camaronewbie

1990 305 LO3 TBI. Just did the LT1 cam swap, ported/polished 416 heads, headers, carb intake with adapter, new wires, new plugs, new MAP sensor.

Timing: Had to set timing to 10* to even get it to run - anything below and it dies. At 10*, it wanted to die at stop in gear. Set it to 14* - ran better, but worried me that high. A "Tech" told me would be fine, and that I could advance further if needed, and told me to set timing by connecting vaccum guage to manifold, and turning distributor to the point that I got the maximum vacuum. So I tried that - car ran little better, I never checked timing with a light because I know it's way past the marks now - I'm assuming that maybe the mark on balancer is not right anymore for whatever reason.

But - I still have this really bad surging idle, and not the power that I should, and wants to die at stop in gear. At any throtlle position, the engine surges up and down, changing about 200-300 rpm's. I cleaned IAC. EGR valve moves with throttle, and both it and it's solenoid get vacuum. I'm at a loss.

dimented24x7

iTrader: (2)

there definatly must be something wrong if your having that much trouble. The setup you should have should get along well with the efi. Im not 100% sure about the surging but i had/still have a similar problem now with my engine. It doesnt cause any trouble but it has that same sinusoidal surgeing when at idle and revving. The rpms go up and down about the rpm that the engine should go at if it wasnt surging. This also happens when i accelerate. I think it may be due to the vacuum signal that the system is getting from the 112* cam i have. Everything else looks ok so I see no other reason for it to occur. Maybe someone else knows the real reason for this. First. If you dont have winaldl or a similar data logging program, stop what you are doing... NOW and go get it. Winaldl can be found at JoBy's webpage. Do a search for his name and he has links to it in his sig. The data that winaldl will give you will give alot of insight into what the computer is seeing ad how it responds. Second, what does the vacuum gauge say? Does it show around 20 inHg with a realativly steady needle or is it giving a really low reading with the needle going all over the place? Another thing to check is what, if any codes that your getting and whether or not you have any knock counts. Your CR ratio should be good enough that you can keep bumping up the timing untill you see knocks occuring. If you have too little time, then it will run like crap. I tried this with my 8.5:1 crap 350 and the power dumped off before i got alot of knock counts.

As for what is probably wrong, id guess at a large vacuum leak. Post what you see from the vacuum gauge at teh very least and any codes that the computer might be giving.

dimented24x7

iTrader: (2)

oh, how did you install the cam? Did you make sure the dots where lined up at 6 o'clock (cam sprocket) and 12 o'clock (crank sprocket)? Ive never put one in with the cam off o tooth so i dont know what it would run like but im sure it would cause trouble. Id guess that youd probably get alot of backfiring out the intake or the exaust. Prbably not the problem anyway but ill throw it out there.

camaronewbie

Cam I installed normally, 6 and 12, like you said. No codes unless I disconnect something, then I get normal codes for that item (like MAP). I was told by several here and elsewhere that I just did too much for the computer, and it's choking on it. I did headers (breathing), intake (breathing), gutless cat (breathing), LT1 cam - higher lift (breathing), 1.6:1 rollertip rockers (breathing), ported/polished #416 heads (breathing), - all this breathing and I've done nothing about fuel yet - I need to do the AFPR at the very least I think.

Computer choking also makes sense for this reason:
As I understand, these computers save data and try to "learn" from it. If I disconnect battery for over 5 minutes, and restart it, it runs better, then slowly gets worse over the next 20-30 minutes or so of driving.

My brother just made me a cable, so I'll try the WinALDL and see what I get.

dimented24x7

iTrader: (2)

just a thought, how did you set the lash? That will cause similar simptoms if the valves are set too tight. Try redoing the lash with the engine warm and idling. do a search for this, the question of how to do this comes up alot. It could aslo be other things as well but the lash might be worth looking at as a bad vacuum signal to the ecm will cause all sorts of problems with the operation of the car.

Air_Adam

Check for vacuum leaks?

DURTYBIRD

Will the motor rev right up to the redline like it is supposed to? When I installed a cam a tooth off, it would rev to 2500-3000 or so then just sputter.

Sounds to me like its a vacuum leak. The car is able to provide fuel for 6000 rpm when stock, I dont think that the fuel system is the problem down near idle even with all the breathing the car is doing.

Does the car smoke at all when running? How about when you rev it?

dimented24x7

iTrader: (2)

have you hooked a vacuum gauge up to it? That will tell alot about how the vacuum is.

camaronewbie

Vacuum:
I had a vacuum guage hooked straight to the intake - I get at best (with timing adjustments) 15 on the guage. I was adjusting timing via this vacuum reading, I was told I could set timing at the point I received the highest possible vacuum - I was setting timing in this fashion because if I set timing according to the marks, she won't run at all - it's my feeling that the timing mark on the balancer has moved - my timing is now set at about what would be 16* BTC, IF the marks continued that high. And this is the point that I get the best vacuum readings, which was 15 on the vac guage. I'll check for vacuum leaks again.

*** what reading for vacuum should I get? ***

Lash:
I set the valves while engine was warm. I ended up setting them while it was running (major PITA), because I could never get the "tick" out of them by just setting to "0 lash" and then 1/2 turn. So, while running, I set each one where the "tick was gone, then went between 1/4 and 1/2 turn more, depending on the valve (some wanted to kill engine if I went beyond 1/4 turn after "no tick"). I'm not sure valves are 100% right, but it's got to be pretty close.

AND - thanks for all the ideas and responses!!! :hail:

DURTYBIRD

If I remember, my guage came with a guide that said vacuum should be closer to 20...but don't quote me on that.

If your timing tabs are THAT far off...and they weren't before the cam install...$5 says that you got that cam in wrong. Did you intall a new timing chain? One that has settings for 2* advance/retard/straight up? When I installed my cam, I had lined up the cam gear dot with the 'circle' indicator showing which keyway to use when installing the crank gear. This resulted in a car that wouldn't rev, smoked, had low vaccum (stock cam- vacuum should be high) and high compression readings. With only an LT1 cam, I'd think your vacuum is pretty low.

Before pulling the motor apart, set the motor to TDC on #1 cyl. Remove the valve covers. Slowly rotate the motor (manually) and watch when the intake/exhaust valves are opening/closing. If you are at TDC or close, both should be closed (or close to it). If not, then the cam is in wrong.

Good luck, let us know how it goes.

camaronewbie

I never checked the timing before the mods, so I don't know if the timing mark was off before or not. I didn't put in a new chain - I had just installed a new chain about 3 months prior to the tear-down, so I didn't see a need - so no mistaking which marks on gears to line up - there's only 1 dot on each gear. But I'll check the valves at TDC this weekend to verify.

camaronewbie

Another symptom I forgot to mention:

Car never wants to start the first hit - there's a fuel problem there - injectors not spraying at first. On second or third hit, it'll start, but NEVER on first hit, even if I let starter go for several seconds. I had to put in my own fuel lines, and used rubber hose for the moment, with brass fittings to match up to the rubber hose. Any ideas - could that indicate a fuel pressure problem, or could I be leaking air at those fuel connections? Or, a problem at the purge canister?