i dont know what the size of the opening in the head gasket is so you may be right about that.

i talked at lunch today with two men who own and operate heavy equipment. both say they have seen rods bent under starter only loads. they say it is not 100% and sometimes it will just stop the engine. a third guy who used to own a ready mix concrete with about 30 trucks said he thought so but wasnt sure. (that was before the other two guys showed up).

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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.

hey brian, did the guy with the bent rod pull it apart yet and determine the cause of it?

strongly thinking mine has a bent rod. will be doing compression test soon.

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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.

He did pull it apart, but, as you know, the cause is elusive.

Here are his original comments regarding the incident:

My mother was on a 4 hr trip driving up 101 to Eureka CA, doing highway speeds up a large grade. She called me very concerned about a large plume of white smoke that came out the tailpipe while she was going up the hill. The smoking ceased, but ever since then she complained about very rough idle in the am and knocking. The mechanic replaced the injectors, but knocking remained. A compression check showed low pressure on cylinder # 3 but that pressure didn’t drop. Assuming rings and valves were okay, they guess it to be a bent rod. I didn’t see any cracks in the head. Just some white staining on prechamber #3.


The engine did have a bent #3 rod. Pressure in the cylinder measured 275.

did they find any evidence of hard objects in the cylinder?

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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.

Don't think so. But, don't have any hard info one way or the other.

I'd be confident that he would have mentioned it if he saw anything.

The bent rod only caused the piston to drop ever so slightly. I think it was just visible to the eye that it was not quite at deck height when at the top of the stroke.

i dropped my 350 off today to have the compression checled... suspecting a bent rod. so am driving my 82 240 with newly rebuilt motor. damn 240s are ok.

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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.

You too??

All this discussion is not academic??

Who would have thunk it?

a week ago i thought it was fine. now i am convinced it is bent. the test will tell i guess.

know any body who has built a 603 with a 300 bore and a 350 crank? this may be simple if the wrist pin to top of piston is the same on both engines.

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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.

I believe this is impossible. The longer stroke of the 350 would require the taller block of the 350. Or, were you considering using the 350 block with new sleeves and boring it to the size of the 300? In addition to requiring a new set of costly pistons, why would you consider this relatively high risk proposition??

do you know the 350 block to be taller? i had assumed that the difference was only in the crank and rods and possibly the pistons.

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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.

Well, if the engine has a longer stroke, the crank throws are longer and the block, therefore, must be taller to accommodate this.

I would assume that a 350 crank in a 300 block would allow the pistons to travel above the deck. But, I have no personal experience.

shorter rods will make the difference, if it is not too great. one need to change a block completely is if there is not enough room in the bottom for a bigger crank throw. small block chevys for example can be built to many different displacements by boring out and swapping cranks, rods etc. on the other hand i know of instances: 177 slant six chrysler vs 225 slant six where it is true that the block is taller.... ditto for 351 cleveland ford vs 302. so it all depends and it could be either way.

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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.

Many times a “stroker” crank and shorter rods are used with the same pistons, you can also use a stroker crank with the same rods and shift the wrist pin connection up higher on a new piston without changing the deck height of the block. I suspect (I do not know) that the "improved geometry" rods and pistons for the 350 involved a longer rod and a relocation of the wrist pin. The ideal stroker would be to add to the deck height and increase the rod length to maintain the best geometry. Shifting the wrist pin location up higher will also reduce piston rock (another discussion).
So the question remains. What is the deck height for the 603.96x and 603.97x. and what are the differences in rod length and pistons.

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Don Martin
Bakersfield, CA
87 300SDL