I am trying to figure out if these heads would be good for a 403 and if so what would have to be done to them?? Thanks for the help I am very very new at this.

1967-69 Oldsmobile 442 'C' Big Valve Heads

They are in good condition and originally came on W-30, 425ci & 455ci motors.
These have the 80cc chambers, the valves are the big 2.072. Many people believe
these are the best flowing big block heads. These came off a good running 455ci
motor. On the center exhaust ports, the center wall was lengthened to the outer
surface of the head to increase power and also works better with headers.
That was the only modifications done to these heads.

 

That depends on what you are doing to the engine. If you are just doing a head swap and not touching the bottom end you will end up dropping you compression quite a bit due to the larger combustion chambers.
If you are going to do a complete rebuild you should talk to cutlassefi about pistons as he just finished a 403 with BBO heads and it is a stump puller.

 

Actually both those C heads and 403 heads measure 80 cc plus. Most say the BBO heads are 82-84 cc. My 4A's cc'd at 86. You need a piston like the KB 6cc or Arias 3cc to provide adequate compression.

 

The other thing to be aware of is that C heads are from a "big block" 400-425-455. Small blocks are 260-307-330-350-403 The deck height is different and so the intake will not match up correctly. I don't build small blocks typically but if I understand them correctly you would be better off with a set of 7 heads. They are small block so the intake will work without having to do some machining. I also remember that 403 head bolts are larger than the earlier ones so you have to enlarge the bolt holes on earlier heads.

Others who are much more versed on small blocks can help you more but I am pretty sure this is accurate.

Hope it helps
Larry

 

There are a few intakes that have enough material in the ports to be able to match them up on the C heads.

 

Yes I understand I would need to go with flat top pistons ( suggestions on those would be good, most I find are KB). I also planned on a new intake, which one goes best with the "C" heads.

I am trying figure out what would be cheaper, If I get 350 heads I know a lot of machine work has to be done. What has to be done with the "C" heads?? Do they need bigger bolt holes?

An the ultimate question is can i get away with using my 4a heads and get a more out of them by using flat top pistons and porting and adding headers?

Again I am new at this and have been trying to do a lot of reading but each thing pulls me in a different direction. This is a street build as a school project budget is Low. Thanks for the help.

 

For intake, on a 403 with big block heads, the only option (other than custom) is Performer RPM. It has extra material at the top of the intake ports that can be ground out so it matches the larger big block head ports.

For pistons, there aren't many (off the shelf) options. KB are good units. The Arias are a bit lighter. Either of those work well with big block or stock 403 big chamber heads. Otherwise there's cast deep dish replacements which work well with older small block heads. Or get a custom piston made.

Any head other than stock 403 heads will need the bolt holes enlarged. Any machine shop can easily do that.

4a heads have some truly horrible ports which is a part of the terrible HP/TQ figures for the stock engine. Jim at J&S Machine can get 4a heads to work well, but it takes a lot of time with the grinder, which means it's more economical to get some aftermarket heads or better condition big block heads.

First thing's first. Set your budget. Then define your goal (HP/TQ, overall driveline combination, usage). Then you can build a combo. Throwing parts at it will almost certainly disappoint, or lead you to spending money in the wrong places.

The engine build forum on ROP has some 403 combos, plus there's the one Mark (cutlassefi) just posted here in the small block forum. FWIW, Mark warned me that the Lunati Voodoo is a noisy cam. And it is. I consider it culture.

 

That is not correct. There are several intakes with sufficient meat to be port-matched. The out-of-production E-brock OL4B as well as some stock intakes can also be used.

To the OP, I suggest you read this thread.

 

Thanks, My goals are to have a street car that sounds good will get up and go a little. Nothing to crazy. I would say I would like to keep it $2500 for the engine. Not sure if that to low though.