| Author | Message | ||
     Berkshire |
but of course! | ||
| Fast1075 |
Berkshire....did you get my PM? | ||
| Reuel |
Just how high can the compression be pushed if you can adjust ignition advance to compensate? I really want to know. Anybody have detailed theory behind it, beyond the difference between mechanical and dynamic compression ratios? | ||
| Berkshire |
Fast1075 - no, um... how do I check? | ||
| Berkshire |
OK, figured it out - needed to update my email address. It's fixed now, but I think you'll have to send it again - sorry! | ||
| Gearheaderiko |
10.5:1 is considered 'safe', 11:1 chancy, according to the info I've been given. Maybe Fast can explain the theory behind it,but basically you run into combustion chamber problems that need to be sorted (squish band, quench, hot spots, valve/piston contact, etc.). The XB head combustion chamber is better than the Blast head. If you do a search of Badweb I'm sure there is tons of info on running the higher compressions and problems associated with it. | ||
| Fast1075 |
The best explanation I have run across on the web regarding the topic is available at nrhsperformance.com CLICK on tech tips. There is P3 (Blast) specific information about quench and a host of other Harley/Buell specific info. While I have quite a bit of knowledge about import bike engines, specifically the old KZ series Kawi engines and the GS Zuks...it's not always apples to apples due to design differences..If the P3 had a pent roof 4 valve dohc head....sigh...wishful thinking.... | ||
| Bandito90 |
Hey guys,I'm new here but have been lurking for years.I'm having trouble with the push rod cover fitting at the bottom of my 515 cylinder.It is an nhrs iron one.Any help would be appreciated! | ||
| Ezblast |
Dremel | ||
| Bandito90 |
How much can be taken off the cover?Is this common with most 515 installs! | ||
| Ezblast |
With NHRS - yes - don't take it off the cylinder - as long as you do not create a hole - your fine. EZ | ||
| Gearheaderiko |
Concur! Kinda... Its probably an XL cylinder.I was told to grind the cylinder (all the holes are the same so it shouldnt matter), but it is probably easier to grind the cover! If you waste it, I have extra covers. If you converted to collapsible pushrod tubes, you dont have that clearance problem! (henceforth, I have extra covers!) | ||
| Bandito90 |
I ground a small amount off the cover with a dremel.I do like the look of collapsible push rod Tubes so maybe when I get some head work done I'll replace this.Thanks guys.Also with a 515 and b70 cams and no head work will I notice a big difference? | ||
| Gearheaderiko |
Uh...NO head work? Did you clearance,cut or replace the valve guides? The stock head doesnt have the clearance for the B70's or the necessary valve springs. | ||
| Gearheaderiko |
PS You'll like the power gains, but they're mostly at the higher rpms. The B50's have a broader torgue (power) curve, but dont make as much max HP. | ||
| Ezblast |
Concur! | ||
| Bandito90 |
I did put the necessary valve springs in,But was told nothing about the valve guides when I purchased the parts. | ||
| Gearheaderiko |
Do you still have the head off? Berkshire ground his stock valve guides down for the clearance. Not sure who sold you the parts, but Andrews Cams clearly states the B70's need extra (non stock) clearance. I dont know another way around the clearance without new or modifying the guides. Hopefully your valve springs are good for some high rpms (they should be), with those cams you'll miss out on some power at the top end if you dont raise the limit. Oh, and if you do get the B70's installed, you will like the high rpm punch! If you get the B50's instead, you'll appreciate the broad powerband. Either way, 515 kit,10.5:1 piston, cams,exhaust, you're gonna like it! | ||
| Bandito90 |
I could always just take the head off.It is on but pipe and all the other stuff is still off. | ||
| Gearheaderiko |
http://www.badweatherbikers.com/buell/messages/201 64/340990.html?1204605830 There's the link to the thread where Berkshire modified the stock valve guides. I dont really know how much trouble it was (hours, minutes, straight cutting or a lot of freehand, etc.). If I known it would be helpful later I would have taken pictures of my heads with all the different clearances and valve seals. Maybe you should contact him before you pull the head and see if its something you'd want to do (but now is the time since all you've done is just install the head-just be careful not to disturb the cylinder base gasket). | ||
| Fast1075 |
Listen to Erik...don't be tempted to run it without the needed mods...at BEST you will kill the valve guide seals...at WORST you will kill the valvetrain...if you kill the valvetrain, it will most likely happen at high rpm...if that happens and you break a spring, retainer or valvestem...it's GAME OVER! | ||
| Bandito90 |
Thanks guys!Do you know if the guides are pressed in.I am going to this right and not half assed!Also I know xb heads have been used what about lightning heads.They have some in the clearance area of my local hd shop for 400.00 | ||
| Gearheaderiko |
Pressed in. If by lightning heads you mean pre XB heads then yes, but they're not as good as XB heads, but you might not need to change the piston (as with XB heads) {I dont remember if the Blast piston is a match for the old Lightning heads, I believe they are since the Blast is a Sportster piston-again going by memory without verification}. Either way you'll need to fabricate engine mounts. However, a stage 3 Blast head, complete, isnt much more than the $400 you'd be spending on the lightning head (which isnt that great of a deal and I consider it a step backwards). | ||
| Gearheaderiko |
Did you get a new ignition too? It already sounds as if you've gone to the 'Dark Side'! | ||
| Bandito90 |
I don't know what specific year the heads are.They say lightning on them.Thats all I know.I didn't get that good of a look at them.Who is good at porting blast heads.I can't really afford the nrhs stage three port job at the moment.Also what ignition to go with now that the pro series is discontinued and I was told that the screaming eagle is also discontinued and you would have to trick one off a twin and it would be difficult. | ||
| Gearheaderiko |
Revolution Performance or Cyclerama. At this stage I'd just modify or replace the valve guides (or switch to B50's). Then save your money and go for the stage 3. Getting a twin ignition to work is not that hard, provided you start with a 'nose cone' ignition (an ignition thats fully contained behind the cam/points cover like stock). A Scremin Eagle ignition for a 883-1200 1998-up XL Sportster will bolt right in and the wiring is the same. You'll lose the TPS and auto enrichener though. A VOES can be wired in for the TPS and the auto enrichener (I theorize) could be wired up to a switch. The TPS/VOES can be done without, but I've found the auto enrichener wont come completely off (unless really hot) unless its wired in (or switch to a v-twin carb with manual choke). The coil should probably be switched out for a 3ohm coil, but it will run very well with the stock Blast coil (you do run the risk of burning out the ignition though-or perhaps a resistor can be wired in, I'm not the electronics expert there). Then modify a timing cup. Not hard or really as complicated as I make it sound. http://www.badweatherbikers.com/buell/messages/201 64/253601.html?1213803567 | ||
| Gearheaderiko |
PS skip on the Lightning heads. If you want to change heads wait for a deal on an XB or 2004XL head. Better performance, better gas mileage! I also send a PM to Creepingme to see if his ignition uses the carb auto enrichener. While he's still a Blast owner, he doesnt spend much time over here on the Thumper side. (Message edited by gearheaderiko on June 22, 2008) | ||
| Ezblast |
Concur! | ||
| Berkshire |
Valve guide mod is easy - remove the seals, mark top of guide with a sharp pick or something to show how much needs to come off, use a drill bit that's larger than the guide O.D. and drill down to the mark (holding bit aligned with guide and steady so it doesn't jump around!), de-burr and round sharp edges w/ a dremel. Honing the guides would be a good idea, if you have the right size (dingleberry type hone). Re-install seals (you're supposed to use new ones - I didn't, and oil use has never been lower, go figure. Another option - instead of cutting guides, just don't use the seals... might use oil, but who knows - you can always put them back on. Retainer/seal clearance allows about .55" valve opening before interference, IIRC (see "replacement heads" thread to double-check!), so subtract that from your cam's advertised lift to get minimum required amount to be removed, then add a little extra (maybe .02") for good luck. A machine shop (or a HEAD shop!) could do a much better job, probably pretty cheap too - but my setup is low-budget and intended to be temporary, so I just winged it... | ||
| Gearheaderiko |
.060" is recommended. Once again you've done a nice write up. I hadnt though of using a drill to just cut it away. Seems much easier than grinding! |
