B18A Engine Block queries

[sleek lemur]

Yes, things have moved on. We're lucky in the UK to have Brookhouse as well, who can recommend combinations of parts to get the results I'm looking for.

Took the block, head and crank to the machine shop today. One of our correspondents on this forum suggested that the damage to the 5th main bearing thrust face could have been caused by the clutch and this is immediately what the boss of the shop suggested. He sees this damage often caused by people sitting at traffic lights with the car in gear. Luckily he pronounced the crank in good condition.

His method for shiifting the oil gallery plugs is to weld a lever to them...

In view of the age and high mileage of the engine, he recommended replacing valves and springs. Sounds like I'm going to need a new rocker shaft and....

Plenty to do now, starting with giving the garage a good clean.....

No doubt, as soon as I pick up the next part, I'll be back on the forum with more questions!

[142 Guy]

I am not denying its possible; but, I am struggling with how riding the clutch at a stop light could cause damage to the thrust surface on the rear main bearing. Premature wear on the release bearing and fork, absolutely; but, damage to the thrust bearing, not seeing it.

That said it is good that the crankshaft appears in good condition otherwise that would put a serious financial dent in the rebuild plans.

[sleek lemur]

Well, the fellow was absolutely clear that he had seen this many times. He went on to say how in extreme this causes wear/damage to the crankshaft and can result in it moving fore and aft as the clutch is depressed. He mentioned the Triumph 6 pot engines from the 60s and 70s were particularly prone and coincidentally I had suffered this on a TR5. The car was crunching it's gears, even after rebuilding, then replacing the stave cylinder. I remember I was living in a rented bedsit and was working on the car in the street. I changed the clutch after work one night, problem still existed, the did the whole thing again the following eve, thinking I might have reversed the clutch plate.

I had read about the crankshaft issue and with sinking heart to my disgrace, on night three I solved the problem by threading a stack of nuts on the slave cylinder actuating rod. I then sold the car and bought a Volvo 1800S for £1,600!

PS, damage to block is easily repairable.

[Vintagewrench]

Originally Posted by sleek lemur

Well, the fellow was absolutely clear that he had seen this many times. He went on to say how in extreme this causes wear/damage to the crankshaft and can result in it moving fore and aft as the clutch is depressed.

Yes, it is a fairly common issue caused by abuse and I've seen it quite a few times in engines that come into the shop for rebuilding. Follow this link to "Motor" to learn about the various different causes of this wear and how to prevent it @ https://www.motor.com/magazine-summa...ntion-analysis

[Derek UK]

AFAIK the Volvo crank design isn't prone to this problem. The Triumph engines are prone and a test is to use a lever on the front pully. I think that thrust shims are used to get the correct "float". The shims then wear and are replaced as required. When worn the crank moves forward when you dip the clutch.

SL, are you willing to reveal the shop you are using for your work? Ask them first maybe.

[sleek lemur]

Coltec near Woodbridge in Suffolk. Recommended by a friend who has used them for years, and his father before him. Very approachable and patient with questions from a novice.

I used B&E Randall in Stanton for my B20 and was very pleased with them. Brian Randall used to build Volvo race engines in the day !

Scholar Engines are only a mile away from me and I know Amazon Cars use them. I did call them, but I was put off by something in their answerphone message. They sounded a bit unapproachable. Perhaps more used to dealing with people who know what they are talking about! They do have an excellent reputation.

[sleek lemur]

Originally Posted by Vintagewrench

Yes, it is a fairly common issue caused by abuse and I've seen it quite a few times in engines that come into the shop for rebuilding. Follow this link to "Motor" to learn about the various different causes of this wear and how to prevent it @ https://www.motor.com/magazine-summa...ntion-analysis

Thanks for this article. The bit on the extra care to be taken when installing the main bearings is really interesting. I need to read up on this stuff or I'm going to make some expensive mistakes, so this is much appreciated.

I have much to learn (was that a line from Kung Foo Kid?).

[142 Guy]

Originally Posted by Derek UK

AFAIK the Volvo crank design isn't prone to this problem. The Triumph engines are prone and a test is to use a lever on the front pully. I think that thrust shims are used to get the correct "float". The shims then wear and are replaced as required. When worn the crank moves forward when you dip the clutch.

This I can understand. Excessive clearance on the crankshaft thrust faces results in forward movement of the crankshaft when the clutch is depressed.

As to the Motor article, I suppose that it is possible that if the rear thrust face is of marginal design or the car is equipped with a performance clutch with high clamping force riding the clutch could result in wear on the rear thrust face (which is there to restrict forward movement of the crankshaft). However, I would have thought that type of wear which could result in excessive thrust bearing clearance would cause circumferential scoring of the thrust face associated with lubrication failure, not the gouges in the thrust bearing surface present in Sleek Lemur's bearing.

Perhaps at this point more of an academic interest.

[sleek lemur]

I must admit that my damage does look more like trauma than wear. Luckily it's an easy repair. The Motor article pointed to the likely fault being somewhere in the transmission.

[Vintagewrench]

Originally Posted by 142 Guy

Perhaps at this point more of an academic interest.

Yes, with Volvos its not an issue. The link to "Motor" was included only to show that it can be an issue with some thrust bearing designs that are abused.