bubbleguinea Posted September 30, 2004 Share Posted September 30, 2004 hey guys, got a problem over here. some guys on zcar.com think i have the wrong camshaft... i just got done building my engine. N42 combo overbored .020, matched dished pistons and rings, new valves, port and polish, all that sort of stuff. anywho, i put a stage 3 camkit from MSA in her, and some guys are saying the car wont run good with that cam on a 8.4:1 engine...what do yall think? i talked to eddie radatz (southern z guy) and he said it should work fine, but i wanted a mass opnion...perhaps i should switch to a stage 2 kit before i turn the engine over and run the cam? Quote Link to comment Share on other sites More sharing options...
RacnJsn95 Posted September 30, 2004 Share Posted September 30, 2004 Big cams bleed off compression... If you really have 8.4:1 (no one really knows, not even you) you'll be down into the 7's. You can kill an engine in a big big hurry if you have too much cam with no compression. This thing will be a sogy dog down low, and it will be no fun in everyday stop and go driving. I'm not just saying this because I want you to sell me your cam way cheap, but because it's the right thing to do, before it's too late! Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 30, 2004 Share Posted September 30, 2004 http://hybridz.org/nuke/index.php?name=PNphpBB2&file=viewtopic&t=31206 When those videos were taken I had 8.5:1 and .490/280 cam, triples, and 2.5" exhaust. Ran pretty good. Runs better with the new flat top piston bottom end... Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted September 30, 2004 Share Posted September 30, 2004 Big cams bleed off compression, AT LOWER RPM. At the design rpm range volumetric efficiency is as good or better than a stock/mild cam. Your setup will work, but a much higher CR is of course possible with that cam. I think a more pertinent question is will your FI setup breathe enough to take advantage of the cam at higher rpm. If not, you're sacrificing low-end with the cam but not getting the benefit up top. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted September 30, 2004 Share Posted September 30, 2004 Is that the cam with a split profile, like 460 lift and 260/270 duration? If so that cam was always pretty finiky about what kind of head I used, and it really liked a shaved E88, which had combustion chambers like an E31. I ran it with an open chamber E88, and it ran pretty poorly, even with a flat top 280 bottom end. I also ran it in a p79 milled 80 thous. and it ran prety good there. If your cam is larger, I think you will want some compression to make it run to its potential. I liked the MSA cam that is 274 duration and 480 lift or whatever, its milder then the one I listed above. It always ran good in any engine/head combo I ever tried, and with a nice high compression 2.6, it would turn 7500 rpms with my triples and header. I got froggy one time and put the first cam in my turbo engine, man it sounded good, but it wouldn't fall out of a tree. You can always snatch your head off and mill it some, probably be a good idea to check with Norm and see how much he thinks would be safe for you. Quote Link to comment Share on other sites More sharing options...
bubbleguinea Posted September 30, 2004 Author Share Posted September 30, 2004 hmmmmm to keep or to exchange for a stage 2.... Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted September 30, 2004 Share Posted September 30, 2004 What will the car's mission be? There's something to be said for being able to hit the throttle and GO from 2000rpm in a real-world street car. Quote Link to comment Share on other sites More sharing options...
Pyro Posted September 30, 2004 Share Posted September 30, 2004 Years and years ago. And way before the internet. I used a dish piston L28 with an E31 head, SU's, 6 into one header, 2.5" exhaust, 5 spd, 2+2 clutch, R200 3.90 gear, holley electric pump, and a 290/.500" clifford research cam 6=8, in a 71 240. And the engine pulled hard after 3500 and pulled up to 7K rpms. It ran low 14's at over 100 mph. Thinking back......that was a low compression set up also and it ran pretty good with a big cam. A lot of ignition timing will help and advance the cam. IMHO A big cam in a low compression L28 engine: Will not work so well with a stock EFI manifold Will not work so well with a 3.54 gear. Will not work so well with a heavy car. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 30, 2004 Share Posted September 30, 2004 Wow Pyro that sounds familiar. Except for very slight differences in the rear gears, clutch, and cam you basically had the same setup I used to have. Quote Link to comment Share on other sites More sharing options...
bubbleguinea Posted October 1, 2004 Author Share Posted October 1, 2004 well i made the descision to get the stage 2 instead of the stage 3...hopefully that will work out better! thanks guys for all the info! Quote Link to comment Share on other sites More sharing options...
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