2 bolt mark IV hp-boost limits ?

[78 propduster]

Had to pull the pan and discovered it's a 2 bolt.
700-800 hp, 9 lbs boost, 6000 rpm.
Was hoping to kick up boost to 12 lbs.
What do you think ?
Thanks!

[IMPATIENT 1]

is it studded?

[78 propduster]

yes

[IMPATIENT 1]

as long as your clearences are right, bearing caps fit tight to the block and its studded, 12lbs wouldn't scare me. i've ran 10lbs on a studded 2bolt;) 9.2 to 1 compression also:Dspinnin a b-cut dom impellor to 6900

[78 propduster]

Wow!
Thanks for the good news.

[DetroitJim]

Yep, what he said. You won't hurt a thing. I tried pretty damn hard to blow up a 2 bolt 454 with a Kuhl 8-71 blower, 7000 rpm on a regular basis. Couldn't hurt the damn thing. Sold the boat to a guy, it's still going strong 5 years later.

[IMPATIENT 1]

Wow!
Thanks for the good news.
you are runnin a balanced rotating assembly right? if your goin to 12lbs of boost, your gonna pick up alot of rpms, and get into a range wear totally balancing the motor is a necessity, not just runnin "internal" balanced stuff.
have fun at 12lbs, its a huge difference from 8lbs, gonna be FAST:devil:

[78 propduster]

Yes, I have the balance sheet that came with the motor. How do I determine if it's internal or external?

[IMPATIENT 1]

Yes, I have the balance sheet that came with the motor. How do I determine if it's internal or external?
if the flywheel has a weight on it or if your balancer has a weight built into the backside, its external. if there's no weights on the flywheel or balancer, good chance its internal. should say it though, but i've never herd of anyone spending the money to have a bbc or bbf balanced external, makes no sense to me. i bets it internal, sounds like a good motor!

[78 propduster]

The front hub is weighted, Flywheel is similar to a Clutch type, heavy.
The build sheet says its a "Hank the crank"
H-beam rods
Solid roller

[sleekcrafter]

The studded two bolt is better than 4 bolt, the two bolt, converted to splayed 4 bolt is the better yet.

[steelcomp]

The studded two bolt is better than 4 bolt, the two bolt converted to splayed 4 bolt is the better yet.
Huh???:confused:

[sleekcrafter]

Huh???:confused:
I should clarify.... Stock 4 bolt mains vs studded 2 bolt main, splayed 4 bolts are better yet, reaching towards the side walls rather than the webbing. Nothing fact in my statement, just remember reading this when I was running 2 bolt 468's years ago. Don't taze me bro:D

[steelcomp]

I should clarify.... Stock 4 bolt mains vs studded 2 bolt main, splayed 4 bolts are better yet, reaching towards the side walls rather than the webbing. Nothing fact in my statement, just remember reading this when I was running 2 bolt 468's years ago. Don't taze me bro:D
I won't taze you but you should qualify your statement of fact as heresay. Even though going into the main web, the four bolt is a better scenario. It really isn't about physical strength, more about distribution of harmonics. Four bolts do a better job of that than two. Outer splayed bolts distribute harmonics into more surface area toward the outer edges of the block than just into the main web. Better harmonic distribution, better control of cap and bearing movement. It may never fail, but look at the difference in cap walk between a two bolt (even studded) vs. a factory four bolt being pushed to their limits. Clamping force only plays a small part in the design.
Read that somewhere. :D

[sanger rat]

Put a main stud girdle on it.

[rat tuned]

where does a studded non-splayed 4 bolt stand? i have an ARP studded 4 bolt gm block with a gm steel crank(10-10) and gm 7/16" dimple rods floating with arp bolts. it is a 1980 block. i plan on a solid cam with an rpm limit of 6.5k and 10 #'s of boost. this is in a car also so mostly will be low boost and less i'm feelin frisky. mike

[steelcomp]

where does a studded non-splayed 4 bolt stand? i have an ARP studded 4 bolt gm block with a gm steel crank(10-10) and gm 7/16" dimple rods floating with arp bolts. it is a 1980 block. i plan on a solid cam with an rpm limit of 6.5k and 10 #'s of boost. this is in a car also so mostly will be low boost and less i'm feelin frisky. mike HP wise, you can pound the snot out of one so you're plenty safe. Some will tell you that studs don't get you anything. I know of some guys running high hp blown alky setups with stock main bolts and stock caps. On the 489 I'm building right now, I opted for ARP bolts instead of studs.