Simple question of is it worth putting 455 heads on a 350?

 

I don't know all the details. Yes they can be bolted on but it not a good idea. Compression is lowered, intake has to be customized, exhaust manifolds/headers will not fit. Just not worth it. Others will tell you the specifics.

Adam

 

The only thing is a RPM or Victor is needed due to the larger ports. Compression will be lower due to large chambers. SBO headers will fit the same. The Edelbrock or Pro Comp heads milled will work great on a 10 to 1 350. Much better flow and better combustion chamber.

 

Yes, it can be done. the 403 heads had about the same combustion chamber sizes as 455 heads. I have a friend running a 403 with E heads on it. as far as the intake, yes, you can use a RPM, BUT you can also use a 403 manifold. That casting has beefier runners that will need to be port matched to the heads. If you plan to run some flat top pistons, I'm not sure about header/exhaust fitiment, but my friend has that small block in a 78 Cutlass, and yes, its got headers that fit just fine.

Can it be done, yes. But it will cost you some cash.


John

 

Heck yeah it's worth it.

You'll have to have the heads milled .060" and the intake side of the heads milled the same and a RPM or Victor intake will bolt down on the heads without any milling. Of course you are going to have to do some intake porting so the ports match up but Aluminum is easy to port compared to porting cast iron heads that have a high content of nickel in them.

Checkout my website, there's a link to porting SB #6 heads toward the bottom of the page, you'll see that you can make the intake ports on a small block head just as big as those in Big Block heads but it's alot of work.

 

Ask yourself this: Since in reality it's pretty easy to install BBO heads on a 350, why didn't Olds do it on the W-31 motors? Probably because the SBO heads made more HP. Note that I've been a big proponent of using BBO heads on the 403 (hey, they worked great on the 400 BBO), but not on the 350 unless you are building a high RPM race only motor that can use the airflow.

 

Actually Joe I would have to disagree here.

Part of the reason they didn't do it would be the intake port difference, they'd then have to come up with another intake to better fit the BBO ports.

Look at the flow data I've posted on both small block heads as well as BBO Aluminums, which have the same port alignment as irons. They're only about 10-15% different in flow and both plateau at around .550-.600 lift. The valve angle doesn't help but that also tells me the runner capacity will only handle so much.

In stock form they're not too big for a decent 350.

 

Ok I have a balanced lower end, JM-20-22 cam, flat top pistons, edelbrock Performer intake, holly 650 carb. I have not done anything to the heads. I have a chance to buy 455 G heads. So I am trying to make up my mind on weather to just rebuild my #7 350 heads or get the G heads and rebuild those.

 

With that cam and intake you have, it would be best to just have someone do a valve job on the #7 heads and forget about the G heads and you'll have a 350 that will make around 260HP & 360lbs of Torque.