v80z Posted August 3, 2006 Share Posted August 3, 2006 It runs smooth to 3000 rpm and then starts to stumble. No matter where I set the timing. Or is it because of the heat 90 - 104 ambient temp outside setup 1970 10.25:1 CR 350 SBC .030 over Stock heads med. performance Intakes are the 1.94 not 2.02. Exhaust 1.60 stock bottom pistons have pressed rods with Hypertectic pistons heads have new valves, fresh cuts, fresh stem seals, press ins removed and replace with screw in. Crane race roller rockers Cam Solid circle track Cam I picked for upper end power not drivability Solid Lifter Cam specs Valve adjustment Hot .030 Gross valve Lift .508 Lobe Lift .339 Duration at .020 tappet lift Intake 298 exhaust 294 Duration at .050 tappet lift Intake 251 exhaust 248 Valve timing at .050 intake Open 23.0 BTDC Closed 47.5 ABDC exhaust 54.0 14.0 Edlebrock air gap peformer intake edlebrock 750cfm carb HEI shell connected to a crane CD ignition and crane PS2 coil Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted August 3, 2006 Share Posted August 3, 2006 "Am I under carbed for this cam " NO! a 750 cfm carb can supply a 600 hp/406 sbc engine easily with the correct tunning but you might want to install a open center spacer under the carb to increse plenum volume, but thats NOT your problem, It may be the floats are set to low, the fuel pressures not set correctly,the jettings wrong,or you may have accellerator pump shot problems, the carb may not be the problem at all, it may be the ignition, or the ignitions advance curve. or even the cams installewd a few degrees off or lifter lash clearances are wrong or even a clearance issue in the engine Quote Link to comment Share on other sites More sharing options...
jnjdragracing Posted August 3, 2006 Share Posted August 3, 2006 I think the dissy is advancing to much at 3000 rpm. Can you lock it out and set the total timing to around 36 to 40 total degrees. Just my thought.... Quote Link to comment Share on other sites More sharing options...
Mikelly Posted August 3, 2006 Share Posted August 3, 2006 Yup, WHat Grump and J-N-J said... That carb is MORE than fine for that application... Mike Quote Link to comment Share on other sites More sharing options...
jt1 Posted August 3, 2006 Share Posted August 3, 2006 Lots of possibilities. Some things to check: Mag pickup in distibutor. Bad coil. Check grounds/connections on ignition Inadequate fuel supply-low pressure-stopped up filter Secondaries not opening correctly Going lean when secondaries open- step up springs/rods How much initial/total timing? Are you using the vac advance? John Quote Link to comment Share on other sites More sharing options...
280Z28 Posted August 3, 2006 Share Posted August 3, 2006 Aside from all the above for making it not stumble, your constrictors right now are your heads and your intake, which aren't optimal for that cam. That DOESN'T explain the stumbling. You should see the car pulling HARD to 5500ish rpm as is. Quote Link to comment Share on other sites More sharing options...
v80z Posted August 8, 2006 Author Share Posted August 8, 2006 Thanks guys. Broke out the timing light and set it for 34 total. Went over valve train again to make sure nothing was loose. Much smoother now. 280Z28 jnj grump anyone have any decents heads they want to let go cheap? 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.