VW 8v cams
Posted by Ckgtimk2
Corey Kline Mod Moderator Location: Lancaster, PA Join Date: 11/22/2011 Age: Settling Down Posts: 103 Rally Car: Used and abused Mk2 GTI |
Andrew Steere Super Moderator Location: South Central Nude Hamster Join Date: 12/29/2005 Age: Possibly Wise Posts: 2,008 Rally Car: too rich for my blood, share a LeMons car |
Corey Kline Mod Moderator Location: Lancaster, PA Join Date: 11/22/2011 Age: Settling Down Posts: 103 Rally Car: Used and abused Mk2 GTI |
John Vanlandingham Elite Moderator Location: Ford Asylum, Sleezattle, WA Join Date: 12/20/2005 Age: Fossilized Posts: 14,152 Rally Car: Saab 96 V4 |
What's all this crap mean?
Backtrace: Function phorum_database_error called at {path to Phorum}/include/db/mysql/mysql.php:205 ---- Function phorum_db_interact called at {path to Phorum}/include/db/mysql.php:920 ---- Function phorum_db_post_message called at {path to Phorum}/include/posting/action_post.php:149 ---- Function include called at {path to Phorum}/posting.php:595 OK here's some pertinant stuff from Turbopricks just a day ago, read the whole thing then I'll tailor it a little bit. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ where to begin? You're doing it wrong. Here loo at this: intake Duration exhaust Duration Overlap lift intake lift exhaust lobe centers intk / exh degrees ret/adv ................................................................................valve events intake / exhaust..btdc abdc bbdc atdc 256 256 38 .469 /11.9mm .469 /11.9mm see text zero .............................19 57 57 19 Intake opens 19 degrees Before TDC, closes 57 degrees after... so at TDC its only opened a liiiiiiiiittle tiny amount. Max valve lift will be somewhere about right in the middle or right around 104 degress AFTER TDC. So remembering the crank only goes 180 degrees from TDC to BDC where's the piston when the crank has turned 104 degrees? way down the hole.. Many of the furriner Cam specialist list "valve lift at TDC" here's a way way wicked cam for a volvo 8v SOHC from Piper in Pommieland: http://www.pipercams.co.uk/pipercams/www/product_nav.php?type=C&cat=CM&man=29&engine=89 OP! Here's a cam that would be innerestin Lookie: fawking formatting! Part No. VB18B320 Application RACE Power Band 3700?7500 Power Increase Duration 314° 314° Valve Lift 0.506?....12.85mm 0.504?/12.80mm Timing In 53?81---Ex 81?53 Full Lift 104° 104° Lift @ TDC with clearance In 0.180?/4.57mm Ex 0.178?/4.52mm Valve Clearance In 0.016? / 0.41mm EX 0.018? / 0.46mm Now that's a nice camshaft But look at the highlighted thing lift at tdc, and max lift at 104 degrees . No worries of interference even with this much nastier, rad-der, much funer-er cam (That's the one beauty of valves inline with bore) And we just got some contemptuous condescending crap from the guy who wrote about what so many of you have taken as a trurth, the absurdity, the insane folly to sugggest "rods stretch 001' per 1000 rpm". That misunderstnding or misreading was shown to NOT be a rule of thumb with the simple thought excercise: Is the rod stretching .001 at 1000 rpm? no is the rod stretch .001 at 2000 rpm? no-- See? Alsow a moments thought and we see theorertical stretch is entirely dependant on weight of half the rod and 100% of pistons weight x speed Ie a 880 gram piston and the reciprocating half of an 890gram rod at 7000 rpm is going to stretch a lot more than a 340gram piston and half of a rod 140g lighter... at 7000 rpm. So when I say "You're doing it wrong" do you see the error? All your assumptions and methods are all wrong. OP!(This is the most pertinant stuff) Conclusion: mill the hell out of the head and get a gnarly cam, just get some valve spring.. (And note: when I say mill 050-060 off it is because even with that K cam the crank is still only going 180 from BDC to TDC BUT intake valve is open for gawddamn near enough to 1/3 of crank rotation from BDC to TDC and it probably isn't making much compression when there's a big 44 or 46mm hole open in the head until 57 degrees ABDC (60 woulb be 1/3 of 180) So in order to have ANY compression worth a damn in the 2/3 of rotation left to do everything in, you gotta mill the hell out of the head. also. don't guess. measure. Don't believe, know. No, go and sin no more. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ So all the yakity yack is making the point that TORQUE isn't long stroke or 8v vs 16v it is more or less: Engine volume and dynamic compression ratio... Therefore, as we have seen on Special Stages and in a nice road car that Andrew references: even a remarkably short stroke V4 (66.8mm stroke for the "Big Block" 1700 and 58.6mm for the "Small block" 1500) cast iron, pushrod, 8v with really disgusting ports can make surprising amounts of torque when it has some compression---the rally motor and the one he's talking about both had around 11.3:1--it IS cast iron after all and I do use pump premium...aluminum head can stand another point. So IF you want a motor that has some POP! (good pop=good poop) there's an inseparable relationship between the SHAPE of the camshaft and intake valve closing ABDC.. close it later then you only have "this much" crank rotation to squeeze the charge, so you better have what seems to amateurs 'scary compression, but after a little reflection, isn't.. Now you said ABA, so I's gonna guess its an 8v, but I don't know if its a crossflow or a old 8v.. Does it look like this: 
Your piston crowns look like this? 
If so that's a pretty open chamber, not the biggest quench pads, and that means when milling the volume reduction isn't as fast as we see like in my V4 which has a more compact chamber and more quench pad... Now allegedly the stock MLS gasket is 065" thick. A Cometic available from Rallyanarchy's own professional engine builder could be had at around .028-030 a reduction of .035-037" or damn near 1mm (0393"  .
Cost-benefit fu is strong....some Vortex-ers say disassemble the stock gasket and remove the center part, hmmmmmm Whatever way ya do it IF you want a big cam AND MOAR TORKZ you need lots of compression.. Oh don't buy a cam without discussing the cam here. What final drive? John Vanlandingham Sleezattle, WA, USA Vive le Prole-le-ralliat www.rallyrace.net/jvab CALL +1 206 431-9696 Remember! Pacific Standard Time is 3 hours behind Eastern Standard Time. Edited 2 time(s). Last edit at 03/23/2013 09:42PM by john vanlandingham. |
Corey Kline Mod Moderator Location: Lancaster, PA Join Date: 11/22/2011 Age: Settling Down Posts: 103 Rally Car: Used and abused Mk2 GTI |
John Vanlandingham Elite Moderator Location: Ford Asylum, Sleezattle, WA Join Date: 12/20/2005 Age: Fossilized Posts: 14,152 Rally Car: Saab 96 V4 |
Josh Wimpey Mega Moderator Location: VA Join Date: 12/27/2006 Age: Midlife Crisis Posts: 649 Rally Car: Sneak the Golf |
Out of this dumpster fire Senior Moderator Join Date: 08/15/2010 Posts: 1,236 |
Corey Kline Mod Moderator Location: Lancaster, PA Join Date: 11/22/2011 Age: Settling Down Posts: 103 Rally Car: Used and abused Mk2 GTI |
Chad Eixenberger Mega Moderator Location: Grafton, WI Join Date: 02/01/2007 Age: Midlife Crisis Posts: 484 Rally Car: 1988 VW Golf #687 |
When you lose second gear and then have to try to climb Brockway, you'll be under three grand for what feels like FOREVER! 
I had a "street" car that had an ABA block with an old 8V head...made damn good power, but still no top end to match the 16v. |
John Vanlandingham Elite Moderator Location: Ford Asylum, Sleezattle, WA Join Date: 12/20/2005 Age: Fossilized Posts: 14,152 Rally Car: Saab 96 V4 |
Personally I can't unner-stand why in this day anybody would bother with 8v when there's 25 years of 16v laying around and getting scrapped . VW chamber isn't as minty fresh slide off the bar stool, oh baby oh baby bitchin as some 16v heads but it is a fawkavalot better than 8v... Power is ultimately limited by valve area, and the area of 2 x 32mm intakes in about 27% more than MY one big 44.5mm intake...How much bigger than the biggest 8v intake valve? Only problem is 2 cams to buy and 16 springs... John Vanlandingham Sleezattle, WA, USA Vive le Prole-le-ralliat www.rallyrace.net/jvab CALL +1 206 431-9696 Remember! Pacific Standard Time is 3 hours behind Eastern Standard Time. |
Out of this dumpster fire Senior Moderator Join Date: 08/15/2010 Posts: 1,236 |
You could also make the argument that power isn't everything in 2wd. Cheap($100) 8v are abundant. The last 16v I looked at that was running, was about $350. The parts are also drastically cheaper as well. CIS and CIS-E are very simple fuel injection systems. The only thing that fails are the fuel pumps, and as you say John, we should all be running two. |
John Vanlandingham Elite Moderator Location: Ford Asylum, Sleezattle, WA Join Date: 12/20/2005 Age: Fossilized Posts: 14,152 Rally Car: Saab 96 V4 |
OK, but to make a 8v have any poop you have to find small chamber-big valve 8v knowwhatImean, Vern? John Vanlandingham Sleezattle, WA, USA Vive le Prole-le-ralliat www.rallyrace.net/jvab CALL +1 206 431-9696 Remember! Pacific Standard Time is 3 hours behind Eastern Standard Time. |
Out of this dumpster fire Senior Moderator Join Date: 08/15/2010 Posts: 1,236 |
John Vanlandingham Elite Moderator Location: Ford Asylum, Sleezattle, WA Join Date: 12/20/2005 Age: Fossilized Posts: 14,152 Rally Car: Saab 96 V4 |
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