carburetor heat shield

[airbob01]

How important is the heat shield under the carburetor? Seems to be a big PITA! If it's not that necessary, I would like to remove it.
Bob

[jordan]

Im not using a heat shield and everything seems fine.

[tekenaar]

Originally posted by airbob01 How important is the heat shield under the carburetor? Seems to be a big PITA! If it's not that necessary, I would like to remove it. Bob

Keeps exhaust manifold radiated heat away from carb, specifically carb bowl, to reduce fuel percolation and "hot start" problems due to this. Overall temperature reduction of carb body is NEVER a bad thing.

I always use one and even fabricated one for my single sidedraft installation (see pic). Especially important to use one with the stock "joined" manifolds setup, as you already have to deal with a lot of heat from the "stove" under the intake plenum. That's JUST my opinion, though.

[West Coast GT]

From other discussions in this forum, its been said that the original Solex carbs are made of cheap metal and have a bad habit of warping from heat, thus making them impossible to adjust properly and effecting performance.

So it sounds to me that maintaining the heat shield is a good idea for an aftermarket Weber, and critical for the original Solex.

[tekenaar]

Originally posted by West Coast GT . . . So it sounds to me that retaining the heat shield is a good idea for an aftermarket Weber, and critical for the original Solex.

While we're on the subject of "heat retention", if ANYONE is still using the original metal line across the front of the engine and a metal can fuel filter, I STRONGLY RECOMMEND that you replace the metal can filter with a clear plastic one and wrap the entire exposed length of metal fuel line with 1/4" plastic "split wire loom".

You'd be amazed at how quickly and thoroughly any underhood exposed metal absorbs and retains radiated heat. NOT GOOD! The plastic split wire loom and the small air pocket it has effectively shields your metal fuel line from this radiated heat. Replacing the metal can filter with a plastic one is pretty self-explanatory.

[opeldean]

I have insulated my gas line with rubber and plastic,i also use a plastic filter.

i am plagued by lengthy starts when hot and garage that smells like gas when the engine is warm...irregardless of outdoor temp.

what do you think?

[opeldean]

this is weird...the exhaust manifold is designed to heat the carburator..with its heat riser....now we talk about heat cooling it with a heat shield....


ps: i saw something similar at "best buy electronics" it was an refrigerator-oven....keeps food cool for up to 24 hours..then the timer goes off ..cooks your food..then keeps it warm till you get home from rush hour traffic.if you work late.goes back into cool cycle ..so it doesnt spoil.

[GTJIM]

From the look of the carb pic there is not a heat shield under the carb.

The stock one is made of two thin formed sheets of ali with ASBESTOS sandwiched between them so run a mile if you come across one of them as it can KILL you - slowly!

You could make one from an ali sheet 1/16 th thick. It just goes under the carb base with a gasket each side and sticks out all round. Some even bend up between the carb and rocker cover and act as a barrier between the motor/exhaust manifold and the carb. They need air flow over them to remove heat as the carb still heat soaks once the engine has stopped.

A simple way to cool everything down in the garage is to just pop the hood as you get out of the car to allow it to cool quicker in the engine compartment. This allows more air flow up past the carb when the motor is stopped.

[kwilford]

I've never seen a GT heat shield that was anything other than a single sheet of aluminum, such as shown below. Maybe the asbestos/aluminum sandwich is a European (or Kiwi) thing?

A heat shield will reduce the amount of heat absorbed by the carb from the exhaust manifold and the engine block. The heat shield acts as radiant "barrier", both during normal operation and during "heat soak".

And while the "heat stove" design on the '68 to '74 Opel CIH engine aids in fuel atomization at low temperatures, it is a bad thing at higher ambient temperatures, and during heat soak, which occurs immediately after the engine is shut down. The outer engine surfaces actually gets HOTTER than when the engine was running, as the engine's internal heat gets dissipated to the outside surfaces instead of to the coolant. This heat in turn gets radiated to the carb, boiling the fuel in the bowl, and causing vapour lock in the fuel pump.

[opeldean]

1-does a weber 32-36 (or other carburated format ) NORMALLY need a heatshield to prevent a "dry bowl when engine is hot"

2-does a sprint exhaust bypass the need for a heatshield?

3-my understanding here..is that most people are running without heatshields...especially if they have changed carbs...

4-should a mechanical fuel pump be wrapped in insulation to prevent its absorption of heat?

[tekenaar]

Originally posted by bucky A: this is weird...the exhaust manifold is designed to heat the carburetor..with its heat riser....now we talk about heat cooling it with a heat shield.... . . . Originally posted by bucky B: 1-does a weber 32-36 (or other carburated format ) NORMALLY need a heatshield to prevent a "dry bowl when engine is hot" 2-does a sprint exhaust bypass the need for a heatshield? 3-my understanding here..is that most people are running without heatshields...especially if they have changed carbs... 4-should a mechanical fuel pump be wrapped in insulation to prevent its absorption of heat?

A:
Exhaust manifold is actually designed to heat plenum UNDER carburetor to help emulsify fuel/air mixture FROM carb, NOT really the carb itself, though that IS a byproduct of the design and, hence, the reason for the heat shield under the carb.

The better the mixture is emulsified, the better it burns. In cold weather, gas in the mixture in plenum is more likely to return to liquid state and, remember, liquid gas doesn't burn very readily.

B:
1. ALWAYS a good idea!

2. No, still a good idea!

3. What about good idea is not clear?

4. May be worthwhile, but "vapor lock" usually occurs in the gas line itself (smallest passage, easiest for "vapor lock" air bubble to form).

:o

[cristian68rekor]

When I was using the SOLEX carb on my 1.9 Rekord CIH-engine I had the same problem -> the engine doesn't start after 10 minutes stop at air temp bigger than 18 degrees Celsius . After this I tuned the engine with 2 side draft Solex C40ADDHE and one OP244 KENT CAM ( the rc is around 10:1) . The intake and the exhaust manifolds are hand made ( a lot of work) . Yesterday I installed one heat shield under carbs ->see picture , may be is a usefull idea .
Cristian (from Romania)