Re: [DML] Head assemblies

[Martin Gutkowski <webmaster@xxxx>]

Hi Dave

It's also true that milling the heads (not grinding) increases the 
compression, but from what little I know, the "warping" _is_ at a 
microscopic level - we're talking a couple of micros here (a micron is a 
millionth of a metre) - a human hair is roughly 60-70 microns in 
diameter. My old BX's head gasket went and the Diesel Centre had the 
head machined before replacing the gasket, saying "if we didn't do this, 
the gasket would go again within 3000 miles". I've seen this prediction 
come true on two other identical engines. It's a known problem on that 
engine that the head warps between 120 and 150,000 miles. Mine's done 
30,000 miles since the repair and is still going strong. A lot of it's 
down to just making sure the surface is perfectly clean to get a good seal.

#2727's heads were machined and replaced with new gaskets and head 
bolts. It's true you can only have then skimmed a small number of times 
because eventually they wouldn't fit, but the moral is not to let the 
engine overheat in the first place I guess...

Knowing the respect the Diesel Centre have for their machine shop (they 
send work there regularly), I'm certain if the head was warped so much 
that skimming it would result in it not fitting, the shop would say so 
(maybe being warped that much would probably result in cracking???). 
#2727's engine was in quite a state and the shop also replaced 4 inlet 
valves as well as skimming the heads. It's now sweet.

This is what they looked like when they came back (if you haven't seen it).

http://www.delorean.co.uk/pictures/DCP02509.jpg

It's worth noting that our mechanic was originally Renault trained, and 
ended up working from his Reanult manuals instead of the DeLorean one 
because they described different procedures for the same tasks (eg 
replacing the heads one at a time).

Cost-wise, I think the work on the heads was £300 or so (<$500)

Martin
#1458

Dave Swingle wrote:

> Also - you are NOT supposed to grind heads on the PRV, if you do more 
> than microscopically the front end plate will no longer fit. (This 
> plate covers the whole front(belt end) of the engine, including the 
> heads.) If the heads are much shorter than as-designed you'll have a 
> problem.