CMC Speedster running hot follow up

I think you should not have closed off the circular hole in front of the engine.

I don't know the whole story of what you are running for an engine but I assume some version of a type 1 VW. If you have all the engine bay sealed so the cool air coming in is separated from the hot air coming off the engine and out underneath the car and you are still running hot then it is one of the following. You timing is not set correctly possible too retarded. The fuel mixture is way lean caused by incorrect carb jetting or a vacuum leak. I have also found a shop rag that got sucked into the fan and what's left of it laying on top of two cylinders thus blocking the cooling air. Rats, mice and other pests can build nests on top of the engine under the fan shroud and block the cooling air also.

I can't for my life understand (maybe someone else will enlighten me) figure out why a mechanic would tell you to run 87 octane. In my experience running the highest octane non race gas you can find in these little air cooled engines is best. Running them a little rich will help them run cooler as well. It will cost you some miles in engine longevity but we don't tend to drive our cars more than 10-15k miles in the the time we own them, (I know there are exceptions).  Here in Indiana 94 octane is at the pump. We can also get 110 octane race gas at many gas stations, we are in Indiana the home of racing. Good luck getting your baby sorted. When you get it just right the joy of driving her will be immense!

Don't block that 1/2 moon circular area in front of the engine -- that's for the cooling fan to suck up fresh cooler air!  I see the bus H gasket on either side of engine --- but not across the back above the exhaust. (Build manual has 2 shields in that area to keep exhaust heat out of engine bay).  I'd trim the tin and continue the H gasket there. Some have cut out area behind the rear license plate.

What size engine?  Any added oil sump of external cooling/oil filter?  Stock 2.5 quarts just isn't much oil in a hopped up air cooled engine.  Are there lower cooling tins (sled tins) below heat exchangers/J tubes - to direct heat out to rear.

Octane, timing, mixture all influence heat generated by engine.  Exhaust too -- a ceramic coated exhaust gets heat away from engine.  Remote oil cooler with electric fan can increase oil capacity and its cooling. Some have mad a 2-3" prop to keep back of engine lid slightly open too.

Love those wheels!

I can't tell, but it does not look like you have all the doghouse tin in place over the cooler. The doghouse tin ducts the superheated spent air from the oil cooler BELOW the engine tin, rather than inside the engine bay. This could be the source of your high cylinder head temps, but could also be any of the things Jimmy stated.

Also it could simply be carbon buildup has upped compression and caused the overheating to occur. How do the spark plugs look?

The tin over the cooler everyone has(the one with the Porsche shield sticker). The two after it that fit into a special front firewall tin(not shown here) are the three pieces you may need.

I'm with Jimmy on octane. 91-93 is available everywhere. Ten percent ethanol actually HELPS with cylinder cooling and detonation resistance.

@DannyP

@DannyP i just went over to my ebike shop and took a bunch of photos to try to show you what i have there as im not mechanically inclined and some of what people say goes right over my head

@John Bungen

Hey John, very nice score on that Speedster. Looks great!

1. Get one length of that rubber engine seal (Vw bus type) so that you can apply it all around the engine, not just the sides. Without that properly sealed your engine is still sucking in heat from the exhaust system.

2. It may be just the picture angle, but it looks to me that the pulley on the alternator is too large (diameter). You may need to replace that with a smaller diameter pulley. It may help to compare the diameter of a stock VW alternator/fan pulley to the one that's currently on your car. This would enable the crank pulley to spin the alternator pulley at a much faster rpm, thus pushing more cooling air to the engine cylinders.

3. Once you have sealed off the engine from the exhaust heat, get that pulley/cooling fan spinning faster try checking your temps. If that seems to help, then try re-opening the opening in the firewall and see if that also helps.

I'm sure you'll be able to sort it all out and then really start enjoying your new ride!

@MusbJim i just posted a bunch more photos above maybe you can see pulley better. i replied to danny p.

Photo 121700 shows that the doghouse tin is all in place. So that should be good, follow the rest of Jimmy's suggestions.

It looks like the sled tins are missing. Maybe not.  It is hard to tell. the photos are dark in that area.

The sled tins are definitely missing. They seem to lower the cylinder heads and oil temp by 10 degrees F in my experience. Any free temp lowering is a good thing.

Factory sled tins would definitely have to be modified and metal added/cut to work with those J-tubes and exhaust.

Sled tin and 2 pieces to rear missing -

Here's where two pieces go -

yes and the lower cylinder tins(?) I don't think we should be able to see unshrouded cooling fins in those pics from underneath; sled tins would attach to the front of the shroud at both sides of the engine and curl under, above the exhaust pipes, to funnel the air through those fins and out the back, away from the car as you drive.

@edsnova so these are the two sled tins? Do i need to have someone makes those like the sheetmetal up top i had made and screwed on?

Also needs the industrial tins.  I am not familiar with the CMC.  What is that metal plate on the fire wall in photo 20210818 (third row, 4th picture)?

@Bobby D i was told to block the air from that collared circle area and sides to force fan to pull air from truck lid area?

@John Bungen posted:

@Bobby D i was told to block the air from that collared circle area and sides to force fan to pull air from truck lid area?

I'm running a 2110cc with 150 hp and I don't have the opening in the firewall and my engine runs just fine. Others here have said you need it but yours is covered and I don't think it's necessary. I am running an external Setrab cooler with a fanpack and a deeper sump. I am also running with all of the tins in place. You can buy the tins but they MIGHT need some modification to fit just right.

John

My Beck speedster has one hole in the firewall directly across from the fan.  I don't know how everyone else's is setup.

John look go to https://www.awesomepowdercoat.com/.  This guys show all the Tins and how they should be installed. 

Besides the lack of any of the bottom sled tins, which it certainly needs, has anyone other than me noticed the lack of a thermostat bellows under the cylinders?  The stud is there, but no bellows.  For all we know, there might not be any air vanes inside of the fan shroud, OR they're in there and partially closed.  Either way, that, alone, will make it run hot

Jon wondered: "@edsnova so these are the two sled tins? Do i need to have someone makes those like the sheetmetal up top i had made and screwed on?"

No - They are available from places like CIP1 or Bugcity or Bugstuff in PA.   Look on their websites under Engine or Cooling or Engine Cooling.  Maybe someone could come up with a part number list for you?  They all just screw on with 6mm slotted/philips screws (get the screws at a local ACE Hardware store).  The commercial sled tin modifiers (Left and right) might be a little more difficult to find, but I think Gene Berg sells them.

Alternator pulley size:  The pulley size affects how fast the fan spins versus engine RPM.  YOUR pulley should be about 4-1/4" across the middle, lip to lip.  Larger than that, the fan spins slower.  Smaller than that, the fan spins faster.

While you're checking that, you should also check the diameter of the crankshaft pulley, as they are related.  Mine is 6-3/4" to 6-7/8" lip-to-lip  (it's dark down in there).  

Your two should be similar or at least a similar ratio.

@Bobby D posted:

Also needs the industrial tins.  I am not familiar with the CMC.  What is that metal plate on the fire wall in photo 20210818 (third row, 4th picture)?

What do you mean by that? It has the correct cylinder tins above the pushrod tubes.

In addition to Gordons post those of us that are using transaxles with taller gearing cruise with the engine turning much lower RPM's than VW engineers intended.  We have twice the HP or more and turning the fan up to 30% slower than designed to cool the engine. When we do this it is important to use a smaller alternator pulley. I used one from a 356 engine that is smaller and fits our alternator shaft. So now the fan speed is increased to compensate.

I'm not running taller gearing but I compensated some by using a 7" crank pulley instead of stock 6.75"

Danny

There are industrial tin that go between the J-tube and cylinder heads.  These are used when the heater boxes are deleted.

@Robert M posted:

I'm running a 2110cc with 150 hp and I don't have the opening in the firewall and my engine runs just fine. Others here have said you need it but yours is covered and I don't think it's necessary. I am running an external Setrab cooler with a fanpack and a deeper sump. I am also running with all of the tins in place. You can buy the tins but they MIGHT need some modification to fit just right.

I'm just a Robert M fanboy today, but my experience is the same. My IM came with no firewall hole. After reading rave reviews (from people generally either not living in a hot place, or with no actual running car) I cut two large holes and put fans in them. The car ran hotter.

I believe in sled tins and all of the oft-forgotten (and left off) lower tin at the back of the underside of the engine. I've paid for flaps and thermostats, but haven't found them to be particularly effective either in allowing the engine to warm up more quickly (their intent), or in reducing head temps on hot days (the apocryphal logic).

I haven't found shrouds from The Sainted German Engineers to be appreciably better than a good 36 hp copy with a doghouse cooler. I always run a T4 cooler on the stand and widen the doghouse accordingly.

I can say with 100% confidence that the stock rain tray under the deck-lid grill won't allow nearly enough air into the engine compartment, so propping the hood or opening the rain tray really helps.

The Raby (now LN Engineering) DTM shroud works. Looking at how cheesy it is makes you think it shouldn't, but it does.

I've tried power pulleys, and they work to make a given engine more snappy - at the expense of head temps. I won't do it unless the combination is really, really asking for it, and even then... I've run a 356 generator pulley on my alternator, but it didn't do as much as I'd hoped. I'd always get a welded/balanced fan.

I've also experimented with the Gene Berg theory of fan speed (that an engine turning higher RPM will run cooler), and also found it to be untrue. What is true is that the fan speed has to be higher at higher loads, but a large engine almost always runs cooler turning 3000 RPM than it does turning 4000 RPM, unless it is under heavy load (like climbing a mountain under WOT in 4th gear lugging). Heat is much more load dependent than RPM dependent, but there's no shortage of friction in the cylinders and valve-train to make turning a lot of RPM just to keep fan-speed up a bad idea.

I've heard guys report that their car runs cooler with a suitcase on a luggage rack mounted to the deck-lid grill. I have no idea if this is true, but I can tell you that this is a really, really bad place to be trying to draw air, and that anything that might create a disturbance in the force might be helpful.

... but no matter what you do, if you live where it ever gets hot - you're going to need a remote oil cooler with a thermostatic bypass and fan if you have anything more than a 1600 running 8:1 compression. You just are. This is the point where somebody will pipe up and talk about how their 2332 with 7:1 compression never runs hot where they live (in Fairbanks, Alaska) even though they only run a stock T1 cooler on the doghouse stand. Gene Berg (he of 6:1 fame) says that's all you need. Pay them no mind.

Somebody else will chime in and say, "these engines are oil cooled", which is sorta' true, but the only thing that's crappier than air as a cooling medium is oil. Just keep the oil cool because your engine needs cool oil to be happy. Don't overthink this.

There's more folklore and common knowledge regarding the cooling system than any other part on your engine. Proceed with caution - lots of guys (me included) will tell you everything they think to be true. None of us (not even The Sainted German Engineers) had it figured out completely because air is such a poor cooling medium.

With time, if you hang with it, you'll have a strong opinion too. When you do, share it with the class, and be sure to frame it as the absolute gospel truth (all other heretics will be burned at the stake)! These cars bring out strong feelings - especially regarding cooling.

@Stan Galat Two months into ownership I think this was kind of solved long term with the subaru conversion but I don't know if I will ever have one of those so trying to get this one to go 60 miles at under 350 degrees. Baby steps.

@Stan Galat posted:

I'm just a Robert M fanboy today, but my experience is the same.

I know it might only be for today but I’ll take it. 😂

@John Bungen

Stan brings up a great point that is easy to try out:

Figure out a way to hold the engine compartment lid open while driving.  Just prop it open with something like a short length of pool noodle or something to hold the bottom of the lid up 3” - 4” or so.  Someone on here might recommend a tried and true method.

Some of us, particularly on the west (wicked hot) coast have done this on very hot days and it seems to work for them to reduce engine temps.   It’s easy, it’s cheap.  Try it out and report back.

@Stan Galat

It kinda makes sense that a suitcase on the luggage rack might act as a small air dam, forcing some air that would normally be pulling up away from the body (due to the “wing” shape) and forcing it down into the space between suitcase and body to actually increase air pressure speeding past the grill.   Unfortunately, we would need someone with manometers or pressure sensors in there to test it, but it makes some sense, doesn’t it?

.

Yes, all, please do chime in here and let's hope that cool heads prevail. (Rimshot)

I think the sainted engineers did have it pretty well figured. There's plenty of natural cooling in our engine compartments for a 70 hp engine.

When they went over 70 hp, they eventually punched another big hole in the deck lid - not because it looks better, but it was the right thing to do in a thermodynamic kind of way.

For their super-duper four-cam 130-hp wunder motor (which mostly ran in 80-100 mph airstreams and never had to stop for a light), they added an external oil cooler.

I also have a hole in the firewall and a fan behind that. It's not any cooler with the fan running, but I see no evidence the hole is a bad thing. The sainted engineers could drill no such hole, as they would have poked through into the passenger compartment.

I have an estimated 120 hp and an external oil cooler with fan. On a hot day, the engine is warmish but happy at a steady 4000, happier at 3500, and most happy at 3000. After 30,000 miles, there's no blue smoke, grunt feels about the same as new, and it hasn't developed a drinking problem.

Me neither.

.

Just another approach that's been mentioned on SOC before: it was noted that Intermeccanica cut a rectangular hole into the engine compartment from behind the license plate. My old '79 IM didn't have a plate hole, but I added one.

I agree with you, @Gordon Nichols, it would be nice to have some instrumented data on engine compartment air pressure and temperature so we could quit jawboning about it.

@Gordon Nichols posted:

It kinda makes sense that a suitcase on the luggage rack might act as a small air dam, forcing some air that would normally be pulling up away from the body (due to the “wing” shape) and forcing it down into the space between suitcase and body to actually increase air pressure speeding past the grill.

It really does, Gordon... which means it probably isn't true. But it's so elegant that it ought to be.

@Michael Pickett posted:

Just another approach that's been mentioned on SOC before: it was noted that Intermeccanica cut a rectangular hole into the engine compartment from behind the license plate. My old '79 IM didn't have a plate hole, but I added one.

Like most things Henry does, this just works. Pretty slick too.

@Michael Pickett posted:

I agree with you, @Gordon Nichols, it would be nice to have some instrumented data on engine compartment air pressure and temperature so we could quit jawboning about it.

Where would the fun be in THAT?!?

Is this the fan in the shroud?  Is it the camera angle or are the fins flattened? Top ones look ok.

Generic picture - guess just angle.

Last night I installed Andrig's new fan design.  Its going to be raining here today so I can take the speedster for a test run.  I should of measured the airflow before I removed the old fan, but I didn't have a meter.  I also have the 356 smaller alternator pulley sitting on a shelf that might install this weekend.

Hello John....I noticed that your car has the same gauge set up as mine. How are your gauges working? ...do they stick in a position (don't zero out) when you shut off the car? just wondering....all my gauges are questionable at this time and may need to be replaced. Sorry from deflecting from you original Heat problem......Thanks

Larry

Sitting it the original box those CMC Vintage gauges are reading something - with tach sitting at 2k. Must be cosmic rays or wifi.  CMC sold them for $325 back in '80s.  Came in black face and white faces with brass, silver and black bezels. I have an old ad for them from Hot VW's somewhere.

@WOLFGANG posted:

Sitting it the original box those CMC Vintage gauges are reading something - with tach sitting at 2k. Must be cosmic rays or wifi.  CMC sold them for $325 back in '80s.  Came in black face and white faces with brass, silver and black bezels. I have an old ad for them from Hot VW's somewhere.

Thanks...mine are all wonky!

Here's instructions from build manual on the "fire wall" part - behind the cooling shroud: