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MG Midget and Sprite Technical - Oh b****r - that wan't there before!

The good news - the sun is shining and my midget passed it's MOT today with no problems (first time out in months).

The bad news - on the drive back I noticed that my beautiful pristine bonnet had developed a small power bulge! Clearly my new engine does not sit as low as the old one and the top of the HIF44 now has zero clearance (confirmed by putting a blob of bluetack on it). So much for being smug about not having any problems fitting a HIF on a Titan manifold.

My question is this - is it possible to lower the engine or even cant it slightly over to the left to give that all important clearance? I suppose I could get the manifold machined to give less of an angle. I don't want to raise the bonnet as it is already rather high in relation to the wing edge. Nor do I want to fit a proper power bulge. Any other suggestions?

Chris - I wondered what that banging was - Hasluck



Chris H (1970 Midget 1275)

Chris,
Has you HIF got the short or the taller damper cap. If it is currently one of the tall ones a simple fix might be to get hold of a lower profile cap?

Photo of my HIF which hasn't added a mini-power bulge to mine.

Guy

Guy

... or you could fit a K series
;-) had to be first to say it
David Smith

Guy

Your HIF looks like mine so I don't think that is the issue (and it fitted before). In fact I think I have just found the answer. I've just been out the garage and compared the new engine mounts with the old. To my surprise the new ones are around 1/4 inch thicker. If you factor that change into both sides, the engine will rise up quite a bit on the new ones (we could be talking 1/4-1/2 inch and that is all it takes.

The new mounts are OE from Dave O'Neil - much better than the pattern stuff they replaced BUT being better seems like a problem in this case. I will try changing the mounts back to the old ones and see what difference that makes. The only trouble is the sun is shining and I anticipate I will be conscripted for gardening duties over the weekend but I'll try to find the time to do this at some point.
Chris H (1970 Midget 1275)

Must admit I have not taken the blue tack test. Maybe mine is closer than I think! I shall try and avoid replacing the engine mounting rubbers!
Guy

So the next question will be - how do you get a ding out of a bonnet panel?
Chris H (1970 Midget 1275)

I'm sure that if you knew the angle of the mount it would be possible to work out how much that would drop the engine. If it was 45 degrees wouldnot a 1/4 inch difference in mount thickness drop the engine a 1/2 inch?
Chris H (1970 Midget 1275)


I am going through the process to HIF44 & have the Titan Manifold but also got a Machined downed damper & flat top piston cap - triple protection (I hope).

Guy - can I hijack this thread & ask you what cables and fixings you use to attach to the throttle spacer?

Thanks
Gavin Rowles

Gavin,
The throttle cable is the original Spridget one - as formerly attached to my twin SUs.
The ferrule where it attaches to the bracket is out of a "useful bits box" accumulated over some 50+ years, so I couldn't say! I suspect it is off a bicycle or maybe an old British motorbike control cable.

Does yours have the quadrant guide thing attached to the throttle spindle as in my photo? Not all HIFs seem to come with that but it certainly makes cable attachment and operation easier.

Guy
Guy

I use a standard MG Metro cable (with a white plastic thing on the end that clips into the semi-circular slot in the heatshield. You need a longer choke cable though as it has to reach to the forward side of the carb.

Chris
Chris H (1970 Midget 1275)

We had a similar power bulge appear. Fixed it by taking a wedge out of the manifold to lower the angle and welding it up again, as there isn't really enough meat to change the angle by machining.

I investigated the options on the damper cap, but found that the lower profile caps don't allow full upwards travel of the piston - the high cap has a recess into which the piston assy's tube goes.

Fixing the bonnet entailed shrinking the bulge back and repainting it, a job for a skilled panel man. Mind you, our bulge had grown somewhat after enthusiastic use in a gymkhana in a lumpy field so there was quite a bit to shrink.

We also had a similar bulge appear in another of our Midgets with std SU's on it. This was caused by an engine mount breaking in a reverse flick turn in an autotest. (J-turn according to Clarkson but done properly it's never J-shaped, just a straight line).

Fixed it, repainted bonnet. Happened again at the next autotest. Not wanting to either slow down the flick manoeuvre or pay for another shring & repaint we have devised a simple restraint bracket which allows the normal range of engine movement but stops it trying to leap off its mounts when seriously provoked.
Paul Walbran

Just to round off this thread, I have refitted the previous engine mounts (which are in reasonalbe condition) and that had dropped the engine by around 1/2 an inch providing a similar amount of clearance between top of HIF44 and bonnet. I hope that is enough.

I guess that if your fitting a HIF44 you might want to check the thickness of the engine mounts you use.
Anyone want a pair of O/E engine mounts (only 12 miles use)?
Chris H (1970 Midget 1275)

Chris, if the paint isn't damaged badly I'd try using dry ice and a heat lamp. You warm the bonnet panel well using the heat lamp, just to the point where it's quite warm to the touch and then immediately apply dry ice to the top of the ding. In many cases the rapid cooling will shrink the panel enough to pull out the dent. This is an old trick used in the US to repair cars damaged by hail.
If that doesn't work then you'll have to resort to standard panel repair techniques which will require repainting the panel.
That's the sort of damage that responds well to the use of a shrinking disc and hammer.
B Young

I wedged the manifold like Paul, and cut a little off the HS6 dashpot top, too.

You might also consider shortening the engine mount.

A
Anthony Cutler

On my HIF44 I cut down the centre tube that the damper slots into, cut down the damper and fitted a flat cap from HS6 ( I think ). Previously had the tall cap on the damper, which just about fitted under bonnet, until a violent movement in the engine prior to stalling gave my bonnet a few little dings. Ah well.

Geoff Mears

Would it not be easier all round to fit the normal heat proofing block found on a lot of A series engines, only wedged to tilt the carb back down a bit? That would allow everything to remain standard with both the carb and inlet manifold. It's the black thing between the carb and manifold in the pic. Or if not the heatproof block, than a wedged bit of steel or ally would do.

S Overy

I might be wrong but I'm sure I read somewhere that the Triumph Dolomite Sprint had shortened dashpots similar to the one in Geoffs picture.

If this is the case I don't know how available they are?

Mark
Mark Whitmore

Wedging the block can help, but there are two draw-backs:
The holes for the studs will not be in full alignment.
The further out (from the head) that the wedging occurs, the greater the angle of wedge needed to drop the carb. We wedged immediately behind the mounting flange to the head.

When shortening dashpot etc, you need to check that the piston is still able to get full lift.
Paul Walbran

This thread was discussed between 25/03/2011 and 01/04/2011

MG Midget and Sprite Technical index

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