Hi guys need some feedback from those in the know. I am finished (well kinda) putting in my rebuilt engine.

I did two major changes when I did this. One is I put a comp cam CS 268AH-14 cam in it. duration on this cam at .050 are 222 for intake and 226 for exhaust. lobe seperation is 114.0. lobe lift is .3090 for intake and exhaust.

Also I took the air pump off as I had pretty much bypasses all the vacuum anyway in the past.

OK car is timed at 6 btc and is running, but idle is terrible, the whole front of the car shakes and it idles at like 700 rpm, over 1500 rpm it seems ok. I noticed that at idle Vacuum is way less than it used to be (brakes are hard at idle.) the brakes dont bother me but this ide is right at the edge of stalling and is not cool, Im gunna shake out all the bolts!

car had from the last engine, headers, free flow exh, jet stage 3 chip, ported intake plenum ya know all the usual stuff.

WHatcha think is the prob? or did I just go too agressive on the cam?.



Dan

 

Maybe double check the firing order 18436572 and re-check the rocker arms. Could be something simple...

 

firing order is right. Im going to do a relash later today. I cant see it should be that far off though.

Dan

 

sounds like a vaccuum leak. check around the intake, throttle body or carb (not sure which engine you have) and the brake booster.

That cam is pretty mild to be causing vaccuum problems on it's own.

Try turning the idle up a bit so it will smoth a little, then use your hand or a rag to partially choke off airflow. It should make any vaccuum leak more apparent by sound

 

You have to open up the throttle blades . Turn the set screw on the TB untill you get the idle between 1000RPMs and 1200RPMs. Lingenfelter told me that when I had a idle problem after installing a bunch of his parts. When you put the car in gear it will drop down to about 700 to 800 RPMs. Once I got all the bugs worked out I was able to drop the idle back down to 900RPMs at idle. Some cams won't let you idle at less than 1200RPMs.
Also check your vac canister in the left front fender and make sure the hose didn't come off. Not the charcoal canister but the vac canister. You have to go from under the car to get to it. There is a plastic shield over it. It is below the horns on a 87 IROC. Hope this helps.

 

You guys bring up some good points. I got tied up with the family thing today so I was not able to get to the re velve lash adj. Im going to do it running this time. Also the vacuum leak is a valid concern and Ill do the brake clean spray test to see if that helps. If all is lost Ill turn up the idle and will call it done. Its time to finish this 4 month project allready!!!!

Thanks guys.

If anyone reading this has any other Ideas Im all ears. Ill post when I figure this out and tell you whats what.

Dan

 

Well I relashed the valves. I tried to do it while running but I cant even hear the clacking of the valves the engine runs so loud/rough. So I relashed it the chart way but did it hot this time. Well afterwards it runs worse~!!!!! WTF!!!! Ill redue it cold tommorrow or so. BUt this is getting old. I talked to the guys who should know at work and they say a vacuume leak would make it idle higher not lower. It now runs like it is very out of time. I tryed to move the dist around while running but it just gets from generally bad to awfull. I may have to get the professionals from my work into this as I am sucking so bad..

Dan

At least I know the problem is in the heads ......

 

dan, i dont think its the valve lash or an vacm leak. I think your problem is in teh timing. my car idles at 600 rpms and my cam is wayyyy bigger then yours. how about 236/242 and has 110 lobe seperation. lobe sep. is generally the part that gives it a rough idle. not the duration. plus, my cam being solid means its act. seeing those duration/lift #s. the reason why hyd. cams make less power then solid cams is the plungers operation takes away some duration/lift whenit collapses as the eng. is spining. anyways, you need more timing at low rpms. it should smooth out when you advance it. my car likes 15 degrees at idle. the lower I take it at idle, the worst it idles. ofcourse, my car is carbed, but they are both still an engine, which operate on the same basic ideas. no matter which way the fuel is delivered. also, I think its time for a custom chip. I know nothing about making them, but I think it sounds like you need one. anyways, glad to hear its running and good luck to ya. it'll all be worth it in the end. later
chris

 

I played with the timing with very bad results but I understand that it is really handled by the computer. THe cam I got should be able to work with a standard chip, let alone the jet stage three chip I have in it. Im not sold that this is the problem. I think it has to be a valve issue as messing with the lash makes such a dramatic effect on the idle (for the worse right now). I want to relash it cold to 0 degree lash and run it like that to see what it does. Ill play with it again today after I get my lawn mower ready to go (hopefully that wont take that long as I have to do that after work. Or else tommorow is another day.

dan

 

Dan,

Did you set the timing with the ECm disconnected? You have to unplug a tan wire over by the blower motor in order to set base timing. Just a heads up in case

 

WE HAVE IDLE!!!!!!!!!!! Ok it now idles after lashing the valves to 0 degree lash and setting the timing by ear. I now have a bit of a lifter noise but Im sure that can be solved by playing more with the lash (never thought Id have the valve covers off so much). anyway Im on the right track.

Dan