[540 RAT]

Here is some interesting reading:


http://www.rehermorrison.com/techTalk/51.htm

 

[oger]

I had a real good engine builder tell me that over 30 years ago. At the time I really didn't know for sure but believe what R&M says.

 

[fatblock]

I read the article.Did Rehr give a thumbs up to a stock cross drilled crank...just not todays aftermarket units?My 427 has a stock cross drilled crank.

 

[540 RAT]

No, he did not endorse any cross-drilled crank. See Wolfplace's comment below:

http://www.chevelles.com/forums/showthread.php?t=165959

 

[fatblock]

Thanks for the link from Mike...540.I spin the 427 to 6500 rpm max.Should I be concerned at this rpm level?

 

[SY1]

I wouldn't lose a minutes sleep fretting over this. A racing engine designed to live at high rpm continuously is a much different animal, with much different design criteria than your street motor driven occasionally at the strip. Especially with short stroke motors there is no concern for us with strength as the overlap cross sections between the rods and mains on a short stroke motor isn't an issue for anything short of an all out racing motor. I've run cross drilled 302, 331 sbc motor for years with no issues and they see more than an occasional 8000 + rpm burst.

I have burned up a good 331 in 30 minutes time due to insufficient heat transfer at the rods. The crank turned blue on the rod and main journals when the heat from the combustion chamber transferred just fine down the piston into the rod but couldn't transfer into the main webs to be carried away by the coolant. So it just sits there getting hotter and hotter until the oil breaks down and the crank is destroyed. But the problem wasn't with the lube system.

He does offer a good reason to continue to run the higher oil pressures keeping in mind the 10 psi per 1000 rpm consideration. For a sbc the Z28 high pressure spring works well for this.

This is probably good advise for those running long stroke motors on the edge that will see heavy loads and high rpms, but I wouldn't hesitate to use one for a street or street/strip car.

 

[fatblock]

I wouldn't lose a minutes sleep fretting over this. A racing engine designed to live at high rpm continuously is a much different animal, with much different design criteria than your street motor driven occasionally at the strip. Especially with short stroke motors there is no concern for us with strength as the overlap cross sections between the rods and mains on a short stroke motor isn't an issue for anything short of an all out racing motor. I've run cross drilled 302, 331 sbc motor for years with no issues and they see more than an occasional 8000 + rpm burst.

I have burned up a good 331 in 30 minutes time due to insufficient heat transfer at the rods. The crank turned blue on the rod and main journals when the heat from the combustion chamber transferred just fine down the piston into the rod but couldn't transfer into the main webs to be carried away by the coolant. So it just sits there getting hotter and hotter until the oil breaks down and the crank is destroyed. But the problem wasn't with the lube system.

He does offer a good reason to continue to run the higher oil pressures keeping in mind the 10 psi per 1000 rpm consideration. For a sbc the Z28 high pressure spring works well for this.

This is probably good advise for those running long stroke motors on the edge that will see heavy loads and high rpms, but I wouldn't hesitate to use one for a street or street/strip car.

Dave...Was it the bearing shells that did not transfer the combustion heat to the coolant system via the main webs??

 

[zdld17]

If it was not for street cross drilled cranks, where would the oil come from to lube the rod bearing? We go back to stock dipper type rods?

 

[oger]

All cranks have one hole. The cross drilled cranks have two.

 

[zdld17]

All cranks have one hole. The cross drilled cranks have two.

I should know better but maybe I am misunderstanding the wrong use of the term cross crilled crank.
Off a main journal one hole is going in at an angle drilled into the crank to the throw of the rod journal feeding one rod.
180 degrees away of this same journal, is another hole drilled into the opposite direction feeding the opposite rod throw on one other rod journal. Is this the cross drilled?

This is what I have always used and mainly stock steel cranks cut on the low side either nitrated or chromed. These were days when we never heard of the California cranks or Hank the Crank , etc.

Is there another cross drilled method? Did I say that correctly? Am I asking about something that is too old school? This has been an ideal crank feature for as long as I can remember. Even GM did this many years to all of their hipo cranks. So its hard to understand what is being said that its a no-no now. Guess I have to ask my self , what would Smokey or Jenkins do?