Is there anything to begained swapping a mid 70's iron intake for a 80's 307 ho alum intake, other than taking 20-30 odd pounds off the car

 

No.

 

All 307 aluminum intakes up through 1984 will fit and work on an earlier 350 just like the stock units (and only the 442 in 1985- same as the 84 flat tappet engines). As far as flow, I doubt there's much difference. 307s were more for fuel/emissions efficiencies. Agreed, weight savings is the only real, tangible plus. However, a good benefit is that it works with EGR-era SBO engines or without if you block it and plug the ports under the removable carb EGR nozzles. The 85 and up roller cam engines had peanut port intakes and not a good match for the larger port heads as far as performance. Note, early 307s had cast iron intakes, so don't just grab one automatically thinking it's alumimum. It doesn't much matter which intake you get. They only had a couple of part number changes which just had this port or an EFE port drilled/tapped or not. The casting is pretty much the same.

The key is, if you want one, look for the A4 on the intake. If you see A5, that's the peanut port job. You don't want that one.

Here's an NOS one I got for a project. Note the A4.




Also has A4 on the bottom, too.

 

The A4 definitely isn't a performance intake, and I've always heard that iron intakes do offer better fuel mileage. Of course the last part is based on a stock engine.

 

No factory SBO intake was a "performance" intake, IMO, no matter the materials used. Even a W-31 intake. But an A4 is more desired than an A5, unless it's a restoration thing, because it can and will bolt to a 350. A5s should not even be in that equation IMO. That mileage claim about cast iron seems dubious to me. Otherwise they'd have kept the cast iron ones. They were after mileage increases and emission reductions in the 80s. And the A4 came standard on many 83-85 non-roller cam engines so why would they risk hurting fuel effienciency by using crappy aluminum?

Other than weight savings, and maybe quicker warmup of the fuel for atomization, regular driver guy wouldn't notice a real performance difference between aluminum or cast iron stock intake. Some intakes will inherently flow better than others. It all depends on the construction and casting design, and not so much the matrial used.

I still maintain that simply swapping to an aluminum intake searching for performance gain potential would be a waste of effort and time. Now, aluminum would be easier to modify for performance gains perhaps, but that's another story for another day.

 

Greater minds than mine have commented of the mileage differences, whether you choose to believe my repeating it, or not!

 

That could be gearing, driving style, foot heaviness, and other factors. One issue is, there's not that many small block Oldsmobile factory aluminum-intaked engines running around to say that a stock aluminum intake gets worse mileage than a cast iron unit on the same exact engine. I've never seen any testing data on that, although I'd be welcoming to see it. Not saying it isn't true, but there's been no facts given other than someone said something sometime at some place. All my 307s have 3.73s out back standard equipment, so gas mileage is #46 on my top 10 list of concerns. I'm betting hardly anyone else with a V8 Olds gives that much of a hoot about gas mileage, either.

The original question was whether swapping to a stock aluminum intake would be worth doing as a performance enhancement over a cast iron unit. I still stand by my original answer- no. There are advantages to using cast iron or aluminum, but performance isn't a major one.

 

69HO43, it wasn't Oldsmobile specific info, sorry for the confusion.

 

I am not sure why Olds flipped back and forth on iron to aluminum for intakes. The A4 is really rare up here, I had to buy one from state side. Every big 307 powered car I worked on, probably about 20 in shops plus what I owned, 2 cars, one a parts car, had #16 or #17 iron intakes. Obviously except the 85 and later A5 intake. Only one or two and a 87 Caprice with the 307 we were selling. The fuel economy is conjecture, hard data would need to be gathered. There is quite a weight difference, the iron would very slightly penalize fuel economy because of the extra weight. We also never did a single intake gasket and these were 20 year old, abused cars. We actually sent two 307's to the machine shop, not really that worn out. Father and son cars, a Blue 85 Delta 88 for the Dad and a Brown 83 Delta 88 for the son. Also pulled apart the severly blown up 307 in a 85 Buick Lesabre wagon. I kept the carb which was actually a 80 301 Pontiac Qjet.

 

Back when A4 intakes could be found for $25, this was an easy way to shed pounds. Today people are asking stupid money for them.

 

Yeah, mine from the US was maybe $100 due to shipping 15 years back. Probably doesn't help the price of new Edelbrock intake manifolds. Heck the Chinese RPM copy is what Edelbrock intakes cost a couple years back.

 

Guys, the iron vs AL mileage claim was info I picked-up from Speedtalk and I don't doubt it's veracity, but don't believe if you don't want to. The gentlemen around there are very well versed and I'm sure if you went there and asked you'd be filled in on someone's details. I'll just believe that source, and ya'll can debate it.
I can guarantee that there was testing done before that statement was made. Better vaporization - it's not really a stretch to believe, and the weight difference is negligible !

 

Sounds like you're a bit upset that some of us just don't take people's word for something found on the internet. Believe what you will, I won't ever stop you from believing what you want to. I just don't take it as gospel when someone tells me that cast iron intakes are always better at mpg than aluminum intakes. Which is, in effect, what your statement alludes to. Maybe they are, maybe they aren't. But I have a hard time believing that as a rule of thumb.

So what specifically does your guarantee cover? You haven't given any details that matter. Need facts to change minds. So you're believing whatever is mentioned? What evidence do you have on hand that we doubters should believe it? What brand/type intakes did they test? What MPG difference was it? Negligible? Probably. When it comes to squeezing MPG out of a 307, I think I'd trust the Olds engineers over a pack of racer guys looking for max power out of their setups.

From what your earlier post mentioned, you even stated it wasn't Oldsmobile specific. Blanket statements like that without empirical data to back it up are pretty much worthless. Who did the tests? Why would anyone do a test like that? Everything would need to stay the same except the intake. Where's the data sheets? I've been around this game long enough to know that unless it's written down, there's a good chance it didn't happen.

 

Thanks everyone. I may grab it when my local pick and pull has the all you can carry for 100 bucks week end at the end of fall .

 

here’s some empirical some data. Aluminum dissipates heat at 2.5 to 3.5 times the rate of cast iron. Therefore, like for like, an engine with an aluminum intake will make more HP because of a cooler denser fuel charge.

Also, an intake that runs cooler and transfers less heat to the carburetor , will be less likely of going into vapour lock.

those are factual blanket statements