pendletonpounder Posted August 21, 2007 Report Posted August 21, 2007 finally broke down and bought an aftermarket head but need some advice on what size of domes to run. whats the lowest cc that can safely be ran on 93 octane? my quad just has basic bolt-on upgrades(pipes reeds,boost bootle ect.). live at approx. 500 feet above sea level. thanks Quote
bentvalve Posted August 21, 2007 Report Posted August 21, 2007 if you find out that you need 21 mm domes a hair a new pair. $50 shipped don Quote
5150banshee Posted August 21, 2007 Report Posted August 21, 2007 i would run 20 or 21 jusr cause 22 r stoke size and you have some decent upgrades Quote
peak-j Posted August 21, 2007 Report Posted August 21, 2007 I'm around 1000 ft above sea level, I run 20 cc domes and that came out to be 150psi in each cylinder. I started out with 125psi in each, so I'd say how safe do you want to be, I think I'm borderline cause the highest octane near me is 89 so that's what I run. I haven't had any problems yet, can't hear any detonation and the plug chops look good so I'll keep running. It has been like this for about 6 months and I've ran the hell out of it. Went to Little Sahara for 4 days and never cut it any slack. I'm not sure what 21cc domes would be as far as psi. You might do a compression check and see where you are now. Just my 2 cents. :biggrin: Quote
Bansh-eman Posted August 21, 2007 Report Posted August 21, 2007 to be safe go with 21's the only way to be 100% sure is to do a compression test with your new domes. you dont want to slap them in and just take off. if your running to much compression for your octane your going to f that motor up Quote
Snopczynski Posted August 21, 2007 Report Posted August 21, 2007 (edited) finally broke down and bought an aftermarket head but need some advice on what size of domes to run. whats the lowest cc that can safely be ran on 93 octane? my quad just has basic bolt-on upgrades(pipes reeds,boost bootle ect.). live at approx. 500 feet above sea level. thanks 20cc dome is more than safe, that will put you around 155psi. Thats ok on 93 octane. Just make sure you verify it with a compression test. If you absolutely want to remain safe, just make sure its no more than 165 psi compression. Edited August 21, 2007 by Snopczynski Quote
shanYE west Posted August 21, 2007 Report Posted August 21, 2007 I'd run 21cc domes... 20cc domes will put you right near the limit and If you have your timing advanced it could be a problem. Quote
Snopczynski Posted August 21, 2007 Report Posted August 21, 2007 Just to specify here. I run a 19cc dome in a stock bore, lightly ported motor. My compression with a 19cc dome is 169 psi. 169 psi is borederline 50/50 race gas and 92 octane. I run 50/50 so I can keep my heat down in the holes out in the sand. Based on what my motor said with 20cc domes (155 psi) and what the noss machine charts show for 19cc dome it could be a toss up. I would tend to think you would be low enough though. Quote
TJ10 Posted August 21, 2007 Report Posted August 21, 2007 Just to specify here. I run a 19cc dome in a stock bore, lightly ported motor. My compression with a 19cc dome is 169 psi. 169 psi is borederline 50/50 race gas and 92 octane. I run 50/50 so I can keep my heat down in the holes out in the sand. Based on what my motor said with 20cc domes (155 psi) and what the noss machine charts show for 19cc dome it could be a toss up. I would tend to think you would be low enough though. I wanna run at around 150-155 psi range. I know that its recommended to get the crank welded, but is it neccessary with this range of psi? Quote
Snopczynski Posted August 21, 2007 Report Posted August 21, 2007 I run 170 psi without the crank welded. I would not worry at all at 155 psi. Quote
dajogejr Posted August 21, 2007 Report Posted August 21, 2007 I run a 19cc dome in a stock bore, lightly ported motor. My compression my motor Snop...I think you'll agree no two motors are the same. 21cc is definitely safe...20 cc...it's a crap shoot. It also depends on his state of tune....he also has a boost bottle, so...well, you know. TJ... Get your crank welded as soon as you split the cases. I've seen quite a few stockers split, with stock compression and pipes/jets. There is no guarantee on what is safe, what is not. Stock banshees have 122 to 128PSI...you're increasing that... Welded cranks are a good piece of mind. Stock cranks are actually very strong and reliable, once welded and trued properly.... Snop...unless you're willing to spend your money for his repairs if something happens, that's not very safe advice... Quote
TJ10 Posted August 21, 2007 Report Posted August 21, 2007 (edited) Snop...I think you'll agree no two motors are the same. 21cc is definitely safe...20 cc...it's a crap shoot.It also depends on his state of tune....he also has a boost bottle, so...well, you know. TJ... Get your crank welded as soon as you split the cases. I've seen quite a few stockers split, with stock compression and pipes/jets. There is no guarantee on what is safe, what is not. Stock banshees have 122 to 128PSI...you're increasing that... Welded cranks are a good piece of mind. Stock cranks are actually very strong and reliable, once welded and trued properly.... Snop...unless you're willing to spend your money for his repairs if something happens, that's not very safe advice... I don't have a problem with tearing the motor down to get to the crank, I have a problem finding someone in my area who will weld the crank for me. I have a tig welder but I dont think I trust myself enough to do it. Is it worth it to tear the motor down and search for someone who can weld it for me or should I just wait till I split the fuckin thing and get a stronger aftermarket crank? Also, if I do decide to weld it, anyone have an estimate on what the shop will charge? Edited August 21, 2007 by TJ10 Quote
dajogejr Posted August 21, 2007 Report Posted August 21, 2007 A stock trued and welded crank is just as strong as anything out there for your needs. There is no reason at all to buy another crank, unless you're going to buy a stroker crank. My buddy charges 100 bucks to completely dissasemble the crank, inspect all bearings and the webs, true it and weld it. If someone is not going to check the true on it...probably 40 to 50 bucks. Just make sure the outer and inner sides get welded. Are you planning on rebuilding the top end anytime soon...or getting porting done? If so...then I'd wait. If you plan on riding on that motor as is for a while, yeah...my advice is to weld it. Quote
Bansh-eman Posted August 21, 2007 Report Posted August 21, 2007 i have noticed that snop likes to do his own thing to prove other wrong. the simple fact is that taking your compression to 170 isnt not advise that is recommended. can it happen? yes. is it smart? no. theres no point in testing the waters. for the amount of differance in power from 21cc to 20cc vice the reliability its an ez choice. Quote
shanYE west Posted August 21, 2007 Report Posted August 21, 2007 (edited) the simple fact is that taking your compression to 170 isnt not advise that is recommended. can it happen? yes. is it smart? no. theres no point in testing the waters. for the amount of differance in power from 21cc to 20cc vice the reliability its an ez choice. I agree, :thumbsup: Edited August 21, 2007 by Fouledout420 Quote
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