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MG Midget and Sprite Technical - 12G940 head pushrod sleeves

Attention all,
I notice on the head I have just had ported that two of the pushrod holes are sleeved, one of which is preventing the pushrod going through.
The head was bought second hand, and I cant say I noticed this, but am I ok to take a drill to relieve the sleeve, ideally keeping some of it in situ to do what ever job is was put into do.
I assume it has cracked at some point hence the sleeve but having had the head vacuum sealed recently I am hoping that this has potentially cured this defect.

Over to you lot !
P Bentley

That's an intriguing problem!

Are the sleeves newly inserted? One of the hazards in porting a head is breaking through into the pushrod holes. I wonder if the sleeving has been added, either in the recent porting or at an earlier attempt, in order to cure such an issue.

If it was sleeved previously, how were the pushrods inserted before? If its new sleeving, take it back to the shop that did it and complain! They should have to sort it out, not you! Maybe the flared end of the pushrod can be turned down a fraction? If the pushrods came with the head, check that they are all the same.
Guyw

Cheers for a quick reply, I didn't notice the sleeves when I got the head, and I strongly doubt they were fitted by the guys I used without them saying so, although that's my hunch rather than me categorically knowing. To answer your other point, The head did not come with the pushrods.
I guess the thing to do is use the smallest drill I can get away with until clearance is achieved. And on that subject what would the sleeving likely be ? the ends are well within the pushrod hole, so I cannot even tell you what colour the material is.
P Bentley

Not sure I have anything to add. But thinking about this, if the sleeving isn't new, and the head was actually used by a previous owner in some other engine, they must have either adapted their pushrods to fit, or maybe there are different types of pushrod available? Assuming that the was previously used, I would be investigating the possibilities for the pushrods, before attempting to drill the sleeving oversize. I am sure others here will have more knowledge of this; Peter, for example.
Guyw

I have sleeved one pushrod hole with a brass insert which I made on a lathe. Only problem with the sleeve is that I have to drop the pushrod in before fastening the head to the block.
Alex G Matla

Sleeving is quite common on ported heads. You can reamer out the sleeve to accept the push rod or take it off the bottom of the pushrod. I have favoured the former as its easier.
Bob Beaumont

Competition-spec lightened pushrods are turned down fractionally at the cup end and will likely fit through the sleeves when fitted Alex's way. It's hard to fit the pushrods with the rocker gear in place so that's the usual way of doing it anyway.
David Smith

ISTR having to modify the bottom end of a pushrod to fit through a sleeve.
Dave O'Neill 2

cheers gents, pleased to read that its not a bodge having just forked out for the porting !
Will ream it out, fit and report back.
P Bentley

Ok, fired up the grinding wheel and shaped the pushrod to fit, I was surprised by how little I had to take off, couldn't have been more than ten-fifteen thou. so job done.
The head is now fitted and runs fine, now I need to sort the carb needle as something isn't quite right just yet, as the car feels very similar from the head I have replaced to the modded one.
So more tinkering yet.
If anyone happens to run a 1293, mild cam, (I think it was from a MG metro) electronic ignition, high lift roller rockers, single HIF carb on a maniflow intake, LCB exhaust and want to offer an opinion on where to start, then I am all ears.
If the answer as I suspect it is, would be a trip to a RR, then I am based in Surrey, so keen to have a recommendation.
P Bentley

I currently use Novatech in Slough, he's conversant with carbs (less and less are these days) and they are not stratospheric on price.
http://novatech.info/index.html
David Smith

I use Slark Race Engineering in Amesbury. Very experienced with A series and they race in the mighty mini and suoer mighty mini series. My engine has a similar set up to yours.
Bob Beaumont

many thanks gents
P Bentley

booked it in to Novatech, will report back with how I get on.
thanks again gents
P Bentley

I'm at Novatech myself in the morning, will also report back.

David Smith

PS - yes I did remember to strap the car down!
David Smith

Given it was hottest day of the year so far and 30+ ambient in the workshop I'm happy with this. Upped the main jets to get the a/f below 13, ignition max advance 28 degrees.

David Smith

good engine you have there David
P Bentley

Well a good morning was spent at Novatech, Andy went through the car and we ended up at 84 BHP, which I am happy with. On a BDL needle there was more at the top end but it ran leaner for the more useable part of the rev range. So, we ended up at with a BC? needle, might be BCE which gave a much more even AFR through the revs.
Not only am I pleased with the figures but the engine sounds so much better than before, with a consistent idle and very sharp throttle response.
If you are in two minds to get your car set up, then I urge you to give it a go. For me it was money well spent.
P Bentley

This thread was discussed between 14/07/2016 and 29/07/2016

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