273ci thoughts?

[273]

If I remember right I think the OP decided to go with 318 not posting to changes his mind, Just think this dyno of a 4.6l some of the info could be useful since we don't have much dyno info for 273 4.5l if anyone is thinking of doing a 273.
Similar displacement obviously but 4.6l ford has a smaller bore. Think you could get similar performance out of a 273 if built this way.

I think down the road I might do a magnum version of the 273 and put my valiant back to 273, think it would be a good performer especially with OD and deep gears, Swap to Magnum heads maybe with a beer barrel intake with mild porting and milling with zero decked quench. Mild roller cam around 265 with high lift and maybe 1.7 roller rockers.

 

[66fs]

Every Magnum 5.2L piston I've ever seen had 5/64" rings with no valve reliefs, basically a smogger LA piston. The 360/5.9s did get the narrow ring pack and that soap-dish recess. I always wondered why, when even the 4.0L Jeeps went to the narrow rings in 1996....

I checked my 92 5.2 Magnum pistons, + .04 higher, no valve reliefs, will accept pre-magnum rods 1.55 between pin bosses, 5/64 rings.

 

[Bighead440]

I checked my 92 5.2 Magnum pistons, + .04 higher, no valve reliefs, will accept pre-magnum rods 1.55 between pin bosses, 5/64 rings.

Yep, as I said: LA piston. I lined a used '87 318 D250 piston up with a used '92 5.2L Magnum D150 piston on a common pin. Identical compression height. I even checked them against a NOS MoPar Performance "9.0:1" piston (a cheap Silvolite/Badger/etc. cast piston with the top milled LESS, valve reliefs appear deeper than a '67-style 4-eyebrow but only due to less top milling) and they have less CD by a good bit.