Author Topic: '70 T/A carbs/cfm  (Read 588 times)

crossboss

  • Member
  • ***
  • Posts: 397
  • ^ My old heap.
    • View Profile
'70 T/A carbs/cfm
« on: July 10, 2020, 01:31:43 AM »
Jon (and others),
For the 1970 Trans-Am, I was wondering as this was discussed on another forum and hopefully we can get some answers: Were there any rules implying a limit on cfm for the single carb rule? I am aware no Dominators were to be used and 'exotic' stuff like Ford's Inline carb set ups. Thanks ahead for any input.
Just another T/A fanatic. A new project in the works.

Jon Mello

  • CRG Member
  • *****
  • Posts: 4305
    • View Profile
Re: '70 T/A carbs/cfm
« Reply #1 on: July 11, 2020, 09:45:03 PM »
The rule limited throttle bore size which essentially ruled out the Dominator carb.  The '70 rule book says the cars "must use a single SCCA approved four barrel carburetor with throttle bore size at the butterfly no larger than 1-11/16" diameter.  Extensions or addition of material, except for throttle linkage, to the exterior of the carburetor body is prohibited.  The carburetor must be a readily available, reasonably priced production model to receive SCCA approval."

The last sentence seems to be aimed squarely at the Autolite in-line four barrel carb.  1970 is the first year you could use an aftermarket intake manifold if you wanted to.
Jon Mello
CRG

crossboss

  • Member
  • ***
  • Posts: 397
  • ^ My old heap.
    • View Profile
Re: '70 T/A carbs/cfm
« Reply #2 on: July 11, 2020, 11:13:05 PM »
Thanks Jon!
I will pass along your info.
-Scott.
Just another T/A fanatic. A new project in the works.

Jon Mello

  • CRG Member
  • *****
  • Posts: 4305
    • View Profile
Re: '70 T/A carbs/cfm
« Reply #3 on: July 12, 2020, 05:08:07 AM »
You're welcome, Scott.  Glad to be of help.
Jon Mello
CRG

crossboss

  • Member
  • ***
  • Posts: 397
  • ^ My old heap.
    • View Profile
Re: '70 T/A carbs/cfm
« Reply #4 on: July 13, 2020, 05:39:34 PM »
Jon,
I received this bit of info from Randy Gillis, and hopefully you can store it in the archives for how things were done for racing aka cheating!

 Scott,
      Yes that is typical of SCCA. Make it something they can easily measure.  There are several SK carburetor listings that note "big" CFM with 1-11/16ths throttle blade callouts. I have one of those that I am in the midst of "validating". I am very confident Harold Droste ( rip) , Holley's cutting edge liason to Ford , was making some "special" carbs for Ford that flowed really well yet passed "tech".
    Randy

Scott , the CFM rates are noted on the particular SK numbers. To avoid a debate from well meaning people , I will say "over 900" for six different listings . NO , not dominators ( Model 4500 to Ford) or "three barrels". Remember I'm not saying they "worked"  correctly but they were made. I have a large collection of "development" Ford / Holley carbs and notes on even more. None of which have #180 throttle blades.
   Randy
Just another T/A fanatic. A new project in the works.

Jon Mello

  • CRG Member
  • *****
  • Posts: 4305
    • View Profile
Re: '70 T/A carbs/cfm
« Reply #5 on: July 14, 2020, 12:33:05 AM »
Thanks, Scott.  I have no doubt on those cheater carbs and parts being made back in the day.
Jon Mello
CRG

 

anything