Roller LA Deck Height
Since you are getting specific about some of your thoughts on this build, please provide a little more info. What exact head gasket do you want to run and what compression ratio are you hoping to achieve. I assumed a FelPro 1008 because it is common, but since you keep bringing up quench I would now assume you will also want to limit the crevice volumes, so a Cometic MLS gasket may be a better choice if the budget allows. The Cometic is available in many different thicknesses, so you can get a thinner one to help bring the compression back up if the pistons end up sitting below the deck surface.
The 92 LA does have different connecting rods than older LA 360. The 92 connecting rods are narrowed at the small end like a Magnum, allowing you to run Magnum style pistons. These are actually same casting number and dimensions as a 5.9 Magnum connecting rod.
You mentioned worries of engine balance. Whichever piston you choose you will probably need to balance the rotating assembly anyways, so that is not an issue or concern for you. Just know that it should be factored into the cost.
I'd love to talk specifics, just didn't want to scare people off with a thread starter that was even longer than it already is.
The engine is going in a daily commuter. Car is a '77 Volare, slant six/auto, manual everything, no A/C car. As rugged as the slant six has been, its cold weather manners are terrible, and the pathetic compression ratio is made even worse up here at a mile plus elevation. I figure it's making around 85hp up here, which is leaving a lot to be desired maneuvering in modern city traffic flow.
Powertrain upgrades going along with the engine:
-I already swapped to an 8.25" rear diff out of an an M-body. It's a 2.92 open diff currently, but will likely be getting a Cherokee 3.55 suregrip in the near future.
-Along with the V8, it's getting a Jeep 46RH trans swap (converted to 2WD). Trans is a basic rebuild with a Transgo shift kit and lockup neutral balanced converter. I believe the converter is rated for 1800-2000RPM.
-ZJ Jeep Grand Cherokee Magnum exhaust manifolds (reasonably good flow without the headaches of headers on a daily driver). Manifolds are a great fit on an F-body, but require a passenger side starter, hence the Jeep 46RH. Exhaust will be either 2.5" dual straight back, or maybe a Y into a single 3" to defeat the issues with the early F-body gas tank offset.
-ZJ Magnum Cooling and electrical system (radiator, factory trans cooler, trans lines, alternator, starter, cabling)
-I'll be keeping the manual steering and manual brakes, car will not be getting A/C. I will add a Taurus electric fan, as it's a simple upgrade, will relieve the drag of a clutch fan, and the Magnum charging system will easily support it.
And the engine:
Basic plan is for a pump-gas friendly higher-compression engine. Shooting for 9.5-10:1 to compensate for altitude. The car lives at 5500' elevation, and will see up to 10k occasionally, but rarely if ever less than 4000'. Winter temps can get well below 20F, sometimes in the single digits. Summer temps hover around 100F. It needs to start up and go in either environment.
Aside from the Magnum exhaust manifolds, I've chosen some Hughes-built Magnum EQ heads, a Weiand Action Plus intake, and an '85 Mopar quadrajet that I'll be rebuilding with a Cliff Ruggles kit and making appropriate mods to the idle fueling circuit and rod/jet combos. I've already converted the slant six to a GM HEI ignition system, and plan to carry this over to the V8 distributor.
I've got two engines available, an '88 318 and this '92 360. The 318 is low miles, and likely ready to throw in as is. If I go the 360 route, I'll be looking at a comparatively larger cam, and a B&M weighted flexplate to stay with the neutral balance 46RH converter. After a lot of research, I think the build goals would be well suited with a Lunati 20200714 cam (for the 318)
Lunati 20200714 Lunati High Efficiency Camshafts | Summit Racing, or a 20200711 cam (for the 360)
Lunati 20200711 Lunati Voodoo Camshafts | Summit Racing. The 318 would probably just need a basic refresh while it's out (oil pump, timing chain, gaskets, etc). The 360 has 184k miles on it, so I'm sure it's time for a complete rebuild. To me, that would entail decking the block, minimum overbore I can get away with, new rings/pistons, balanced rotating assembly, and all new bearings. Head gaskets are undetermined, but you are right, something with the appropriate bore diameter would maximize quench and combustion efficiency. I think I'd prefer a zero-decked motor with a ~0.040" headgasket, but a .027" gasket with a piston .013" in the hole, or a .050" gasket with the piston .010" out of the hole obviously accomplish the same result. Target piston to head clearance of .035-.045" to maximize combustion efficiency with the closed chamber Magnum heads.
The build is best described as max efficiency, not max effort, but I'd love to get over 350hp out of it for some decent fun in a 3200lb car. It shares a garage with a 700hp+ supercharged Holden that I finished up last year, so I've already got something for serious social work, and I'm trying to avoid going crazy with this one. I like to tinker with the unusual and I've a penchant for detail work, so my builds tend to reflect that. They also typically come together much greater than the sum of their parts.
I hope that sheds some more light on my goals. I'm in the serious planning phase right now, with a mid-spring build start date. I'm not above throwing the 318 in for the time being and taking my time developing the appropriate combo for the 360 with adequate machine work for a later exchange.
