I'm trying to work out an engine combo. Usually this ends up as a what cam question, but I know it's all in the combo. I am building a 2 liter engine and really trying to get it right this time. I have done 2 rebuilds before, but have been defeated by trying to reuse worn parts, most notably a bent crank which the machinist didn't catch as well as lack of experience. I am starting from scratch this time. I have a new to me case that has been align bored, decked and galley plugs tapped. It's a Type 4. I am using a stock 2 litre crank and rods from DPR machine in southern California. All the parts have been balanced as well as balance of the rotating assembly. AMC 2 litre heads redone with new hardware by Len Hoffman. I will be running stock Kolbenschmidt 94 mm pistons and cylinders. They are unused but have a couple light scratches. I have balanced them within .2 grams. Diddled with micrometers and bore gauges endlessly to make sure sure all the clearances are within spec. I was planning to run my stock PDSIT 32/34 Solex carbs which have been nicely rebuilt, rebushed, etc and have all the original parts for the 1973 stock air cleaner. Another consideration is that it is an early 003 automatic. I also prefer a 4 in 1 extractor type exhaust. I will be using the stock heating system which I have carefully repaired. I am trying to choose between the Web 142 stock grind and the Web 73. I have them both with matching lifters and have run them both in previous builds...with a single progressive carb and a Monza style exhaust. Both ran quite well. I didn't experience a lopey idle with the 73, though the progressive was tuned puke rich to avoid off idle stumble. My bus is a fair weather camper. I do mostly long trips. I prefer 2 lane state highways where the speed limit is 55 but everyone drives just under 65. That seems to be the sweet spot for cruising in a bus. Sometimes interstate driving is unavoidable and I have also cruised at 75 for short periods when necessary but that's about all I get out of a bus and the handling starts to feels iffy. I am planning to do the great American road trip with my kids this summer provided the pandemic, riots and wild fires settle down. My biggest considerations are reliability and longevity. Many have raved about how well the stock dual carbs work. When I got my bus 30 years ago, I hated them. They were great when tuned, which would last until I hit the first big bump. Then they would be all over the place. So I have my doubts. Still, I would like to give them a good try and run them with the Web 73, stock dual advance distributor, 4 in 1 extractor type exhaust. I realize I would be in for a lot of tuning and rejetting. Am I defeating myself with an impossible combo? What would be the best route to go? Sorry to write a novel and thanks for reading along.
I hated my stock carbs. Several tuners atempted their trade and pronounced the spindles worn - it wouldn't go over 55mph. I had them refurbished and they were set up on a similar engine as part of that. I bolted them on and flew up to 80mph - it was still going when I lost my nerve. 1700 type-4. Just don't get a cam that isn't doing it's thing at the revs you like to drive at. That means mild. Funny that you've tried both those cams yourself but you're asking us?
It looks like you’re building a stock engine - stock 1971cc, stock small valve heads and a stock or near stock cam. You won’t really gain much with a 4 in 1 exhaust but it won’t do any harm if that’s what you want to use. For what you want the engine to do flip a coin for the cam, there isn’t much difference between a Web 142 and a 73, either should work fine with the auto. Performance should be more or less the same as a stock VW 2.0l.
The cams were used in 2 different builds. The build with the web 73 had new heads and maybe ran a little better as a result. Honestly, it was hard to feel much difference between the 2. Neither gave me poor idle or kicked me in the pants at some magic rpm but I don’t think the single progressive helped either build. My 1800 crate engine with the stock cam, bent crank and dual Weber ICT’s would also go and go like your 1700, until I lost my nerve. I am leaning toward the 73, my biggest worry is that it won’t work well with the stock carbs. They really have been thoroughly gone over, rebushed, shiny bits replated, not just re-kitted by Tim at Volzbitz. And thanks.
You won’t feel much difference because there isn’t much difference; both the Web 142 and the 73 are very mild and either will work with stock carbs.
I guess I spend a lot of time on a forum where the differences between these cams and many other small differences are hotly debated. It makes sense that is testing both these cams with my butt dyno and finding no real difference that I could just trust that observation. I know that both cams are slightly more aggressive than stock but neither is a “camming up” plunkety plunkety kind of cam. They are baby cams really. I do believe that the 73 might yield lower CHT’s but so does good tuning and sensible driving. The 4 in 1 extractor also gets talked up a lot, but the stock muffler is quiet. I guess there can be a lot of hype that exaggerates small differences and opinions just become more extreme. So I will go with the 73 and give the stock carbs my best try. I know they will probably require some creative rejetting. I won’t be going back to the progressive. It wasn’t awful and kept me rolling while my stock carbs were being rebuilt. Thanks again folks
I don't think your carbs will need rejetting personally. As you say, they would split every HP on some other forums but their references are usually car based too and that really is a different set of requirements and reactions. What would be a noticeable difference in a Beetle can be undetectable for a bus. All a bus really wants IMO is more torque throughout the revs and the only meaningful way is more capacity. If one is prepared to loose power at some revs in echange for more power at other revs that's a cam thing but a bus NEEDS power at all revs just to cruise.
That car bus difference is stark. Beetle drivers below about 55mph are cruising on idles, the mains are just for accelerating. It doesn't much care what the cam is cruising as it needs so little power. There lies the opportunity for aggressive cams and acceleration fun. We buses, we're on mains cruising at 30-35mph and above. We can't put up with not being "on cam" because we need more power, travelling at 40-45mph for example. Who wants to be in 3rd ? It's worse at 55mph in 4th. Even a mildly aggressive cam won't be doing it's thing which results in too much heat - the engine wants to be in 3rd, the driver does not.
Yes, there are differences between the two cams. The 142 is supposed to be a copy of the Porsche 914 factory cam. Its split duration with 0.393”/0.368" valve lift and 210/206 deg. duration at 0.050". The 73 is a solid version of the factory hydraulic cam. It’s not split duration but it has more lift. 0.426" valve lift and 224 deg. duration at 0.050". They’re both mild cams although the 73 is the more ‘aggressive’ of the two and I’ve just noticed that aircooled.net don’t recommend the 73 with Solex 32/34 PDSIT carbs, however, I ran a Scat 25 with about the same lift but more duration and it was fine with stock carbs. In my opinion either cam will work, if I had to choose I’d go for the 73 and I agree with zedders I don't think your carbs will need re-jetting either- but what do I know, don’t blame me if it goes horribly wrong.
No, I won’t blame anyone. If it doesn’t work out there are other options. I find these engines to be quite forgiving. The last one I built was probably the best I running engine I’ve had yet. The reason for the tear down was because I had installed an aftermarket oil pump with a drive shaft that was too long and ended up wearing out the cam thrust bearing. In tearing it down and measuring it all out, I found the issue with the crank which had been there all along. The only issue I had with it when driving was an off idle stumble which is a well known problem with the progressive. I ended up running ported vacuum to the power valve which keeps it open all the time. This eliminated the stumble except in very cold weather. The only real difference with my current build performance wise will be the jump from 1800 to 2l, dual stock carbs vs the progressive and ditching the Monza exhaust. I am also thinking that the 2l will rev lower than the 1800 at higher speeds which should give me a better top end.
It'll only rev lower if you change the gearbox. I'm sure there are other factors, but seems to me that as the stock 1.7, 1.8 & 2l cams are the same, each increase in capacity lowered the peak torque rpm and that bares out with my 2.4l So, despite my not doing it to mine it looks like a 2l could stand a bit of cam and still be as stock as a 1.7/1.8 if you see what I mean...and on that theory I really should have given mine some more overlap and lift.
My problem with the dual carbs was that they lost their accelerator pump tubes. I had them replaced once and they were great until they spit them out again. I explained this to the rebuilder. The 73 seemed to give the bus a bit more pep and still seemed to do fine in the low end but it still drove like a bus, a nicely running bus, but still a bus in every way. Makes sense. I get why displacement would help a bus more than cam choice. I did look up the C25 and it is more aggressive than the 73. It’s reassuring that it can work well with stock carbs. I’m good with stock performance. It’s a joy to drive when kept after and running well.
The 142 in the tintop seems to work great, stock 2ltr solex carbs but I think I've got that tuned just nice for now. The 73/86 cam in the pick up (2056) still settling in with DRLA36's needing a bit more tweaking and Vintage speed exhaust to quieten down. The 6 rib vs 3 rib boxes make it hard to compare but early days yet and should settle in. Sent from my SM-T580 using Tapatalk
Those sound like nice combos. There’s no substitute to driving them to a good tune. They just need to be driven and kept after. The crate engine with the bent crank didn’t give me any problems during a 10 year span whereI drove it often. After toasting another crate engine driving from New Hampshire to California I changed my driving style, installed an oil temp gauge and used it to tell me when I was pushing too hard. You just can’t drive it in the desert in the summer the same way you would drive it in coastal New England.
