Engine Ventilation

We are going to need a photo of the situation to properly assess the situation.

VS uses a circular cut out in the forward firewall behind the fan intake.  I assume no hot exhaust gases get into the engine compartment thru the wheel openings?  On a FF/CMC the wheel well sides go clear to the back and the back above the exhaust is sealed with a double layer of fiberglass panels to seal it off (even fiberglassed to back portion of car). 

From what I gather then, besides the opening in the forward firewall and the grill in the lid, the engine compartment should be sealed off. Is this correct?

Don't think this is any cause for alarm.

Mine has the same thing (bought new from VS), although I'd say the gap is more like four or five inches. The engine compartment sidewalls couldn't really be carried all the way back on my car because they would run into the back of the tail light housings.

My take is that these engine compartments need all the venting they can get, and as noted, these are vents into the wheel wells so heat from the exhaust isn't a factor.

Yes, leaves and small pebbles do find their way in that way. I guess some mesh screening would fix that.

Some people obsess over sealing up every opening into the engine compartment except the grill in the deck lid because that's the way the holy fathers in Zuffenhausen did it. But what the Karosserie clergy were so carefully sealing up made only 70 hp. When they finally rocked out with a mighty 90 hp on later models, they doubled up on the grills.

Most of us see the wisdom in beefing up the oil cooling for the engines we run. It makes equal sense to me to increase the airflow through the engine compartment.

On my builds  I install a aluminum place over the area behind the license plate area above the exhaust. I do leave 2.5" across the bottom of the engine bay bulkhead open. for increased air flow, I place a piece of 1/4" "hardware cloth" over the fan intake on the shroud so that the engine fan doesn't ingest debris. I've never had excessive engine temps to date.

I disagree that the opening Kirk leaves in the rear of the engine bay is not important, it is.

And it needs to be sealed. I spent a fair amount of time and work making and installing a piece of aluminum that fit tightly to the body-including the taillight housings so that exhaust heat would be shielded from entering the engine bay, especially at low speeds around town and at stop-lights.

I love how we "experts" can claim this or that contrary to VW/Porsche engineers scientific conclusions.

If the engine tins weren't necessary, they wasted millions of dollars in tin and labor over the years!

No question about the importance of the tins, Will.

But the gap near the tail lights is well up in the wheel well and pretty much away from exhaust heat. I don't doubt it was laziness that kept VS from sealing things up there, rather than any engineering concerns. If it takes an extra hour or two to fabricate a complicated shape, then it ain't happening in Hawaiian Gardens.

That said, though, I think Porsche's concerns in sealing up gaps like that would be more for weather sealing than anything else. I can see potential problems if the car were driven in heavy snow and slush - something a production car company needs to worry about.

Me, I'm avoiding driving the Speedster in the snow - unless I do another Tour D'Hoe.

Some very good points being brought up here. My 2 1/2 cents (I'm Canadian, eh)-

Yes, it's generally not wise to question (or go against) the factory engineering without some serious thought (and a little bit of experimentation to confirm your hypothesis), so we make sure the rear of the engine is sealed so no radiated exhaust heat and spent cooling air are re-introduced into the engine compartment. It has been proven (again and again and again and...) that leaving the rear of the engine compartment open to said exhaust heat/spent cooling air drastically shortens an aircooled VW engine's life. A local VW shop owner once drove his Cal Look Karmann Ghia convertible down to L.A. for Bug In in June without filling the heat tube holes in the rear breastplate (that sits over the exhaust) and the engine made it there and back, but it was done by the end of the summer.

Now the front of the engine (think front of the car) is a bit of a different situation; it turns out that the factory wasn't so much sealing off the engine from the outside for heat reasons but more to keep road debris (dirt, sand, small rocks, leaves, and ???) out of the compartment. Unchecked, the small stuff would eventually clog cylinder/head cooling fins and the bigger crap (leaves, paper, rags, and now with the wonders of modern technology, plastic shopping bags) would quickly plug up the fan. This would have cost VW  thousands? hundreds of thousands? millions??? of dollars in extra service and warranty work, so you can understand the thinking here. Their answer- make it foolproof.

Any amount of reading on this great Interweb thingie (thingy? I never know...), including our very own  forum, is filled with evidence that air entering the front of the engine compartment from below, whether it's through holes in the firewall (this works with our beloved Speedsters only, as in a Beetle the firewall is also the rear of the passenger cabin and not open to the positively pressurized under car airstream at speed as Speedsters are), leaving the front breastplate (the one that attaches at the bellhousing) off completely (this does work in Beetles), and even through holes in the inner fenderwells (up and forward far enough from the radiated heat from the exhaust) directly adjacent to the air cleaners is of great benefit to the engine, especially when bigger and wound higher than stock. Hell, even a stock engine would benefit, running cooler from the extra airflow through the engine compartment removing the radiated heat from the fan shroud, cylinder covers, alternator and even the engine case itself.

Bottom line- The more air you can get into and through the engine compartment, the closer to ambient the air the engine ingests (through the fan and carburetors) will be, and that will show itself as cooler running, the "tune" staying stable longer (ever notice that when your engine gets really hot the power seems to go away?), and ultimately, longer engine life, which if you've built something substantially bigger (and spent a fair bit of $$ca$h$$ on) should be a major attraction on it's own... Al  

PS- For those that are still driving their Speedster during the upcoming (for some of us) winter months- if you car has no carburetor pre-heat and during this time has trouble (or takes a substantially longer time) reaching operating temps (and maybe even forms that dirty mayonaisy [sp? need a little help here!] gunk around the oil filler), try running with the rear breastplate off. Short trips at first, and if it's too much, maybe a breastplate with a couple of 2" holes in it? A friend here in Vancouver (and the only guy I know of with a VW as his only transportation year-round these days) takes off the rear breastplate on his dual carbed 2 liter about now, puts it behind the rear seat and re-installs it at the end of March or beginning of April, with no ill effects. This way it warms up faster, actually reaching normal operating temps but never getting close to overheating...

Yeah, back to bed Yoda will now go...

It gets hot here in Cali and when I bought my car the engine bay was not sealed well. When I mentioned this to some of the folks I know I was told to "Just drive it". Well I knew better. My car ran very hot in the summer months and so it sat. Then after sealing the engine bay completely to where only air from the top deck lid came in I can now drive my car any time during the year. 

Make sure that there is no air from the bottom (exhaust area) able to get back into the engine bay and recirculate over your engine getting it hotter and hotter.

ALB posted:

...the only guy I know of with a VW as his only transportation year-round these days...

Make that two guys you know!

Ryan in NorCal posted:

ALB posted:

...the only guy I know of with a VW as his only transportation year-round these days...

Make that two guys you know!

That may be true, Ryan, but you don't live where there's snow, salt, and freezing (or near freezing but wet) temps for a good part of the year. It's a lot harder to be of the faithful up here. I gave up driving an aircooled car year-round over 30 years ago.

Took me 5 minutes to cut some foam hot water pipe insulation and stuff it up around the light housing...Done!

I agree with Will and Rusty. The engine compartment needs to be TOTALLY sealed so that air can only come in from the rear deck grill. I have a VS too and that area behind the rear2" square cross beam and the tail lights MUST be sealed. I even sealed off that 5" hole in the firewall in front of the fan intake. Using a manometer, I have measured the negative air pressure in the air compartment at 70mph and found it to be about 1.5 ".  This I have found to not be enough restriction to cause overheating but at least I'm aware of it.  Here's a few photos of what I installed/fabricated back there to seal up that area totally.............Aircooled Bruce

PS...I'm back in Arcadia Ca, again !

Nice solution, Bruce!

Speaking of sealing the engine compartment, I found my black foam dragging behind my car on the way home the other day. I just picked up some Type 2 Bus Black Foam from Bugformance, but it looks pretty narrow for the gap. Is this really what you all are using?

Thats what I use, yes.

Ryan in NorCal posted:

Speaking of sealing the engine compartment, I found my black foam dragging behind my car on the way home the other day. I just picked up some Type 2 Bus Black Foam from Bugformance, but it looks pretty narrow for the gap. Is this really what you all are using?

That gets used between the metal tins that go around the back of the engine.

Ryan,

It lays flat and you will find that it has slots that run horizontally down the length of the seal. One side slips over the fiberglass panels and the other side over the engine tins. You will only use about half of what you have there.

Robert - clean your engine compartment. It's filthy.

I used the same foam.  It has a shiny side and a plain foam side. The shiny side should be on the top. It's more oil resistant.........Bruce

I thought it was shinny side down as it was more heat resistant???? 

=I thought it was shinny side down as it was more heat resistant????   Ya!

Jeez !  Totally got that backwards...Senior Moment ??........Bruce

OK. The foam I bought is definitely the same as the old foam. But I’m concerned about the gap. Is the fiberglass and tin supposed to be approximately level? Mine has a significant gap. See photos below. Is there a bigger problem here?

(also, the shiny part was down on the old foam)

Yeah something wrong there for sure.  Have you been driving it?  Looks like front motor mount gone or issue with rear frame horns/rear motor mounts (shifting would be issue with either).  Looks like engine has dropped 3-4" and that's quite a bit.  The H stuff won't bridge but maybe 3/4" gaps.  Yours appears to be a VS?

Have you got pics of the sides and rear of the car? It appears that the body is setting too high or the engine is setting too low. I don't remember seeing a vertical gap like that ever, but I'm not the expert. Those two planes, the tins on the engine and the fiberglass of the body are roughly level with each other on my car, and others I've seen. The "H" shaped rubber gasket above, from a VW bus application, should easily bridge the space between the two surfaces and can be secured with a little silicone if it slips out.

Where is DR. Clock? 

I'd start by checking the front motor mount and the frame horns.

I'll make a BIG assumption that a VS and a CMC are roughly the same back there and say that the engine tins and the heat shields attached to the underside of the rear body frame member are almost on the same plane so all I need between them is 1/8" - 1/4" of weatherstrip - almost like you don't even need something between them.  

If your heat shields are mounted to the TOP of the body frame member, then that might explain the big gap between the shields and the engine tins.  I looked pretty closely at the photos but couldn't tell if they were mounted top or bottom.

Thanks for the help. I took a quick video. Do I show the right connections? (Fish out of water, here)

What do you recommend?

one more video, if it helps

i also tightened the one bolt on the drivers side from above video. Still a gap. Maybe less? I’ll see if I can jack the engine up a bit and tighten more. 

@Panhandle Bob, here are some rear and side shots. Is this what you were asking for?

From your video - I can't tell if what I labeled as attempted fix is emergency brake line and axle or welded in metal?  I can't see same in still photo.

From still shot - I bet if you put 2x6" side to side under heat exchangers and jacked it up, you'd see frame horns are bad at the kinked part.  Unfortunately, frame horns are difficult to repair.

Yeah, those frame horns look like they point down to me. 

One too many jumps?

That’s bad. Don’t drive it. 

Here's what it should look like from above -

Thanks so much for your help. Here is a close up on the frame horn. So it should be straight? Ouch. Ok, can you share roughly how this will be fixed?

This makes sense, save the jumping part. I have a great time in my car, but I'm not jumping it! Here's a video I found about repairing a bent VW Baja frame horn: 

Looks like about the same effort as an oil change. 🤦‍♂️

Yup. That looks awful. Ouch. I wonder if that’s why my clutch cable broke too.

Thanks for letting me hijack the thread for a bit. I'll open a new post when I have a game plan on fixing it. Already sent @Anthony a note about it. Thanks for all of your help.

Probably.  Is it a recent VS build?  If not, it's on you.  Moisture and mud get inside and over years they rust out.  It should have addressed when car was built - bondo is not a fix! Berrien Buggy makes a nice $99 fix for it.  Of course, engine and trans will have to come out to have new bits welded in. http://www.jimscustomvw.com/bebutufrho.html