how to measure piston protrusion?
 

Does anyone have specific info on measuring piston protrusion?

I'm trying to figure out if a 603.971 has a rod problem. The #1 piston seems to sit at an angle relative to the other pistons. The piston protrudes seemingly normally on the intake side but much less so the exhaust side.

Should I set a level across the piston and measure protrusion at several points? If so should all points be within the single spec?

Which way does a 3.5 rod typically bend when it collapses?

Does any protrusion less than spec indicate a bent rod?

Thanks,
Sixto
93 300SD

not sure about the protrusion, but if you have a bent rod, it will be obvious- use any other one, typically #2 or 3 dont bend so crank it around with one of those up, it should stick out slightly higher then the deck. your bent one will be noticibly below deck level.

This should help ... 0.74MM would be the min spec & as shown measure at both front & back

are those values the same for a 603? unless I'm reading it wrong, that document excludes that model.

only exclusion is for the 602.98_ engines..that is correct for all other 601/602/603 engines. They just worded it badly.

on second look, i see what you mean.

I don't have a dial gauge but I have the 603.971 beside a 603.961 and the protrusion of the 603.961 leaves no doubt. Consequently it's clear that the #1 rod of the 603.971 is bent forward. Dang! That's some sweet torque I'll be giving up :(

Thanks,
Sixto
93 300SD

what do you mean? you going to put it back together without that piston?

just kidding.

but really, what do you mean?

tom w

I mean putting a rev happy 3.0 block in place of the torquey 3.5 block.

Sixto
93 300SD

aha!

good idea!

tom w

If the bores and pistons were good in the 3.5,

You could destroke the engine with the 3.0 liter crank and rods. Then you'd have a 3.3 liter. But, I'm guessing if you've got a bent rod, then the block would need sleeving and new pistons($$$$).

On a good note, the 3.5 liters heads are the later style. IE more crack resistent than the oringinal 3.0l.

Michael

Not so easy because neither the 3.0 rods nor 3.5 rods would work in that hybrid.

Sixto
93 300SD