I searched the site but cant find anything on this. I noticed on some VS cars you can see the ground thru the engine bay. Doesn't this let a lot of heat into the engine and maybe cause carburetor troubles? Mainly I'm wondering if there are seals available to cure this. Thanks, Frank
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It's the source of a lot of people's overheating troubles. The motor needs to be sealed off from the bottom so the fan and carbs can't recirculate spent, hot cooling air. You may have to make up a cover plate seal off the offending areas. I believe some people have incorporated a bus engine seal to allow for motor movement. Al
Post a photo - you shouldn't see ground on sides or the back (above the exhaust). Above flywheel isn't critical and there is usually a vent there.
Ahh Wolfgang, you are correct. The gaps I have seen are between the firewall and the rear vertical flywheel tins. It has a grille there so even completely closed off the grille will vent air. My engine is not in yet so I will make sure to check out the seal fit first. Thanks Guys.
While the engine does need to be sealed off from the hot exhaust and spent cooling air, Wolfgang's right (and I should have mentioned that in my reply); don't worry about air leakage into the engine compartment from the flywheel end of things (and that's the front of the motor, btw). Since the decklid in some of these cars actually has very little for air intake (my older Intermeccanica has 10-12 square inches of openings and for comparison, the later model beetles have 50-60 sq. in.) some people leave the flywheel breastplate off or cut a 5 or 6" hole in the firewall right in front of the fan intake (as it sounds like yours has) so the motor gets enough air. Remember, these motors are primarily aircooled, and starving the motor for air intake will produce overheating problems that even adding an extra oil cooler and a sump will not fix. With the extra cooler (and lower oil temps) you may think the motor is fine, but without enough air getting to the fan (and carbs) the heads could be happily cooking themselves to oblivion and you won't know it until it suffers a premature death (and leaves you stranded) at the most inopportune time. A cylinder head temp gauge (as well as an oil temp gauge) will tell you what's going on back there.
As we modify these motors from stock, the air intake requirements go up dramatically; the stock late model carburetor ( Solex 34-3) draws about 125cfm at full throttle, while a pair of kadrons pull over 300cfm and a set of 44IDF's or 45DLRA's can use 900cfm or more (34-36mm venturis on a > than 2 liter motor). Couple that with the late model doghouse fan's air consumption (1200-1500cfm at 3500rpm, depending on how the fan belt rides on the alternator pulley- think highway cruising rpm's here), the physics of all that air trying to enter the engine compartment at higher speeds and you can see why an alternate source of a steady flow of unimpeded cool air is so important. Unless you've cut the rain shield completely out of the decklid from under the grille, the decklid will not supply enough air for the engine's needs.
A simple way to tell if your motor's getting enough air? Drive around with the decklid wedged open 3 or 4"; if temps drop noticeably, that should tell you something. Someone on here (very recently) found this out (he used a piece of pool noodle, iIrc) and I can't remember who it was...Al
I'm thinking of leaving that back plate off when my engine is installed (sometime between next week and the next millennium 
). The only concern I have is hot air exiting from the oil cooler making its way back into the engine compartment.
Ron- Extend the air exit's sheetmetal downward.
Good idea-thanks Al.
That was me!
~WB
That's who it was; thanks Bill!!!!
And Ron- Have you noticed a temp difference running with the lid open like that?
No change in oil or CHT temps. I did notice a big change in the temperature of the engine/shroud/carbs/alternator. When the engine hood was closed, while driving on a summer day, I couldn't keep my hand on any of the above mentioned parts. Very hot.
When I drove around with the hood propped open 4 inches I could rest my hand on the shroud, carbs, etc.
Do these grill badges, that some of us mount, reduce the cool air intake thru the grill?
I think they increase the velocity of the air flow - Bernoulli principle. Honestly unless you have 5 or more I can't see it would have an impact.
Ah ha, how did an ol' sailboat guy like me, miss that. Increased lift, the higher you point.
I saw a difference on my temp gauge with the lid open.
