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"Steve has a car?"
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Discussion Starter #1
I've just installed an EF BBM manifold to my EA 3.9litre. ATM it's running off the EA mpfi comp, uses EF injector rail, injectors, regulator etc and an EF fuel pump. Still using an EA head, cam etc...

What I'm getting is a flat spot when booting it from stand still. The car will hesitate for bout half a second, then make it's way to bout 30k's before the power finally kicks in. What do people think is the likely cause of this. There is an extremely slight puff of smoke from the exaust when it hesitates, then it stops. I'm assuming that it may be running a little rich down low??

ATM the I have not got a dual runner switch hooked up, so i've just cable tied in the valve in the up position. Is this switched to long runners or short runners?? I've had it run in the down position and I'm getting the same flat spot, but low down power is even worse.

Any ideas???
 

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"Steve has a car?"
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2,207 Posts
Discussion Starter #3
Well, the base timing is spot on, and when I check the timing without diagnostic mode turned on, it's 10 degrees advanced. From what people have told me, this is how it should be...
 

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RIP Sox.....
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Perhaps the harmonic balancer has slipped and the mark isn't at true TDC.
Check it and re-time it if necessary.

Rick.
 

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"Steve has a car?"
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Discussion Starter #5
The balancer can't slip, it can only go on one way as it has a locating notch where you slide the balancer back on.
 

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RIP Sox.....
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Harmonic balancers can, and do slip.
They consist of 2 seperate cast pieces, 1 the center hub which slides onto the crankshaft and is located by the key, and 2, the outer ring which is seperated by a high density rubber. This is to damp out harmonics, hence the name.
The outer ring quite often slip out of adjustment when they get old and the rubber starts to perish.

Check to see if it is on true TDC by removing number 1 spark plug and use a bit of wire to locate exact TDC, then see where your mark is on the balancer.

Rick.
 

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feed me hey
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4,692 Posts
Ive had 2 engine both of them had slipped. We used a spark plug gutted with a steel rod welded in. Screwed it in, turned engine till piston touched, made a mark,turned back till it touched again, made another mark then measured halfway in between. This gives the true TDC. Was suprising at how much one of them had slipped.
 

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Looking in YOUR bathroom.
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Yeah sounds timing related. Also the EL ECU (if you were using one) would use a diffrent spark map down low to work with the long runners. Advance the timing 5deg and take her for a spin, keep on advancing it till you get slight pinging then STOP. retard it a few deg and try again.
 

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Rmyers said:
Well, the base timing is spot on, and when I check the timing without diagnostic mode turned on, it's 10 degrees advanced. From what people have told me, this is how it should be...
it should be at 10deg adv when in diagnostic mode dude..
 

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feed me hey
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Just to add if your not completely sure its in self test mode, ping the throttle open and watch the timing stay the same. If it shifts off the mark its not in self test.
 

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feed me hey
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He has the EF timing chain cover and they only have the one mark. Is this mark 10 degrees or TDC?
 

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im pretty sure its tdc
 

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YES its a 5 Speed!!
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Harmonic balancers slip quite often on the I6s... last week i changed 4... a new record!
 

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Not a Joe Lunchpail
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NZ said:
Ive had 2 engine both of them had slipped. We used a spark plug gutted with a steel rod welded in. Screwed it in, turned engine till piston touched, made a mark,turned back till it touched again, made another mark then measured halfway in between. This gives the true TDC. Was suprising at how much one of them had slipped.
Now that's an excellent way to do it - great lateral thinking. :hy: Is there a place for all these ingenious little tips here anywhere? If not - there should be!
 

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feed me hey
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I would have never thought of it - I was shown it by my mechanic friend. I also read it in Street Machine mag once. But yeah its pretty simple.
 

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I use a screwdriver :)

Rymers - just do it by 'ear'. The way I usually do it, and never have any problems, is to advance the timing with the engine at idle until just the point where it hits its fastest RPM. This always produces the best power. At least on a stock motor, modified motors are not something I know a lot about, but then yours pretty much is stock yes?
The only problem with this method is sometimes you can go a little too far and get pinging, but it's not hard to retard the timing a little. Most of the motors I do seem to want about 15 degrees or so to run best, EF manifolds want a little more I find.
 
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