Decoke anyone?

[Robert in Cumbria]

Rain forecast today, so some indoor tasks to do, like the head...

When I found the Marlin in the wood and was told it had been there since 1988, it didn't quite sink in how badly the corrosion had affected it. At Easter I had a naive idea of getting the engine running! Ha, no chance, it was totally seized, a big socket on the crankshaft front bolt was met with the most solid resistance, either tightening the bolt or releasing it, but no turn engine. I had even taken a battery and some fuel!

The bores were reasonably free of corrosion, the pistons were bad around the rings and that was why the engine wouldn't turn. This is perhaps the most spectacular corrosion I have come across inside the engine. All the ports were similar, I had to hammer this inlet valve out. I kept one chamber to photograph before I cleaned it.

A bit of valve grinding to do today I think.

Marlin Port Corrosion.jpg

Marlin Port Corrosion c:u.jpg

[b_caswell]

Re: Decoke anyone?

Just needs a bit of RedeX

[cameronfurnival]

Re: Decoke anyone?

Just needs a bit of RedeX

and maybe a tickle with a wire brush?

[Mike]

Re: Decoke anyone?

Blimey - are you really going to try and save that head?!!!!!

And I thought I was the only mad one around here...........

Here's some moral encouragement:
From this rusty old scrap brake disc:



To this, is possible: ( but it is only being used as my spare wheel fixing plate to the boot lid !)

[Robert in Cumbria]

Re: Decoke anyone?

Very well done Mike, nice machining. The encouragement is appreciated!

After three hours of lapping and cleaning I have admitted defeat. The pits are far too deep to be removed by lapping. When I collect the block from being bored on Friday Malcolm has promised to reface the seats and valves for me while I have a coffee. All being well I will be engine building this weekend, although the boys want to go to the Edinburgh Trial...

The head will be pressed back into use though. I have acquired a late 'S' head but it needs new seats and porting before it's brought into use, I am looking for quick fixes for now. I can enhance the spec once it's on the road.

[cameronfurnival]

Re: Decoke anyone?

That's going to be one hell of a cup of coffee Robert but hats off to you - I am inspired enough to go out into my garage tonight and do some work myself!

[Dane_Rescueman]

Re: Decoke anyone?

Robert you say that you are going to reface the seats. Why not ask the guy to fit unleaded inserts for the exhaust valves?

[Robert in Cumbria]

Re: Decoke anyone?

Right now every penny counts.

Mike was right when he suggested this head is rough. It really needs inserts, guides AND valves but for now it will get me through the MOT and allow me to register the car. At the moment that is my priority.

I intend to do a 'proper' job on the late 'S' head I have found, it already has 36mm valves so I will get unleaded seats fitted and with a little work on the ports and chambers, balanced and done nicely. That will be one of my first jobs once the car is on the road. Then this head will then become a spare.

You are right though, it would make more sense, if the budget wasn't so stretched.