Needed a new challenge... rebuilt Vantage V8 4.7L engine last summer

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  1. #1
    Pavel is offline Junior Member
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    Default Needed a new challenge... rebuilt Vantage V8 4.7L engine last summer

    I would like to document an engine rebuild I did last summer on a 2009 Aston Martin Vantage V8 4.7L. Engine was seized due to oil starvation and spun main bearings. Even with all bolts loose on the main bearing girdle, and myself hanging on a 3 foot breaker bar off the crank pulley, it would not turn.

    I called Lake Forest Sports Cars in Lake Forest, IL for parts. Right away I was told they can sell me everything needed except engine bearings. Those were not available at all. I could have went next door to Imperial Jaguar, but I had a better idea in mind. I contacted ACL bearing company to discuss custom bearing options. In the end of the day I was able to source main and rod bearing in tri-metal contruction from the ACL Race Series.

    Original fasteners in the engine were torque to yield design. This means fasteners have to be replaced every time they are tightened and loosened. Official Jaguar and Aston Marin literature suggest main and head studs can only be tightened 2 times before requiring replacement. I contacted ARP for custom fasteners. Head stud option from ARP was possible at a cost of almost $1000 for a set. It did not seem bad for custom made studs but the lead time of almost 10 weeks was a definite turn-off. I talked to ARP about main stud as well and they were of great help. They were able to provide main studs at a very reasonable price and shorter lead time.

    I contacted CP/Carillo for forged piston and connecting rod option. Cylinder bores were worn and AM does not offer an oversize piston option from the dealer. I sent a sample piston, pin, clips, and ring pack to CP for measurements. Three weeks later I had a set of forged piston in 0.5mm oversize. Carillo made a set of connecting rods as well. They are H-beam design and actually lighter weight than the stock powder metal units. Carillo rods were made in custom big end size, crankshaft rod journal was machined smaller in custom size as well, so that an off-the-shelf ACL Race Series rod bearing could be used.

    There was a lot of machining involved in repair of this engine. Oil starvation cause then engine to seize, crankshaft damage, camshaft damage, and cylinder head journal damage.

    Block machining:
    1. cylinders bored/plateau honed
    2. crankshaft main journals align honed

    Crankshaft:
    1. rod journals spray welded
    2. rod journals reground to custom size
    3. main journals reground 0.010" under also for custom size bearings
    4. custom wood-ruff key machined from 4140 chrome molybdenum steel used for retaining oil pump gear

    Cylinder heads:
    1. camshaft journals polished(luckily did not require grinding)
    2. cylinder head journals align hone to size(way too much oil clearance)
    3. cylinder head machined for exit of align hone mandrel in Bridgeport mill
    4. cylinder head plugs machine in a CNC to be used after head is align honed

    Pictures say a 1000 words so I will proceed.

    Engine disassembled for inspection to find the following carnage:

    metal in the oil pan




    This is how pistons looked


    Disassemled the oil pumps and rotors were worn


    Crankshaft journals


    #3 rod pin was damaged the most requiring spray welding and regrinding


    Custom forged piston from CP (comparison to stock)




    Custom forged connecting rods from Carillo (comparison to stock AM 4.7 and jaguar 4.2)


    Crankshaft after machining and plasma nitride treatment




    Complete rotating assembly


    Checking piston ring gap


    Filing piston ring gap with a grinder


    ACL Race Series main bearing close-up


    ARP main studs


    next time I would like to machine out the small M8 outer studs and convert them to M10 just like the ARP inner studs. This will make for a tru 4 bolt main engine.

    Girdle tighetened


    Rods on the crankshaft


    Pistons in block


    pip, Roland and MazzaFiveOneFour like this.
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  2. #2
    Pavel is offline Junior Member
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    Additional Pictures:

    Rod bolts tightened using a rod bolt stretch gauge, not a torque wrench. This is a more accurate method.


    Machining performed on the rear of both cylinder heads to allow align hone mandrel to overstroke the journals


    CNC machined inserts that were later cut in half and used as plugs in the back of the cylinder heads


    All valves refaced using a Sunnen centerless valve grinder, hand lapped, and seal checked with Prussian blue


    Closeup of combustion chamber


    Cylinder head with caps on


    This fixture was used to measure valve spring install height and check stock valve spring pressures


    Combustion chamber and piston dish volume measured and exact compression ratio calculated and confirmed


    Aston Martin does not positively fix the oil pump drive gear to the crankshaft. This gear is held in place by friction and the torque when it is pressed between the timing chain gear and the crankshaft sprocket. If the crankshaft pulley bolt loosens the engine will keep spinning but the oil pumps will stop, causing catastrophic engine failure. This billet 4140 key was made to retain the timing chain gear and oil pump gear together. Next time I would like to machine the crankshaft snout to accept a full size key.








    Cleaned dry sump oil pan


    Dry sump oil pumps installed


    Engine assembled and camshaft degreed


    So far the engine has 2,000 miles and runs flawlessly. The car had to go back to the dealer only to have the transmission recalibrated.
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  3. #3
    chidoks's Avatar
    chidoks is offline Senior Member
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    This is badass.. Stock compression? Any plans for forced induction in the future?
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    Sikklightning's Avatar
    Sikklightning is offline Senior Member
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    very cool!
    A world where medical advances allow us to live forever is a terrifying thought...
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  6. #5
    .G.'s Avatar
    .G.
    .G. is offline Senior Member
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    Very nice write-up. I love threads like these.
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  7. #6
    Pavel is offline Junior Member
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    Quote Originally Posted by chidoks View Post
    This is badass.. Stock compression? Any plans for forced induction in the future?
    Compression increased slightly to 11.5:1 due to bigger displacement with cylinder overbore. Intent was a more reliable engine rather than performance gains.

    Next V12 DB9 engine will be a much more performance oriented project
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  8. #7
    SpecB's Avatar
    SpecB is offline Senior Member
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    Wow, right on!

    Awesome project, thank you for sharing!
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    Quote Originally Posted by Pavel View Post
    Compression increased slightly to 11.5:1 due to bigger displacement with cylinder overbore. Intent was a more reliable engine rather than performance gains.

    Next V12 DB9 engine will be a much more performance oriented project
    11.5:1 on a V8 Vantage? That seems like alot. What was stock compression?

    BTW, just from the instruments you used to complete the build, I can tell this is a quality build. Good job man, I know that this takes MUCH more effort than it seems.
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    Diego V's Avatar
    Diego V is offline Senior Member
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    Does AM not have replacement engines? Or was this a more cost efficient way than a full replacement? or just for performance?? I always wondered why would people not put more miles on their higher end cars. I know depreciation is one thing, but do engine replacements cost that much?

    Great work BTW! do you own your own shop?
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  11. #10
    Pavel is offline Junior Member
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    Quote Originally Posted by Diego V View Post
    Does AM not have replacement engines? Or was this a more cost efficient way than a full replacement? or just for performance?? I always wondered why would people not put more miles on their higher end cars. I know depreciation is one thing, but do engine replacements cost that much?

    Great work BTW! do you own your own shop?
    AM wants $28,000 for V8 longblock and $34,000 for V12 longblock. You have to give them your old motor as core. If there is any damage to the block, even spun main bearings, they charge you full price and don't accept core. I think core charge is in the neighborhood of $12-15k. This rebuild with all custom made parts and immense amount of machining was still $20,000.

    Better motor, stronger components, less money= Win :-)
    Chevelles and Diego V like this.
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