C409

..... What is the recommended piston to head clearance for LS7 Ti rods in a 421 ...........

glenB

Same as in a 427

The Ti rods don't grow like an aluminum rod does, if that's your concern.

I build for '0' deck and use the head gasket to adjust for clearance, and since the LS standard is .050"

BTW, the Service Manual doesn't list that spec

C409

..... Would .039 be too close ? ........

glenB

Minimum spec for aluminum rods is .010" over a steel rod. Total clearance per most manufactures of aluminum rods is .060", so steel would be .050. Couple factors that relate to rod life and stretch is HP and RPM. At zero deck for a typical street engine and 6700 RPM I've used .039 - .040, using a zero deck.


http://pauter.com/parts/technical/faq/rods/

How much do your connecting rods stretch?
What is often referred to as rod stretch is actually a result of flex of corresponding parts combined with movement allowed by necessary operating clearances involved within the assembly as well as thermal expansion inherent in the internal combustion engine. Truth is any true physical rod stretch would likely be from deformation of the big and/or small end bores which could in turn lead to serious engine damage. In short, actual steel rod stretch itself should be near zero with exception of thermal expansion but all aspects mentioned above need to be considered during engine planning / assembly stages with regard to rotating and deck clearance minimum requirements.