Best way to block heat crossover in intake

[Scott Marzahl]

What would be the best way to block off the heat crossover in the intake manifold for my L-79 327. Does GM make an intake manifold gasket set that has the crossover blocked? I have a new set of Fel Pro Printo Seal gaskets that have a restricted crossover, it's about a 3/8 or 1/4 inch hole in the gasket.
Is this restriction enough to curb the boil over and carb warpage problems? I am also thinking about installing one of the Z-28 type carb insulators.

[John H.]

Re: Best way to block heat crossover in intake

Scott -

The restrictor holes in the Fel-Pro gaskets should help a lot (make sure your heat riser valve is either working freely or is wired open); if you completely block the crossover passages, it'll take a LONG time for your remote choke coil to pull off the choke - it needs heat under it to unwind and open the choke.

[Scott Marzahl]

Re: Best way to block heat crossover in intake

John,
I plan on welding an old riser valve open from the inside so that it appears to look stock. That should help matters out too.

[John H.]

Re: Best way to block heat crossover in intake

Scott -

Keep in mind that if you plan to have your car judged, they will check to ensure that 1) The weight points outboard (and it will be straight down if you weld it open), and 2) That the weight moves freely between outboard and straight down against the spring. I wire mine open for regular driving and remove the wire for judging.

[Joe L.]

Re: Best way to block heat crossover in intake

John and Scott----

Another option for the heat riser elimination is to carefully remove the "butterfly" valve from the shaft using a Dremel Tool or cut-off wheel. Then, the valve outwardly operates "normally" but is otherwise functionless.

[Mark Ring]

Re: Best way to block heat crossover in intake

Scott,
I just went through this on my car. If your car has a cast iron intake it will take a long time to heat up if you fully block both sides. I have an aluminum intake so it is less of an issue. I used a flat piece of thin stainless steel sheet metal 1-3/4" wide by 2" long with a 1/8" 90 degree lip along the top to prevent it from falling into the engine (thanks Clem). I stuck it between the 2 center intake manifold bolts on the drivers side of the intake gasket sealing surface and installed the restrictor insert into the passenger side intake gasket. This allowed some small amount of heat to the choke coil area in case I ever went back to the stock non-electric choke. This did the trick to reduce percolation but allowed for some heat to reach the carb for better drivabillity.

-Mark.

[Clem Z.]

Re: Best way to block heat crossover in intake

just unhook the spring and it will hand open because of the weight.