Wow, did not realize the 4.7L were square bore motors (bore/stroke same).... No wonder its such a well balanced motor. 91mm bore / stroke is already pretty aggressive, I don't think you really need to go any bigger than 4.7L to get stupid power. I don't see why 490+ isn't easily obtainable with more rpms and full free flowing exhaust & tune.

Based on these most recent V12 issues I have been hearing, that only makes the case for the later 4.7L Motors even stronger. I think that has confirmed my choice of Vantage S.

 

Bamford Rose have the 4.7 to 450 BHP in GT4 spec & manifolds/cats, with the N400 intake and twin throttle inlet manifold they can get close to 490 BHP
They have also developed a 5.0 conversion get up to 550 BHP!
Who needs a V12.
You just need deep pockets

 

490hp in the 4.7 is more than enough power IMO, when you factor in the almost 200lb difference between the V8 & V12 that puts them at almost identical power/weight ratio

 

So true...as the GPA approaches 0, so does the likelihood of becoming a business major.

Love it !!

 

Engine balance does not have a lot to do with a motor being square or oversquare. V8 engines are balanced with bob-weights. The weight of this bob-weight is calculated based on 100% of rotating and 50% reciprocating weight of engine components. Every time you change out for a heavier, or lighter, connecting rod or piston you have to rebalance the crankshaft.

91mm bore being aggressive is a relative term and all depends how much parent material you have in the block to allow overboring or support the sleeve you have. Subaru 2.5L flat 4 engines have a 99.5mm bore stock. Going to 101mm on stock sleeves in those motors is not possible and not advised. On the other hand Nissan sr20(2.0L I4) has an 86mm bore and when sleeved can be safely bored to 90mm.

Overboring the 4.7L AM from 91mm to 93mm is possible with respect to bore spacing and material left for proper headgasket sealing but it is not possible with stock iron sleeves. So if you really wanted to do it you can but it is not easy or cheap since sleeving the block is required.

 

Horsepower goal is a relative term. To some a 500hp car is something fun to play with, while others its a dangerous scary weapon. I met Tonis Kasemets on several occasions. He drove the Vantage V8 and said the car is a dog. I would be more concerned with weight reduction than power adders. Tonis Kasemets use to drive Formula Atlantics. I met him years ago through my mentor and then one day I stopped by a neighbor's CNC shop and he was there on a lathe making some parts for his person projects.

Pictures of Tonis:
http://multimaticmotorsports.com/pho...ce-day-barber/

 

It is strange not to find bearing clearance or piston ring specifications in a 800+ page service manual but that is the case for a lot of "high end" cars. I have the service manual for the Vantage V8, Vantage V12, and the DB9. They list torque specs but not bearing clearances. They expect you to read journal size engraved on crank, read housing size engraved on block, and find correct bearing in a spreadsheet. Working backwards from then recommendations I purchased 2 of each grade bearing shells from Jaguar dealer(same bearings as AM) and went through the time consuming process of installing shells, torquing the caps, and checking clearance. This process I repeated for all grade main and rod bearings.

My friend recently fried an engine in his 997 Carrera S and asked me if I wanted to take a stab at it. I sources the complete 997 service manual and then same clearance and ring gap situation exists.... there are none.

This rebuild after all was said and done cost about $15,000. That includes all machining, custom parts, oem AM parts, and labor.

 

By Well balanced I meant Balance of HP & TQ in the powerband, not the actual "balance" of the engine, that part is obvious lol.

 

Until you mod a v12, now we're taliking 650 - 700 bhp... All things considered in the NA world without forced induction, v12>v8 stock to stock and modded to modded, any day of the week and twice on sunday ! Besides the torque, power deilvery, and glorious sound of the v12 is unmatched!

 

this! :-)

 

Not sure but I think BR use the same crank on their 4.3 to 4.7 GT conversion.

 

Impressive work and nice writeup/photos. Thank you for sharing your knowledge - people like you are what make the internet so great!

 

Did you get a chance to degree the cams?
I would be most interested in this data.

 

I have to look back in my notes for details. I checked camshaft lift and total duration. I did not check camshaft opening and closing. Static numbers do not mean much on these motors anyway since the intake camshafts have timing phasers and the ECU constantly changes timing. If total duration, both seat-to-seat and at 0.050", is known then the diagnostic scan tool can be used to check camshaft timing at different engine RPM and loads. (at least I hope it can be).

 

Wow! good job on the rebuild! I'm looking at a 2009 vantage which is flooded but i don't know if the engine was running at the time. Do you think it's worth getting a flooded aston martin?