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The 4A Engine Rebuild


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Hi Folks,

this lunchtime I popped the crank and rotating parts into the machine shop for working on.

I'm using TMI in Leighton Buzzard on Harry's advice - they seem quite able to do what I want.

 

I asked them about the undercut at the back of the crank - the machinist that made the crank put in a radius and not an undercut.

The workshop man (Paul) explained that the original undercut would have been rolled during manufacture and before machining as mentioned by Motorsport MIckey in a previous post. Machining in an undercut would be worse than the radius that is there at present - so that will be left alone.

 

When I got home I forgot to ask about the push rod tubes in the head (fiddlesticks).

 

Battle will begin on the gearbox when the 5/16" 8 point socket turns up for those wedgelocks.

 

Roger

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Now I know why I don't recognize the bit: I use an MGB front pulley and narrow belt

I do use a spacer to match the oil seal

Michael

 

Keep checking looking for cracking from the keyway, I've done 3 that way.

 

Mick Richards

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Hi Folks,

whilst parts of the engine are away for machining I will be looking at the leaks on the gearbox

I think the three seals on the selectors are one major area.

 

However I also want to fit a reverse inhibit switch. reversing light switch.

Where would the switch fit on a standard 4A gearbox with A type OD. Does anybody know the precise spot.for drilling.

 

Roger

Edited by RogerH
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Hang on, he's doing mine first :angry:

 

Roger - why do you want a reverse inhibit switch ? overdrive is already inhibited in reverse via the normal switches, or do you want a reversing light switch ?

 

Bob.

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Hi Bob,

not a reverse inhibit switch - a reversing light switch - well spotted.

 

 

Anyway this afternoon I was fitting new bushes to the rocker arms and then reaming. All went well except one bush. I had a spare arm with a good good bush to replace it.

Tomorrow I will assemble the rocker shaft.

When the 8 point socket turns up I will attack the GB to replace the leaking selector rod seals.

 

This morning I was showing one of our forumites what I'm up to to give a bit of inspiration. It must have worked; when he got home he put in a big order for engine parts for his rebuild.

Tomorrow

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+1 for TMI Leighton Buzzard Roger. I entrusted my cylinder head to Paul Barbe earlier this year (also on Harry's recommendation)

after the dropped insert problem and he did an ace job in saving it.

 

He fitted new push rod tubes and for the first time in over 40 years I now have no leaks in this area!

 

Tim

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Hi Folks,

whilst parts of the engine are away for machining I will be looking at the leaks on the gearbox

I think the three seals on the selectors are one major area.

 

However I also want to fit a reverse inhibit switch. reversing light switch.

Where would the switch fit on a standard 4A gearbox with A type OD. Does anybody know the precise spot.for drilling.

 

Roger

I have a T2000 gearbox in my '3, & it has a reversing light switch on it, I would guess that the position would be the same on a TR4A box.

I can take some photos / measurements if that helps.

 

Bob.

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post-9449-0-98046600-1448563854_thumb.jpg

Hi does this help? the switch end sits in a cut away in the side of the reverse gear selector rod - so it is compressed when in reverse as the rod moves into position switching reversing lights on

so switch and rod have to match - from memory I put in the switch and marked the rod from the hole and ground the cut away

The switches are a funny metric thread

Regards

Michael

Edited by MichaelH
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Hi Folks,

the 8 point socket arrived this morning and within twenty minutes two of the square headed screws were broken :o

 

Removing the remnants was not funny.

 

Now for the odd bits -

the interlock balls that mate with the little pin in the middle shaft were absent/gone/not there :blink: . They haven't fallen out; where they ever there!!! :(

 

The three selector rod seals were drenched in oil - this goes with the serious oil leak on top of the OD.

 

The holes on 2 of the selector rods where the square headed screws were located were tickled by the drill so some repair action is required.

 

Regarding the reversing switch - does anybody know what thread is used. It is 11TPI and 5/8 diameter

 

Roger

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Regarding the reversing switch - does anybody know what thread is used. It is 11TPI and 5/8 diameter

 

Seems to be 5/8 13TPI but I made a plug recently in M16x2 that fitted nicely

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