sholdowa Posted January 13, 2007 Share Posted January 13, 2007 I'm working out whether or not to shave my 205 block, and how far. To do this, I really need two pieces of info: 1. What's the approx capacity of the combustion chamber on a std. 2l head ( I haven't got an injection one ). I think it's about 55cc's. 2. What's the safest CR to run on BP Ultimate? I'd expect 10.5:1? Any relevant info would be gratefyly received. Cheers, Steve Quote Link to comment Share on other sites More sharing options...
Gaz Posted January 14, 2007 Share Posted January 14, 2007 Id say 10.5:1 would be ok. I ran around 11:1+ and it was too much for ultimate. Also it sucks getting 98 around the country, id advise against it. Real high comp is for race cars IMO. Ive done it, and am now selling head as its unpractical. Just my 5c worth. Quote Link to comment Share on other sites More sharing options...
sholdowa Posted January 14, 2007 Author Share Posted January 14, 2007 I got out a big bit of paper, and worked out what I could expect... with 50cc's for the head, and 6cc's for the gasket, that works out at 9.8:1. I checked, and the piston tops are flush with the block as standard. Now comes the scary bit... the valves open into the block - below the head. How can you work out what lift/duration is safe if you start skilling the head? Quote Link to comment Share on other sites More sharing options...
Gaz Posted January 15, 2007 Share Posted January 15, 2007 haha, You can get recesses put in the pistons for the valves to open into. Thats what they do on the big HP pintos. Or why not increase the CR via the head instead of decking the block? Quote Link to comment Share on other sites More sharing options...
sholdowa Posted January 15, 2007 Author Share Posted January 15, 2007 Don't want the pistons to protrude above the block, so probably leaving that alone... I reckon 1mm off the head should be enough to get it up to about 10.5:1 on a standard bore. However, If I go to 93mm pistons, then that raises the CR to 10.2:1 without skimming anything, and 0.5mm raises it to 10.8. I reckon that raises it plenty high enough for 98. I might just get the head refaced and that should do it. Should be safe enough. Either that or get the 0.5 mm off and clean up the combustion chamber a bit. Quote Link to comment Share on other sites More sharing options...
nismo.capri Posted January 16, 2007 Share Posted January 16, 2007 I got out a big bit of paper, and worked out what I could expect... with 50cc's for the head, and 6cc's for the gasket, that works out at 9.8:1. I checked, and the piston tops are flush with the block as standard. Last head I cc'ed was a while ago (RT's turbo pinto) and that came in at 54.XX cc's I think.... Now comes the scary bit... the valves open into the block - below the head. How can you work out what lift/duration is safe if you start skilling the head? What ever you do you should check piston to valve clearence with the head on the block. The quick way is to put plasticine on the pistons put an old head gaskit on and a few head bolts to pull it down then crank the engine over by hand. The squished plasticine sould give you a god idea of the clearence. Quote Link to comment Share on other sites More sharing options...
nismo.capri Posted January 16, 2007 Share Posted January 16, 2007 Id say 10.5:1 would be ok. I ran around 11:1+ and it was too much for ultimate. Also it sucks getting 98 around the country, id advise against it. Real high comp is for race cars IMO. Ive done it, and am now selling head as its unpractical.Just my 5c worth. Good advise! ....nothing worse than having to pull timing because the CR is too high. Quote Link to comment Share on other sites More sharing options...
Sparkle Posted January 16, 2007 Share Posted January 16, 2007 I run just over 10:1 and Im fine on 98 and fine on most 95s. Lot of the time cant tell any difference. Quote Link to comment Share on other sites More sharing options...
nismo.capri Posted January 16, 2007 Share Posted January 16, 2007 I run just over 10:1 and Im fine on 98 and fine on most 95s. Lot of the time cant tell any difference. Detonation depends on a lot more than just the CR. The cam, piston to rod ratio and combustion chamber shape come in to play. What works for 1 engine may cause another to detonate. Loads of info http://victorylibrary.com/mopar/cam-tech-c.htm Quote Link to comment Share on other sites More sharing options...
Gaz Posted January 16, 2007 Share Posted January 16, 2007 Was just bout to say similar. Execpt not as technical... cause I didnt know why Quote Link to comment Share on other sites More sharing options...
sholdowa Posted January 16, 2007 Author Share Posted January 16, 2007 What ever you do you should check piston to valve clearence with the head on the block. The quick way is to put plasticine on the pistons put an old head gaskit on and a few head bolts to pull it down then crank the engine over by hand. The squished plasticine sould give you a god idea of the clearence. Must be the alzheimers kicking in... either that or od'ing on Paddy. I knew that, just forgotten. I wonder how much relearning other lessons is going to cost! There's a Toyota W50 gearbox for sale with prop... is it worth it $350? The gears seem to be very widely spaced. Thanks Quote Link to comment Share on other sites More sharing options...
Gaz Posted January 16, 2007 Share Posted January 16, 2007 Whats wrong with the type9 or the 4speed cortina box. Either of them should handle most worked NA pintos Quote Link to comment Share on other sites More sharing options...
sholdowa Posted January 16, 2007 Author Share Posted January 16, 2007 Dunno how much it's going to cost to get a gear linkage, and a propshaft made up. I've bought a T9 off RT, but I've changed the diff from 3.89 to 3.54, but small flange to big, so I need to source and replace both ends of the prop as well as shortening it, and buy a quickshift. If that's going to come near to $250, then this gets to be a more interesting proposition. Opinions gratefully received. Quote Link to comment Share on other sites More sharing options...
Gaz Posted January 16, 2007 Share Posted January 16, 2007 Just get new holes drilled on flange. Quote Link to comment Share on other sites More sharing options...
nismo.capri Posted January 16, 2007 Share Posted January 16, 2007 Dunno how much it's going to cost to get a gear linkage, and a propshaft made up. I've bought a T9 off RT, but I've changed the diff from 3.89 to 3.54, but small flange to big, so I need to source and replace both ends of the prop as well as shortening it, and buy a quickshift. If that's going to come near to $250, then this gets to be a more interesting proposition.Opinions gratefully received. Circule track on park house rd did me a new drivshaft for $180. I shelled out and got a quaiffe quick shift $270 (Worth every cent) This is the best prog for mulling over gearing issues http://www.locost7.info/gearcalc.php Quote Link to comment Share on other sites More sharing options...
SYKOV6 Posted January 17, 2007 Share Posted January 17, 2007 the bigger the cam you go the less your static comp ratio will be as the increased overlap in the cam timing bleeds comp off. my corty was 10.5 -1 but had a 310 dur cam so static comp was about 8.9-1 there is a formula to work it out but my drug hazed memory is fucked and i cant remember it. was sumthin tho do with both valves being open longer as piston is cumin up not startin to compress the mixture till the piston is farther up the bore as the vaves fully close. some people go too far on static comp with a big cam and then run into massive detonation probs further up the rev range Quote Link to comment Share on other sites More sharing options...
RT Posted January 18, 2007 Share Posted January 18, 2007 There's a Toyota W50 gearbox for sale with prop... is it worth it $350? The gears seem to be very widely spaced. thats probably my one that I'm selling with driveshaft, and the Dellow bellhousing etc. Considering the W50 is worth at least $250 by itself and the dellow bellhousing is $600 new.. plus sleaving the input shaft etc etc.. $350 is a good deal. Quote Link to comment Share on other sites More sharing options...
nismo.capri Posted January 18, 2007 Share Posted January 18, 2007 had a 310 dur cam so static comp was about 8.9-1 there is a formula to work it out but my drug hazed memory is fucked and i cant remember it. Did you run a 310 dur cam on the road? How was that? some people go too far on static comp with a big cam and then run into massive detonation probs further up the rev range Yup, once on the cam the momemtum of the mass of air will actually start it compressing insted of leaking like at low rpms Quote Link to comment Share on other sites More sharing options...
sholdowa Posted January 18, 2007 Author Share Posted January 18, 2007 There's a Toyota W50 gearbox for sale with prop... is it worth it $350? The gears seem to be very widely spaced. thats probably my one that I'm selling with driveshaft, and the Dellow bellhousing etc. Considering the W50 is worth at least $250 by itself and the dellow bellhousing is $600 new.. plus sleaving the input shaft etc etc.. $350 is a good deal. Will you take a T9 in exchange? Very similar to the one that was in your garage until a few days ago! Quote Link to comment Share on other sites More sharing options...
cute wee gem Posted January 18, 2007 Share Posted January 18, 2007 had a 310 dur cam so static comp was about 8.9-1 there is a formula to work it out but my drug hazed memory is fucked and i cant remember it. Did you run a 310 dur cam on the road? How was that? some people go too far on static comp with a big cam and then run into massive detonation probs further up the rev range Yup, once on the cam the momemtum of the mass of air will actually start it compressing insted of leaking like at low rpms Thats quite interesting as I'll be upping static comp in the mini, not sure what to set the comp at though.. engine builder should be able to help Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.