Intake question

[Swefd]

Hi, my name is Henry and I live in Sweden. I have a 66 fastback with a 260 (driveline from a 64 falcon) undergoing restoration. A couple of weeks ago I bought an intake for my mustang. Is there any way to determine if it's a real Shelby intake or a repro? There is some port-job, but it seems to be in decent shape. Is it possible to use without the heatshield? Kind regards from Sweden

[Coralsnake]

I believe all the original intakes have four holes in the top, not an open plenum

[shelbydoug]

I think that is just an original '65 small letter manifold that has had the plenum modified.

There was some discussion, "back in the day" of an improvement in horsepower with increasing the size of the plenum.

When those manifolds were less then $150, it wasn't uncommon for racers to work them for more power.

I think the number gained was in the 10 to 12 hp area? I don't remember that clearly. That's a 40 year old modification.

It will run fine on a street car. It may have lost some of it's crispness off of idle but will have a little more top end.

Those manifolds were noted for their throttle crispness/response. It's also a $3,000 manifold in nice original condition.

[gt350hr]

   As ShelbyDoug said it is heavily modified , BUT is a genuine '65 intake , also used on the first 252 '66 "Carry Over" cars . "Small letter" intakes have never been reproduced . The amount of modification may work for your application or not. Someone obviously felt the need as that is not a factory mod.
   Randy

[Dan Case]

   As ShelbyDoug said it is heavily modified , BUT is a genuine '65 intake , also used on the first 252 '66 "Carry Over" cars . "Small letter" intakes have never been reproduced . The amount of modification may work for your application or not. Someone obviously felt the need as that is not a factory mod.
   Randy

When we bought CSX2551 it had a 1965 intake installed with severe interior work like that. Manners below 3,000 rpm were troublesome. I changed the coolant thermostat and did some development work on the carburetor to improve low speed running and off idle manners but it was never great. I removed the intake and gave it away.
Dan

[Swefd]

Thank you for all your replies - it's very helpful. Were the intakes sold over the counter?

[427heaven]

That's a nice piece don't let it get away!

[Dan Case]

Thank you for all your replies - it's very helpful. Were the intakes sold over the counter?

Yes, there was several different line items with intakes alone or in kits in the spring 1965 catalog including a semi-finished casting racers could finish as they liked.

[pbf777]

      As stated, it has been popular to remove the plenum divider to some degree in the past on many different 180° manifolds, and did generally increase top-end power, but sacrificed particularly the tip-in throttle response value some.  Note that is possible to reinstate a simple divider in the plenum at a reasonable expense, recouping the originally intended driveability behavior, as we have done many over the years.   

     Scott.

[camp upshur]

Sadly the S1MS was a manifold of poor materials, poor design and poor performance. Early well intentioned attempts at enhancing its performance were ineffectual and it was quickly superseded by a sequence of  similar, but improved, dual plane manifolds by Shelby and the aftermarket. This appears to be detritus from that period.
The S1MS was an Offenhauser gravity sand casting of poor aluminum integrity, also the design was not robusted to compensate for this poor materials quality. It appears the posted intake has had its rear ears broken off and 'repaired'. This is sadly common and that design is in no mans land at 10-15 ftlbs tq. Expert repair and reskinning is available ($$), but then what do you have?
The holes have been enlarged / hogged out so be careful on port alignment and barely snug those last two bolts!
On a 260 this intake may well diminish that engine's efficiency.
The S1MS does live on in lore though, and it is of value to a restorer uninterested in performance.
(If on a budget there are a lots of F4Bs cheaply available)
Same intake broken and repaired/reskinned:

[gt350hr]

   For "it's day" , the S1MS was the best thing going!  Yes , we all jumped to the S2MS version when it came out. Except for multiple carburetion , there was nothing better until the "Torker" came along in the very late 60's Remember we didn't have any cylinder heads that would flow air. While Webers "were" looked at as the ultimate then , a single plane , single four will make MORE power NOW. The venerable 289 hipo head is now just a "restoration piece" compared to current offerings.
        Randy

[pbf777]

   For "it's day" ,........... was the best thing going!  ..............................Remember we didn't have any cylinder heads that would flow air. ........ Webers "were" looked at as the ultimate......... , a single plane , single four will make MORE power NOW................ 289 hipo head is now just a "restoration piece"....................
        Randy

     Now I'm feeling old & depressed,..............THANKS RANDY!!!!!!!!       

     Scott.

[Swefd]

Again – thanks for all your answers. I'll have to think about whether I'm going to put it on my 260 or sell it and use the money for a modern intake. If I sell it, how much is reasonable to ask for it? Is it enough for a preformer and maybe a couple of headers?

[JohnB]

Again – thanks for all your answers. I'll have to think about whether I'm going to put it on my 260 or sell it and use the money for a modern intake. If I sell it, how much is reasonable to ask for it? Is it enough for a preformer and maybe a couple of headers?

Henry

Its not worth much. You could sell it to me cheap! Shipping cost would be low too. I live in Norway.

John

[shelbydoug]

On a 260 with either an automatic or a manual, you will probably be very disappointed.

With maybe a 331 or a 347 that you turn maybe 7500rpm with regularly, a manual transmission with maybe 4.33 gears, and aftermarket heads that flow 300 at .500 lift it will be probably be ok. Just ok though. There are so many better manifolds then that now.

This one needs to have the plenum devider put back in and maybe a 600cfm carb used to get some torque back.

Other then that you just hang it on the wall as a display.

I don't know if it's worth $500 but it might be? Who knows? Get what you can for it.