D612 PNT One of these days...

Moderator: The Midas Forum Staff

Re: D612 PNT One of these days...

Postby ACourtney » Tue Jul 04, 2017 9:07 pm

With a new BBW needle fitted Ralph was able to get the mixture set properly and the car ran smoothly at last. A power run revealed that the engine had a really good spread of torque, giving over 90lbft from 2500 up to 5500 rpm. I can't recall the peak figures, they were something like 96lbft and 98 bhp, but it was the wide flat torque curve that left the biggest impression and that was confirmed when we subsequently took the car on the road.

Ralph then surprised us by saying that he didn't think that it was worth optimising the setup just yet as he felt the engine needed to bed in again after being laid up for so many years. In his view if he optimised the engine there and then all the settings would drift from the optimum as the engine bedded back in. He then surprised us again by taking the oil filler cap off and sticking the exhaust gas analyser probe inside. I've certainly not seen that done before, but what Ralph was looking to show us was the relatively high CO level inside the engine - the sign of some combustion gases blowing past the rings. Ralph's view was that the level of CO indicated a small amount of blowby, most likely due to localised circles of glazing where the rings had been sat static over the years. If an engine isn't turned over regularly then the contact points, i.e. the piston rings and cylinder bores, start to form metallic bonds and this leaves a small ring of glazing on each bore.

Ralph's advice was to treat the engine as if it was going through the second phase of being run in. The prescription was to use basic 20w/50 mineral oil (synthetic oil works too well such that it can prolong the running in period) and change it after 1000 miles and then change it again after 2000 miles and then again at 3000 miles. Chris could use all revs across the power band, but not work it too hard in the first 1000 miles. After completing the three 1000 mile service periods, the engine should be bedded in again, but Ralph said he would want to check that the blowby had reduced before doing a final setup.

Chris reached the 1000 mile mark earlier this year and brought it over to my workshop for a service. The oil level had kept up well and the oil was looking nice and clean on the dipstick, but we were in for a surprise when I drained the oil out. It seems that the oil filter had been doing a fine job as the oil at the top was nice and clean, but as the oil drained from the gearbox it carried out a black sludge that hadn't been evident on the dipstick. I imagine that the sludge had formed during the period that the car had been laid up and had stuck to the surfaces inside the engine so well that it resisted the flushing oil I used. Then during that first 1000 miles the sludge must have loosened off after several temperature cycles. The sludge also showed the wisdom of the early oil change approach. The magnet on the drain plug had collected a small amount of fine swarf, perhaps what you might expect to see after 6000 miles, or so. Hopefully when Chris brings it back for the second service there will be no signs of sludge and swarf will also be reduced.

Chris reported that the engine had been running well, but he had experienced a couple of instances of clutch slip. Since the clutch had only seen a small mileage we wondered if there might be some oil leaking from the crankshaft seal into the clutch housing. I sprayed some brake cleaner into the bellhousing, whilst Chris cranked the engine over, with the objective of clearing any oil off the clutch plates. This cured the clutch slip for Chris's homeward journey and I'm waiting to hear if he has had any more instances. Unfortunately, if it is oil getting on to the clutch then eventually the leak will have to be identified and fixed and the clutch plate will probably also need replacing. However, this can be warded off for some time with regular applications of brake cleaner, or Coca-cola. Yes the brown sticky drink has many automotive applications, but probably none more famous than when Jaguar won Le-Mans in 1988 by dousing the clutch with Coke, to ward off clutch slip, at each pitstop in the last six hours of the race.
User avatar
ACourtney
 
Posts: 488
Joined: Thu Dec 04, 2008 12:22 pm
Location: Oxford

Previous

Return to Mk 3 Coupe

Who is online

Users browsing this forum: No registered users and 2 guests