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MG Midget and Sprite Technical - De-coking a 1500

Hello, all.

Realizing that I've never had the head off of my engine during my 19 years of ownership, I figure it's due to lose some carbon. I used Seafoam on it once, but would rather take a more direct route this time.

What are your recommendations for removing carbon accumulation from the head, valves, etc. once it's all disassembled?

Thanks in advance,

-:G:-
Gryf Ketcherside

Once disassembled I washed the head thoroughly with Jizer degreaser in my parts washer and then scrubbed it with a scourer and a scrubbing brush. I then let loose with a power washer. When thoroughly dry I gave it a blast in the cabinet and finished off with a rag and carburettor cleaner.
Nick Nakorn

I picked and rubbed at mine (in a rush to get it back on after HGF) Then later needed to top up one night far from home and only had modern Castrol 10/40. The 10/40 run for 70 miles back home cleaned everything very well. Next HGF a week or so later and the sump off after showed very clean everywhere. Only down side was all cleaned so much it developed oil leaks in the bottom of the engine (including the rear oil seal. Not good :-(.)
Dave Squire 1500

Gryf

Are you going as far as these guys with your cleean up? I usaully chuck a wire wheel in the drill
and clean off the heavy deposits...Ive never gone as far as these guys have. I fit went to the machine shop they always came back looking new. I always wanted to see how its done.
Steven Devine

When you think how much time it takes to take the head off and put it on again (I know it can be done really fast if you're in a desperate hurry and nothing goes wrong - but often that's not the case)it doesn't add much time to clean everything really thoroughly. The pay-off from obsessive cleaning is that rebuilds go according to plan much more often. Anyway, it's good when things look clean and shiny. When a head or block comes back from the machine shop, I tend to repeat the power-wash to ensure there's no swarf or grit in the oilways or waterways. With my current midget project, I've greased up the head, crank and block for storage and so will degrease and power-wash again prior to assembly. They will have been cleaned 3 times. Overkill? Possibly, but I want my engines to last.
Nick Nakorn

Hi Gryf. Just curious

How does the engine go? If it's going ok, and isn't showing any particular signs of needing a decoke, why not leave it alone? 19 years, 25 years, I don't see that as being a sufficient reason to pull the head on an otherwise working engine.
Lawrence Slater

Lawrence -

It runs like a sewing machine, and is quite nice to drive. But when I last had the manifolds off, the valve stems looked very gunky. That, plus performance seems to off a bit, and I think I'm hearing some mild pinking. That, plus I've never had the head off, and am just curious to see what conditions are like in there.

-:G:-
Gryf Ketcherside

I think this is rather timely as I have just been working on my engine for the first time.
Had the cylinder head off and sump and oh boy!!!!!

James Paul

oh boy oh boy!!!!

James Paul

oh well better get the fairly liquid out!

James Paul

Should be fun cleaning this up!

James Paul

But what I really wanted to ask was some of the cooling channels seem to be rusted up or the holes are irregular.

After I had used WD40 and wet and dry paper the head did come up quite nice for a first once over.

Please let me know if these need to be widened?

Kind regards

James

James Paul

The water way openings are irregular in a 1500 head. (sort of triangular shaped on mine).

Clean them out. Its this that probably causes hot spots in the head and maybe therefore HGF. If you clean the water ways in the head and block and back flush all the cooling and heater system components, and de louse the hoses the system will run cool with normal fan.

IMHO its just accumulated crud that causes overheating in a road car.

BTW thought mine was bad but now I know otherwise.
Dave Squire 1500

Took the head of mine when i first got it because i did not know condition got a suprise at condition

mark 1500 Lights on at the end of the tunnel

and block

mark 1500 Lights on at the end of the tunnel

Nice surprise!
High comp pistons too, so very likely an uprated cam as well? Didn't the PO say what had been done, it was obviously very recent and hardly run if at all since the work was done.
Guy W

no just bought a shell and a box of bits and 7 years later nearly there.
mark 1500 Lights on at the end of the tunnel

going to show complete ignorance whats the differance with normal pistons

mark 1500 Lights on at the end of the tunnel

Mark,
I may have jumped in too soon with that comment - I was thinking standard 1500 pistons were dished, but now I am not sure if that is right. Mine were certainly flat topped, and were high compression competition pistons, but maybe the standards also have a flat top on the 1500 engine.
Guy W

Mine are flat and pretty much sure they are original. Cruddy I know but going fine.

Dave Squire 1500

I think all UK pistons are flat top for standard compression ratio of something like 9.5:1.

Only US cars got dished low compression pistons to meet emissions guff. Ended up with a pretty rubbish compression of something like 7.5 or 8:1.

Will dig out some pictures of my engine rebuild before and after. I was lucky in that everything had been balanced and the thing bored out + 40 thou. It means I am stuck if I ever need to rebuild again, but it appeared to have been properly machined and built in the past and should be a fairly powerful engine once it goes (also added a nice cam to help things along!).

Malcolm



M Le Chevalier

pic 2

M Le Chevalier

pic 3 - after strip, skim, clean up and valve lap etc. by machine shop.

M Le Chevalier

Bottom end rebuilt. Block was degreased by the machine shop. Crank, con rods, pistons etc. I cleaned up myself with de greaser and scour pads.

Malcolm

M Le Chevalier

Hi, Just for the record mine is a 1965 10cc engine hence round not triangular holes.
James Paul

And so back to Gryf, and the "sewing machine" :).

How's it coming? Head off yet?
Lawrence Slater

This thread was discussed between 11/04/2014 and 25/04/2014

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