... Originally I had 190psi cold, within 10% all cylinders. Now I have 170psi average, with cylinder 4 at 125 psi and cylinder 8 at 135psi. I believe that's all I need to convince me.
You are reading the tea leaves correctly the rings their ring seal are tired and need to be freshened up. In the rings department you want to use a TotalSeal AP Steel or Stainless Steel top. With today's ring technology I would opt for the AP Steel Top. TotalSeal also offers a Tool Steel Top ring, a little more pricey but also a little better. That said the AP steel ring is the right pick 95% of thtime.
For a second ring you want a TotalSeal cast iron second with a Napier cut edge that helps squeegee excess oil the oil ring missed off the cylinder walls. This will help avoid detonation used by the oil's presence in th combustion event.
For your oil ring (and all your rings) you want to use a 0.005" oversize ring set. The oversize will also apply to the oil ring expander / rail combination. It will provide a little higher oil ring tension which is good for blown engines - again it is another assist in keeping unwanted oil out of the combustion chambers. If anyone attempts to persuade you to use a low tension oil ring they are uninformed about building supercharged race engines. Politely acknowledge their contribution and go elsewhere for your engine building counsel.
I hope to be able to keep crank, rods, heads and cams. I may change pistons for higher comp (I'm running 114 octane) if they don't mic round anymore. Also, I'm tossing the block to go to the aluminum block for weight savings.
As long as they pass inspection (and they should) there is no reason the crank and rods can not be reused as long as they are both the forged steel variety. All Kellog cranks were forged steel so you are good to go there as long as you are sure it is a Kellog. If the rods are Manley H-Beams they are forged 4340 steel and reusable. Be sure to have their big ends checked for concentricity. your machine shop has the required equipment to make this determination. If the big ends need to be rebuilt then freshen them otherwise they are good to go. If they use 8740 rod bolts you ought to replace them with ARP 2000 bolts. Small cost but a big improvement in bolt toughness.
Your pistons will need to be changed out. Unless specifically called out on the original custom piston order all pistons from that time period are highly likely to have thin skirts which collapse under supercharged loading allowing the piston to rock in the bore and rounding the faces on the rings and progressively reducing their sealing quality. This could be part of your compression variances ad losses cylinder to cylinder. I can not recommend the Gibtec piston highly enough for your application. The piston was designed is a Solidworks 3 space model to remove all material that did not contribute to piston strength and integrity, Pistons, H-13 heavy wall tool steel pins, locks and the piston rings I described earlier are all available in a single $1,200 package. No matter how you look at it they are a stunning piston and they come with skirt wall thicknesses of 0.187" to 0.200" which is really important to preventing skirt collapse and premature ring seal failure.
You ought to modify your crank counterweights to be round rather than the OEM disproportional shape Ford used to get additional mass down they for balaoncing purposes. Your rotating assembly will need to have the crank rebalanced for the new pieces. By cutting the counterweight just enough to get a radiuses surface you make room for additional piston skirt which helps stabilize the pistons in the bore (just like the heavy skirts) and extend ring life. Your crank balancer (if it is not your machine shop) will add tungsten to the counterweights to bring the assembly back into balance.
O would give serious thought to using either E85 or pure methanol for your fuel rather than race gas. The cheapest and best fuel by far is the methanol. E85 is a close approximation but race E85 begins to cost like the high octane race gasolines. You can usually find methanol locally for less than $200 for a 50/55 gallon drum. Methanol will require you to go to methanol compatible injectors and a much higher capacity fuel pump bt it is the King of race fuels. For all intents and purposes it is detonation free, allows very high compression ratios in boosted engines and provides a chilling effect at the point of injection that can reduce incoming charge temps at the intake valve below zero!
You will have to purge the system of methanol after each weekend of racing but that is easy. Switch to a gasoline table in you EFI system, drain the tank, pour in some gas fire the engine and wait for the fuel system to purge the remaining methanol from the lines with the gas from the fuel tank and you are done. When you are ready to race reverse the process. Drain the gas fill up with methanol fire the engine and run it to purge the gas from the fuel lines.
Since I've been out of the engine building game for this long, what is some current advice/tips/tricks?
See abovee and below ...
This engine was built when the terminator was the best out there, and cams were all re-grinds. I know the game has changed and the aftermarket has a solution for every problem. The same suggestions would be welcome for bearings, rings, gasket brands, etc. there are some upgrades I'd like to do such as mmr's billet timing guides and maybe adjustable cam gears, but a lot of others that I probably don't need. And as much as I respect other engines, It will stay twin turbo 2v 4.6!
Something you might want to consider is the use of 4V heads for a race engine. There are a number of benefits you realize beyond improved breathing. Possibly the most significant is the ability to change camshaft Lobe Separation Angle (LSA) without buying new cams. Once you get close in duration the final improvements usually come down to LSA and actual cam phasing (advance or retard) of the selected profiles. To change LSA on 2V engines requires the purchase of new cams. To change LS on a 4V engine requires re-timing of the intake vs exhaust cam. One is your physical efforts and the other is your wallet. It would be very unusual to hit the LSA correct for your engine car combo right out of the box or even after one or two attempts, hence the 4V suggestion. An extra added attraction is the 4V head has stunning flow capabilities and requires much less lift (0.420" to 0.470") to get the job done which makes everything valve train related live and work better.
Block-wise, Look for an Aluminator block. They were the standard offering on 05 - 10 3V Mustang GT's. Ford's internal testing has shown the Aluminator blocks to more than doubled the duty cycles of any other aluminum 4.6L block they have produced. It has many improvements in internal block webbing, main web structure, main caps and most importantly casting process.
This is how to identify an Aluminator block. Look for a casting ID like in the pic below on the rear passenger side of the block by the #5 side bolt;
Bearing-wise you want to run King MB5281-SI bearings. A lot of resellers of bearings will want you to run the black hard race bearings. Those are great for NASCAR style high banked oval racing where the engine will run at high rpm for hundreds of miles each race. They are not good for short duration high load applications like supercharged drag racing. The SI bearing gives optimal service in this environment. You also want to get a King MB1329-SI bearing. It is a fully flanged #5 upper (and an unusable lower) from an early 90's LNG 4.6L engine Ford has offered. It provides a fully flanged upper and lower insert for your build instead of th emultipiece erector set approach Ford took on the other 4.6L engines.
Head gaskets - just use Cometics.
Ed