While I've got the head off, is worth pulling the plenum chamber and manifold apart to clean out the gunk? It was running very smoothly before blowing the head gasket, so I would do it only if it will improve fuel economy significantly.

old fart found that the small channel
used for the brake booster vaccume cloggs up (he may have a post about it )
this may also effect economy

dont scratch the gasket surfaces when digging out the channel

now I do this as routine

water may be inside after a head gasket blow
the brake vaccume hole was almost fully blocked
I used a twist drill by hand to get the hole clear


this is my pic of the channel of the TR 4 cyl plenum after a head gasket blow

The inlet manifold is not hard to clean.

You can use carb cleaner, get a small wire brush from a parts shop, brass or steel is ok. Give it a good soaking and you will be fine. The cleaner the better to be honest

In so far as the booster goes, unless the car has been under water which I doubt you have little to worry about, you probably have more old brake fluid in it from master cyl seepage than anything else.

Thanks for your replies guys. A small amount of creamy oil, from the blown head gasket, got sucked from the pcv valve line into the plenum chamber. I took the throttle body off, stuffed a rag in the plenum chamber, and cleaned it up OK. The plenum chamber has a very rough surface, from the casting, so I can't see how a thorough cleaning would improve smooth air flow. But yeah, cleaning out the manifold certainly would smooth out the air flow. So you convinced me, will take it apart and clean it properly. When I posted the question, I was thinking I couldn't be stuffed breaking a perfectly good gasket seal, if I don't need to -got enough gasket surfaces to clean up, without creating more. If I was planning on keeping this car for a long time, I wouldn't think twice about it, but I'm not planing on keeping it for more than a couple of years. But then again, you never know. I wonder what it would go like on LPG. On LPG i might keep for a long time. At the moment, my old ford wagon on lpg is much cheaper to run than the magna on petrol.

add a cheap inline fuel filter to the hose
between the rocker and the the plenum chamber

this is a good way of capturing the oil in the vapours
to reduce the build up