Road Test, Slow acceleration and valve chatter Options

[VA_914]

I am finally road testing my 2.0 restoration and haven't quite got it right yet. It starts fine, runs smooth idling or revved up in the driveway but on the road test it accelerated slow, with what sounds like valve chatter when I give more gas to accelerate. It wouldn't go over 3000 rpm in 1st, 2nd or third. I tweaked the timing a bit and it seemed to get better, less chatter and almost up to 4000 rpm. Suggestions, comments; am I on the right track?

[VA_914]

Yes, I now run premium in it, but that didn't seem to have much of an effect. Also, the injectors were checked when the engine was rebuilt. I have installed both a fuel pressure gauge and vacuum gauge in the engine compartment. The fuel is typically 28, but I have taken it up to 31 at times. My reasoning was that the displacement was 10% larger so I should up the pressure by 10%, assuming the injector pulse width remained the same. The vacuum is typically 10-12 psi at idle and goes up to 16 or so at higher rpm.

For O2 monitoring, I would need to weld a sensor into the heat exchanger? What other tweaks have people done for a 2056?

A couple other things wrt the mixture: There are two vacuum ports on the distributor bellows; one for advance and one for retard (I assume). The throttle body I am using only has one port that size, so I connect it to the port on the distributor side of the bellows and leave the other side of the bellows open to the air. Do I have this backwards?

The throttle body has an idle adjustment that allows air to pass around the throttle valve through a tube in the body. It also has a small screw that protrudes into the throat and keeps the throttle valve slightly open, depending on how you set the screw. Both effect the idle speed, presumably because they effect the mixture? I have a second throttle body that has two ports the same size as the distributor bellows, one above and one blow the throttle valve. It has the same type idle adjustment but no screw to keep the throttle valve slightly open. Should I try that one instead?

Lastly, I have two pressure sensors, one that Greg Robbins sent to Jeff Blysing to recalibrate for the larger displacement when the engine was rebuilt and one from the second injector set I bought. Unfortunately, I have mixed them up and don't know which is which. As it turns out, they perform a little different, but neither resolve the major issues (ping and 3-4000 max rpm).

BTW thanks for your comments and I appreciate the advice about the detonation damaging the engine. I have never gone more than around the block and my intuition told me to back off when I heard the "ping".

[BeatNavy]

Yes, I now run premium in it, but that didn't seem to have much of an effect. Also, the injectors were checked when the engine was rebuilt. I have installed both a fuel pressure gauge and vacuum gauge in the engine compartment. The fuel is typically 28, but I have taken it up to 31 at times. My reasoning was that the displacement was 10% larger so I should up the pressure by 10%, assuming the injector pulse width remained the same. The vacuum is typically 10-12 psi at idle and goes up to 16 or so at higher rpm.

For O2 monitoring, I would need to weld a sensor into the heat exchanger? What other tweaks have people done for a 2056?

A couple other things wrt the mixture: There are two vacuum ports on the distributor bellows; one for advance and one for retard (I assume). The throttle body I am using only has one port that size, so I connect it to the port on the distributor side of the bellows and leave the other side of the bellows open to the air. Do I have this backwards?

The throttle body has an idle adjustment that allows air to pass around the throttle valve through a tube in the body. It also has a small screw that protrudes into the throat and keeps the throttle valve slightly open, depending on how you set the screw. Both effect the idle speed, presumably because they effect the mixture? I have a second throttle body that has two ports the same size as the distributor bellows, one above and one blow the throttle valve. It has the same type idle adjustment but no screw to keep the throttle valve slightly open. Should I try that one instead?

Lastly, I have two pressure sensors, one that Greg Robbins sent to Jeff Blysing to recalibrate for the larger displacement when the engine was rebuilt and one from the second injector set I bought. Unfortunately, I have mixed them up and don't know which is which. As it turns out, they perform a little different, but neither resolve the major issues (ping and 3-4000 max rpm).

BTW thanks for your comments and I appreciate the advice about the detonation damaging the engine. I have never gone more than around the block and my intuition told me to back off when I heard the "ping".

From my experience and listening to others I don't think a basic 2056 is going to run that poorly using stock FI. It won't run great, but I think (as others do) that you have something else going on: timing and/or fuel delivery issues.

A couple of comments and feedback to questions.

1. Yes, a wideband sensor would be very helpful. You need to weld a bung in somewhere in the exhaust stream. Different schools of thought on where exactly. If you put it in the HE you're only getting one side of the engine, although the gasses will be hotter as it's closer to engine. It also depends on your actual muffler. Might want to search here to see examples of how it's been done.

2. I don't think there's a linear relationship between fuel pressure, displacement, and volume of fuel injected during the pulse. No matter, 31 psi shouldn't be terribly off.

3. Idle vacuum should be around 15 psi, although it depends on the cam. If you have the Raby 9550 (IIRC) cam, the only Raby cam designed for FI, then you may not. I've had two of those. One on D-Jet and one on Microsquirt. Neither pulled 15 psi in my case. They are also a little finicky cold, but that quickly goes away with some heat. That's my experience anyway. At WOT a vacuum gauge should show 0 psi. How are you measuring?

4. You aren't sure of the compression ratio? That is a wildcard. According to Jake the Raby 9550 really shouldn't go much above 8.5 (at sea level, which you are). Not sure that would cause what you're experiencing, but may impact idle or other behavior.

5. Not sure what you mean about throttle body and the small screw that keeps the valve open. Can you post a pic? AFAIK on a stock TB there's the idle air bypass valve which is that throat with the big screw that protrudes into it. That simply lets in more air into the manifold. If you have one port on the TB it goes to the retard port on the dizzy, the one that faces the dizzy body. Leave the advance port on the dizzy open.

6. I agree with Seahawk and John (wndsrfr). Focus on timing - verify the timing marks and your timing procedure -- and fuel delivery issues. Seahawk mentioned possible clogged injectors. I'd highly recommend sending them out for cleaning if they've been sitting around for 10 years. That's a cheap and effective way to remove that variable. Wndsrfr is a great resource local to you. If he's offering, let him help before you get too much further.

Good luck.

EDIT: I see in your post you said you "checked the injectors when the engine was rebuilt" What does that mean? Cleaned? If they were run at all at that time and have had ethanol sitting in them for 10 years....