### Help Support Homebuilt Aircraft & Kit Plane Forum:

#### Pops

##### Well-Known Member
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I have found the air passages from completely blocked to very clean. Just make sure that all the passages are clean if you want max cooling for your engine. Also use black painted valve cover pans and black painted pushrod tubes for max heat transfer. I know the stainless and chrome looks better, but will not cool better. VW engineers knew what they were doing.

#### N8053H

##### Well-Known Member
Looking at my vw engine installed in my airplane, the exhaust comes real close to the bottom of the jugs and those tubes. Because of this I wrapped my exhaust pipes with header wrap. But I did not stop there. I also wrapped the intake tubes both coming into and out of the carb. I am doing this hoping to reduce the heat in the cowl. I also replaced the baffle seals and sealed the baffle to the engine a little better. Not that it was bad or not sealed before, just paid a little more time to the details. Heat has never been an issue, but that exhaust looks to be a little to close to that engine then I like. This may help.

Tony

#### N8053H

##### Well-Known Member
Pops let me ask would you cover those fins on the heads like that? I am not done yet. All those wires are getting redone. I don't like them wired to the tubes. I will stand them off the tubes. Getting close to being done but not rushing this installation. If you notice the cylinder heat probes are attached to the fins on the cylinders. They came installed under the jug hold down bolts. I did not want to remove these nuts and then retorque them. I also did not want them under the spark plugs. This was my solution to this problem.

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#### Pops

##### Well-Known Member
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Pops let me ask would you cover those fins on the heads like that? I am not done yet. All those wires are getting redone. I don't like them wired to the tubes. I will stand them off the tubes. Getting close to being done but not rushing this installation. If you notice the cylinder heat probes are attached to the fins on the cylinders. They came installed under the jug hold down bolts. I did not want to remove these nuts and then retorque them. I also did not want them under the spark plugs. This was my solution to this problem.

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No pictures.

#### N8053H

##### Well-Known Member
Well heck, let me try this again.

#### Pops

##### Well-Known Member
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Pops let me ask would you cover those fins on the heads like that? I am not done yet. All those wires are getting redone. I don't like them wired to the tubes. I will stand them off the tubes. Getting close to being done but not rushing this installation. If you notice the cylinder heat probes are attached to the fins on the cylinders. They came installed under the jug hold down bolts. I did not want to remove these nuts and then retorque them. I also did not want them under the spark plugs. This was my solution to this problem.

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The covering of the front of the fins are to keep from the air coming in and cooling the front of the cylinder or heads more than the rest for more even temps , I have had to do the same thing before. I used a point to shoot temp gun for getting the temps of all parts of the heads and cylinders while running at WOT. Have to be careful.
If you don't want the CHT probe under the spark plug or cylinder hold down nut, that looks a good as any.
I don't like the plastic oil pressure line over the hot cylinder. Would feel better if it was re-routed or changed to a 1/8" copper line.
Is there cotter pins in the castle nuts on the top engine to engine mount bolts, can't see any in the pictures, but they could be positioned where I can't see. ( I see them now).
I see you have the P-lead off the mag, you must have been working on the engine when taking the pictures.

#### mcrae0104

##### Well-Known Member
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Also use black painted valve cover pans and black painted pushrod tubes for max heat transfer.
Food for thought about black paint and heat transfer by convection:

#### N8053H

##### Well-Known Member
Pops you are correct, The cotter pins are missing and the mag lead is unhooked. I have not done this side of the engine yet. I hung the engine and moved on to installing it from the front back. I am now working on the back side of the engine. The cotter pins will be installed at this time. Thanks for the info on the shields. I was wondering if they helped with heat transfer and reduce the chance of shock cooling of those front cylinders.

#### Pops

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Food for thought about black paint and heat transfer by convection:
VW engineers would disagree with him. He said "insulated layer" speaking of paint. You don't put on a thick layer of paint, just enough for a light coat, no more. Look at the stock pans made by VW. Just a light coat to protect from rust.

#### Vigilant1

##### Well-Known Member
Food for thought about black paint and heat transfer by convection:
This was a good video and he does a good job of describing radiative and convective heat transfer, and of showing (quantitatively) that the shiny intercooler does a better job of convective heat transfer than the black one.

But, he doesn't quite close the deal.

This is the weakness in his argument: He says that the intercooler is designed to transfer heat via convection (true, that is what it is designed to do), and then he proves that the shiny intercooler transfers more heat by convection than the black one (based on the change in air temps of the cooling, ambient air across each). He does not address how much heat transfer occurs due to radiation (from the intercooler body). While this may not be the heat transfer mechanism it is designed for, it does occur as long as the intercooler is at a different temperature than the surrounding objects. He addresses this obliquely when he says the black intercooler will tend to pick up more heat than the shiny one from hotter objects nearby (true), but he doesn't give it "credit" for losing more heat via the same mechanism to other cooler objects.

Since the exterior surface of the black intercooler is over 97% efficient at radiating heat and the shiny one is probably less than 5% efficient (emissivities), the radiative heat transfer might make up the rather small 3% advantage that the shiny one has in convective heat transfer.

The only way to really know is to put both intercoolers in cars and measure the delta T of the engine intake air (not the delta T of the ambient airstream). He didn't do that, so we don't know.

My gut says the shiny one probably does work better, but this argument doesn't quite prove it.

Now, if we are talking about valve covers and pushrod tubes, convective heat transfer is not "designed in" (with masses of cooling air directed over them, etc). And, at least in the case of the valve covers, they are well oriented to radiate heat to the cooler surfaces of the engine cowling. I don't know the relative importance of convective vs radiative heat transfer in this case, but it's certainly a much different situation than we have with the intercooler. We could run a test with thermocouples attached to a black "stock" VW valve cover and a shiny aluminum one, see which gets hotter (would need to run a second test after swapping them to the other side to assure differences between left and right side aren't affecting things).

And >when< are we going to stop calling them "radiators?"

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#### N8053H

##### Well-Known Member
In the third picture showing firewall does the wires exit threw a grommet ? I see some screws and was wondering what you have going there? Don

This pic may help. But yes they do pass through a rubber grommet. I am removing that white sealer and putting a clear silicone in place of this. I don't like the white. This is used in high heat area's and I should not have used it here. It will be removed.

#### mcrae0104

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V1, really good points. I suspect the amount of radiation vs convection is minuscule in the case of the intercooler. And Pops, I agree that the VW engineers were smart, but I strongly suspect it had more to do with rust protection on these steel parts than heat transfer. Otherwise, they would've pained the heads black too. Back to V1's point about radiation, black pushrod tubes are more susceptible to picking up heat from the cylinders. I don't know if they came from the VW factory that way. The Corvair guys tend to paint their tubes white for this reason.

#### Pops

##### Well-Known Member
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V1, really good points. I suspect the amount of radiation vs convection is minuscule in the case of the intercooler. And Pops, I agree that the VW engineers were smart, but I strongly suspect it had more to do with rust protection on these steel parts than heat transfer. Otherwise, they would've pained the heads black too. Back to V1's point about radiation, black pushrod tubes are more susceptible to picking up heat from the cylinders. I don't know if they came from the VW factory that way. The Corvair guys tend to paint their tubes white for this reason.
On the VW, the cylinders temps are cooler than the heads temps. Heads run hotter than the cylinders. So the air from the cylinder sould be cooling the pushrods tubes some, I haven't checked. Try recording the temps of the cylinders and heads with a point to shoot temp gauge at WOT. The hottest place will be between the spark plug and the exhaust valve seat area of the head. Right where the dual port heads crack.

#### Daleandee

##### Well-Known Member
The Corvair guys tend to paint their tubes white for this reason.
On William's Fly Corvair site he list the reasons for the white push rod tubes on the Corvair conversion:

Notice that every engine we build at colleges has white painted or powdercoated push rod tubes. This is an importiant element in protecting the pushrod O-rings, (#1603) from heat damage.

While many people believe that oil returning to the crankcase through the pushrod tubes is cooled by airflow through the motor, our testing has shown that just the reverse is true; the pushrod tubes run significantly hotter than the oil in the sump. We paint the tubes white to help them reflect heat.
https://flycorvair.net/?s=white+pushrod+tubes

Dale
N319WF

#### Pops

##### Well-Known Member
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Yes the oil will be slightly hotter than the oil temp in the sump because the hot oil is being cooled as it runs down the tubes towards the sump from being under the slightly cooler cylinder barrels compared to the hotter VW heads. In other words, the oil is hottest in the valve cover pans, then is cooled at a lower temp as it flows down the tubes from the cylinders that are at a lower temperature than the heads.

#### Vigilant1

##### Well-Known Member
On William's Fly Corvair site he list the reasons for the white push rod tubes on the Corvair conversion:
While many people believe that oil returning to the crankcase through the pushrod tubes is cooled by airflow through the motor, our testing has shown that just the reverse is true; the pushrod tubes run significantly hotter than the oil in the sump. We paint the tubes white to help them reflect heat.
Painting the pushrod tubes white only makes sense if the things they would exchange heat with >via radiation< are hotter than the pushrod tubes. On most installations, these would primarily be the inside of the cowl (definitely cooler than the pushrod tubes) and the outside of the cylinders. The temp of the air around the engine is irrelevant to this issue, since the air has a very low emmissivity and will transfer very little heat to anything via radiation, regardless of the color.
In general, as far as radiative heat transfer:
- If the objects that are "seen" by the pushrod tubes are predominantly hotter than the tubes, paint the tubes white (or, even better, chrome plate 'em). This will reduce the amount of radiative heat transfer to the tubes
- If the objects around the tubes are generally cooler than the tubes, then paint the tubes flat black to increase the radiative heat flow from the tubes to these other objects.

But, probably the best reason to paint VW or Corvair pushrod tubes white is to make it easier to find the oil leaks.

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#### N8053H

##### Well-Known Member
Pops here is a better pic of the firewall.

#### Vigilant1

##### Well-Known Member
Some housekeeping: These were some posts about the Casler VW engines in another thread that might be useful to somebody reading this thread.
1) I mentioned the Hummel/Casler "2400" cc engine here: https://www.homebuiltairplanes.com/forums/showthread.php?t=30244&p=436113&viewfull=1#post436113 . In part:
Hummel (Scott Cassler) sells a "2400cc" engine: (85 HP max, 94mm bore x 86mm stroke, unspecified CR). It looks like the weight is 167 (incl carb?) and the price with dual ignition, alternator, starter, Force One hub, and Zenith carb would come to $7,475. That would be$88/HP, which is quite good for a pre-assembled engine in this HP range. It would be interesting to see what heads he uses and to compare them to the Revmaster 049 heads. Keeping the CHTs reasonable will be the challenge.
One advantage (IMO) of the Hummel/Cassler engines is the use of the Zenith carb and "stock" parts (alternator, ignition) that are available from several sources. But, the Revmaster engines and their proprietary parts are well respected, no doubt.
Edited to add: Topaz confirms that the Casler weights include the carb.

2) Pops replied in part:
I do like Scott's 2180 cc engine, but I don't know what he is using for dual ignition, there again, I want to be able to hand prop. Not that much infro on his website. I know Scott, and would trust him at his word and he sells a good product. That means a lot to me.
3) I posted a picture showing the ignition parts of a Casler 2400cc engine and this:
Here's a picture from the website of a Onex builder who bought a Hummel/Casler 2400cc engine. I see a magneto going to the top plugs. The botom plugs look like they a fired by an ignition system triggered by a unit in the distributor hole--maybe this one from Great Plains (\$470, incl plugs). If so, it can be hand-propped using the magneto, then turn the secondary ignition on >after< the engine is running.
4) MarcW posted about the ignition on his Casler engine. In part:
I have a 2180 built by Scott. It has the electronic ignition and surplus magneto like the picture. I believe the electronic ignition is the one sold by Great Plains. The mag only has 15 degrees of lag. People have modified the mags to increase the lag so you can hand prop. 25 degrees of lag is better to hand prop. I bought one of the surplus mags on ebay to experiment with.
Sorry for the disruption, but this is a good VW thread and I wanted to make sure the info in that other thread didn't get lost.