I have a '91 350SD with 162,000 miles on it that I converted to run on vegoil about five thousand miles ago. It seems to run very well and is not burning any oil between 3,000 mile oil changes. I have some things that I would like to fix on the car, anticipating that I will be driving it for quite some time. However, I know about the rod bending problems with the 350's. If it has gone this far, do I have one of the good ones?

imho, they are never truly safe.

i think the problem stems from too much block flex and differential movement between the aluminum head and iron block. eventually the head gasket leaks and seeps fluid into the cylinder. as soon as you have an accumulation of more than 1.5 cu in in it when you start up the car it bends a rod. this could be a very slight bend or more. the less it is bent the less the symptoms will be. but if it is bent it is a slippery slope which leads to massive failure if the head gasket is not replaced very very quickly.

so i advise watching your water and oil like a hawk for any fluids in either that doesnt belong...IE oil in your water or vice versa. at first sign of either get the head off and the gasket renewed pronto.

the problem seems to be more prevelant in city driven cars.

if the rod is bent i would substitute a 3.0 block and use the head from the 3.5 block. the 3.0 engines are known for cracked heads so finding a good block with a cracked head should be relatively easy.

good luck

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.