Rochester Quadrajet secondary fuel pull-over ports

[My68SS]

Hi Crew, Hope everyone is well. It's been a while since I last dropped by here. [My house resembles a warzone with electronic items in just about every room demanding my attention]
I wasn't quite sure which board to put this question in, so I played safe and decided that here might ok, but I'll leave that up to the Admins if they think it's best elsewhere. 
My question is in regard to the secondary fuel pull-over ports that are just above the secondary air valves as per this pic with the ports arrowed.


It's my understanding that not all rochy quadies had these ports, it was a later refinement by Rochester to stop any possibility of lean out bogging of the engine when the secondaries are cracked open or jumped on to WOT.
In any event, I've picked up two 7028218 EH carbs for my car [L34/M40] and neither of them have the pull-over ports in the air horn, yet I see other 7028218 EH carbs on the net which unmistakably have the ports, so I'm a bit mystified by all this.
One explanation of course is that someone has fitted the wrong air horn to these carbs I have. [which would be typical of the trip wires 'Murphy' is constantly laying out for me!! Murphy and I have a close working relationship.  ]

So the key question is 'Did all 68 Camaro L34 7028218 carbs have the secondary fuel pull-over ports?

As always, thoughts and/or pics from anyone warmly appreciated! 
TIA

[Mike S]

 I'm going to do some research on this but one thing that caught my eye immediately is the use of torx head screws in the picture. They were not used when they were built originally. Is there a P/N on the air-horn assembly? There may be a date casting too near the right side front  bolt area down in a lower casting.

Mike

[Mike S]

 I checked both my '67 396 w/Q-jets (one manual and one A/T) and neither have those holes. So, it looks like they appeared afterwards.
Here is a link about the Q-jet function and it covers up to '81 but the design philosophy still is the same. Page 15 in the PDF explains the holes functions and it is as you suspected. The next question is, 'when did they appear'. Hopefully others in can chime in if their Q-jets have those holes.

http://www.bdub.net/manuals/Quadrajet_Service_1981.pdf

Mike

[My68SS]

Thanks Mike for your input and the link to that pdf, I have added it to my collection of all things Rochy!!  which has grown to be quite substantial over the years.
I haven't seen that pdf before - more bedtime stories that have to be read and understood in microscopic detail!!
I did note with interest that they say in the pdf that some rochy's had the ports but they were located just below the leading [front] edge of the air valves, so anyone that looks for them on their carb will have to just rotate the valves open a bit and check for ports above, ports below or no ports.

I don't think I've ever seen a rochy with the ports below, but then I didn't know until now of such a possibility, will have to look more carefully myself in the future.
For those rochy's that have the ports just above the air valves, there's carful adjustment needed to the linkage that runs from the slotted sector on the end of the air valve shaft to the choke pulloff diaphragm and even careful selection of the choke pulloff itself. That diaphragm does more than just pull the choke open a bit when the engine starts!
Some aftermarket diaphragms are not set up correctly and the whole air valve action is messed up because of that!!
But I'll talk more on that in another thread, I'll leave this thread to just concentrate on the secondary ports or it will get too messy.

Just one other point of interest, for those carbs without the ports, it seems that all the air horn metal and fuel wells in the bowl are present, just the necessary holes and fuel pickup pipes haven't been drilled/fitted.

Out of interest Mike, what are the numbers and app codes on your carby's that you have looked at?
Oh, forgot to mention, yes it does have torx screws in the carb picture which are as you say, not original [should be slot head] It's not my pic, just one I found many years ago.
Will check and report air horn casting numbers back here.

Till later and thanks again!!
Rob

[Mike S]

Hi Rob,
 Here are the P/N and dates:
7037210 - Rochester - C7
7027211 - made by Carter for Rochester - D7

Mike

[My68SS]

Hi Mike and other members reading this,
I've had a close look at the air horn off one of my 7028218 EH carbs for stamps and casting numbers and can report the following with pics.
It has casting number 7032741 on the underside and a stamped number at the front rh corner - 35810
I've only posted pics of one of the 7028218 air horns here, the other is still bolted to the body. Will gladly pull it if more x-checking needs to be done, but it does have the same stamped number on the outside as this one.




A pic showing the total absence of any fuel pullover ports, above or below the air valves.


A general view of the underside of this airhorn - note the absence of fuel pickup pipes that are normally fitted for the fuel pullovers [if present] even though the casting does have the holes ready for them to be fitted.


A view of another [somewhat ratty] air horn I have with pullover ports and pickup pipes [no idea from what carb, possibly 350] with casting number 7037307 [no stamp on the outside] which shows the fuel pickup pipes pressed in the holes.


And a view of one of the pullover ports in the air horn above, just above the air valve in this case and exactly in line with the pickup pipe [though you can't see that in the pic].


Cheers all, we'll compare notes soon! 

[My68SS]

Hi Mike and all, have a look at this carb that's on ebay at the moment http://www.ebay.com/itm/68-CHEVELLE-CAMARO-ELCAMINO-396-350HP-CORVETTE-427-ROCHESTER-QUADRAJET-7028218-/371279423163
There's no time clock on the auction, so hopefully it hangs around for a long time or until someone buys it, maybe I will so we can put it under the microscope!! 
It's clearly a 7028218 EH and you can clearly see it has the secondary pull over ports just above the air valves, but has a very elaborate choke pull off assembly  [different emissions carb - maybe a corvette thing??] or maybe previous owner fitted that as a replacement [perhaps it was all he/she/mechanic had or could readily get at the time?? not quite correct but it'll do - better than nothing or non-working orig.]

Edit: Heck, just noticed the name with ph to call for questions - Kurt - not our Kurt surely - but?

[My68SS]

Another interesting 7028218 quady.
Have a look at this carb advertised here http://mail.2040-parts.com/7028218-dh-quadrajet-68-camaro-chevelle-el-camino-396-w-350hp-auto-date-e8-i1135522/
It's a 7028218 but also has E8 which is presumably a date code. [may 68] and [a rather faint stamp] but according to the seller, is app code DH???
Though not a clear pic of the LHS, it does appear to be a Carter Carb which would explain the E8 date code. But an app code of DH on a 7028218 is something of a mystery.

Also, I'm not entirely convinced that the airhorn, body and throttle plate are all originally from the same carby.
Note also that there is only a hole in the plate attached to the air valve shaft for the choke pulloff linkage, instead of the usual long slot.

Unfortunately, there's no pic that shows wether or not it has the fuel pullover ports. I have written to the seller asking if they can send me [or upload] a pic of the secondary barrels in the air horn, shot from the rear and looking forward with the air valves held open a bit - Still waiting for a reply.
Though if it is a 'bitsa' carby, then the presence or absence of pullover ports may not mean much anyway.

[My68SS]

Decided to pull the top of the other 7028218 EH carb to check numbers and the air horn casting is exactly the same as the one above - 7032741 with the same [RH front corner] stamped number 35810.
The body's also have identical casting numbers 7035530. Not that same casting numbers necessarily mean much anyway, as two identical castings may have different drillings or hole sizes for completely different applications, though in this case it may carry some meaning as both bodys are also stamped with the same application number and code.
The date codes stamped into the throttle plates are quite close as well - 3397 for the one above and 2947 for this one.
Of course, the date stamps would only have any meaning if you can be sure that the throttle plate is original to the body and/or air horn.

The fact finding continues. If any one wants me to post or pm back a pic of any other aspect of the carbs I have, let me know, glad to help with anything.
Cheers