Carb. insulators

[sujitroy]

There's a person who goes by "MrDodgedollar " on my YouTube channel. This person says to replace the baker lite insulators with replacements and that the replacements are a better material than the original, all be a little thicker so be aware. It makes a world of difference hot starting. Also mentioned is to do away with the spring washers and replace with fiber washers.

My auto Stag has hot start issues, but not my manual.

I'm willing to try this theory out. MrDodgedollar hasn't mentioned yet who carry these insulator, but are new insulators made differently? I'm aware TR6 folks here in USA run into similar hot starting issues as well.

Sujit

[Philip Wardle]

Hi Sujit,

I came across these insulators for Stromberg CD175 carbs, apparently they are fitted to the V12 E-Type and also USA spec XJ6 Series one - I'm not sure these work for the Stag arrangement

https://www.etypeparts.com/c33060-e-type-carburetor-insulator-gasket-stromberg-carbs

[jbuckl]

I can’t fathom why the insulators would need changing unless they have been taken out & damaged…. Never seen a damaged one.

[trunt]

I wonder if thicker insulators would affect the linkage? On a TR6 it doesn’t matter as they are parallel but on the stag they are angled so you would perhaps mess up the relationship enough to go outside of the adjustment limits?

[RNF]

If you had access to a mill, or were just patient, you could purchase some Phenolic material from McMaster of the thickness of your choice and make your own. Phenolics are definitely better than the fiber spacers at isolating the heat.

These "look" to be made from phenolics https://www.goodparts.com/product/sp...anifold-175cd/ 175-Spacer-Insulator-175CD.jpg

[Wheelz]

Dont change the thickness, it will mess up a number of things (including the fit of airbox to air intake elbows and throttle linkages). I know this because when I designed adapters to use the Stroms as EFI throttle bodies, that became evident.

It might be possible to 3D print using a better heat insulator. (low thermal conductivity) for example PLA 0.13 whereas Phenolic is only 0.02.

[Philip Wardle]

Good idea, phenolic resin looks viable - thermal conductivity is low, about 0.2 W m^-1 K^-1 and the material is easy to cut and shape. I saw that a chap made some insulators from one of those white plastic kitchen chopping boards. Apparently these are usually made from high-density polyethylene which is good for hygiene although its thermal conductivity is 2.5 times higher than phenolic.

Out of interest fibreglass = 0.04, cork board = 0.04, asbestos = 0.08, aluminium = 205, copper = 385, diamond = 1000

[sujitroy]

If you had access to a mill, or were just patient, you could purchase some Phenolic material from McMaster of the thickness of your choice and make your own. Phenolics are definitely better than the fiber spacers at isolating the heat.

These "look" to be made from phenolics https://www.goodparts.com/product/sp...anifold-175cd/ 175-Spacer-Insulator-175CD.jpg

This could be interesting. Let me follow up on a TR6 FB forum I'm on.

[jbuckl]

in a stag engine bay, carbs will get hot whatever insulation material is used.

certainly way above the boiling point of modern pump fuel.

A test might be useful to determine the delay / lag / latency of temperature transfer with different materials…. (Who’s up to test that?) …. Not me at the moment.

the insulators also have gaskets don’t they? Will affect transfer.

my electric cooling fan was only installed to assist with heat soak after key- off, but can also help the other cooling requirements if needed.

5 or 6 fan cycles are required after key - off before carbs are below fuel boiling point…. (36 deg C) On a 30 deg ambient temp day…. (Revotec thermostat thermocouple on stainless braided fuel line) battery copes fine with that cycle.

The above illustrates the amount of heat-soak available after key - off.

I can’t see improved insulator material helping much with overall heat soak to be honest…. The carburettor elbows collect & transfer rising heat to the carburettor bodies after all.

But a test & temp survey is needed to be definitive regarding insulator material…. Quite a big job to undertake….. no doubt worthwhile in terms of solid information for all stag owners. But somewhat costly in terms of time & effort.

In the industry , the failure to acknowledge heat soak as the worst case cooling system temperature condition or duty - cycle has caught many OEMs out…. Even higher up the tree than uncontrolled warm -up cycles… which has caught a few out too…. Not withstanding system failures.

Theres one exception as far as I’m aware…. That is a high speed chase…. In reverse (usually only the police) …. Apparently the cause of some sd1 engine seizures!!! … probably others since those days too.

Think about it…. 100mph forwards for a while, then 40mph in reverse…. Ouch for cooling.

[Philip Wardle]

You're right of course Julian.

The fuel itself is a component in the system - changes in formulation made the original thermal design of the system invalid. As MrDodgecollar suggests it's good systems thinking to re-visit thermal design trade-offs between the fuel and other components. The insulator is an immediate candidate because we can easily experiment, and we've had an interesting discussion. But even if thermally perfect it can't mitigate for the operating environment under the bonnet once the car has wermed-up.

[jbuckl]

You're right of course Julian.

The fuel itself is a component in the system - changes in formulation made the original thermal design of the system invalid. As MrDodgecollar suggests it's good systems thinking to re-visit thermal design trade-offs between the fuel and other components. The insulator is an immediate candidate because we can easily experiment, and we've had an interesting discussion. But even if thermally perfect it can't mitigate for the operating environment under the bonnet once the car has wermed-up.

I'm not sure its that easy to test & validate the insulator material choice.... but would welcome any measurement information