Thread: Intake swap

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Howdy, I have a stock intake on my 1956 265 SBC. I purchased a polished typhoon manifold to replace it with. Some people say there is a slight difference between the 55 and 56 manifolds and the 57 and later. Is there any truth to this?

Not that I am aware of in terms of interchangeability.

Thanks what I think too. They mentioned oil leaks.

I also bought a Street Demon carb with the polymer fuel bowl to go with it. And a new set of ceramic coated headers to replace my tarnished stainless ones.

Your on the move should be a good mod.

A 265? I think you may be a bit over on the carb/intake. Is the setup for strip or is this a driver?

Originally Posted by Scooting

A 265? I think you may be a bit over on the carb/intake. Is the setup for strip or is this a driver?

I think Scooting's right. The Street Demon only comes in two sizes, 625cfm and 750cfm, and I'd think both are going to be too much flow volume for your 265. Maybe something like Edelbrock's 500cfm Performer might be a better fit? Got that from an on-line cfm calculator - http://www.gtsparkplugs.com/CarbCFMCalc.html

Originally Posted by Scooting

A 265? I think you may be a bit over on the carb/intake. Is the setup for strip or is this a driver?

Agree with over the top on the intake manifold. That design (same as Performer RPM) was first used on a 302 Chevy that used a mechanical flat tappet cam and could easily rev to 7000 or more. I think it is way too big for a 265 streeter and will result in a soggy bottom end due to insufficient mixture velocity. I wouldn't be concerned as much about the carb. Its vacuum-operated secondaries will only open as far as they need to based on demand from intake manifold vacuum. As long as the primary bores and venturi size are not out of proportion to any other 4-bbl, you should be ok. At street revs, you may not ever get into the secondaries with your limited 265 cubic inches.

I would offer that driveability would be far better with a stock manifold from a 70's or 80's 350.

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If it's an older Street Demon, it could be a 525 cfm, I've got one on my 302 (347) and it works well.

Tom, not trying to be critical of your approach. You may be more interested in the appearance of the new parts & pieces, and not looking for improved/ultimate performance. You're definitely making changes to dress up the old truck, for sure! It would be great if you have time to post some pictures of the project, before & after?

I am more concerned with looks and sound than perfomance. The demon is a 625 cfm. I have a pretty radical cam in it and it's been bored and had some head work done. I've been driving it for a couple years and have never had the secondaries kicked in or had it on the highway. I just cruise my neighborhood and local car meets.. We will see what happens. I'll see if I can post before pics. These are going to be big.

do whatever cranks your boat .. many folks have put wrong combinations together and learned to live with them ...

Are you running a road draft tube? The valve covers appear to have the mounting bolts straight across, if so the heads are not stock 265's. All 265's and 283's from 55 to 57 had staggered mounts on the valve covers and they also have no motor mounts on the side, that changed in 58. You won;t be over carbed if you have a fairly stout cam as I ran a 30-30 in a very bored out 55 265 block and it ran the 2-4 setup from a Vette along with a Sheiffer 10lb aluminum flywheel and it would easily grab 7 grand and then some if I kept my foot in it.

I am running a road draft tube and the heads are stagger bolt. We will see how it works if there are problems I will go another route.

Is there a small triangle cast into the pads at the bottom end of the heads? If so they are power pack heads. As far as changing the intake you shouldn't have any problems except for sealing the ends and I would use RTV instead of the supplied gaskets.