RS Motorsport :: Classic Speed Restored

I got a pinto to rebuild which had been run with little more than litre of oil in the sump. The engine had been loosing or burning oil but it was not obvious as the top of the dipstick had worked loose so each time it was dipped the dipsitick pushed a little further into the sump and registered ok. The engine finally gave up a mile into a rally when the oil pressure started jumping around and it began to tighten up and make some bad sounds.

I started the strip down and found that 6 of the cam followers were so badly worn that they could easily have been removed without loosening the adjusters. The cam lobes were in surprisingly good shape with only some scoring on two of the lobes. However the groove at the end of the cam for holding it in place had worn badly so that it could be pushed forward or backwards by a few mm.


Worn followers :note the mismatched one at the end


Scored cam lobe


Worn retaining groove

I stripped the bottom end and found some more surprises. The first thing was one conrod which was different to the other three. All were manufactured by Farndon and were the same lenght but one was 2mm narrower at the big end than the others (not worn but machined to this width) The big end bearings were showing some signs of wear but not too much but the centre main bearing was very badly worn. Possibly caused bu the imbalance caused by the ligher conrod.


Two different conrods

Compression ratio 11:1, Cam is Kent GTS4 and pistons are forged Acralite. The bores looked very glazed. The valve guides were a little worn and all valve seals were lifted but the centre spring of the double valve springs.


Looking down into the bore. Lots of carbon builbup

I have a few questions for later

Tom

Engine back together at last. It is basically all new. Replaced Cam, Followers (Newman), one valve, New conrod, All other conrods checked, lightened and balanced by Farndon. Pistons were basically new Accralite. Bores honed, Main bearings honed to restore alignment and appropriate bearings fitted. All other bearings replaced including cam shaft bearings. Cylinder head ported especially the exhaust port which was very bad. Inlet manifold ported to improve on a mismatch between the head and the manifold.


New bits all lined up ready to go in


Conrods look really nice after the work done by Farndon.


Newman followers


Block Assembled


Nice and shiny


All Fitted yesterday

After a bit of time to run in the cam and get things adjusted it was out for some testing. Worked really well, good oil pressure and no nasty knocks or rattles. Only thing not quite right is a bit of a flat spot down low in the revs but maybe that is to be expected with a cam with 312 degrees duration (Kent KC-GTS4)

I am going to fit longer velocity stacks in hopes of fixing the flat spot and maybe a bit of adjusting of the cam an carbs might help

Tom

tom - is it maybe ? the exh side ? as they transfer more heat .
only stands to reason that the temp is higher on exh side over inlet .

Checked the cam and wear is evenly distributed between inlet and exhaust. The best and worst lobes are exhaust. All others have varying degrees of wear. There are two perfect lobes which I am sure were over the followers with inserts.

Now I'm going to throw a dampener on that theory as the Newman's and the Crane followers ARE NOT a chilled casting or a hardened insert as you will find if you do a rough hardness test with a centre punch that the inserted pad is actually softer than the regular follower pad as it is made from a sintered material which is a great deal softer and has a very open grain so that the oil will trapped on the followers face inproving the overall lubrication where as the harder followers will have a finer grain and will be more likely to squeeze any oil trapped between the two surfaces and wipe it dry.
The reason I asked about whether it was inlet or exhaust is because an inlet will wipe from the top of the pad downwards so it will start with the least amount of leverage increasing as it rtorates and wipes down the pad where as the exhausts start at the bottom with the highest leverage and digs it's way upwards to the top with the least amount of leverage and you will see that the exhaust tend to wear out first and as far as heat goes there doesn't seem to be alot in it


Danny

The following are photos at 32 mag of two used followers both at the edge of the contact region


Standard Follower


Crane follower with insert

The insert definitely looks like a sintered material which would act as a very good bearing material.

Not sure about the hardness but will do a test soon

Tom

Ran out of time so did not get to do too much measuring. I checked the contact patch on the follower and it was well centred so I was happy with that. I then checked the lift and I was getting 12.5 mm on both inlet and exhaust. The spec for the cam is 13.69/13.36 so I was down on the lift numbers which would indicate that the valves are too long. I checked the lift at TDC on both inlet and exhaust and had 4.55 on the inlet and 4.35 on the exhaust so the cam is advance a little. Kent spec is 4.7 on inlet and there is no spec on the exhaust. I decided to leave everything as it was. The car was starting and running well and the owner says that it is well up on power. The following is a video of its first drive after some initial setup. The carb jetting was changed and the carbs balance a bit better after this video. The very noticable flat spot down low in the revs went away after this

http://youtube.com/watch?v=1KKifvNX4-M

The engine did about 15 kilometer or possibly less of driving before its first rally this past weekend. It performed very well and did not miss a beat over two days. The car won its class 2.0L 8 valve modified class but there were only a few other cars in the class.


photo of car going through Molls Gap on the Killarney Rally of the lakes


The only problem with the car was the gearbox started leaking oil into the bell housing and the clutch started to slip on the last two stages but the driver was far enough ahead at that time to win. There are talks of putting a sequential 6 speed gearbox in the car next. The engine should also get a proper rolling road session so also to dial everything in properly.

Rgds
Tom