Engine/gearbox disaster ??
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GOOFY
New member
Dropped valve occurred mostly on later 1971 twin port engines as a result of increased compression and leaner mixtures:
From 1971 Beetle engines had increased compression ratios, twin ports, and for California EGR (exhaust gas recirculation) - all to produce less emissions with more power. These engines were the 1300 and 1600 twin ports, the 1500 single port dropped. However these new engines ran hotter and used different carbs design to comply with emissions compared to earlier pre1971 models. So a "dog house" cooler was needed - hence the different air cowling on these engines. They still ran very hot compared to earlier pre1970's and were more sensitive to fuel, idle timing variations, air leaks in the intake manifold twin port gaskets. All this caused hotter cylinder heads especially on no3 cylinder - a direct result of this higher compession, lean mixture hence lower emission and poor tuning - leading to dropped valve. In my 40 +years experience of various VW air cooled engines ( I rebuilt my first one when I was 15) I never experienced dropped valve. (We had 1200 original oval bought new, 1500 auto, 1500, 1303s drove to Spain and back, 12001972, and Type2 1600 drove to Portugal and back !) (miss the 1500 the most - best engine, but 1303s for all round handling ! ).
From 1971 Beetle engines had increased compression ratios, twin ports, and for California EGR (exhaust gas recirculation) - all to produce less emissions with more power. These engines were the 1300 and 1600 twin ports, the 1500 single port dropped. However these new engines ran hotter and used different carbs design to comply with emissions compared to earlier pre1971 models. So a "dog house" cooler was needed - hence the different air cowling on these engines. They still ran very hot compared to earlier pre1970's and were more sensitive to fuel, idle timing variations, air leaks in the intake manifold twin port gaskets. All this caused hotter cylinder heads especially on no3 cylinder - a direct result of this higher compession, lean mixture hence lower emission and poor tuning - leading to dropped valve. In my 40 +years experience of various VW air cooled engines ( I rebuilt my first one when I was 15) I never experienced dropped valve. (We had 1200 original oval bought new, 1500 auto, 1500, 1303s drove to Spain and back, 12001972, and Type2 1600 drove to Portugal and back !) (miss the 1500 the most - best engine, but 1303s for all round handling ! ).
JCB..
Non-member
A pair of Type 3 Variants, a 412, 1200 1302 and a 98 Mexican Beetle in our line.
I can't dispute what your saying about twin ports but you omitted to mention the proximity of the oil cooler to number 3 cyclinder which in my book is the fundamental reason why this cylinder is invariably the one that suffers the drop. This was clearly an oversight by someone in the design office.
I can't dispute what your saying about twin ports but you omitted to mention the proximity of the oil cooler to number 3 cyclinder which in my book is the fundamental reason why this cylinder is invariably the one that suffers the drop. This was clearly an oversight by someone in the design office.
GOOFY
New member
Short of completely re-engineering the fan shroud (as they did in some other models) and thus the shape of the car at the back, they created the dog house cooler as a compromise . There was no oversight by anyone in the design office. Indeed they were well aware of the no3 running hotter due to lack of cooling - that's why in the design the no3 ignition is slightly retarded (using an offset on the distributor lobes) - to keep the heat down. There was no oversight. Indeed fitting aftermarket 090 distibutors as some did can cause more harm as this offset is not on them. Oil cooler up front under the front bumper was a solution most modifiers installed.
GOOFY
New member
The engine design was based on the very original engine design, that had the oil cooler positioned above no3 (not no1 as you state) cylinder - and had the retarted ignition on no 3 designed in at the original engine. This design engine went on to give the Beetle its famed reliability as you are aware. If you then believe that someone somewhere did not get it right - then perhaps you should take it up with someone called Ferdinand Porsche who designed it. You do make me laugh.
With a little help from Hans Ledwinka of course [
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JCB..
Non-member
The 1 was short for one and I'm fully aware of where the cooler sits. [8D]
Last time I checked the man had been dead for over fifty years so I'm going to find it difficult to carry out your suggestion, but then I'm sure you would know that already. [&:]
I wasn't laughing when I had to replace the engine in our Variant which despite being well maintained, dealer serviced and used mainly to cruise between Stroud and Fareham still managed, to drop a valve.
GOOFY
New member
As I say, in probaby over xxx,000's miles in various air cooled bugs, since the 60's through to 80's, in driving in high temps summer in Spain, France, and even Africa, flat out at 80mph for hours on end, and also back here in freezing UK (!), never experienced dropped valve. Mind you they were all expertly maintained by a trusted VW mechanic & friend (& myself!).
BTW, from the exhaust on the orange 1302S (pic), looks non standard and is probaby the 4 into one extractor with silencer, or zoom tube. Be aware that your intake manifold is not going to get the pre-heating effect through the pre-heat pipe - which will lead to lean mixture at idle to mid range (or icing when cold). If you have twin carbs on top of each cylinder bank then OK.
BTW, from the exhaust on the orange 1302S (pic), looks non standard and is probaby the 4 into one extractor with silencer, or zoom tube. Be aware that your intake manifold is not going to get the pre-heating effect through the pre-heat pipe - which will lead to lean mixture at idle to mid range (or icing when cold). If you have twin carbs on top of each cylinder bank then OK.
Nice debate on air cooled cars and most informative too. nailing my colours to the mast I've had 1300's a stunning 1500 66' vintage 1303 and a 67 that I built from a rotten basket case. I've rebuilt a few air-cooled engines too, including building a full on 1835cc conversion with modded case cc'd heads etc at the tender age of 18. But I digress. I can't help thinking Porsche got it wrong at the design stage with the boxster and 996 engines. Take a good look at the layout of both the 993 bottom end and the water cooled engine's bottom end and tell me where you think the best place to put the shaft is? Clue how many intermediate shaft failures on the air cooled engines?
Put simply the intermediate shaft is a shaft with a sproket chain drive that acts as "intermediate" drive from the crankshaft to the camshafts. This shaft also drive the oil pump.
GOOFY
New member
Porsche have had a decade to sort this out, but they still churn out these fundamentally flawed engines. Then when you get a replacement - you don't even get a new engine, even though you may have covered less than 20,000 miles and taken out an expensive warranty ! Remember Porsche only really build one car - a 911, with variants of same engine behind the axle or in front ! The front's are the same and maybe add some 4 wheel drive, turbos etc. How much is spent on R&D - other makers such as Ferraris have v10,s v12's, engines in the front, back. Mercedes, BMW , AUDI - many engine and model variants. So you cannot compare Porsche with them.
Why can't Porsche build a good solid reliable engine anymore. (Cayeene engine a VW engine +more cylinders is more reliable)) Perhaps £8M profit a day !!?
Sorry I have to ask ... ? I have had 5 Boxsters, since they where launched evey one a peach .. no issues .. cars replaced because I wanted to ..So re your a "fundamentally flawed engine" statement ?? sorry I dont get that ... Was I so lucky that my engines never fell to bits since 1999 when I got my first one ??? And as you say .. its pretty much the same engine in the 911 now ... how many of them also "blow up" ??? I know you now a lot abou the engines Goofy but saying "fundamentally flawed engines" is a bit strong isn't it ????
Is not 20K "Original purchase warrenty" on a Boxster now ?? I cant remeber as I dont worry about it ..(I think its 2yrs or 20K isn't it ?)
And is the only Cayenne engine which is a VW "derivative" the V6 ... The 4.8 V8 (S / Turbo / Turbo S) has nothing to do with VW.. (I have a V6 Cayenne as well)
[
]Now senseless personal experiance statement now .. I used to drive Vauxhall Cavaliers when I was a lot younger .. Had 3 engines go one me in 3 cars .. same problem .. Snapped Cam belt ... WHY can GM not build a proper engine they have had at least 50 years .....[
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metric_thumbs
New member
I have a 110 BHP road Beetle - along with half shares in a 210BHP drag Beetle. Both dyno'd figures back drag calculated for the flywheel.ORIGINAL: JCB..
Not a poor choice at all Mike
Number 3 cylinder's exhaust valve regularly used to drop off at around 60-70k miles due to the oil cooler restricting the air flow over the fins. At least they cured the problem with the "dog house" fan housing.
You have a 600 BHP Boxster or a 90 BHP Beetle? [
And the regular 3 valve drop is a myth. I think someone else above points this out. I have 10's of friends running Beetles and Busses for many many 100,000's of miles collectively and I do not know a dropped valve at all.
I do know of rods coming loose and cutting the crank case in half, but even then the valves were still there "" cam cut in half though!!
And love the Hans Ledwinka reminder above. Top work. I wonder what language Porsche spoke to Ledwinka when he as visiting?
Whatever language they first spoke, they ended up talking money - to the tune of DM3,000,000! [
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JCB..
Non-member
ORIGINAL: metric_thumbs
I have a 110 BHP road Beetle - along with half shares in a 210BHP drag Beetle. Both dyno'd figures back drag calculated for the flywheel.ORIGINAL: JCB..
Not a poor choice at all Mike
Number 3 cylinder's exhaust valve regularly used to drop off at around 60-70k miles due to the oil cooler restricting the air flow over the fins. At least they cured the problem with the "dog house" fan housing.
You have a 600 BHP Boxster or a 90 BHP Beetle? [
And the regular 3 valve drop is a myth. I think someone else above points this out. I have 10's of friends running Beetles and Busses for many many 100,000's of miles collectively and I do not know a dropped valve at all.
I do know of rods coming loose and cutting the crank case in half, but even then the valves were still there "" cam cut in half though!!
And love the Hans Ledwinka reminder above. Top work. I wonder what language Porsche spoke to Ledwinka when he as visiting?
Myth - I can still remember it clearly!
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