I have gathered a treasure trove of parts through the years and I’d like to put some of this stuff together. Please feel free to shoot down the idea but explain why. If moving forward makes any type of sense feel free to fill in the gaps or point me in the right direction.
Somehow I’ve managed to accumulate my fair share of 5.3 & 6.0 HE engines, Pre HE flat heads, AJ6 Engineering Pre He intake trumpets, new HE Pistons, new cylinders, completely rebuilt & upgraded Getrag R154 transmissions, Getrag dogleg 5 speed trans, Lister 5.3 5 speed 3.54 parts car, and many more parts that are to numerous to mention.
I’m guessing a standalone ECU will have to be sorted but that conversation is outside the scope of this fact finding subject matter.
So here are the two scenarios that I have in mind:
Mount Pre He heads on a 5.3 block
The reasoning is the 5.3 is over square which (IMHO) makes is a much sweeter engine and much more lively and free revving.
Is there any additional hp to be gained?
Is this worth the trouble?
Mount Pre He heads on a 6.0 block
The reasoning is the 6.0 starts with about 325 hp right out of the gate.
I’m not trying to answer my own question here but should this head swap be all about hp with nothing else to be considered?
Is there any additional hp to be gained?
I am fairly certain that utilizing the Pre He heads in either scenario will require custom dished pistons but my guess is I’d have to have at least one Piston as a guide in order to have new ones made some specified spec, which brings me to the question of compression. What would be the ideal compression to be built into the pistons that will allow the engine to run on high octane fuel throughout the country? More specifically I’m thinking of places out west like California. Many places only have 91 octane and these days one really has to sniff out fuel stations that sell Ethanol free fuel.
What head gasket to use?
Because where talking 12 cylinders I guess that means the added expense of two sets if they are normally sold in sets of 8.
What about rods? Would new rods be required?
It would be foolish of me to think that any one so called upgrade would in and of itself make the world a better place. Finding nirvana will encompass the full breath of the build and will include implementing an AJ6 intake runner, two larger throttle bodies, Euro down pipes, full custom 2" exhaust (curtesy of an old contributor Rob Wade), 5 speed transmission, 3.54 or 288 rear?, and 18" wheels.
AFAIK (correct me if I’m wrong) other than refinement there doesn’t seem to be any real differences in any of the camshafts between V12 models. Having said that, I do have a pair of Isky cams although I don’t know the profile.
Should there be any fear of enlarging the cylinders to accept larger pistons? If so, how best should this be accomplished? Would boring be safer if the cylinders were mounted in the block first or would free standing be ok?
Again, correct me if I am wrong, AFAIK boring the cylinders will yield way more torque than it will hp. HP will come from the compression built into the dome of the piston in relation to how well the heads are setup? Which would be the reasoning behind utilizing the flat heads in the first place? Although, I’m sure Chad Bolles would beg to differ.
The purpose of the exercise:
I spend a fair amount of time driving between coasts and anyone that has done it can share their own experiences dealing with altitude and mountain passes. Colorado, Nevada, and California quickly come to mind and IMO driving around just about anywhere else is child’s play in comparison. Out west is where you truly get to see what you brung.
As an aside, I picked up a really nice low mileage 4.0 XJS convertible from guy in Sacramento over the holiday’s. He told me that he had checked the oil and charged a new battery that had gone flat from sitting in the garage (I still have to track down the cause of the parasitic battery drain). He handed me the keys and I climbed into this completely unknown XJS without ever once pulling the dipstick, nor checking the tire pressure. I gassed her up and proceeded to drive the 2k miles home. On two separate occasions the car failed to start after cranking (panic set in) but after waiting a few minutes she fired right up both times (haven’t had a chance to look at it yet but hoping it’s a ground wire). Morel of the story, I love the car but will never look to drive it across country again. That little 4.0 engine makes for a great local grocery getter but a cross county runner, not so much.
I’m looking forward to the prevailing words of wisdom.