Starting on rebuilding my w-30. The engine is number matching but early in its life the heads where changed to c heads. The motor has 22k miles on it. I was hoping not to spend extra money on d heads. Will the c head have the same performance.

 

better photo

 

C heads and D heads have the same flow characteristics and will make the same power. C heads $200 each D heads $2000 each. W cars use D heads. What's important to you is all that matters.

 

did you ever confirm that the car is a W30, not that the OAI parts were added when the car was painted?

carb, dist, axle codes & numbers?

did you discover or get the story why a 22K mile car had been painted so early in its life?

 

The engine dropped a valve so thats why it was parked. Still a lot of unanswered questions. Why was it painted,why the c heads and was it raced early in its life. The original owner can no LONGER talk. Trying to get information out of the family but going slow on information. IT is A W-30 BOTH FENDERS HAVE W-30 MARKED IN THE INSIDE FENDERS ALL ENGINE PARTS ARE DATE CODED TO THE BUILD DATE. ALL ENGINE TRANS AND REAR END MATCH TO THE CAR. Also its has the oringinal w-30 cam.

 

date coded parts

 

the D heads are smaller chamber cc then C heads so they give you more compression and IMO find D heads if it really is a w30!

 

Minor milling of the C heads will equal the CR of the D heads, and frankly, with today's gasoline, it isn't clear that 10.5:1 is your best bet. Also keep in mind that the FelPro blue head gaskets will drop CR about 0.5 point due to the greater compressed thickness.

Obviously, missing D heads will significantly impact the value of your car. If this matters to you, pony up for the correct heads. If not, be prepared to hear about how it's a clone every time you open the hood.

 

Or you can put a big block chevy or LS in it like many other people already have, as Joe said it's your car but questions will come up on why you don't have the D heads on it

 

Here's an in between step, instead of spending that much money for correct D heads. We lost Chris in a motorcycle accident last year. But if his widow has any of these left, they would have the right appearance for much less money. John


http://www.ebay.com/itm/REPLICA-68-7...axHPxQ&vxp=mtr

 

That is an incorrect piece of info that has been carried around for years... the NHRA minimum spec on the D heads is 69.75cc, and the Mondello tech manual also said they were smaller. Mine were untouched virgin D heads and cc'd at 82cc before surfacing, just like most other BBO heads. We took a minimum off just for flatness and surface finish so they are at 81cc now.

The biggest difference between D and C heads is that the D heads have the exhaust crossover cast differently so only one of the center exhaust ports feeds the intake per head, instead of two. I believe the F and H heads do this as well, but I can't confirm that.

Performance wise, you'll gain nothing with the swap, but most people will likely question the validity of the car with C heads. I would say the cost of the D heads would add at least the equivalent value to the car if all the rest of the "born with" parts are there. If you search here, you'll find an old thread compiling D head date codes that are available... there were only a handful of dates when they were cast.

 

Yes, this is true for F heads as well. I'm not certain about H, but probably the same.

This is also why it's a misnomer to say that C and D have the same flow characteristics. Olds engineers changed the exhaust ports on W-30s for a reason. Now instead of having half of your cylinders sharing an echo chamber, only two of them do, and the other six all get nice, smooth exhaust runners. Match this up with a set of headers and you have the potential for a significant power increase.

 

Here is a hood read for you on head flow numbers

http://realoldspower.prophpbb.com/topic13679.html