big-phil Posted November 10, 2007 Share Posted November 10, 2007 its a regrind cam intake dur 290 lift 490 exhaust dur 280 lift 480 112 deg lobe sep. I used .230 lash pads to get the wipe pattern to look good. The first thing that seemed strange was I has to lean the entire map out, even in boost. The vac at idle was 21lb, now its 9-10lb. It just seems to not have any power unless your using the turbo? When the turbo does hit it feels good, and seems to make power above 6200rpm (thats as far as I have pushed it) I had the cam gear in the #1 hole, I changed it to the #3 hole. It might of made a diff. but I'm not sure? My timing at idle is 30deg, goes up to about 40 until boost, then drops to 24 at 17 lbs boost with the meth spraying. All in all it just is not as powerful before or after boost than the stock cam? It revs higher, but thats about it?? Am I missing something? Thanks **specs. holset hy turbo, supra 440cc injectors. stock p90 head no port. 60mm TB stock intake. 3 inch exhaust isky valve springs. Quote Link to comment Share on other sites More sharing options...
TimZ Posted November 10, 2007 Share Posted November 10, 2007 its a regrind cam intake dur 290 lift 490 exhaust dur 280 lift 480 112 deg lobe sep. I used .230 lash pads to get the wipe pattern to look good. The first thing that seemed strange was I has to lean the entire map out, even in boost. The vac at idle was 21lb, now its 9-10lb. It just seems to not have any power unless your using the turbo? When the turbo does hit it feels good, and seems to make power above 6200rpm (thats as far as I have pushed it) I had the cam gear in the #1 hole, I changed it to the #3 hole. It might of made a diff. but I'm not sure? My timing at idle is 30deg, goes up to about 40 until boost, then drops to 24 at 17 lbs boost with the meth spraying. All in all it just is not as powerful before or after boost than the stock cam? It revs higher, but thats about it?? Am I missing something? Thanks **specs. holset hy turbo, supra 440cc injectors. stock p90 head no port. 60mm TB stock intake. 3 inch exhaust isky valve springs. Hi Phil... Hmmm - as I recall, I had to play with the cam timing to get that cam to run well. If you are having to lean the map out, then that says you aren't breathing as well as before, as you've probably figured out. Sounds like you have already started, but play with the cam timing and take note on how the mixture is affected for different settings. Seems like advancing the cam timing would be what you need, but the #3 hole does add 8 degrees of advance (assuming the stock 3 hole cam gear), and that's quite a bit. Sorry I'm not that familiar with the Holset turbos - how big is it's hot side? Also, the idle vacuum you mentioned is pretty much what I would have expected with that cam. Quote Link to comment Share on other sites More sharing options...
big-phil Posted November 10, 2007 Author Share Posted November 10, 2007 I'll have to check for sure what the hot side is, I'll also try the #2 hole, yes stock cam gear. I was going to port the other p90 I have also, and my intake aswell. Thats what it feels like, it just not getting the air. The cam sounds great at idle:-o Quote Link to comment Share on other sites More sharing options...
johnc Posted November 10, 2007 Share Posted November 10, 2007 Maybe I'm ignorant when it come to turbo charged engines, but 30 degrees of ignition advance at idle sounds crazy. Quote Link to comment Share on other sites More sharing options...
TimZ Posted November 10, 2007 Share Posted November 10, 2007 Maybe I'm ignorant when it come to turbo charged engines, but 30 degrees of ignition advance at idle sounds crazy. Oops - I missed that. I agree, I only run around 10 degrees at idle. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted November 10, 2007 Administrators Share Posted November 10, 2007 I saw that to. Being as you are running Mega squirt, are you also allowing MS to control your ignition timing or are you still using the mechanical flyweights and vacuum advance canister? Maximum of 20 degrees advance at idle, 15 is a good compromise. Quote Link to comment Share on other sites More sharing options...
big-phil Posted November 10, 2007 Author Share Posted November 10, 2007 Yes MS is controlling it all. I'll try 15, or 10 at idle it just seems like it likes 30. At least that was with the stock cam. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted November 10, 2007 Administrators Share Posted November 10, 2007 First, you need to get your idle timing back down to 15-20 degrees BTDC, verify that timing figure with a timing light and also verify that your timing mark on the damper hasn’t slipped, (i.e. inertia ring that has slipped due to an old wore out damper, that is if your timing mark is on the inertia ring that is), and once your ignition timing at idle is where it should be, then recheck your idle vacuum. If it still 9”-10” inches, (not lbs), then read on… Something else that caught my eye was the amount of vacuum you lost at idle. I don’t recall off the top of my head what the LSA of OE L-28ET is supposed to be, (112 rings a bell, but I’m not 100% sure. LSA is Lobe Seperation Angle, which is the angle between the intake and exhaust centerlines, as ground into the cam). Being as your new cam is a more radical profile in duration and lift, yes a drop in idle vacuum should happen, but the amount of vacuum you lost at idle seems a bit much, though it does coincide with the exaggerated lag you are experiencing, i.e lots of valve overlap equates to over scavenging/reversion, (depending on exhaust back pressure etc), resulting in loss in low RPM off boost performance, which also means less exhaust flow to spool the turbo. Do you have the means to verify cams specs and Lobe separation angle, i.e. do you have a degree wheel and a dial indicator set up to measure valve movement? It would be nice to verify the 112 LSA. Your idle vacuum figure is more in line with your duration and lift specs for a cam ground on 109 LSA. Again, get your ignition timing at idle in check and make “absolutely” sure that your timing mark hasn’t slipped, if the mark is on the inertia ring of the damper. Then report back… Quote Link to comment Share on other sites More sharing options...
ktm Posted November 10, 2007 Share Posted November 10, 2007 Phil, I have a 1983 L28ET. I am running the factory spec of 24 degrees BTDC at idle, 27 degrees at 1000 rpm (where I set my idle instead of 800 rpm). The other idle values others are posting are for N/A engines. What pistons are you running? Stock turbo or flat tops? Quote Link to comment Share on other sites More sharing options...
TimZ Posted November 11, 2007 Share Posted November 11, 2007 The other idle values others are posting are for N/A engines. No - mine is a turbo. Another thing you might try playing with is the valve lash - less lash will translate to less duration on that lobe (and correspondingly less lift as well). As I recall, the rule of thumb is 0.5 degrees of duration per 0.001" of lash. I think that's the right rule of thumb - hopefully somebody can verify (Paul?). Quote Link to comment Share on other sites More sharing options...
big-phil Posted November 11, 2007 Author Share Posted November 11, 2007 First, you need to get your idle timing back down to 15-20 degrees BTDC, verify that timing figure with a timing light and also verify that your timing mark on the damper hasn’t slipped, (i.e. inertia ring that has slipped due to an old wore out damper, that is if your timing mark is on the inertia ring that is), and once your ignition timing at idle is where it should be, then recheck your idle vacuum. If it still 9â€-10†inches, (not lbs), then read on… Something else that caught my eye was the amount of vacuum you lost at idle. I don’t recall off the top of my head what the LSA of OE L-28ET is supposed to be, (112 rings a bell, but I’m not 100% sure. LSA is Lobe Seperation Angle, which is the angle between the intake and exhaust centerlines, as ground into the cam). Being as your new cam is a more radical profile in duration and lift, yes a drop in idle vacuum should happen, but the amount of vacuum you lost at idle seems a bit much, though it does coincide with the exaggerated lag you are experiencing, i.e lots of valve overlap equates to over scavenging/reversion, (depending on exhaust back pressure etc), resulting in loss in low RPM off boost performance, which also means less exhaust flow to spool the turbo. Do you have the means to verify cams specs and Lobe separation angle, i.e. do you have a degree wheel and a dial indicator set up to measure valve movement? It would be nice to verify the 112 LSA. Your idle vacuum figure is more in line with your duration and lift specs for a cam ground on 109 LSA. Again, get your ignition timing at idle in check and make “absolutely†sure that your timing mark hasn’t slipped, if the mark is on the inertia ring of the damper. Then report back… I don't have a way to check the LSA. I will check to be sure my timing mark has not slipped. Quote Link to comment Share on other sites More sharing options...
big-phil Posted November 11, 2007 Author Share Posted November 11, 2007 Phil, I have a 1983 L28ET. I am running the factory spec of 24 degrees BTDC at idle, 27 degrees at 1000 rpm (where I set my idle instead of 800 rpm). The other idle values others are posting are for N/A engines. What pistons are you running? Stock turbo or flat tops? yes turbo motor all the way 1983. Quote Link to comment Share on other sites More sharing options...
big-phil Posted November 11, 2007 Author Share Posted November 11, 2007 No - mine is a turbo. Another thing you might try playing with is the valve lash - less lash will translate to less duration on that lobe (and correspondingly less lift as well). As I recall, the rule of thumb is 0.5 degrees of duration per 0.001" of lash. I think that's the right rule of thumb - hopefully somebody can verify (Paul?). So would I want to go smaller on the lash pads? .230 now, try a .225??? also I forgot to mention that I have a 2mm head gasket. could it be as simple as a flow problem? my exhaust has a gnarly bend after the down pipe. Is this cam flowing Sooooo much more exhaust that its getting restricted? And also the head itself not being ported or the intake? Quote Link to comment Share on other sites More sharing options...
TimZ Posted November 11, 2007 Share Posted November 11, 2007 So would I want to go smaller on the lash pads? .230 now, try a .225??? also I forgot to mention that I have a 2mm head gasket. could it be as simple as a flow problem? my exhaust has a gnarly bend after the down pipe. Is this cam flowing Sooooo much more exhaust that its getting restricted? And also the head itself not being ported or the intake? No - just the valve clearance adjustment - if your wipe pattern looks good, then don't mess with the lash pads. Quote Link to comment Share on other sites More sharing options...
big-phil Posted November 11, 2007 Author Share Posted November 11, 2007 its now set at .008 intake .010 exhaust. Are you saying tighten the clearence? .007 intake etc.? Quote Link to comment Share on other sites More sharing options...
Chris240zTurbo Posted November 11, 2007 Share Posted November 11, 2007 I'm going to bed as I have to get up in a few hours to go to work. I'm helping Phil tune his car, and have read the posts so far... TimZ, I think maybe you posted backward on the less lash thing? less lash (reduced clearance between the rocker and cam) would result in increased actual lift and duration, more lash (larger distance between rocker and cam) would have the opposite effect. Maybe I'm just confusing 'more' and 'less' as it applies to valve clearance? Anyway, I have no doubt that Phil and I will figure out what is up with his cam swap. Goodnight! Quote Link to comment Share on other sites More sharing options...
big-phil Posted November 11, 2007 Author Share Posted November 11, 2007 I'm going to bed as I have to get up in a few hours to go to work. I'm helping Phil tune his car, and have read the posts so far... TimZ, I think maybe you posted backward on the less lash thing? less lash (reduced clearance between the rocker and cam) would result in increased actual lift and duration, more lash (larger distance between rocker and cam) would have the opposite effect. Maybe I'm just confusing 'more' and 'less' as it applies to valve clearance? Anyway, I have no doubt that Phil and I will figure out what is up with his cam swap. Goodnight! You know its funny, Chris has 21 posts in almost 3 years of being a member and his car walked mine Thursday night in a pull in 3rd gear. I was at 17 lbs of boost, he was at 9 lbs of boost. NINE!!! fricken "9" POUNDS I walked a Vette at 14 lbs, Now mine feels laggy and all that with the whole cam thing. But still he F-ing WALKED me. I still can't believe it. Chris you bastard! (I still say I was lagging, when he was pulling) For those who don't know, this is Chris and his car. Quote Link to comment Share on other sites More sharing options...
TimZ Posted November 11, 2007 Share Posted November 11, 2007 I'm going to bed as I have to get up in a few hours to go to work. I'm helping Phil tune his car, and have read the posts so far... TimZ, I think maybe you posted backward on the less lash thing? less lash (reduced clearance between the rocker and cam) would result in increased actual lift and duration, more lash (larger distance between rocker and cam) would have the opposite effect. Maybe I'm just confusing 'more' and 'less' as it applies to valve clearance? Anyway, I have no doubt that Phil and I will figure out what is up with his cam swap. Goodnight! Yes - you are correct. I meant more lash, like 0.010 and 0.012. Sorry about that. Quote Link to comment Share on other sites More sharing options...
TONY C Posted November 11, 2007 Share Posted November 11, 2007 wouldn't setting the lash on the exhaust side to say .008 open the valve sooner and keep it open longer alowing for more evacuation of the exhaust gasses. sounds like it may help.? being a regrind I am sure that it should really be installed with a degree wheel. but you still only have 3 cam gear positions. so I would play with them too. Quote Link to comment Share on other sites More sharing options...
big-phil Posted November 11, 2007 Author Share Posted November 11, 2007 Yes - you are correct. I meant more lash, like 0.010 and 0.012. Sorry about that. Thanks for your help Tim, and Paul. I will check the timing, play with the lash sunday and report back. Quote Link to comment Share on other sites More sharing options...
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