Engine: Blocking off the Heat Riser ?

[BassMan]

Hello to all----I'm trying to finish my rebuild of a 1957-- 289---out of my Silver Hawk. I decided I would watch the Jim Maxey video . He blocks off the middle hole in the heads (ie heat riser ). I've looked thru the posts on this subject, but I really don't understand the reason for this. What would you do this for? I take it there are pros and cons. From what I read, this procedure may solve certain problems that some have in hot climates? I'm getting ready to install the intake so I'm wondering if it is something that I should consider. This would be the time to do it , considering the engine is on the stand now. I live between Cinc and Dayton in Ohio. Would you just put in a manual choke cable ? Anyway, I'm a newbie so if anyone knows the pros and cons it would help me decide---Thanks BassMan

[PackardV8]

Pros:
When tuned for racing, keeping the intake as cold as possible makes more power.
On very hot days, keeping the R1/R2 intake cold reduces pinging.

Cons:
Reduces fuel economy
Takes longer to warm up
Carburetor can ice in humid climes

jack vines

[BassMan]

Thanks Jack----Do you just install a manual choke cable for starting? And...Do you remove the butterfly in the exhaust as well ? Thanks----BassMan

[oilnsteel]

You can install an electric choke, and use a spacer in place of the manifold heater valve. Many Stude vendors have the spacer. I am a true CASO, but prefer buying the spacer to
ruining a good valve. JT

[altair]

Personally myself I would not block off the heat riser. When the system is working properly the heat riser heats the intake manifold to assist to atomize the cold fuel. This system also provided heat to operate the automatic choke. Heat risers can fail sometimes open and sometimes closed and can cause some unwanted behavior. The unit require periodic maintenance to assure it is functioning properly. With a functioning heat riser and automatic choke your car will run trouble free for many years. Many of the modifications just cause unwanted behavior. The engineers got it right and it works well. In my opinion don't modify it.

[BassMan]

Thanks everyone ( oilnsteel-altair--packard v8 ) for chiming in. It is appreciated. I will make sure everything is in good working order. I think I will put it back to factory like altair suggested. Regards
BassMan

[Bud]

In my 62 Hawk I still have the heat riser that I wire open in the summer and leave operational in the winter. My 63 Avanti has an aluminum intake manifold with a blocked off exhaust crossover which works well in the summer but not so well in the winter when the temperature is in the low 30's. Both engines have later AFB's with an electric choke which work well. The Avanti in cold weather is prone to stumbling for the first few minutes until the engine warms up where the Hawk with the heat crossover in the manifold doesn't have problems. In Kingman, AZ we can see temperatures in the summer in the low 100's and in the winter, the temperature in the morning can be in the 20's. Bud

[mw2013]

causes vapor lock, po took it off the exhaust, so it was on all the time, i bought block off plates, that and the phenolic spacer for the 1403 carb put an end to the no start after driving syndrome

[bensherb]

I blocked off the ports in the head years ago. The valve in the exhaust was gone when I got the car. Even with the head ports blocked, I still had to do many things to keep fuel from boiling in the carb. The temps here run from as high as 115F in the summer, to low 40's winter mornings with highs in the mid 50's. I've never had any real starting problem aside from the electric choke, but it does take a few minutes to warm up in winter. A manual choke makes starting and warm up super easy; I converted my electric choke to manual and it now fires up first time every time.

[DEEPNHOCK]

If you block off the heat crossover, you will need to wire open the heat riser under the RHS exhaust manifold.
Wire the heat riser open, remove the blade, or gut it. Removing the whole heat riser will cause exhaust pipe fitment issues.
I have sold hundreds of AFB conversion intake manifolds, and many of those happy customers have also purchased my intake manifold installation kits.
The kit consists of a pair of composite intake gaskets that have no hole in the heat crossover passage. The exhaust pulses will erode the composite gasket so a pair of .015" stainless plates get sandwiched between the head and the composite gasket. The stainless plates reflect the hot exhaust pulse to keep the gasket from burning.
The conversion manifolds all have the choke port in the crossover plugged, so an electric choke or manual choke carb will be needed.
I admit, this is not for the purist, but does fit the "I'd rather fix than switch" mantra.
Reducing the heat input into the carb is key. Won't stop convective heat, but it does help stave off hot fuel vapor lock issues in warmer climates.
Most of our Stude's are driven in fair weather, so this is an alternative that has some good history behind it.
HTIH (Hope The Info Helps)
Jeff

[Hawklover]

You can install an electric choke, and use a spacer in place of the manifold heater valve. Many Stude vendors have the spacer. I am a true CASO, but prefer buying the spacer to
ruining a good valve. JT

I have a 1403 carb on my Avanti, I removed the heat valve and replaced it with a spacer purchased from Jon Myer. The car is never utilized during the winter months, and generally gets put to sleep just before Thanksgiving, so winter drive-ability is never an issue. I also purchased special spacers for under the carb. The car does not vapor lock, and in the interest of honesty is not driven during the extreme heat of the summer. Only spring and fall.

[stude1964]

I used the block off on my '64 HT. I didn't like the sound of the exhaust as the duals whistled. I fixed my AFB issue along with a better base gasket from Phil Harris and returned the intake and heat riser to original . I run only ethanol-free gas and now find I can bang third and it wants to go instead of stumbling. It's fun again! I prefer keeping my vehicles original as possible-that way I know what I have.
Rob in PA.

[BassMan]

Many thanks to all of you for your input---it helps a lot. BassMan