I have a stock 360 that's in need of a rebuild. It's in a 78 Cherokee that presently has the TH400, QT and 3.08's in the axles with stock 29" tires. When I pull the motor I'm going to also change over to a TH700R4, a Dana 300 t-case, 3.90 gears and jump up to 31" tires.

Plans are as follows...

Bore: +0.030" (4.110")
CR: 9.0:1
Heads: #502 Cast Iron with 2.08/1.74 valves
(from Areohead Racing)
Intake: Edelbrock Air-Gap (since I have it already)
Carb: Holley Truck Avenger (670 or 770cfm?)
Dizzy: HEI
Ignition Box: ??
(Naturally the usual oiling mods and prep will be included.)

Now here are my questions:

Having done some math on the motor, I can't for the life of me figure out how Silvolite and Speed Pro claim a 9:1 CR with their pistons having a 1.58" compression height and a 24-28cc dish. Even milling the decks 0.020" to make up for the change in compression height, the piston will still be 0.013" down the hole and the CR comes out to 8.5:1 (0.045" gasket and 58cc heads).

Naturally I don't want to drop $700+ on custom forged pistons for a daily driver, so I took a look at the Egge L2336 flat-top 343 pistons AMC69PHATTY found. http://www.bulltear.com/forums/viewtopic.php?t=6782

Unfortunately the piston would still be 0.013" down the hole. The up side is that the decks could be milled 0.018" leaving the piston 0.005" out the hole and net a perfect 0.040" quench height with a 0.045" gasket. The downside is my compression ration would be 10.9:1 which won't cut it for a daily driver.

Also note the problem Painted Rat had when installing these pistons in a 360 as indicated in this thread: http://www.bulltear.com/forums/viewtopic.php?t=6620

Would it be possible to enlarge the dish on these pistons to 26cc? A 26cc dish would give you a 9:1 CR, which is much more in line for pump gas and a daily driver. (Note: a 20cc dish will give you a 9.5:1 CR for those running Edelbrock heads.)

Considering they will already need to clearance the skirts at PaintedRat found out, I don't see why enlarging the dish would be a problem so long as it doesn't affect the structural integrity of the piston's head.

What cam would you suggest for this combination? My biggest gripe about the motor now is that it has no top end power and falls flat on it's face around 3000rpm. It's pretty sad when you kick it down to pass someone and it makes a lot more noise but doesn't go any faster. I don't do any rock crawling or serious off-roading with this rig, so I'd rather focus on mid to top end without taking too much away from the bottom. Something that will pull well from about 1500 up to say 5000 or 5500rpm.

The heads will be #502's with larger 2.08/1.74" valves from Aerohead Racing (see link for full details: http://www.aeroheadracing.com/id9.html).

I've been looking at the XE262H cam and get decent numbers with it from Desktop Dyno (see Fig. 1 below), but it leaves me about 25HP shy of the 400hp/400ft-lb marks I'd like to attain. The XE274H gets me the HP I'm looking for, but does so at the expense of 30ft-lbs at 2000rpm (see Fig. 2).

Figure 1

Figure 2

The change to an OD transmission could cause a problem though as that will greatly reduce my cruise RPM, even with the gear change. My calculations show 2066rpm @ 70mph.

What do you suggest for ignition upgrades? I've been looking at the HEI options, but what about an ignition box? And please don't say MSD....if you'd seen how many came back when I worked at Jeg's you'd NEVER buy one either. lol