Couple questions- Weber Velocity stacks and SSIs?

[BobNorman]

I’ve bought a 3.0L from a 1978 SC ROW that I’ll be putting into my 1970 911E project car. Sorry in advance for all the questions, but I’m learning as I go, and for the moment, am collecting parts and info before I actually have the time to start in on the car.

Velocity stacks for Weber 40 IDA 3C1 carbs:

The engine was modified to run carbs, but I’m not sure what year the carbs are from. Just wondering if these carbs would have originally had metal stacks or plastic ones? And, what is the difference? Is one type better than the other? I have 5 plastic velocity stacks, trying to figure out if I should find a sixth, or if I should just try to get 6 metal ones.




SSIs and muffler:

I think I have SSIs on this engine, not sure how I can tell other than they are stainless steel heat exchangers. Are all stainless exchangers SSIs? Or was this a brand name? From what I’ve read it seems desirable to have them (I assume for increased HP). Would this have been stock for this engine?




I ask, because I have a 2-in 1-out exhaust, but it is about ¾ of an inch too narrow to fit the heat exchangers.



I know this type of muffler was not the stock arrangement, so, was there a 2-in 1-out that would fit this set up? If not, is it better to modify the exchangers or the muffler? At the moment I’m leaning towards modifying the muffler and leaving the exchangers as they are in case I can find a muffler that fits.

Thanks for any help.
Bob

[RarlyL8]

The muffler is correct, the heat exchangers are off. Loosen the exchangers and guide the flanges to mate with the muffler then re-tighten everything.

[Tom Elder]

Hi, Bob, when I was looking into velocity stacks, I flow test both the plastic and metal versions. They both have a similar profile and flow was near identical within the accuracy of the flow bench. On my website (see below) you can download an article on elliptical profile stacks.

[1QuickS]

Those Webers were made by the Carter Carburetor Corp in Sanford, NC

Plastic horns are as brittle as egg shells and easy to break their edge during installation in OEM air cleaners. You can get metal horns from eBay seller Alfa1750 or very nice ones here:

https://www.carburetion.com/products/productdetails.aspx?part=52845.014

[SWS911]

Ditch the plastic stacks and by all means keep the tall AUX venturis

[BobNorman]

Thanks for the responses. So glad to hear that the muffler issue is just an adjustment. I really wasn’t looking forward to cutting and welding it.

Sounds like performance-wise the plastic stacks are fine, but not that durable. I think I’ll just get a sixth one for now, and look at replacing them all with metal ones later.

As for the carbs, what is the indication that they are US made? Any idea what year they are from? Is there anything that I need to know based on where they were made? I noticed the taller venturies, was this a mod? Or did they come that way?

Also, regarding the heat exchangers, are they SSIs?

Thanks again for the help folks.

[Trackrash]

From the picture it doesn't look like your exhaust is stainless. Confirm using a magnet. If the magnet sticks you have the stock exhaust "heat exchangers". SSI is a brand name associated with stainless 911 exhaust.

You may want to consider having those exhausts coated to prevent rust, if they are indeed not stainless.