4.7E or 5L hybrid...... Choices choices
07-24-2010, 11:40 AM
#61
Thread Starter
Thats true! one of the things i am thinking of doing is building this motor with the TEC GT engine system in mind. so that would defiantly help in the tuning area.
08-06-2010, 04:08 PM
#62
Thread Starter
Alright so i got good news and bad news from the machine shop today. the 4.7 number 5 cylinder is ballooned out .006 at top and tappers to the bottom. the 4.7 crank checked out great. the 5.0 has a scratch on number 1, but looks worse then it is, the shop thinks there is no reason not to run it. the 5.0 crank has to be ground and the connecting rod ( #6) was fixed. so on the one rod i will need 10 under bearings, but the rest of the block looks good.
sounds to me that the 4.7 is a good candidate for steel liners and stroking.
thoughts?
Duc
sounds to me that the 4.7 is a good candidate for steel liners and stroking.
thoughts?
Duc
08-06-2010, 08:39 PM
#68
Nordschleife Master
Bores aren't plated, not if you use a Porsche piston that coated. You bore, then lap the surface to expose the silicon. What I don't know are the normal oversizes for pistons.
08-06-2010, 10:22 PM
#70
The entire engine is alusil - something like 14% silicon in the aluminum. Hyperuretic I think its called. Anyway, its cast this way, and the bore surface is honed in a final step with FELT PADS and PASTE, which slowly wears away the aluminum but allows the silicon to stand proud. This is what the piston rings ride up and down on.
08-07-2010, 12:31 AM
#71
Nordschleife Master
First oversize 97.50mm is about 3.8385826771695
Stock 97mm is about 3.8188976377994
thats about .020 inch, seems like it might work, if a source for one oversize piston could be found.
Stock 97mm is about 3.8188976377994
thats about .020 inch, seems like it might work, if a source for one oversize piston could be found.
08-07-2010, 01:10 AM
#72
Nordschleife Master
The entire engine is alusil - something like 14% silicon in the aluminum. Hyperuretic I think its called. Anyway, its cast this way, and the bore surface is honed in a final step with FELT PADS and PASTE, which slowly wears away the aluminum but allows the silicon to stand proud. This is what the piston rings ride up and down on.
Do NOT hone the cylinders in a 928 with stones.
There's been more than a few people who arrive on rennlist saying their compression is low, or they had excess oil consumption, and when they opened up the engine, it still had all the cross-hatch like new. What they mean is they took (or the PO) it to a mechanic who wasn't competent to work on an alusil engine, but who charged them an arm and a leg to do the wrong stuff to it.
08-07-2010, 11:17 AM
#73
Thread Starter
Just in case its not clear from Brendan's post.. and for the benefits of others reading..
Do NOT hone the cylinders in a 928 with stones.
There's been more than a few people who arrive on rennlist saying their compression is low, or they had excess oil consumption, and when they opened up the engine, it still had all the cross-hatch like new. What they mean is they took (or the PO) it to a mechanic who wasn't competent to work on an alusil engine, but who charged them an arm and a leg to do the wrong stuff to it.
Do NOT hone the cylinders in a 928 with stones.
There's been more than a few people who arrive on rennlist saying their compression is low, or they had excess oil consumption, and when they opened up the engine, it still had all the cross-hatch like new. What they mean is they took (or the PO) it to a mechanic who wasn't competent to work on an alusil engine, but who charged them an arm and a leg to do the wrong stuff to it.
