Chevy 454 Big Block, Mark IV, 7.4l - Rebuild and more Power.

[Wes Harden]

Are you asking about the roughness of the openings ?
The little bits in first shot need investigation

 

[RayzWorld]

Are you asking about the roughness of the openings ?
The little bits in first shot need investigation

Correct the openings, they didn't look consistent so I figured it might be a problem. So it's normal?

 

[RayzWorld]

I just read back on your comments on what you read about the iron heads not performing and want to make certain that you understand which heads are which.

Factory iron heads come in three basic flavors:
Peanut-port - these are meant to mimic a diesel type powerband and are what a heavy tow rig needs. All low end power and absolutely no upper RPM power band.

Oval-port - these come in all sorts of combustion chamber sizes but if yours are 73~74 castings they should be the 049 or 781 castings and that is a very good thing!
These heads do everything well and have great potential with good power parts.

Rectangular-ports - these also come in several combustion chamber sizes and are meant for upper RPM ranges and NOT suitable for any form of towing or slow offraoading situations.
These heads make GREAT power but may not be what you need according to what you stated with what you want to do with your Blazer.

The aftermarket offers all sorts of options but that will take a nice chunk out of your budget.

Talk with FOLKENHEATH about your goals and he will set you up with the right combination of parts to make it all work.

( 781 ) it is oval port

 

[tarussell]

( 781 ) it is oval port

Not only oval ports but at the top of the list for factory O/P’s - 049’s & 781’s are the ones to get.
There are several other good versions but the larger open chambers on these two sets are great.

Congrats - this means ya got something to work with.

That being said - weigh the options of aftermarket heads v/s putting a ton of money in your castings. All kinds of options out there.

 

[tarussell]

Correct the openings, they didn't look consistent so I figured it might be a problem. So it's normal?

Looks like GM’s lack of attention to detail on their casting process - you can clean them up once you have them off to help improve oil drain back.

 

[Wes Harden]

yes they appear normal.

 

[folkenheath]

So I finally got those numbers.
Block number - 3999289
Heads number - 336781

might have a small issue.

Any ideas ???

The openings are normal. However, what are these? Are they loose?



The block could be 2 or 4 bolt based on the casting number.

Overall is seems like a solid engine in good condition to rebuild.

Not only oval ports but at the top of the list for factory O/P’s - 049’s & 781’s are the ones to get.
There are several other good versions but the larger open chambers on these two sets are great.

Congrats - this means ya got something to work with.

That being said - weigh the options of aftermarket heads v/s putting a ton of money in your castings. All kinds of options out there.

I agree with @tarussell