Pulled the DB4 Motor Today

[pwd72s]

No Hugh, just the old 911S here, but serious offers are approaching 6 figures. It's entirely possible that I have the best UN restored '72S left on the planet...I honestly can't say I've seen one I can compare mine to. I've seen gorgeous restorations, but they all look, well, restored. Know what I mean?

[efhughes3]

Hugh- As I've said before, your car is stunning. I lust for a DB4.
The red color of your car should tack on another $30K to the valuie.....

My vote is that it's in the flywheel. if you're getting that much reaction in the tranny, that makes sense IMO. If it was piston or connecting rod, wouldn't that have manifested itself into a problem with bearings, particularly at that RPM?



Other than parts sourcing, do you find mainterance and repair on the Aston to be simpler than on a 911?

[Hugh R]

Ed:

The Aston is very easy to work on. Plugs, points rotor, no smog, no brains, nothing else. Parts are a pain, but some electrical is common to older jags and healeys.

[JeremyD]

One of my favorite cars on the board Hugh - good luck with your fix.

[pwd72s]

Yeah...I hope it's something simple, a balance thing easily figured out.

[Hugh R]

Ok, here's an update. The pressure plate was out of balance by 25 grams! I don't know how the fu(k that happened. Paid to get it balanced. The shop I used before was recommended, but now out of business, go figure. The crank is straight and balanced, but its been ground 0.020" under and a least one main journal is a little rough. Can't go 0.030" bearings aren't available. BUT I found a set of new standard main bearings (a steal at $650, believe it or not). After communicating with several people on this board, I'm having the crank hard chromed back to standard and re-radius the journal sides (about $1,000). Assuming it passes straightening and mangafluxing). Rods clearances check out within spec. (2-3.5 thou.) and the new Vanolia pistons weight within 1/2 gram of each other. Big and small ends of the rods also are within spec of less than 3 grams, I have within 2 grams. Thought about getting the rods closer, but I don't have enough material at the top and bottom of the balancing tangs that you grind off that I grind off to make a useful difference, besides the rods are factory from 1960. BTW straightened very slightly and mangaflux were OK. Including machining, I MIGHT get this beast back together for under $3k.

[SlowToady]

Hot! Awesome engine.

Does doing any of that negatively affect the value, due to it not being untouched original or something?

[Hugh R]

Slo

I think it will increase the value, alot, or at least keep the value up. From what I've read, hard chroming is a good thing for an old, long crankshaft versus welding which puts lots of heat and bending into it, plus surfacing and hardening which add more heat (nitriding a crank is done by putting the crank in a nitrous oxide gas environment at 800 degrees F for a day or two), plus straightening again after. An unhardened crank has a Rockwell hardness of about 50, a nitrided one about 55 and hard chrome about 70. What people look for in an old Aston is oil pressure, oil pressure, oil pressure. The mains are supposed to be set at 1-1-1/4 thou. cold because the aluminum block expanded a lot when hot and oil pressure would go to crap. I ran my 84 Targa HARD through the Mojave desert last August and it maintained 4.5 druck all day. The Aston could never do that even if it had 1 thou of clearance. Also, while the car looks good in internet pics, its not a show car, its nice, but not a show car. Also, bringing the crank back to standard is good, because the demand for bearings is for 10 and 20 thou undersize. Here's a pic of the head as it came off the car, if anyone is interested.

[Jim2]

Hugh, that is a very interesting car. Rare to see someone stick it out and continue with ownership, versus taking the cash and running. Good for you. I've noticed it in your signature line and was always curious about it.

You say that your pressure plate is out of balance. Pressure plates are normally balanced upon being manufactured, and though the previous balancer might have screwed with it, here is something to check prior to re-assembly:

I presume the pressure plate is similar to most standard automotive pressure plate designs where the engine torque is transferred from the flywheel to the pressure plate cover, then to the pressure plate friction surface via some sets of flexible drive straps. Inspect these drive straps closely as it sounds as though one of them may have broken, or the fastening rivets at the ends of the drive straps have come loose. When this occurs the cast iron friction surface of the pressure plate can shift slightly, and cause a similar type of viabration due to going out of balance.

You also mention that the flywheel was built up with a layer of steel which was welded on. If your flywheel is cast iron, this process is not advisable due to potential internal stress, cracks, and centrifical force at engine RPMs. Exploding flywheels are beyond dangerous. Extra friction surface is best bolted on with countersunk bolts, ala aluminum race flywheels with steel friction surface bolted on. Regardless, you might inspect it for cracks around the weld, or warpage of the mild steel component which may have developed through normal use.

You might also check that they balance one item at a time. First the crank, then added flywheel and balanced it, then added the pressure plate and balanaced it. If they did the crank, then added both the flywheel and the pressure plate at once, it would be impossible to tell if it was the flywheel or the pressure plate which was out of balance.

Jim

[masraum]

I'm really glad that so far you've decided not to sell. I was bummed when you were considering it. That's an amazing car. Not only do they not make them like that any more, but they haven't in many, many years.

It's too bad you've had this problem, but at least it seems to have not been too big a hit on the wallet, all things considered.

[wheatdog]

The head design looks extremely close to the 4.2L Jag I rebuilt about 10 yrs ago. Looks like it has the same dual timing chain/intermediate gear set up with the cam adjustments at each cam gear etc. The Jag was easier to deal with due to iron block. That mother was hugely heavy!! It weighed in about the same as a 440 mopar I was working around the same time.

Mike

[Porsche]

That is one beautiful car.

[efhughes3]

Thanks for the update and pics, it's nice to hear it is going together reasonably well.

[304065]

Hugh, I saw a BRG DB5 on the streets of London a couple weeks ago and thought about this thread. Such an unbelievable car. I'm somewhat awestruck that you are able to fix up the engine for a mere $3k, that is an excellent number for anything from Newport Pagnell. Way to go and keep the cool photos coming.

[Hugh R]

Thanks all for the encouragement! Hey Jim, yes, its a standard pressure plate in that it is the type with flat steel springs, I think its called a Laycock-design, as opposed to the ones that have lots of coiled springs and three "fingers" I had one of those once and it kept slipping. The flywheel is turned, not cast. Upon inspection, I found that the PP had a hunk of metal welded to it from years ago that put it out of balance, don't know why. When I rebuilt it five years ago, I had new pistons made which weight about 2/3 of the original pistons, and are well balanced. It always ran a little rough in terms of vibration, but after the rebuild, I think the only thing really out of balance was the PP and the vibration became more pronounced. I'd had the car apart for so long that when I put it back together, I thought the vibration was the trannie coming apart, because that's where the vibration manifested itself. Took the trannie apart and put it back together and the vibration was still there. Running the engine with the trannie out,and the flywheel and PP on you could barely feel the vibratiion on the engine. Also, yes, we're balancing the crank, then flywheel and then PP one at a time and then checking the whole thing. I really don't want to take this thing apart again in my lifetime. The reason that I MAY be getting off so "cheap" is that the pistons, chains, gears and entire head were gone through five years ago and not that many miles ago. Thanks again. I'll post more pics when I start to put it back together.

[lendaddy]

We have used industrial hardchrome serveral times on the tooling for one of our machines. It is VERY hard indeed, but it does chip under the right(wrong) circumstances. I can't imagine wet bearings being one of those however.

Very cool project, very interesting. And once again just a stunning car!

[Hugh R]

Ok, I'm going with the hard chroming back to standard. I got a new set of standard mains and if everything measured out right, I SHOULD end up with 1.2 to about 1.6 thou. clearances. I get the crank back in two weeks. In the mean time, I'm just screwing around with a little cleaning here and there.

[Porsche-O-Phile]

Where's the switch for the twin .50s?

[beepbeep]

Some OEM and aftermarket pistons have piston bolts (the cylinder that keeps the piston attached to rod) cast slightly off-center, which means that pistons need to be installed in right direction.

I don't know if this is the case in your engine but it's worth checking out.

Great car and great pictures! I really enjoyed reading this thread.

[VINMAN]

Hey Hugh, I have a couple of major HP Big Block Chevys layin around the shop we can drop in there!