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Post by Zed on Apr 2, 2018 16:45:25 GMT
Not me, I know what I like. But this following illustration might help you not to go mad on your cam then expect to pootle about at lower revs. I had a Scat C35 cam in my 2020cc type-1. I know I bang on about this but I was innocent at the time - just like most people buying or building an engine aiming for better than performance. The C35 has advertised duration of 245° at 0.05" valve lift. The chart above shows it performs between 3,300 and 7,000 rpm. That resembles my experience. I kind of got away with it only because I had an aluminium case and a wasserboxer crank. The wasser crank is counterweighted to help prevent it flexing and will rev a lot higher than it's T1 & T4 predecessors. Even so, it was rubbish "on the street". T1 and T4 cranks are NOT counterweighted. A T1 crank max revs are 4600 and purely because it's chunkier, a T4 revs a bit higher to 5400. So an engine with a stock T1 crank with a C35 cam will have a useable power band from 3,300 to 4,600. Pretty much the wrong choice for most people building, say, a T1 stock crank 1776. T4 doesn't fair much better. If you build a much larger capacity engine, or fit it in a light car, shear brute force helps the lower revs, but it'll still be a bit crap for the capacity. So chaps, what cam have you got? If you relate it to the chart, what's it's best rev range and does that relate to your real life driving experience? Be honest please. If you cba looking up the duration, state your cam and I'll do it.
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Post by Zed on Apr 2, 2018 16:49:13 GMT
High lift and fast ramps help, but they wear out the valve train more quickly.
You can't really build an enduring high power driveable bus engine unless you're as devoted to all this stuff as Jake Raby in his prime.
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Post by chad on Apr 2, 2018 17:03:24 GMT
Mines a standard T1 cam, single port, single carb 1641cc but I can't find the duration.
I can't say that it has a 'best' rev range, just that it will move along the road if I keep it between about 2-4k, more slowly if there is a slight upwards gradient.
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Post by Zed on Apr 2, 2018 17:11:34 GMT
Engle W90 "cheater" cam. I can't find a milder cam than this one...
224° @ 0.050 = 2200-5500.
That, I think, is about the only useable bus cam out there!
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Post by chad on Apr 2, 2018 17:15:46 GMT
But if the T1 crank limit is 4600 you lose about 1/3rd of the potential range.
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Post by Zed on Apr 2, 2018 17:17:35 GMT
Mines a standard T1 cam, single port, single carb 1641cc but I can't find the duration. I can't say that it has a 'best' rev range, just that it will move along the road if I keep it between about 2-4k, more slowly if there is a slight upwards gradient. From a samba thread, don't know if it's correct, 212° @ 0.05" = 1500-4500rpm, who'd have thought! Edit to add Webcam says 214° @ 0.05", more or less the same.
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Post by Zed on Apr 2, 2018 17:18:45 GMT
But if the T1 crank limit is 4600 you lose about 1/3rd of the potential range. Precisely and that's the mildest aftermarket cam I've found so far! What a load of crap, it's either stock or race. They say "it's all about the combo" i.e. fit any non stock cam and you're going to have to rev higher so you're in for a counterweighted crank, minimum, and then buzz about like a boy racer, or suffer reduced performance 95% of the time. I've long suspected this to be the case but never bumped into the chart before.
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Post by Zed on Apr 2, 2018 18:01:19 GMT
77westyC25, 234° @ 0.05" = 3000 -6500rpm What say you? This is often recommended as a mild cam suitable for buses but mild compared to what I wonder?
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Post by chad on Apr 2, 2018 18:04:53 GMT
When mine was rebuilt it was balanced. Does that raise the safe rpm a touch?
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Post by Zed on Apr 2, 2018 19:05:01 GMT
When mine was rebuilt it was balanced. Does that raise the safe rpm a touch? In a word... Not really, it's the combustion force through the conrods apparently. I was reading about it today. I read that because the rear two cylinders fire, then the front two fire it creates a twisting force that distorts the crankshaft and pounds out the centre bearing saddle. Type-1s are the most prone to this. They made that saddle much bigger on type 4s and made the case of heavier stuff, then finally on the wasserboxer they also counterweighted the crankshaft to add rotational mass to resist the twisting. VW cranks and flywheels and conrod sets are already balanced. If you send them all off to be balanced, they balance the clutch on your crank/flywheel assembly. If you replace the clutch you loose the balance. Aftermarket parts should be balanced too but who knows how well. I had a bad experience when my 2020cc was balanced. It was beyond terrible. I then put a random old flywheel and a new unbalanced clutch on and it was smoooooth. Aluminium case, wasserboxer crank. 👍 Your builder will also have balanced the conrods and pistons. It all makes for a smoother, longer lasting engine, but the crank design and small centre main bearing still limit it's revs. If you mean you had a new counterweighted crank that would probably let you rev higher, but your valves, stock cam and exhaust won't! All cams have a power band which seems to be limited to about 3,000-4,000 revs wide for our ancient beasts so basically we're screwed whatever we do. 👍
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Post by 77westy on Apr 3, 2018 19:02:10 GMT
77westy C25, 234° @ 0.05" = 3000 -6500rpm What say you? This is often recommended as a mild cam suitable for buses but mild compared to what I wonder? You called. I’ve been lurking here a long time and I suppose I’d better say something. So… I have a C25 cam in 2.0l with 1800 heads, twin 40 IDFs with 30 vents and a CSP Python exhaust. It pulls well from just above idle and runs out of steam at around 4,500 and that suits what I use the bus for pretty well, it’s seldom on a motorway but climbs a lot of Cols. John at Aircooled.Net says “This is a nice upgrade on stockish engines, it's an outstanding bus cam!” I’ll be using the same cam in a 2,316cc that I will eventually get around to building – I’ve had the parts for 18 months. I’ve measured the new cam and it has slightly less lift than advertised and that probably means it has a degree or two less duration too. It’s easy on the valve gear and only needs single springs. A cam with a lot of duration tends to produce power and heat at higher revs, a mild cam makes power (and heat) at low revs. VW wanted heat at low revs to help with emissions so used a cam with not much duration but in my opinion it’s too mild for a big engine. The larger the capacity the more torque the engine will make and it will make maximum torque at low revs, of course in an ideal world we’d have variable valve timing, just like a modern engine. Your engine with almost all VW parts - the 104mm pistons are big and relatively heavy compared to the standard 94mm, it made sense to use H beam rods because they’re lighter so the reciprocating mass is similar to a 2.0l and the crank will tolerate the same revs. H beam rods are not as strong as the standard I beam but they’re certainly strong enough. My 2316cc engine – I no longer have access to a machine workshop and I’m too tight to pay someone to do any machining so the biggest engine I could make has a 80mm stroke crankshaft with 96mm pistons. Bigger stroke cranks are available but then there are clearance issues with the crankcase and the cam – no. 2 and 4 rods get very close to the cam. The crankcase and the heads are VW but almost everything else is from all over the world; the cam, followers, pistons and rings from the US, crank from Taiwan, rods and cylinders (double cast biral that everybody tells me not to use but can’t tell me why not) are from China. Bearings from Brazil and Mexico, the valves, pushrods and swivel foot adjusters from Germany but not VW and the distributor is from the Netherlands.
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Eoin
Full Member
Posts: 101
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Post by Eoin on Apr 3, 2018 20:50:07 GMT
I like my EMW C cam in the 2056 which is pretty much just 1 step above stock. It's really smooth right through the rev range and quiet too. I don't think the big valves and porting help the torque, this cam would probably be better with a bit faster gas flow low down to boost torque. Or more cubes to match the heads better.
I want to try Zed's big bore / small valve combo to see if I like it better than what I have. Keeping an open mind on what is better! The 'hot' cam in my 1911 was definitely shit, everything way too high in the rev range and it beat up the valves / rockers as well. I did learn from that, but didn't want to go right back to stock with an already modified engine.
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Post by Zed on Apr 4, 2018 9:15:02 GMT
I like my EMW C cam in the 2056 which is pretty much just 1 step above stock. It's really smooth right through the rev range and quiet too. I don't think the big valves and porting help the torque, this cam would probably be better with a bit faster gas flow low down to boost torque. Or more cubes to match the heads better. I want to try Zed's big bore / small valve combo to see if I like it better than what I have. Keeping an open mind on what is better! The 'hot' cam in my 1911 was definitely shit, everything way too high in the rev range and it beat up the valves / rockers as well. I did learn from that, but didn't want to go right back to stock with an already modified engine. 231° @ 0.05" = 2500-6000. More cc's would help. Interesting to get this real world feedback from you and 77westy. 👍 Anyone else or are y'all driving turbo diesels and Subarus?
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Eoin
Full Member
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Post by Eoin on Apr 6, 2018 9:56:53 GMT
I like my EMW C cam in the 2056 which is pretty much just 1 step above stock. It's really smooth right through the rev range and quiet too. I don't think the big valves and porting help the torque, this cam would probably be better with a bit faster gas flow low down to boost torque. Or more cubes to match the heads better. I want to try Zed's big bore / small valve combo to see if I like it better than what I have. Keeping an open mind on what is better! The 'hot' cam in my 1911 was definitely shit, everything way too high in the rev range and it beat up the valves / rockers as well. I did learn from that, but didn't want to go right back to stock with an already modified engine. 231° @ 0.05" = 2500-6000. More cc's would help. Interesting to get this real world feedback from you and 77westy. 👍 Anyone else or are y'all driving turbo diesels and Subarus? With the flowed head and 40 mm ITBs it would handle more CCs fine. I'd leave the cam as it is.
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Post by Robo on Apr 6, 2018 10:40:26 GMT
It's like sitting in a back street cafe in a remote village whilst on holiday & listening to the locals chatting among themselves in their own language but I just can't help listening, what I think I'm saying is I don't understand a bloody word any of you are saying but I'm somehow intrigued, impressed and amazed by it all...
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