do I have a Gen IV big block?

[longbedrick]

Assuming my 1973 GMC 454 is all stock, is there a good chance that I have a Gen IV 454 motor? Seems like there is a whole lot of variation. 2 bolt, 4 bolt. oval port, square port, peanut port. oval large, oval small, oval standard. rectangular head. standard head. open chamber, closed chamber heads. can all this be cleared up by the casting #'s? I'm just trying to buy an intake manifold, and I'm getting all these promts at Jegs and Summit

[b454rat]

Yes it's a Gen IV. Should have the large oval port open chamber heads. What is the casting number of the heads?? Get the last three and go to Mortec.com to find out what they are. Last 73 454 I had was 049, good street heads.

[68 TT]

Originally Posted by b454rat

Yes it's a Gen IV. Should have the large oval port open chamber heads. What is the casting number of the heads?? Get the last three and go to Mortec.com to find out what they are. Last 73 454 I had was 049, good street heads.

^x2

I run the 049 oval ports on my Camaro with 2.19 & 1.88 valves. They build great power and torque.

Without the casting numbers you don't know for sure what heads are on it. It could have peanut port truck heads on it or large oval port passenger car style heads. Doubtful anybody put rectangular port heads onto a truck.

[longbedrick]

thanks. I gotta find time to pull the valve covers off and check when the baby goes back to sleep (high maintenance, like her mother). anyone else have trouble reading the block casting in the back with the motor installed. I'm considering bustin' out a work light and a mirror

[longbedrick]

time out. gotta check out a 1971 Chevelle for $1200. Looks like baby and I are going on a trip

[2tons of fun]

you just listed about 9 names for 3 basic types of heads.

oval port and retangle port are completley different.

small oval are peanut port.

closed chambers and retangles stopped being made well before you motor was.

it can have either small or large oval.

[SMiller]

What was the best block and best heads for the big block? What years were the good ones produced?

[2tons of fun]

once again, do some searching.

990 rectangles are going to be great high hp heads and completely wrong if used on a 7.5:1 83 454 towing setup.

[68 TT]

Originally Posted by SMiller

What was the best block and best heads for the big block? What years were the good ones produced?

Depends on what the use of the vehicle is and what kind of RPM you want to turn it.

For a dedicated tow rig or tow truck the peanut port heads are the best choice but for a street car or truck the 049 large oval ports are the preferred heads. Rectangular port heads don't build much low end torque so they should be limited to use on a race car that sees high RPM.

After 65 when they changed the cam oiling method in the block they are all pretty much the same other than 2 and 4-bolt main caps. Many casting numbers can be found with both. The tall deck truck blocks can handle a little more stroke but require a special intake (or spacers) and taller distributor. Some aftermarket intakes have the mount lowered so they can use a standard SBC / BBC distributor.

You can have a 2-bolt block machined for splayed main caps and make it stronger than a 4-bolt block but for the money involved you are better off just getting an aftermarket splayed cap block like the Merlin or Dart blocks.

John Lingenfelter built 2-bolt, cast crank, stock rod, oval port 454's putting out 600 hp reliably with nothing but good rod bolts and main studs so any big block can be easily upgraded to handle quite a bit of power.

[SMiller]

What heads would have come on a '83-'87 K30 454?

[68 TT]

Originally Posted by SMiller

What heads would have come on a '83-'87 K30 454?

Could be either small (peanut) or large passenger car style oval port heads.

[b454rat]

I had one 73 454 with 049s, and the motor in my truck now is out of a 75 and it had 781s. I don't think there is a rhyme or reason why this truck got this head, and that truck got those heads. 049 and 781 are the best "street" head.

[2tons of fun]

Originally Posted by SMiller

What heads would have come on a '83-'87 K30 454?

peanut small ports.