Engine insulation

If you use these materials in higher heat areas, you can wind up with an odor problem every time the engine heats the surface to which it is applied....  This would be heat that the insulation manufacturers never planned on encountering...  

Dynamat does not block heat it is a sound deadening material only. High heat areas will cause it to deteriorate very quickly.

You would need to use something like Koolmat or Thermat and you would also need a hi-temp adhesive because regular adhesive will not take engine heat without deteriorating.

Or pull your engine and use LizardSkin heat shield , you can spray it on to any surface you want to insulate, it works very well

Good comments, I guess I forgot about the adhesive breaking down. I just thought with all the talk about keeping heat out of the engine compartment this may help.  I don't want to create a fire hazard by trying to keep the engine compartment cool, that would be counter-productive!

I don't have a oil cooler installed yet.

Gary

Ummm ... it's an AIR COOLED engine. The cooling tin's main purpose is to direct air but it also acts as a heat sink.  One of the reasons folks don't like chromed engine tin is that doesn't dissipate heat as well as satin black painted tin.  Go with a Subbie engine or VW bus Wasser engine - the water coolant both cools and deadens engine sound.

I'd think one the asphalt base got really hot from contact with cooling fins of piston jugs and heads, it would melt dropping airflow and eventually catch fire ---just like accumulations of grease and oil can.  

Despite the issues you would be encountering by using the wrong material (failed adhesives, melting and possibly burning material) I think you're on to something, Gary. It wouldn't work everywhere, but I think insulating the underside of the sheetmetal above the exhaust (the rearmost piece the heater hoses go through if you're running heaterboxes- rear breastplate?) so it doesn't radiate heat back into the engine compartment would be worthwhile. I'd been wondering what to use for some time now, so thank you G.R. (is it Gary as well?)

The LizardSkin looks like an interesting product (I'm a painter by trade), but I don't know about buying 2 gallons...Al

I haven't messed with thermodynamics since college, but it would seem to me that heat insulation on the underside of the engine tins (if they are complete and the compartment is well sealed) would only be effective when the car is sitting still with the engine running, and how often is that?  Even then, once the compartment heat soaks, the insulation would lose effectiveness (I think that follows a logarithmic function, IIRC).

When it is underway, the motion of the car will flush away the heat from the bottom of the car so I would think that properly sealing the top of the compartment from the bottom would be the most effective solution.

I doubt that it would reduce rocker arm noise, either, since that noise would still be below the insulation layer and the sound bounces off of the road surface and surrounding hard surfaces.

Well, here goes: thermodynamics happens to be what I do -- or did until retirement. The issue here seems to be keeping the heat at the bottom part of the engine bay, where exhaust parts are, separated from the upper engine bay, where carburetors and other heat-sensitive components reside.  In general, heat is transferred from one point to another via radiation, convection &/or conduction.  Radiation transfer only gets interesting when the surface doing the radiating gets pretty hot.  Convection happens when the surface is exposed to flowing fluid, i.e., air.  Conduction happens between and within solids.  The flat engine tin used here to separate top from bottom, mostly blocks the air at the bottom from reaching the top.  Said air having been heated by the crankcase exterior (at oil temps) and the exhaust headers, running at a few hundred or maybe even 1,000 F.  Also, the fan forced air over the cylinder fins is exhausted underneath, and so contributes to the heating of the air generally below the tin.  When the car is in motion, air moving under the car will remove a lot of this hot air, and the tin provides a good fairing to help it stay below, and go out under the bumper.  The tin is also a decent radiation shield, serving to block radiation from the hot exhaust pipes upwards.  Optimization here would call for a reflective surface on the bottom of the tin, like shiny SS, for example.  There are paints that would work well here also.  But even regular old black painted tins will be a decent radiation shield.  The only way I can think to improve the situation would be to apply a fireproof light weight material, like glass wool, on the underside.  Such would tend to block some of the convective heat to the underside of the tin, and to serve as a decent radiation barrier.  Might supply some sound deadening also.  Such material might not be very durable, however, as it would get a lot of road dirt and water.  One could imagine making a dual layer tin, that is, two tins with a small air gap (11/4" or so) between layers.  Such would add a fair amount of thermal resistance from top to bottom (still air is a terrible heat conductor), and it would improve the radiation shield performance also.  I do not see outright conduction as an issue here.  The only significant conduction of heat from the engine to the upper engine bay would be through the intake manifolds.  Here one looks for a balance between too much and too little.  Too much and the manifold heats the carb and could cause vapor lock.  too little, and the gas vapors could condense on the manifold wall, especially in cold weather.  VWs dealt w/ this using a centrally mounted carb some distance from the engine block, thin intake manifold tubing, and a heat riser device that could add heat to the manifold in cold weather.  On the more prominent dual carb set ups most use these days, the big Al casting manifolds that hold our hurky Webers, etc. short-couple the carb to the block and can get a lot of heat from the block.  Here it is best to try to interrupt the heat path between manifold and block using fiber gaskets, vs. the metal ones used on the VW w/ central single carb.

So the deal here is that the original design is pretty good, provided you have a good flexible rubber seal around the tin between it and the body.  The majority of the thermal management here is simply ducting, and anything that keeps the lower air in the lower section is going to work.  If you just had to do better, I'd see about having a dual layer tin made with an air gap between.  No doubt it would perform better, but already the original is plenty good enough.

We're not worthy, O Great One! 

Thank you for the thermodynamics education, that makes sense.  I have had many VW bugs and never had a cooling issue, but I do understand that the bug was designed for a smaller engine and the grills above the rear deck lid did it job reasonably well.  I have seen the rear deck lid "stand-off" that had the top of the rear lid opened by a coupe inches which made sense.  On a speedster, that may not work as well.  I am going to install the h type engine seal as I don't like the current seal on my speedster now. 

Thanks again!

Gary

Kelly took the words right outta my mouth! 

I'd like some of the heat shield tiles off the space shuttle - wonder if they have any rejects available cheap?