Aluminum 4 barrel intake question

[oldskydog]

776 was a Service Package intake for the 61 409,never used in production.

Another misconception from an old article that keeps getting cited.
The 776 was essentially a 540 with the primary throttle bores opened up from 1.56 to 1.625 to accommodate the 3270 AFB which had larger primary and secondary venturi bores as well as larger primary throttle bore.
Unless the intake has had the bores enlarged you should not be able to bolt a 3270 or any of the large mouth AFB's onto a 579 or 540 intake since the throttle blades would not be able to open. Maybe with a spacer adapter.

 

[Aducati4me]

Here is the casting numbers under the shield. Can anyone decipher this logically. If it’s December 18th what year is it? If there is no year is it a service package manifold that could be any year I choose? I’m so confused! (pulling my hair out)
Inquiring minds want to know.

 

[oldskydog]

A lot of the aluminum intakes did not have a year casting date. The 320 hp 348 which would have used this manifold came out in early March of 59....that could be a 59 or later service manifold.

 

[Aducati4me]

Cecil my 3270 bolts directly onto the 579 manifold and opens and closes freely. There is no indication of the primary bores being enlarged, that I can see anyway. Not doubting your research, just curious.

Here’s my take on this whole debacle. It was the end of the 348 era and on to the next, aka “409”. Factories were using NOS parts on anything they could to save $ where they could. They are not in business to throw $ away so they did what they could to balance making customers happy and still make $. So that is why (in my own opinion) why there are weird things at the end of the life of an era. Does it conflict with the books? Yes, absolutely. Does it not make (we have to stick to the book) sense? Yes, absolutely. BUT does it make $ sense? Not so much, and $ is why they are in business. So there you have it. IMHO I feel that in this time period they were just in a struggle to get rid of old stock that they knew they could never dump so they just stuck it where they could. Which might explain why there is so much confusion and mis-information.
Please don’t kill me!!! It’s just a thought not a fact

 

[oldskydog]

Thought I would add what’s on my 61-409.

I don't suppose there is a casting date on that is there? I'm guessing it is identical to a 776 which should be the production version.

 

[oldskydog]

Cecil my 3270 bolts directly onto the 579 manifold and opens and closes freely. There is no indication of the primary bores being enlarged, that I can see anyway. Not doubting your research, just curious.

Here’s my take on this whole debacle. It was the end of the 348 era and on to the next, aka “409”. Factories were using NOS parts on anything they could to save $ where they could. They are not in business to throw $ away so they did what they could to balance making customers happy and still make $. So that is why (in my own opinion) why there are weird things at the end of the life of an era. Does it conflict with the books? Yes, absolutely. Does it not make (we have to stick to the book) sense? Yes, absolutely. BUT does it make $ sense? Not so much, and $ is why they are in business. So there you have it. IMHO I feel that in this time period they were just in a struggle to get rid of old stock that they knew they could never dump so they just stuck it where they could. Which might explain why there is so much confusion and mis-information.
Please don’t kill me!!! It’s just a thought not a fact

OK, I guess I'll have to update my thinking on this. Aparrently even though the throttle bore was smaller on the 348 aluminum intakes (579 and 540) at 1.56 and 1.68 the large mouth AFB's with 1.625 and 1.68 will still bolt on and work on the 348 intakes....it's just that the primary throttle bore and venturi will not be as effective on the smaller bore 348 intake as it would be on the 409 intakes. Coulda' fooled me. I actually went out to the junk pile and dug out my 579 and 540 intakes along with a 3212, a 2897, 3783 carbs. First I measured the throttle bores on the intakes and found them to be spec then bolted on the various carbs to see if there was any interference with the throttle blades and there wasn't. Obviously the throttle bores on the 348 ntakes and carbs are smaller than the 409 but not enough to cause interference with the throttle blades. I had always assumed that there would be interference but apparently the larger bores of the 409 intake were just to better "unshroud" the larger blades on the 409 carbs.
That's only the second time I've been wrong and the first time I thought I was wrong but I was mistaken.

 

[Phil Reed]

BAN HIM!!!!!!!!!

 

[Don Jacks]

NO

 

[427John]

I'm thinking that because the throttle shafts are a short distance above the carb mounting surface that the portion of the blades that actually pivot down into the throttle bores are small enough to not interfere.If you had the blades removed and stuck them down into the bore they would clear until shortly before reaching the mid point.

 

[Aducati4me]

I'm thinking that because the throttle shafts are a short distance above the carb mounting surface that the portion of the blades that actually pivot down into the throttle bores are small enough to not interfere.

Agreed. Plus the thickness of the gasket raises it up even higher.