Base timing on built BP

[323driver]

The base timing on our BPs is 10 deg. The head on my BP was shaved 20 thousanths and now the base timing should be set to something else. I advanced the timing to max (rotating the disty all the way clockwise) but it seems that it's not enough as the ecu always brings the rpm at idle to 1000 and whenever it goes to 750, the engine becomes very bouncy and rough.

Does anyone have any idea on how to figure out the proper base timing for the engine?

I'm pretty sure that timing is the problem as when I retard the base timing, the engine starts sputtering and jumping all around.

[almighty4wd]

are you jumping ten and ground in the ...oh bloody hell....the diagnostic box below the wiper motor? you have to do that to set the ECU into base mode, then you can mess with timing properly.

[matt_fulghum]

shaving the head will make the fuel burn slightly faster in the cylinder, so you'll want to retard the base timing a couple of degrees. I'm not sure how much that's going to help though.

As far as idle speed goes, if the car won't idle below 1000 rpm after adjusting the distributor, you might just have too much bypass air. Try turning the bypass screw on the throttle in just a touch and then letting it go back into closed loop, and see if it's any better. That might bring the idle air controller more into its proper range.

Although, you might just have an engine that doesn't want to idle as low any more. This happens to a lot of performance engines (like mine!). There's not a huge amount you can do about it if that's the case.

Did you put new pistons in or are you bedding something else in like valves? If you are, it could be that the friction from new parts is forcing the engine to produce more power (by speeding up) to cope with the extra load.

[323driver]

Interesting, that's a good theory about new parts. The engine has new Wiseco 8.6:1 pistons along with GTR rods and new bearings. The head was rebuilt and shaved 20 thousandths. I didn't put the turbo right away as I wanted to break in the engine NA first.
So far, compression is 180 across the board.

The idle screw is all the way in. When I start the car cold, idle goes to 700-750 and car feels like crap. Then the ECU raises the idle to 1000-1100 and it feels ok. So the ECU actually senses that something is wrong but through what sensors though?

Tried retarding the timing (counterclockwise) but the car almost died with the initial base timing. So now, the disty is all the way clockwise but I still feel the engine is not producing enough power.

Maybe I should go with different spark plugs but I don't know which ones?!?!?

I'm waiting for the timing light to arrive to check exactly what the timing is set to.

P.S. I discovered that if your TPS is not calibrated and says open while it is actually closed, the ECU will bump the idle to over 2500 rpm, just something to check if you have extremely high idle.

[Lex]

running full NA setup and ECU with NA injectors? The ECU will adjust the mixture mainly based on the feedback from the O2 sensor after the car is warm.

check your coolant (2 pin) sensor

that being said, my car doesn't like idling below 1000-1100 either ... the solid mounts don't help.

[323driver]

Yep, NA ecu, with NA injectors, 3 wire tps, stock intake, everything plugged in properly. The ECU doesn't throw any trouble codes, I'm assuming the sensors are ok but I'll double check them.

To LEX:
Do you remember how much was your head shaved? Did you need to adjust your base timing so drastically?

I guess I'll order a wideband and see if the mixture is good.

I'm not a tunner but will learn this myself, just need to know where to start.

[Lex]

I am running an MS with base timing at 15 degrees at idle with no issues buy my pistons are 9.0. My head was shaved just enough to clean it up. Running less timing - especially less than 10 degrees might make your engine feel very rough because it is making less torque (unless the head shaving is drastic). Adjust your base timing with a warm engine and feel the engine hit a sweet spot where it's smooth.

[323driver]

Ok thanks for the advice.
What I don't understand is that the head was shaved alot (20 thousandths) and instead of retarding timing, I need to fully advance it on the disty to make the engine run.

Anyways, I'll keep you guys posted, just waiting for the timing light now.

[matt_fulghum]

Your compression ratio is not all that high, so it doesn't seem to me that it'd have that huge an effect on anything. If it's dying with stock ignition advance, then I'm gonna go with my previous thought that the engine still needs to bed in, so the tolerances are still pretty tight, and they'll to some extent loosen a little as everything settles in over the course of a few hundred miles.

Did you gap the rings properly? If the ring gaps are too small, it'll drive up your engine's pumping losses, which will in turn force your engine to run faster to make up for them. Also, if you honed the engine then the friction losses will be greater too, for the bed in period, and that'll also settle down.

I wouldn't worry too much about a high idle for a few hundred miles. If it's still hanging around then, then I'd say there's definitely something rotten in the state of Denmark.

[therieldeal]

are you sure your cap/rotor/wires/etc are all on the right way? there is only one correct way but you could probably get it close enough to run crappy in a few other configurations.

[Lex]

check the cam timing ... if you're off a tooth it can certainly hurt ya.

[323driver]

engine was honed since it has new pistons and rings and I did gap the rings, hopefully I did it right though.

Distributor wires are connected properly (If you mix just 2 of them the car runs like crap so I don't think it's that) and cam timing looks good, I even redid it to make sure it is straight on.
I guess it's normal if you all experience similar idle and have built engines as well.

[therieldeal]

i didnt mean the order, i meant the rotor being on right and the wires being on the right towers... if that makes sense.

[323driver]

I see... the car wouldn't run if the rotor is set differently, only works in 1 position... been there once, couldn't figure out why it would't start, lol

[Shades]

.020" is not that much shaven off... that's actually the max allowable before things start to change. So you should be in the clear.