Forum Chat #25 – Engine Rebuild Data

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Welcome to Bamford Rose and another forum chat. As ever, it really helps us if you can like, subscribe, hit the bell for notifications and give us your comments and feedback, we’d really appreciate that.

This week it’s a post about engine rebuilding and somebody has had an issue with their engine. I think in this particular case, it spun up bearing and it needed to be rebuilt. They’ve posted a picture of the engine showing the ladder frame to crankcase bolt and the big end cap bolt, and asking for torque figures.

This is because when the engines were released V8 and DB9, the dealer network was never trained on engine rebuilding. And because of the complexity and time it takes to rebuild an engine, the approach from the factory was to treat the engine like a box. Remove the broken part and fit a new part, an entire new engine. Obviously, this was hideously expensive. The independent world started to rebuild engines when needed to. And the factory then kicked in to supplying remanufactured engines and those remanufactured engines for V12, it’s starting price is 9000 plus VAT. For V8, I think it’s about 10.5-11 plus VAT. That’s actually quite a reasonable price for a remanufactured engine. It makes rebuilding difficult to compete with because we have to buy so many parts that by the time you’ve accounted for the parts and labor our rebuild cost is often more than the remanufactured cost.

So, anyway, somebody is trying to rebuild their own engine. Just before issuing that remanufactured engine, the factory did have a training course for all technicians from dealerships. They could go on to rebuild engines and they were issued I’m sure with build instructions. Previous to that, there were never any build instructions for engines in the Aston Martin world, so there’s no bearing specification, no piston liner specification, and importantly no torque figures. So, these particular two bolts, most two important bolts on the engine torque up and there’s no data out there. And he’s come on a forum asking for data. You know, those of us involved in engine design development. We’re the only ones that are going to remember all of that data and have it to hand.

Some people have come on that forum and stated that it’s a bit of a trade secret. I sort of don’t get the trade secret. There isn’t the power. Knowledge isn’t the power here. So, if anyone knows what torque figure is? Does it really matter? Because the most important thing on an engine rebuild is making sure the liners and piston rings are correctly spec, the bearings are correctly spec and that crankshaft pulley has done up to a [inaudible 03:46], it doesn’t fall off in the car. You know, so it’s actually engine build craftsmanship that’s more important than knowing certain torque figures but anyone that knows them sort of isn’t going to give that data out.

This particular chap, I don’t know, if he went off into the Jaguar world, then it’s the Jag AJ V8 engine, then it’s a sintered rod on that application, so you can probably get your bearing, cap torque from that and the ladder to block. Well, it’s exactly the same bolt, exactly the same ladder, exactly the same crankcase, pretty sure that torque carries over. So, you know, there’s options. There you can get it from the Jag world.

But I’m not that concerned, you get the torque figure from those ways and means, but how did you spec bearing grades because this is in the build book. Unless you have the build book, you don’t know what bearings to pick. So, you know, there’s a few more bits of information to be worried about other than bolt talk. But yeah, that’s why engine build in the Aston world is sort of guarded, secretive or non-existent.

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