dual quad intake

[327]

Maybe ???

 

[427John]

Weren't the 61 409's small port heads? Did they come out with a large port heads and intake service package before the start of the 62 MY? If so could it have been installed before delivery at the dealership on a late MY 61? I know that kind of stuff happened in 62 just curious if it could have happened in late 61 too.

 

[oldskydog]

On 6-8-61, The 61 409 engine line up changed to:
#3795507 RPO 580 High Performance V-8/409 , parts list Q and suffix Q
#3815233 RPO 580 Special High Performance V-8/409 parts list R and suffix QA (380 hp)
#3815235 Dual Four Bbl. V-8/409, parts list S and suffix QB (409 hp)

 

[rstreet]

Yes 61 409’s were small port. I am not aware of a GM official service pak. Certainly late model year end could have had over counter purchases but….there are other pieces or parts relevant to a 61 409 that could have affected performance if one just bolted 690 heads and an 881 intake on a true 61 block. I’m not sure if would have enhanced performance or been detrimental. I’m not certain but I suspect one of our members could speak to this.
Robert

 

[63 dream'n]

6/8/61, It’s just two months prior to the end of the model year, correct…..?

 

[oldskydog]

First, the Tonowanda production records for 1961 MY production from June 1960 to July 25, 1961 show a total of 265 complete RPO 580 engines shipped broken down by part numbers as:

3795507 Pass LD RPO 580 115
3814301 Pass LD RPO 580 150
total 265

Additionally, 84 RPO 580 "Half Motor"s, part no. 3799347 were shipped.
I assume these were either fitted blocks or long blocks. Fitted blocks would not have an assembly stamp, but I'm not sure if long blocks would, or not.

The end of production records very definitively state the number of engines shipped by 7/7/61, as well as the number stored & on hand 7/7/61 and the number produced from 7/7/61 to the end of production on 7/25/61. All 265 full engines were shipped before 7/7/61 and all half engines had been shipped by 7/25/61 with none left in storage or on hand.


The thing I find interesting from the production records is the two different part numbers for the RPO 580. Obviously 3795507 was the first configuration of only 115 engines and 3814301 was the second version of the engine with 150 produced. What is not known is what the difference is in the two versions of the engine.

Even more confusing is that on 6-8-61, the "1961 W8 Engine Production Identification" list was revised to add two more part numbers and suffix codes still under RPO 580. These were:

High Performance V-8/409 3795507 RPO 580 Suffix Q

Special High Performance V-8 3815223 580 QA

Dual Four Bbl. V-8/409 3815235 580 QB

For me, this is proof of the QA and QB engines were authorized in late production 61 but does not prve that any were actually installed in production.

What is still not clear is why the two new part numbers are not referenced on the total 61 engine production records under the RPO 580 totals. They were authorized, but maybe never built or just missed on the total production by part number summary.

There were also 10 COPO 409 engines shipped under a different part number. Perhaps these were QB engines but the part numbers are different from the 3815235 shown above.

 

[Blk61409]

Cecil, you are correct. Obviously more questions than answers.
So I thought I would confuse things a little more.
In my 61 I have a 6-24-61 cast date 068 block, 690 heads 6-17-61 and what would become the 881 intake, L 59819 6-1-61.
All cast during June, 1961.
Thanks to Tom k for the block.
From what I can determine these parts were one of the 10 COPO 409 2x4 engines built for 61’s specifically for O/SS racing.
I’m going to attempt to post lots of photos.
In addition, I located (as posted previously) the exact carbs used to make the 3361/3362 combinations. A retired Carter Carb engineer told me where they were and I was able to secure them. They have some crazy stampings on the air horn and base.
I’m going to attempt to post a photo of Don Nicholson working on his 61 409/409 with these carbs.
Anyway, as Cecil has pointed out there are definitely more questions than answers.
Oh, I have a 61 409 360 HP engine with a 623 block casting date of 5-1-61, which means the appx last 623 and the appx first 068 blocks were cast only a few weeks apart.

 

[Blk61409]

More photos

 

[Blk61409]

A few more

 

[Blk61409]

Look closely at the front carb on the experimental carbs shown above. Not the front carb has air adjusting screws, then note Nicholsons front carb. Same.

It appears Chevy knew they were being beaten by what Mopar was developing and to some degree Ford. So they quickly got all these parts underway. As the performance battle began really heavy in 62 Chevy knew they were behind and had to get moving. This is why they began developing the Special Service Package of parts. Every time a new cam or intake design they released the part numbers this way.
Hayden Proffitt told me Chevy paid him $188,000 in 1962 to race. That’s all he did. They knew they were behind and had to play catch up. Even with the Govt breathing down their neck.
As they moved into late 62 production is when the pre-Z-11 stuff showed up along with the aluminum front end parts.
As Hayden told me “Chevy was hell bent to win Indy”. And we all know he did.

So reflecting on sort of the original question of why 1961’s did not have Special Service Package parts, I think it evolved into this for 62. Knowing they had to catch up “the skunkworks” was slice and well. Keep in mind during late 61 and all of 62, not only did we see the Special Service Package parts developed, so were the pre and Z-11 parts developed along with, get this, the Mystery Motor!!
Believe me they were working 24/7!

 

[Blk61409]

Mystery Motor

 

[Blk61409]

So, 1961 was just the beginning with 1962 being the all out brain trust brain dump!
Winning Indy with Hayden sharing his
“single finger salute” to the Mopar, to launching the 63 Z-11 to building the Mystery Motor that would run 181mph in a “brick” called a 63 Impala.
All I can say is INCREDIBLE!!

 

[Blk61409]

Weren't the 61 409's small port heads? Did they come out with a large port heads and intake service package before the start of the 62 MY? If so could it have been installed before delivery at the dealership on a late MY 61? I know that kind of stuff happened in 62 just curious if it could have happened in late 61 too.

 

[oldskydog]

Great stuff Pat.
The way I see it is that Chevy already had the 409 program in the works well before the 61 model year but they weren't going to jepardize it by rushing it into production for 61 which would likely throw the whole program into chaos. Instead, They left that program to proceed as scheduled for 62 but decided to implement a temporary program for the 61 MY using the basic 348 block patterns with a new 409 core and modified 1147 heads with 3/8th pushrods and different springs for this temporary introductory version of the planned 409. That would explain why the casting numbers for the 62 068 block preceeded the 61 409 block casting number. The 61 block part/casting number was pulled from the list of future unused numbers available and it saw its problems getting the casting number right in the early days of pouring iron where they probably left the 348 011 numbers in the pattern holder and just dropped in the 409 core. After the first few days of pouring, they shook out the castings and discovered the wrong numbers or simply ground what ever numbers were there and stamped what they wanted them to be. The 586 heads were just 1147's modified and the intake was a 540 with the primary throttle bores enlarged slightly and made into a 3 holer instead of 4.
the parts catalogues didn't show any parts specifically for the early 61 409 and the later parts books referred only to the late 61 409 engine (068 block) that was the same as the 62 early 409.
There are many more aberrations that reinforce the theory that the 61 409 was a surprise, rushed temporary program that was probably cobbled together by the experimental side of engineering without the usual documentation of product development engineering.
JMHO

 

[oldskydog]

Weren't the 61 409's small port heads? Did they come out with a large port heads and intake service package before the start of the 62 MY? If so could it have been installed before delivery at the dealership on a late MY 61? I know that kind of stuff happened in 62 just curious if it could have happened in late 61 too.

Not likely, as the 360 hp 61 engine used pistons that would not be compatible with 690 heads. I believe any late 61 service package equipment would have applied to the late 61 068 block, 690 head version of the engine.

 

[Blk61409]

Cecil, I agree. By just looking at casting date info you can see they were in a hurry.
Inside Chevy at the top, management knew they were in trouble as a brand, about 40% market share. The govt wanted to break up GM. This word spread quickly and Duntov, Dick Keineth and all the top engineers knew their efforts were short lived.
After Chevy stopped racing the Special Service Package grouping of parts became Heavy Duty. They kept producing but under cover.

 

[La Hot Rods]

You guy are a wealth of history for the 409 engine development.

 

[rstreet]

I am out of luck. Too late to be a strike over block and too early for the 10 O/SS stuff
Robert

 

[Blk61409]

I am out of luck. Too late to be a strike over block and too early for the 10 O/SS stuff
Robert
View attachment 132419View attachment 132420

Robert, don’t sell yourself short!

You are at the beginning !!!!

 

[Blk61409]

Cecil, I agree. By just looking at casting date info you can see they were in a hurry.
Inside Chevy at the top, management knew they were in trouble as a brand, about 40% market share. The govt wanted to break up GM. This word spread quickly and Duntov, Dick Keineth and all the top engineers knew their efforts were short lived.
After Chevy stopped racing the Special Service Package grouping of parts became Heavy Duty. They kept producing but under cover.

As a follow up to the Heavy Duty stuff, 1970 we received a 430 cu in crank rods and pistons from the secret skunkworks, Barney Krass