Swiss Cheese Engine Bay

Hi Guys....This has been interesting to read! Been down in Baja Mex and am trying to catch up. Since I'm in the middle of assembling an engine, I'm also focused on making sure the engine compartment is sealed but also getting sufficient air as well.

I have a VS with the firewall hole in front of the fan. As far as how I will vent (or seal) the engine compartment, I haven't decided what I will do until I do a trial fit-up of the engine in the car. Here's my question though...Obviously I will need to measure engine oil and cyl. head temp and I am not familiar with what's available for both of these. I prefer to not add gauges to the dash and I would be content to have temporary gauges installed until I am satisfied that the engine is happy.

Also, would/should all four cyls., need to be monitored? Could i not use one gauge and wire it through a rotary switch to four sensors ? (I am using a dog house shroud with stock cooler plus an external cooler)......Bruce

Good morning, Bruce. Do the gauges in your car have an oil temp gauge? If so, you could somewhat calibrate it by using a candy thermometer down the dipstick hole and that will give you an idea where "warm", "hot" and "oh my God! hot" are. And the same if you throw in a VDO oil temp gauge; they don't always read accurately from cold to hot.

Where to put the sender- now that's a subject of great debate (look it up on the Samba, you'll be amazed!). Wherever you put it (in the block, in the full flow line before the filter or???), don't just rely on the gauge; use your powers of observation as well. An engine with a shroud, cylinder covers or dipstick that's too hot to touch is hot! If a couple drops of water (or spit) sizzle on the engine case, that tells you it's really hot as well.

Buy a good temperature compensated cylinder head temp gauge; Dakota Digital has a good one and there are others. The VDO aftermarket unit is not temp compensated, will read different temps depending on the weather and will be as much as 40' low when the engine is at operating temps. Underneath #3 spark plug will let you see what's happening in real time. Any where else isn't close enough to the combustion chamber to be instantaneous and will only measure trends. A lot of VW factory heads have a cht boss already cast in and people are sometimes tempted to use it, but all it was designed to tell the fuel injection brain is when the engine is warmed up.

If the firewall has a 6" hole, maybe oval it out to the sides a little bit- 3" will give you another 18 or so sq." of air intake. Increasing the diameter 1" (I think) is a good idea as well. The shroud's intake hole is about 6" and you'd think the same in the firewall would be enough, but there's the air going into the carburetors to consider as well. And with more than enough air into the engine compartment, the airflow out of the grille at highway speeds will be removing heat radiated from the shroud and cylinder covers, and this will make for cooler air temps into the fan and carbs (and this means there's less heat for the fan to remove and cooler intake air for the carbs; see where this is going?). Hope this helps. Al

Hi Bruce

Just to ad to Al's comments:

Oil temps

If you have an oil temperate gauge in your gauge cluster you can check to see how accurate it is by (as Al mentioned) using a dipstick thermometer like this, which fits down your dipstick hole.

http://www.mainelycustombydesi...gine_components.html

When I used my dipstick gauge I found that my dash oil temperature gauge was way out.  210 on my dash gauge was actually 240 on my dipstick gauge.  Using a digital temperature gun also confirmed that my oil temps were way higher than what my dash gauge was reading.

CHT

I'd stick with one sending unit under the #3 spark plug.  It's a bitch to put in, but worth the effort.

When I looked at purchasing a CHT gauge I ended up with two choices; Dakota Digital or Westach.  Both are accurate, but I ended up passing on the Dakota because I thought the digital gauge might be hard to read in a convertible.

Here's a link to the Westach:

http://www.aircraftspruce.ca/p...westach/westcht1.php

Bruce, if you're worried about how an extra gauge will look in your speedster you can do what I did and mount it under the dash on the passenger side.  It's under the dash enough so that it doesn't stick out, but easy to read from the driver's seat.

Hi Bruce,

A couple of years ago I purchased a Mainely oil temp dipstick.

Difficult for old eyes to read down in the shadows... and hot as a pistol to check oil level...but it works as advertised...

BUT... I found a digital TruTemp kitchen meat thermometer (-40/302F) gives me, instantaneously, exactly the same reading as the Mainely, but at a Walmart price of $5.95 is a hell of a lot less expensive!!! 

You're right about the Mailely being hard to read.

At only $6 the Malmart thermometer is the way to go.

Hello Al, Michael is fine.

I haven't installed a head temp gauge yet, I've been looking at the head temp gauge with dual sweeps to check both banks. When I had my mag case done I had number 3 web welded/reinforced.

My oil temp gauge is right on when I compare it to the dipstick temp readings.

http://www.aircraftspruce.com/...g/inpages/cr-002.php

Hi Al and Ron....I tend to believe that digital gauges are more accurate throughout their range than analog ones so I think I will get a Dakota CHT unit. The point about reading it in bright daylight is well taken as well. Dakota doesn't have much info published about the sensor. I assume it goes in under the spark plug replacing the plug gasket ? How long of a wire does it take ? I see that they go up to 18 feet and cannot be shortened. I also assume that I would need a 14mm size ?

Engine compartment sealing......I'm going to temporarily block off the VS hole in front of the fan and make every effort to totally seal off the engine compartment as it would have been intended originally. This will be my starting point. I will install oil temp. and CHT gauges, a thermocouple temp monitor in the engine compartment, and a + to -,0 to 3" H2O magnehelic gauge. These things should give me a start on the info I need to achieve my goal of adequate cooling. If I can get it from my friend, I'll try to hook up a 6 needle strip chart recorder so I can get simultaneous data. This is a way away though. I haven't even finished the engine assembly yet!  I really love the candy thermometer method ! Thanks for that !

Bruce

Bruce, I can't remember what length I ordered-I know I have a couple of feet of wire looped and secured in the open space behind the firewall.

Finding a spark plug ring that fits properly can be a pain.  I think my old heads had 12mm spark plugs, but at the time a 12mm ring was not available.  I'm not sure what size plugs I have in my new Steve Timms heads.

Be sure to post when you get your Dakota gauge installed.  I'm interested in knowing how visible it is, with the top down on a sunny day.

This will be my next project!