Firewall seal?

OK, I've used the search and have read alot of comments, but what's the ultimate verdict: My VS has a good 1.5" gap between the firewall and engine back there ( over the eng-transaxle flange area out to both sides). Was it left open by Kirk to supply cold air for the fan, or is it just the opposite and potentially letting hot exhaust heat pre-heat the air getting sucked into the eng fan? If concencus is to seal it off along the firewall, what is everybody using? The foam bus "H" seal wont work back there as it appears to be a "right angle" seal situation to attach to the firewall? Or should I fab up thin aluminum sections to close it off? The car's up on jackstands for the Winter and I just realized how big that gap is!
Thxs guys!
Doug

Ties into my bump on firewall post and I would love to know more about how others have approached the firewall shape, location, and general sealing of the engine compartment

When doing my speedster builds, I leave this gap open. IMO this provides additional cool air into the engine bay. I've never had a speedster run hot. ~Alan

Wouldn't a dog house bellhousing cover close the most/all of the gap in front of the engine? It does mine.

http://cbperformance.com/catalog.asp?ProductID=274

Although mine doesn't have the square hole in the left end.

Bruce - Curious, is yours missing the lower air channel piece then? It would go thru that hole to channel cooling air to oil cooler. The older non-dog house breast plate didn't have that square hole.

http://www2.cip1.com/ProductDetails.asp?ProductCode=ACC%2DC10%2D6203

On CMC there is also that rubber splash skirt that gets riveted to firewall -- see CMC build manual.

Bruce & all, my engine does have all the tinware between the engine & firewall ( the pic link you enclosed ). Even with that tinware, there is still agood 1.5" gap between it and the firewall over the tranaxle and extending out to the left & right side of the engine where the H seal is installed that then goes around the left & right side and the rear of the engine bay ( all one piece of H foam assumably from a VW Bus? ) When I looked on C1P, they have a variety of Bus engine seals, but I can't tell which one is the foam H seal that Kirk @ VS uses...and they vary quite a bit in price. Can someone pls tell me which one is the correct foam H seal on the C1P website...or West Coast Metric??
Thxs
Doug

Before I re-did by engine bay insulation I tried a couple different seals that I purchased from numerous suppliers, including Cip1. The best solution was using a self-adhesive foam weatherstrip tape. It sealed the gap quite well. As Allen pointed out, it might not be necessary to keep hot air out. But when you live in the country, with gravel roads and all, it is a necessity to keep the dust out.
When I rebuilt my engine I replaced the insulation and cut the firewall piece long to fill that void.
BTW, here is the proper "H" seal:
http://www2.cip1.com/ProductDetails.asp?ProductCode=VWC-411-813-225

I did try this as well but it worked its way loose and I lost it. If you decide to go this route, make sure you use some adhesive! ;)

I just installed my engine and see that I have the same gap too.

I think I will try nesting together and gluing two pieces of that H-seal.

In effect, that will make a wider H.

I will curve it a bit when I glue it.

Does anyone know how much excess length the H-seal has?

I am a little concerned if I double up in front I may not have enough for the rest.

Mike, I know that there is not enough H' seal to have two pieces out of the roll for across the rear body area of the motor. Not sure if two pieces glued togeter will stay in place on the back side...??? ~Alan

Didn't ALL original Porsches have the cool air on the top completely sealed from the hot air on the bottom? Didn't ALL air cooled VWs have the top sealed from the bottom? Are you smarter than Eng. Porsche? I'm just saying . . . .

Speaking from experience learned as a former 250,000 mile Corvair owner and now a speedster owner who made his own tin, I'm gunna do everything I can to completely seal the top from the bottom. The bus H-seal is good for covering large openings, looks good installed, and is easy to work with.

Robert,

I took another look at my engine bay today. As Wolfgang suggests, I created and installed a rubber splash skirt that I screwed to the firewall and it covers the gap between the firewall and the dog house bellhousing cover -- as outlined in the CMC build manual. I used a brown rubber tread-like material sold at Home Depot.

Wolfgang,

My bellhousing cover is chrome and has two 2.5 inch holes on each end covered by chrome screens, no other holes. I purchased this about 17 years and have not seen anything similar lately.

"Are you smarter than Eng. Porsche ?"

No, I would say not however, I've had limited experience with speedsters having built 15 speedsters to date as well as many other air cooled replicas. I have found that the way I do the engine bays, breather box hose routing etc.....works.
What you need to consider is the design of the VW Beetle having a large grill vent just below the rear window where as the speedster, only has the small deck lid grill.
Your JPS with the additional deck lid venting you should not experience a cooling issue as long as all other aspects are within specs i.e. timing, fuel mixture etc. ~Alan

"Are you smarter than Eng. Porsche ?"

To add to drclock COMMENT - And if you look at cooling changes made to VW T1 over years - they added vents to the engine lid and those gill vents behind each of the rear 1/4 windows.

I peeked inside engine of mine last night (probably woke the mice). I riveted my splash skirt to front side of firewall and there is a 1" gap. If I remove it and remount to the engine-side (and maybe make it 1" longer) it would effectively close the gap. The moon cutout would direct cool air down center to engine.

I did use solid piece of weather stripping to seal engine lid to body opening --- I know some use a few rubber buttons there so there is more air transfer.

Alan, Wolfgang, I completely with you in adding additional cool air inlets, from ANY source. My point was, I don't want ANY hot air from under the car, including hot air off the transmission, to enter the engine compartment without an invitation.

Regarding the tinware-to-eng-compartment-body seal: I bought this from Cip1 http://www2.cip1.com/ProductDetails.asp?ProductCode=VWC-411-813-225 as I wanted to replace this seal anyways ( the one you see when you lift the lid ), and I wanted to also see if it would seal the are behind the eng over the transaxle. The roll that Cip1 sent was 10' long, and the old seal I removed from around the engine was 5'so if you're careful you can get 2 cars worth of this seal in one roll. It was German made & $40, but not as "thick" in cross section "H" as what Kirk used, but it fits perfectly and looks great.

Bottom line: I found something that works better for sealing the "back" of the engine tinware from the firewall: black 1.5" Round foam pipe insulation that comes in 8' lenghts and has a split to place it over pipes. Just about any hardware store carries it. It can be cut and shaped to fit and filled that gap really well.

Just passing this along!
Doug