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smitty24
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Joined: April 28, 2008
Posts: 2723
Location: Salem, Oregon
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 Posted: Mon Dec 15, 2014 5:35 pm Post subject: 58-69 factory decklid air supply and larger displacement |
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What are the limits of this lid on the same year bugs? Is it a fact that they will not supply proper air flow to larger engines? Im running a 2 liter with doghouse and 44s, stock decklid with only factory louvers above. No standoff kit of bottom prop. I have not experienced issues with overheating, but not sure if it is starving at higher rpms. What do the experts say?? My logical thinking says they went to the vented lid in the 70s for a reason. Is there actual benefits and facts to back this up?
Thanks guys and sorry if this is a dumb question! |
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ps2375
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Joined: April 24, 2014
Posts: 2471
Location: Meridian,ID
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| Posted: Mon Dec 15, 2014 5:44 pm Post subject: |
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| The 69 I got from my father has it's original deck lid, and it has a 2087cc motor with dual 44IDF's and the car lived in AZ. The motor was built to do 7K rpm's and did with no issues other than my brother blowing the alt belt off on acceleration. (He drove it in the Phoenix area, and it lived thru him driving it.) |
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vwracerdave
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Joined: November 11, 2004
Posts: 15303
Location: Deep in the 405
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| Posted: Mon Dec 15, 2014 7:27 pm Post subject: |
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VW added more deck lid louvers when they went to the doghouse oil cooler in '71. It is well documented that a larger engine with doghouse fan and dual carbs need more then the solid rear deck lids. You can cut a big hole in the deck lid behind the license plate and space it out 1" for added airflow.
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modok
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Joined: October 30, 2009
Posts: 26785
Location: Colorado Springs
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| Posted: Mon Dec 15, 2014 7:30 pm Post subject: |
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Why you askin this in the middle of winter???
Far as your other question, a no-vent decklid might be a good way to supply warmer air to the carbs  |
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gt1953
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Joined: May 08, 2002
Posts: 13848
Location: White Mountains Arizona
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| Posted: Mon Dec 15, 2014 8:06 pm Post subject: |
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My 68 non vented deck feeds dual 40 Kadrons. As long as I am just putting around I am OK. If a HY trip is in the picture the deck lid is propped open at the bottom. Drops oil temps 10 degrees or more.
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bluebus86
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Joined: September 02, 2010
Posts: 11075
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| Posted: Wed Dec 17, 2014 9:12 pm Post subject: |
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a 1600 DP stock engine with dog house fan is starved for air when put in my 61 Bug with solid decklid. the bigger fan and bigger motor require more air, it is not an issue until freeway speeds. Not only did my engine run cooler, if also had more top end power once I propped open the bottom of my deck lid. I made a hugely noticeable difference in freeway driving, I finally got power!
also note the early bug is geared higher than the later ones that came with the larger motor and louvered deck lids, so if you put a later motor that requires more air in an early car, with early gearing, you will have a combination will require even MORE air at a given speed (MPH) than if the engine was installed in the later cars. I had the stock 61 gearing in my car when I found I NEEDED to prop open the deck lid.
VW added louvered deck lids when they introduced the bigger fanned motor, you should take steps to allow more air to enter the engine bay if you install one of these larger fanned motors.
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Quokka42
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Joined: December 02, 2010
Posts: 3117
Location: Melbourne, Australia
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| Posted: Thu Dec 18, 2014 3:50 am Post subject: |
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| modok wrote: |
| a no-vent decklid might be a good way to supply warmer air to the carbs |
Only if you have left the seals out!
If you do the maths, you do need to provide some more airflow for a doghouse fan and/or high revving engine.
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Slow 1200
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Joined: July 02, 2004
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| Posted: Thu Dec 18, 2014 4:41 am Post subject: |
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| actually the louvered decklid appeared one year before the bigger fan |
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GTV
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Joined: March 27, 2004
Posts: 2084
Location: Si'ahl
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| Posted: Thu Dec 18, 2014 4:54 am Post subject: |
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| Slow 1200 wrote: |
| actually the louvered decklid appeared one year before the bigger fan |
Correct, for the 1970 model year. First year for dual pressure relief, 1600 single port. 4 vent lid was introduced for 1972.
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Anvil
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Joined: September 28, 2009
Posts: 248
Location: Golden, Colorado
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| Posted: Thu Dec 18, 2014 11:41 am Post subject: |
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Haha! Any excuse to post these pics!
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maplesyrup
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Joined: May 27, 2009
Posts: 182
Location: Bristol
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| Posted: Thu Dec 18, 2014 12:20 pm Post subject: |
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| Anvil wrote: |
Haha! Any excuse to post these pics!
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That's bloody great!
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Anvil
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Joined: September 28, 2009
Posts: 248
Location: Golden, Colorado
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| Posted: Thu Dec 18, 2014 3:21 pm Post subject: |
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| maplesyrup wrote: |
That's bloody great! |
Thank you. The work was done by Luftkraft Fabrications and beautiful work it was. This car is a never ending project and as my buddy Pat likes to say, "This won't be the last $400 Volkswagen that winds up costing $20,000."
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VWCOOL
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Joined: June 02, 2006
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Location: Down under
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| Posted: Thu Dec 18, 2014 3:45 pm Post subject: |
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yes the extra vents help performance and cooling.. however Cabrio (vented) lids for the year models you list are rare
Propping the top of the lid open is a good idea; it tends to scoop air from along the sides of the car to help with overall air flow (less restriction via too-small standard vents = greater volume) and slightly, very slightly, pressurise the engine bay.
Hot air rises, so it has the secondary benefit of 'draining' the engine bay in slower conditions to keep carbies cooler... much better in traffic. Less stumbles etc due to hot fuel.
Also reaaaallllly helps in conditions like this
https://www.facebook.com/video.php?v=5537595213427...mp;theater
Propping the base of the lid - such as he 'tennis ball trick' - is nowhere near as effective as it draws already-hot air/fumes, plus road dust etc, from under the car and tends to keep the hot air in the engine bay in slow traffic |
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GTV
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Joined: March 27, 2004
Posts: 2084
Location: Si'ahl
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| Posted: Thu Dec 18, 2014 4:08 pm Post subject: |
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| VWCOOL wrote: |
Propping the base of the lid - such as he 'tennis ball trick' - is nowhere near as effective as it draws already-hot air/fumes, plus road dust etc, from under the car and tends to keep the hot air in the engine bay in slow traffic |
On my 72 that "trick" instantly raised oil temps at highway speeds. Took it out and temps went back down. Same for the infamous Herrod Helper.
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bluebus86
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| Posted: Thu Dec 18, 2014 6:16 pm Post subject: |
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| Quokka42 wrote: |
| modok wrote: |
| a no-vent decklid might be a good way to supply warmer air to the carbs |
Only if you have left the seals out!
If you do the maths, you do need to provide some more airflow for a doghouse fan and/or high revving engine. |
That's how VW ENGINEERED the deck lid, to provide more air for the bigger motor. The VW ENGINEERS knew their stuff well. Engineers are good over all.
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bluebus86
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| Posted: Thu Dec 18, 2014 6:28 pm Post subject: |
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| GTV wrote: |
| VWCOOL wrote: |
Propping the base of the lid - such as he 'tennis ball trick' - is nowhere near as effective as it draws already-hot air/fumes, plus road dust etc, from under the car and tends to keep the hot air in the engine bay in slow traffic |
On my 72 that "trick" instantly raised oil temps at highway speeds. Took it out and temps went back down. Same for the infamous Herrod Helper. |
Interesting, of course a 1972 car, would that already have a louvered deck lid, and the 1972 with stock tranny will have a lower engine rpm for a given mile per hour.
I found in my 61 with stock 61 gearing to see noticeable oil temp decrease and the ability to accelerate at 65 mph, before propping the bottom of the deck lid, the engine lost power at around 65 mph. this with a 1600 DP stock 1974 Bug motor installed in my 61. I certainly had lower temps with the bottom of the deck lid propped open (although I admit that propping open the top of the deck lid is a better idea as far as getting cooler air to enter, however it has issue with collecting rain water, wash water and falling leaf's.
I suppose that raising the deck lid bottom on a car that already has louvers (enough to keep the engine cool, prevent air starvation) allows hotter air to enter than would enter from the factory louvers. For an early car, with a solid deck lid, running at high rpm do to early low ratio gearing, the engine DOES tend to over heat and be starved for air, so opening the bottom of the deck lid, although not ideal as opening the top of the lid, still supplies more air, ending the air starvation issue, although the air is some what warmer from the bottom of lid, it is still better than not enough air, so engine temps do go down in this case.
Evidently from what you report, the deck lid should not be propped open on the bottom if you are already running cool via the factory louvers. if you have no louvers, and have the bigger motor, it appears it is better to let in warm air form the bottom of the lid, rather than restrict the air by not opening the lid at all (or installing louvers)
so lesson is, (I think) if the engine is cool and you have a louvered lid, do not prop open the bottom. if however you have a solid lid and bigger motor and see high temps or experience engine dying off at high speed, then open the lid, even at the bottom will result in lower temps and improved high speed performance.
one size does not fit all.
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GTV
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Location: Si'ahl
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| Posted: Thu Dec 18, 2014 8:00 pm Post subject: |
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It had the normal 4.12 gearbox.
That was my theory as well, it may work for solid lids but it definitely is counterproductive on louvered lids.
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vugbug68
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Joined: June 25, 2006
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Location: sacramento
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| Posted: Thu Dec 18, 2014 8:42 pm Post subject: |
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| bluebus86 wrote: |
| Quokka42 wrote: |
| modok wrote: |
| a no-vent decklid might be a good way to supply warmer air to the carbs |
Only if you have left the seals out!
If you do the maths, you do need to provide some more airflow for a doghouse fan and/or high revving engine. |
That's how VW ENGINEERED the deck lid, to provide more air for the bigger motor. The VW ENGINEERS knew their stuff well. Engineers are good over all. |
Wow still pounding Quokka with sound engineering advice I see 
About the question... I'd say that correct engine tune is more beneficial than what decklid you use. I had a 68 bug with several different engines in it over the years, only had stand offs for a short time with the 1500. Had the lid closed up with a 1956cc and never had any overheating problems even in summer. Good working head temp and oil temp gauges are a good idea too.
1500 single port, non doghouse
1956 dual 44 idfs, doghouse
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Eaallred
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Joined: May 18, 2003
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Location: West Valley City, Utah
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| Posted: Thu Dec 18, 2014 8:57 pm Post subject: |
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All you have to do is look at it the way VW did. By the end, they had louvers under the rear window, four sets of louvers in the decklid itself, and another thermostatically operated opening behind the license plate.
All that for a stock 48HP 1600 dual port engine.
Throw more displacement and some dual carbs to eat some of that air, and it's EASY to see that a solid lid fully closed isn't going to cut it.
Personally, I've found removing the front tin (front is front) and making sure the doghouse air is routed away, provides all the extra intake that you need. But you have to be running ALL the tin that directs the hot air out the back of the car. i.e. sled tins, sealed to heater boxes or industrial tins, etc.
Kept my 2275 daily driver cool enough in 120 degree Vegas temps when I lived there. Highway and stop and go traffic.
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Alstrup
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| Posted: Fri Dec 19, 2014 5:59 am Post subject: |
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| Eaallred wrote: |
All you have to do is look at it the way VW did. By the end, they had louvers under the rear window, four sets of louvers in the decklid itself, and another thermostatically operated opening behind the license plate.
All that for a stock 48HP 1600 dual port engine.
Throw more displacement and some dual carbs to eat some of that air, and it's EASY to see that a solid lid fully closed isn't going to cut it.
Personally, I've found removing the front tin (front is front) and making sure the doghouse air is routed away, provides all the extra intake that you need. But you have to be running ALL the tin that directs the hot air out the back of the car. i.e. sled tins, sealed to heater boxes or industrial tins, etc.
Kept my 2275 daily driver cool enough in 120 degree Vegas temps when I lived there. Highway and stop and go traffic. |
X2
Only problem is, that if you live around here, your engine compartement will dirt up VERY fast. The later deck lid vent area will actually support up to a medium size engine with out problems.
The older models like the Oval needs convertible vents on most anything over 1600 cc. where you use the power, so to speak.
T |
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