Broken Engine ....

[pasini s]

Dear BOC friends,

this is more or less the tale of a developing catastrophe.

I started last Tuesday from Bologna with Anna on our 409 to deliver it as planned to Bristol Cars Services Friday Aug. 19th; the idea was to leave the car to mr Marelli for some repairs/adjustments, fly back to Italy until September 17th and pick it up to join the Bristols-to-Bristol Run.

We stopped in Sankt Moritz (where we picked up close friend and the only other BOC member in Italy, dr Marco Makaus) and Illhaeusern, the car running perfectly. Thursday morning we started from Alsace for the last leg of the trip to London; sadly, the oil pressure began to fall after Basel and even feathering the throttle, the needle fell slowly to 45, 40, 35 psi, without any worrying noise.

Disaster struck as we were entering the Meuse Department, the car suddenly slowing down with the oil pressure abruptly falling to zero and the temperature rocketing to 120°C (it had been 85° all the time), the engine stopping abruptly. We waited a few minutes, but when I restarted it the V8 made a loud clonking noise; main bearings gone for sure, I'm afraid.

The recovery truck carried was mercifully quick and carried the 409 to a nearby depot where it would have to be recovered this afternoon or tomorrow and transported back to Italy for what seems an unavoidable, complete engine rebuild. What makes me sad is that we will not be able to join the Run, after we had so carefully planned the whole thing months in advance....

I'll keep you posted about what Marco Gordini will find when he pulls out the sump of the V8. Lots and lots of tiny metal shards and the perspective of a HUGE bill, I'm sure.

Cheers from Italy,

Stefano

P.S.: how come I do not receive any more messages from the BOC in my mail folder?

--
Dr Stefano Pasini
Bologna
Italy
Stefano Pasini's Homepage

[Thor]

Sorry to hear of this failure. I have noticed your comments and other peoples' comments on the BOC forum.

If the engine was running fine but with low oil pressure, I wonder if the failure was down to a gradual loss of drive in the shaft which drives the oil pump and distributor at the back of the camshaft. This is a complete guess but I can't understand why the pressure would drop off slowly. Then I thought that if the ignition timing subsequently slipped a bit tom give a retarded timing, then the engine would run hot.

If there does turn out to be a problem with the drive and the oil pump then you should know that the oil pumps and oil pump drives from the later Mopar 318 engines also fit your engine.

As has been mentioned on the BOC forum, the 407 to 410 Bristol engine is called the 'Polysphere' engine. This started in production when the very original Hemi was still made. (The late 1960s - early 1970s Hemi was the second range of engines to bear that name.) This 'Polysphere' engine (273 313 318 ??) was originally called the 'A' engine in the late 1950s, but when the later A engine came out in the late 1960s (318 - 340), they did not give it a new name. When I talk to American Mopar people I call it "The early A, polysphere engine" in the hope of not being misunderstood.

Now the Block it self is not interchangeable with the later engines, but the crank can be, although the rear main bearing is a bit different, so you may need bearing shells from the later engine to get a good result. I think it follows that both main and big end bearing shells from later engines should be useable if earlier parts are not available. The oil pumps and distributor parts are also interchangeable. The pistons and rods are not exactly the same but if you can't get the original type of piston and rod it should be possible for a good engine builder to make a perfectly good engine using later pistons and/or rods in your early block. So you could rebore the block +20 thou and use modified late 318 +20 pistons if they are of a type to give a suitable compression ratio. I think they would be pistons giving a low compression in a later engine to be useable for a sensible ratio in the early engine.This would have to be done by a good engine builder with a good understanding of USA V8s.

The cylinderheads are completely different. They are in fact very good heads for performance, but they were more expensive to make than the later wedge heads. The heads and blocks of the polysphere engines are rather heavy compared to the later designs, as well.

That's all for now.

Thor.

[pasini s]

Dear Thor,

thank you for your informative message. I've passed it to my mechanic to warn him to take a close look at the oil pump/distributor drive; as he is now disassembling the engine, I hope that in the next few days I'll know what caused this very annoying failure. I'll keep you posted. Thank you again!

Stefano