289 Hipo Crossovers

[rcgt350]

Has anyone here covered or plugged the crossovers on their factory intake on the small blocks? Could the crossovers make that much extra heat to cause a perculation senario?
Would there be many or few out there including 65/66's that have done the same?
I'm trying to eliminate why my 67 is getting fuel dripping down onto the secondaries after parking the car and it sits for about half an hour or so, the fuel then runs out each side of the butterfly shaft and drips onto the intake, only doing this on the rear barrels, no issue on the front ones.
I pulled the rear bowl off today and the float is set at 1/2"
Checked fuel pump pressure and it's 5-6 psi.

[roddster]

Multiple issues here:
1) The heat crossovers cast into the heads and through the intake help solve drivability issues while the car is in "warm-up" mode.  Where you live (up North), I'd think you would be better off letting the heat warm the intake floor for improved drivability. 
2) Fuel dripping into the intake while off: seems you might want to replace the needle and seats.  Today's fuels eat the soft rubber (ah, whatever its made of) so fuel will continue to leak through even after the car is turned off while the fuel line is de-pressurizing.
3) fuel dripping out of the butterfly shafts: Probably well worn seals.  I think in the old days Holley used leather, but either way likely seals.
4) One more possibility about leaking fuel: 87 Octane fuel here in the States containes 10% ethanol.  Eventually, the ethanol eats through the bottom of the fuel bowl(s) in a microscopic way.  You can tell where the leak is, but might not be able to see the hole.
  Rod T - Former Certified General Master Mechanic (ASE) retired.

[roddster]

   Additional item from Randy:
  Dan Case authored this information on Concours Mustang you may want to look into if you are having these same issues.  The link:
   https://www.concoursmustang.com/forum/index.php?topic=25019.0

   This has photos and pertains to the angle on the float mounting.

   

[69 GT350 Vert]

You may have excessively high under hood temperatures.  I installed a 428CJ 7 blade steel fan and a hayden 2711 viscous clutch on my '69 GT350, which lowered my under hood temps significantly.  If you haven't already, you may want to try checking your initial timing, and lowering it a little to see if it reduces underhood temps to stop the percolation.   

[rcgt350]

I don't believe I have excessive under hood temperatures, so far I've followed through with the information supplied from Dan Case and achieved instant results, I still need to check initial timing and will report back once that's done.