Bench testing a re built Mk1 Hillman Imp engine.

Having rebuilt Imp engines many times I have never then set it up on the bench and test run it, I always placed the motor back in the car and did it that way. Whats involved and what are to pros and cons of doing the bench test?

Number one is just who clean and accessable the engine is. This engine is destined as a display engine and has no actual car to be fitted in, so in this case I have time to spare to work slowly through the test.

The engine is a very very early Mk1 Imp engine and dated 1963, its number is B41/1/501572 WSO the wso means its an export engine and the 1572 means thats the number of engines built to that time.

Test one was to ensure all the oil galleries were filled, once the Shell Oil was in the sump and I had turned the engine over, the oil filter bowl had taken its fill and the sump could be topped up.

Next is to make a jig to offer better support, then do electrical connections, fit a small petrol tank and fire up the motor! Its now 49 years old by the way, it will become 50 years old after the Imps launch date which was May 3rd 1963, this engine will be from that early series.



Roy

Imp transaxle spiders

This subject is probably unknown to many Impers?

Only the very early transaxles had the captive spiders as far as I know, just as well, its impossible To service the seals without taking the large nut off on those boxes, I wonder who thought that idea out?

Note the differences on the corners, the one next to the camera has sharp corners which are best removed if serious hard work or rough roads are expected, as the sharp corners will bite into the rubber drive coupler.

An early Imp drive spider, note the groove at the end of the shaft, the groove held a circlip which stopped the shaft from being removed from the transaxle, only the early Mk1 boxes had this?

The later shafts looked like this and could be removed from the transaxle so that the lip seal could be replaced.

The early shaft with its circlip groove.

Roy

A comment in from an expert is below:

Roy,

I have seen some of the spiders with the the large nut to hold them together.

The spider is also locked into the transaxle by a circlip cut into a groove on the inner spline.

I hope we are not getting confused,over this.

My warning was about the end of the half shaft coming from the rear suspension to the donut.

The end has sharp edges from the way it was forged.

Because it moves in relation to the donut, the sharp edes cut into the donut.

Donuts usually break when the car is accelerating hard, putting a lot of load on the donut, then the donut is also twisted by a lot of compression or droop on the suspension.

The other circumstance is rally stuff, where one wheel is say dropped into a hole and spins, then suddenly finds grip.Then the sequence above kicks in, and the donut shears. The sharp edges will cut and nmake this happen sooner.

So make the end of the drive shaft look like the middle spider and not the one nearest to the camera.

PS Also avoid racing, rallying or anything which might cause exceitement..............life gets so boring.

   

Regards, 

Colin

Colins picture, which was what started the discussion.

You can do this with the shaft still on the car easy enough with a mini grinder and suitable disc, wear the correct eye protection!

Hillman Imp front disc brake kits

They can be fitted on the Singer Chamois, Sunbeam Sport, Stilletto, Commer van and Husky Estate as well. Its a really good move into better braking and of course you will not need to keep re adjusting those front brake shoes anymore.

The kit includes the link plates, stainless steel braided fluid hose and the required spacers, nuts and bolts.

Why bother trying to make these up yourself when a supplier exists in the UK already!

This is another set as fitted to an exported Imp sprint car earlier this year.

A file photo from my suppliers.


Roy

The Imp engine conrod design

When compared with other engine makes, the Hillman Imp has the top of the range design of conrod, the journal end cap is so well located!

This is now 49 years old, bead blasted and washed clean its ready to go again.

The piston is a plus 0.030" size, it took a week soaked in oxalic acid to free off the seized rings and some alloy was lost, it will have been soft from years of water damage anyway?

The rings came out eventually and as far as I can see they are fine to reuse, the dimentions match with a new Rootes Car Co, ring still.

Roy

Roy

How to remove seized piston rings from Hillman Imp pistons

This will apply to most other makes of engines also?

We have a really early Mk1 Imp motor here, the engine number
 is  B / 41 / 1 /501572 WSO (export) which means its engine number 1572 made?

The bores had been fitted with some 0.030" pistons, they were removed when I was gifted the block and parts but all rings were well seized and to remove them risked breakage.

An oil and petrol mix was tried for a week, they were left soaking  and checked daily, nothing very much changed.

I then moved to using Oxalic Acid, its quite mild when mixed to a ratio of a half cup of powder to a litre of water. Daily the rings were tested but lightly, one broken ring will ruin the set.

It took six days before things loosened up enough to attempt to remove the rings that were by now becoming loose. Two second rings are still stuck, I will leave them a while longer, then see what we have and if we can take them out.

Roy

January 1st 2013

The engine was started today and I am pleased to say is a perfect runner, the Solex auto choke carb was a problem, it used too much choke, so we replaced it with a later manual choke Solex carb.

Its starts first time and ticks over around 600rpm and there is no smoke from the exhaust silencer!

Note, some may find sourcing Oxalic powder hard to do, we can post you some easy enough if thats the case?


Note, the rings when fitted back to their pistons and inn the 1963 Mk1 engine worked fine. That engine has now run on about 9 liters of petrol and the engine was run as a demo on May 3rd 2013 to highlight the Imps 50 years since production!

Hillman Imp low compression piston, part two

I have just the one and odd piston, it must have come to me a part of a job lot of parts?
there was no conrod or gudgeon pin but the top two rings were still there, quite worn, so the engine has done some miles.

The piston on the left is the low compression one. Both the skirts are shorter and the top deck is thinner.

The shorter skirt is also shaped and is hollow, check the thinner deck hight on the left piston.

The hight is different due to the shorter skirt, note the gap under the bottom of the skirt on the left piston.

The piston on the left is the low compression one, you can see the valve cut outs are lower and if you look closely you can see a set of half moon marks above the cut outs when the engine was run with the pistons fitted the wrong way around!

Click on the pictures for a closer look.

Roy

The Hillman Imp low compression piston

I have many early pistons from various Imp engines I have stripped but one is different from the rest.

The one on the left has a shorter skirt and the distance from the top deck to the gudgeon pin is shorter. Instead of 18.80mm it is 18.26mm,so 0.54mm shorter, so a lower deck height in the bore and lower compression.

Both pistons are standard bore and both carry the same number inside, 7101025 this tells me they just skimmed the required thickness of the standard piston to get a low compression piston?

This is further prooven when the top lip of each piston is measured, the standard piston is thicker there, 0.153mm to 0.126mm on the lower piston.

This is the lower compression piston, look closely and see that there are half moon marks in the crown of the piston, it was fitted and run the wrong way around!

Roy

Bob Meadows and his Mk2 Imp

A mail to the editor of the Imp Club is below:

Hello Graham,

Did I send you this picture? Its either Wales or Yorkshire?

The registration number looks like a G to me so 1969 and after I came out here, October 1968, so my dad Robert Henry McBride took the picture which was found in some of dads photo stuff.

The guy in the picture is my old friend Bob Meadows, a fellow Camping Club member and also an ex apprentice of Tysons of Dryden St, Liverpool, Bob did brickwork and I did Joinery.

Bob left Tysons and joined Pepsi as a service engineer, he was asked to choose a new model of van for his work, his choice was the Imp Husky and he was very happy with it. His first Imp was a Mk1 green car I seem to remember.

Regards

Roy

Where is Bob now I wonder!