QS442

I went to take pics for a member of the Olds 330 and accessory parts that I was selling. Upon taking off some accessories, I noticed that the heads are BBO "C" Heads. What would these heads do for performance for a 330, if any? or why would these heads be put on a 330?

I don't know history of heads as far as work done. However, the engine sounded great when I purchased it. Wasn't able to drive car because it was wrecked in rear. I bought engine off a guy who stated the car used to be his fathers who passed away. Engine was actually in a low mileage Chevelle. I have recently bought another engine that was rebuilt, however this engine has me very curious now.

Has anyone every put these heads on a 330 or put these heads on a 350, what are outcomes?

txrob779

I cant help but am curious. Somewhere I thought I read that these heads could/would swap out. That was denied last month by one member but still wondering where I read that.
My 1966 Holiday Cutlass has 1967 "4" heads on it and it is most definitely a low mileage original engine.

Was reading some Wild About Cars technical manuals about the 10.25:1 330 4V in my car...was pretty cool too.

QS442

Yes, I'm very curious to see how it would move a car.

oldsmobiledave

Are you 100% sure that the casting letter is a C & not a number 6?

67 Cutlass Freak

This has been done before with mixed results. If you bolt the stock BB heads on a stock SB you will lower the compression ratio by at least a full point. At least the old performance 330 engines had close to 10:1 compression to begin with, so now you're at 9:1, or less. A lot of guys that have had success with this modification have milled the heads down to SB combustion chamber size. The other option would be to use high compression flat top, or dome pistons. The other problem comes in with the intake manifold port mismatch. There's approximately 1/4" of height difference from SB to BB. You might want to contact Smitty about this. It sounds like he's had some pretty good success with his in the past- http://www.mjproformance.com/

QS442

Yes I am 100% sure. Heads stamped C and the inner color on them are blue.

QS442

Thanks for that info man.

captjim

This assumes that the heads have nor been milled, the deck blocked, plus gasket thickness. You can't say he is under 9 to 1, he might be, but you just can't say so definitively without measuring everything.

joe_padavano

The use of BBO heads on an SBO has come up regularly. As noted, unless you mill the heads and/or use different pistons, CR will drop significantly (80 cc nominal chamber size on the BBO heads vs. 64-ish cc nominal chamber size on the 330 heads). The BBO ports are larger, so only certain SBO intakes have enough material to be ported to match. Of course, if the intake hasn't been ported to match, the flow disruption will pretty much negate any benefit from the larger ports. Also, BBO heads typically have larger valves than SBO heads - although it is possible to cut SBO heads to fit BBO valves.

QS442

Engine doesn't have an aftermarket intake on it and appears to be stock. Do 330 intakes have enough material to port?

DoubleV

Wouldn't the larger big block sized ports also reduce port velocity causing the engine to be very lazy on the lower end? This has always been my understanding.

stan 65 cutlass

can you post pics of the engine and numbers?? theres a 425 with 330 numbers? what makes you think its a 330?

67442nut

Easy to tell visually.
Been a while since I've measured them, but, as I recall
small block intake width is approx. 11", big block is 13".

MDchanic

Easy for you, not necessarily the OP.

- Eric

joe_padavano

Actually, it is. I'll reuse this photo from the other thread. Note the rib between the oil fill tube and the casting number, just to the left (in the photo) of the finger. All BBO block castings have this rib.

P1010403.jpg

Now note this SBO block casting, which has no rib. All SBOs are missing the rib. And no, that's still not my finger...

P1010399.jpg

MDchanic

Okay, fine.

NOW it's easy for him.

- Eric

RROLDSX

So does a 350 head fit on a big block? I realize the valves are smaller but a larger valve 350 head with a smaller combustion chamber would increase the compression ratio on a smog engine, assuming they fit and the ports can be enlarged.

I also realize this may be a stupid question.

joe_padavano

It's a question that gets asked a lot. Again, ALL 1964-1990 Olds motors have the same bore spacing and same head bolt locations, so yes, allowing for the 7/16" vs 1/2" head bolt differences, all heads will bolt onto all blocks.

Is it a good idea? Not particularly. The benefit of higher CR is more than offset by the small ports and mismatch at the manifold. You can't open the SBO ports to BBO size, so there will be a restriction. In addition, without careful blending work at the opening, the mismatch at the manifold will cause a flow disruption that will probably make this motor perform worse than with the original BBO heads. It's been tried, people have made engines run with SBO heads on BBOs, but by the time you're done with all the machine work, larger valves, etc, you're far better off both financially and performance wise to just get a set of ProComps ported by Bernard Mondello.

RROLDSX

Your response is once again appreciated.