343 deck to piston clearance

MAXAMX

Hey guys, Newbie here, i was disassembling a 343 today and the piston to deck clearance was around 0.60. Does this sound right? That would give it a quench of around 1.05. The 343s came with 10:1 CR and would seem like it would have more quench. The 343 is stock with the stock heads.

82Waggy

Yup. 290, 343 = .060 PTDC 304, 360 = .012 PTDC 390 = .045 PTDC 401 = .002 PTDC Stock head gaskets were .048 thick except for the 290 at .022 and the 304 at .028.

Rogue Racer

Official blueprint specs from AMC sent to NHRA for 1968 & 1969 343 280hp engine:

Deck clearance minimum - .050"
Head gasket thickness - .045"

290 225hp engine:

1966 - Deck clearance minimum - .021"
1967 - Deck clearance minimum - .020"
Head gasket thickness - .020"
1968 - Deck clearance minimum - .020"
Head gasket thickness - .045"
1967 - Deck clearance minimum - .020"
Head gasket thickness - .028"

See http://www.nhra.com/tech_specs/engine/

AMX69PHATTY

I'd guess that NHRA allowed for a little deck milling or whatever so thier spec is something less than stock nominal AMC ya think ? :-|

Rogue Racer

Generally, the specs supplied to NHRA by manufacturers are the engineering design specs. Production specs can differ, significantly in some cases. A lot of the time, the engineering specs are specified as a nominal range, like the 343 deck clearance COULD HAVE BEEN listed as .050"-.060". NHRA lists only minimums or maximums in areas where racers will push the limits for maximum performance. Production techniques, machinery and procedures usually push for acceptable specs without getting into service issues. Thus, for items that are factors for compression, for example, production is geared to approach the design spec without making situations that might encounter valve-to-piston interference problems or valve train intolerance for geometry and lifter pre-load or a compression ratio that would make operating the engine a hassle for the owner. The observed spec of .060" in the hole would be completely acceptable considering the design spec for the engine, IMHO.