Nuts to you... peanuts, that is...

[TobyB]

In digging around for a manifold for Bill, I found 2- one peanut, one 'US' spec.

So I took pictures, since this question came up a while back, and it was not

easy to find a picture.

(not mentioning that RealOEM has drawings of both, of course)

 

I flopped them top- to- bottom, so the one on the left stays on the left.

Edit- arrgghhh, Cupertino, you always know better, don't you?  The one on the top

is the same as the one on the left

Also, the Peanut's been ground on a bit, whereas the 2- holer is as it left the factory.

 

Do note that the US part number in RealOEM is

11611257725

Which, frustratingly, looks close, doesn't it?

But it's not the exact same as the casting numbers.  Because,

as I ranted earlier, and now again, casting numbers aren't part numbers...

 

Hope this helps someone,

 

t

 

Edited February 28, 2017 by TobyB

['76mintgrün'02]

Ha!  Several years ago I asked whether I should peanut-ize my manifold under my 32-36.  The answer was NO.  I did port match it to the base of the carb though.

 

These were the 'meatiest bits' of that thread.  Simeon gets credit for the Quote.

jimk

• Advanced Member
•  
• 
• Members
•  277
• 3,216 posts
• Denver, Colorado

 

Posted August 24, 2012 · Report post

Quote

Conventional wisdom is don't peanut just taper/ enlarge the holes to match the throats of the carb. Peanut-ting may slow the speed of the charge too much by increasing the plenum volume below the carb.

I am running mine on the stock manifold, untouched. This is just a phase I am going to grow out of on the way to sidedrafts so I haven't bothered. Too many people say that you can't feel the difference, even if the flow bench tell you it's good. Just drive it and rev it 250 revs higher before you change each gear.

+1

Finally there is a guy that understands what a sudden enlargment in an air stream does. It also causes fuel to recondense.

Flow bench testing a manifold alone does not tell the whole story. The flow bench test should be done with the carb installed both before and after peanutizing. And if the test aparatus is good enough, the after peanutizing results will be worse because of the sudden enlargement effect on the flow dynamics (it's another fitting loss coefficient in the air stream.).

 

There was not a lot more to that thread, but I seem to remember another one, which brought up the fact that BMW had made that change... as your parts and realOEM suggest.  The question is 'why would they do that?'

[Simeon]

There was a recent discussion about this led by... Toby I believe. This wondered whether this was an attempt to correct the natural imbalance between charge going to 1 & 4 cylinders versus 2 & 3. Different length paths means greater/ lesser degrees of gas dropping out of the charge. 

 

This may have been the result of the need to run ever weaker mixtures for emissions. 

 

Old school would say that the runners on a downdraft manifold are pretty long, so you probably want to keep the charge velocity as high as possible. Minimising the back space under the carb will do that. 

[Simeon]

Another observation on this subject. There seems to be some variation in the various drilled holes in the top of the runners. Are these blind holes or do they break into the intake runners?

 

My car (73) is fitted with a two port manifold but has minimal drillings and vacuum take off open. Do we know what each of those are for? What are the ones with the bolts are for? Air cleaner brackets?

['76mintgrün'02]

The air cleaner brackets are mounted on the studs that attach the manifold to the head, on cylinders two and three.

The other mount attaches to the far end of the manifold.

The threaded holes do not go through and so they do not need to be plugged, but it bugged me, so I filled mine with round headed aluminum rivets ( and a little bit of sealant just to hold them in ).

My guess is that the threaded holes were used to attach emissions equipment.  It is just a guess, because that stuff had already been removed when I bought my car.  

 

I have an extra intake manifold and am considering shaving off the threaded bosses and possibly welding up the unused vacuum ports on one and four.  It would take a little fiddling to match the texture of the casting where that had been done, but it might be fun.

 

Could one reason for the differences you are seeing be related to emissions requirements/equipment for various countries?

 

These are just guesses, but the threaded hole just in front of the carb might attach the 'fuel diverter valve' and the two on numbers three and four were possibly used to mound a vacuum pod which controlled 'something' on the original Solex; to make it run 'cleaner'.

 

I'll bet we get a better answer soon : )

[Conserv]

5 hours ago, '76Mintgrun'02 said:

The air cleaner brackets are mounted on the studs that attach the manifold to the head, on cylinders two and three.

The other mount attaches to the far end of the manifold.

The threaded holes do not go through and so they do not need to be plugged, but it bugged me, so I filled mine with round headed aluminum rivets ( and a little bit of sealant just to hold them in ).

My guess is that the threaded holes were used to attach emissions equipment.  It is just a guess, because that stuff had already been removed when I bought my car.  

 

I have an extra intake manifold and am considering shaving off the threaded bosses and possibly welding up the unused vacuum ports on one and four.  It would take a little fiddling to match the texture of the casting where that had been done, but it might be fun.

 

Could one reason for the differences you are seeing be related to emissions requirements/equipment for various countries?

 

These are just guesses, but the threaded hole just in front of the carb might attach the 'fuel diverter valve' and the two on numbers three and four were possibly used to mound a vacuum pod which controlled 'something' on the original Solex; to make it run 'cleaner'.

 

I'll bet we get a better answer soon : )

 

Yes, the threaded boss on the Number 1 runner is for the fuel diverter valve bracket, shown in the first photo.  And, yes, the threaded bosses on the Number 3 and 4 runners are for the dashpot bracket -- seen in the second photo -- the dashpot serving to dampen throttle closure which, somehow, reduces emissions.

 

As to the factory "peanut" manifolds, do we have any sense of when they were used?  The dual-barrel Solex appeared in approximately April 1972 in U.S. cars, concurrent with the E12 head.  Is that right?  Late cars, at least '75-'76, appear to have had two individual borings, rather than peanut.  Surely someone here has seen a pattern to the presence of peanut manifolds.  I long assumed they were an ill-conceived home modification, but, yes, there are probably far too many to be home modifications.  Can we differentiate them by part number?

 

Regards,

 

Steve

 

 

 

Edited February 28, 2017 by Conserv

[Simeon]

Looking at the realoem listings, the peanut seems to be the early version. Simplistically this has the lowest part number, lower than all of those listed on the fische showing the two hole version. It also appears to have the least emissions type appendages. There are also VIN numbers listed against US 2002 and US 2002A.

 

Could the peanut manifold be a US only thing, reflecting an early adoption of the twin choke solex? By the time they started fitting them in Europe they had gone to the two hole version?

 

 

 

p.s. Is that your engine Steve? Very nice example with an original carb. What is the bracket for next to the oil filter? Air pump? No other air pump type piping / equipment visible. What set up do you have in terms of emissions equipment. 

[02Les]

According to my interpretation of the BMW Blue Parts Book

The single hole manifold was used up to around mid 1972 (VIN 2532752 auto & 2583405 manual) from these VINs style 1 peanut manifold was used in USA.

Style 2 peanut manifold used from Sep 1973 (VIN 4280000 M & 4220000 A) and a 3rd style for USA Model 75.

 

Basically, a single hole manifold was always used on all Euros, although a peanut manifold was used on Euros, I think, only in 1975 and only for the 2002M & 2002A.