends on the pistons and many other things. Pointless speculation :)
 
Last edited by a moderator:

richiep

Club Member
I'm guessing the 2mm scimitar was to raise compression?

Yes. This is a ported head on a 200hp+ L28 with stage 3 cam and 87mm flat tops, with triple Dellortos and Fujitsubo headers etc., so not a particularly standard engine (although not super innovative either! :D).

TBH, I doubt I'd have chopped 2mm off a head if doing it from scratch, but it came like that and cost me the princely total of 40 quid, and has done just fine for the last 8 years.

Hopefully I can nip the seepage issue in the bud in the next few weeks and remove any additional concern for a while. I may also change the intake manifold during this exercise from the Cannon one I have (which has the longest runners of pretty much all triple manifolds) for the slightly more compact Harada/Kameari one, which will give me room to finally install the cold air box I've had on the shelf for a couple of years doing nothing! :smash:
 

Jimbo

1978 260z in yellow
Club Member
i cant for the life of me find out where but there used to be companies about that made custom gaskets to allow for heavy skimming and for lowering compression for turbo conversions.
they wernt very expensive and i got my last custom gasket from a business in Wolverhampton somewhere.
 

richiep

Club Member
Had an eye opener this evening when doing a little work on things. The head had been lying on its side on a bench overnight and a lot of the residual oil had drained out onto the sheet of clean paper I'd had the head on. I lifted it up to adjust its position only to reveal a couple of patches of aluminium filings. Lots of fragments, ranging in size up to a mm+. I may have uttered some impolite words at this finding. However, there's no evidence of damage on the head, valves, pistons, combustion chambers, or anywhere else to account for it. At a guess, it seems possible that the shavings drained out of the depths of the head with the oil and could have been residue from when the head was skimmed and ported God knows who long ago. Clearly, previous cleanings or years of use did not get them out. Luckily, wherever they were in the head, they stayed there and didn't circulate through the engine, as they surely would've mullahed it. Yikes. :eek:

I think the head will getting the cleaning of its life before reinstallation...
 
Top