2 bolt or 4 bolt mains

['94Blackbird]

'97 chev silverado Z71 with a vortec 5.7 350. Would this truck have 4 bolt mains or did they put 4 bolt mains in the trucks in '97? How could I find out? Also what would be the horsepower rating on this motor? Thanks for any help.

[2000CAYukon]

Most of the time (but not always), the casting number can be used to find out the number main bolts. See http://www.mortec.com/castnum.htm
Most likely a 2 bolt main.

The horsepower was right around 250.

//2000CAYukon

[baxterday]

She's a two bolt main! Don't fret it, it's a great motor. You're spliting hairs hoping for the 4 bolt main.

[jveik]

when did they convert all of them to 6 bolt mains? was that after they junked the 350 and the 454 and went to the slightly larger 6 and 8.1 liter engines? i heard those have the 4 bolt with an addtional 2 going diagonal making it a 6 bolt

[jveik]

when did they convert all of them to 6 bolt mains? was that after they junked the 350 and the 454 and went to the slightly larger 6 and 8.1 liter engines? i heard those have the 4 bolt with an addtional 2 going diagonal making it a 6 bolt

[jveik]

by the way, i heard a 2 bolt can take well over 500 horsepower so ur not in danger of anything bad lol

[acewelderman]

Originally Posted by jveik

by the way, i heard a 2 bolt can take well over 500 horsepower so ur not in danger of anything bad lol

2 bolt cap + 500 hp = spun bearings.Splayed caps are best (they angle the outer bolts in to make two directions of apllied torque)For stock aps two bolts are fine but high compresion over 12.1 should use 4 bolts.Also nitrous & blowers should have the heavy duty stuff.I have spun them at 400 hp on a 2 bolt block but never w a 4 bolt all the way to 800 hp!!!It all depends on quality parts & the right application.