Gene jockey

I have a 63 FI coupe, a barn find of sorts. I had the FI unit refurbished by a senior Rochester technician. I have installed the unit on the car. I have the intake duct, filter and mounting installed. I have set the idle speed, the idle fuel, and the fast idle speed. The fast idle speed setting is off the cam, and the engine will idle at about 700 RPM with a lopey beat that sounds like it's about to stall and then kicks over. So far so good.
The instant I add a touch of throttle to back out of the garage, RPM jumps to 2500 and won't back down. Throttle linkage was my first guess, but it seems free and the return spring is plenty strong. Blipping and releasing the throttle does not drop RPMs. Driving this thing around the block requires a strong foot on the brake. This is all with a warm, but not hot, engine

Background on the car...
NOM, 3959512 engine
unknown camshaft (makes lash setting tricky...)
solid lifters
Newly rebuilt Don Baker distributor

Any suggestions?

jim lockwood

When this happens, have you looked at the fast idle cam to see if it might have rotated back into position?

If the fast idle cam isn't the culprit, then I'd suspect worn air meter bushings and/or a worn throttle blade shaft. Can you grab the throttle bellcrank on the side of the FI and force the idle back down to 700 RPM?

Another possibility, although an unlikely one, is that the throttle blade is hanging up on the gasket for the Air Meter. Strange, but I've seen it happen.

Jim

Jim

Gene jockey

[QUOTE=jim lockwood;1587239268]When this happens, have you looked at the fast idle cam to see if it might have rotated back into position?

If the fast idle cam isn't the culprit, then I'd suspect worn air meter bushings and/or a worn throttle blade shaft. Can you grab the throttle bellcrank on the side of the FI and force the idle back down to 700 RPM?

Another possibility, although an unlikely one, is that the throttle blade is hanging up on the gasket for the Air Meter. Strange, but I've seen it happen.

Jim

QUOTE]
Thanks, Jim,
The fast idle cam is clear of the adjusting screw, and the linkage moves freely. I checked the air meter gasket, and it's fine as is the air meter shaft. I tinkered a bit with the idle speed setting. It was cranked down hard. I loosened the idle speed screw a bit, and this seemed to make a difference. Idle is now a sedate 700.

I still have a bucking problem idling around the block, and the the valve train is pretty thrashy. Next job is to figure out what camshaft I have. i bought a dial indicator and will try to measure the lift.

MikeM

[QUOTE=Gene jockey;1587240710]I would suggest you set the idle speed at 750 after you hook your vacuum advance to manifold vacuum rather than the oem location coming off the air meter pipe.

jim lockwood

[QUOTE=MikeM;1587241036]

Even if you now have the idle speed under control, this is good advice.

wmf62

[/QUOTE]I still have a bucking problem idling around the block, and the the valve train is pretty thrashy. [/QUOTE]

as good natured as they may be, they are not torque monsters and, depending on gear ratios, they really don't cotton to '"idling" around the block'...

Bill

Gene jockey

[QUOTE=jim lockwood;1587242028]Right now, I have the vacuum advance canister plumbed to the air meter line at the top of the FI unit. Where would I find another manifold vacuum port?

wmf62

[QUOTE=Gene jockey;1587244024]see where the brass plug is in the upper right; this is the best and usual place for full manifold vacuum.
Bill

OOPS: generational problem..., right pew, wrong church.... C1 not C2

wmf62

the 1st pic is what i presume you're using...

the plugged hole in the upper left in the 2nd pic is what i suggest you use
Bill

Gene jockey

Thanks, Bill, Jim and Mike. My set up is very much like yours, Bill, with one big exception. I have an aluminum plug (9/16) on the upper back side of the FI box. More important, I have a big hose attached to a fitting screwed into the side of the FI box. This hose points directly to the pipe to the PCV outlet on the block; I have one of the famous 3959512 engines with a big hole. I assumed that the hose from the FI box went to the pipe for the PCV. It looks like it belongs there. I can imagine this affecting all sorts of things. I also have an oil filler tube that is ported to the crank case, so that may be redundant.

MikeM

There is a vacuum port on the left, top rear of the plenum. You can tap in there for vacuum advance. That's normally the vacuum source for power brakes. You can buy a fitting from some of the vendors with the right size nipple. I think the original application for that fitting was for pass car WSW,s.

The hose nipple from the oil fill tube should route a hose to the air cleaner adaptor.

Right hand rear of plenum should have a 45 degree fitting with a PVC valve and a hose to the rear of the block fitting.

Maybe someone can post a picture of this.

wmf62

i presume this is the plug you are talking about, it can be used if you have room with the ignition shielding in place.

or, you can get creative as i did and solder a small piece of the right size tubing to fit the vacuum advance hose into the side of a 90degree fitting to serve a dual purpose.
Bill

Gene jockey

My car has the 45 degree fitting. I was confused about the hose and its purpose. I am ordering a PCV valve from one of the vendors, along with appropriate hose to get to the aluminum pipe for the PCV fitting.

While I'm shopping for plumbing parts, how do I harness all of this vacuum to the vacuum canister?

Thanks for your support!

Once I get this done, I guess

wmf62

same rubber vacuum hose you're using now. for a fitting, check part #755 in the Paragon C2 catalog.
Bill

MikeM

The correct PVC valve threads into the 45. The other end of the valve has a hose nipple on it. A short hose runs between the valve and the metal tube that pushes into a rubber grommet in the large hole in the block.

It's sounding like you didn't have a valve in your system?

wmf62

if that is the case, i would be surprised if it ran at all...; but it would certainly explain the idle problem...
Bill

MikeM

That is why I asked.

Gene jockey

Yes, indeed, it would explain it. I stuck a bolt into the hose from the 45 degree angle to plug the PCV line, and that helped. I'll let you all know how the PCV valve affects the idle once it arrives.

Gene jockey

As it turns out, I had a PCV valve in the system, installed by the senior Rochester technician. Just didn't know what i was looking at. Connecting the hose from the PCV at the top passenger side of the box, to the pipe and grommet on the back of the block, gives a good easy start, and an acceptable idle speed (about 700 rpm). I'm still fiddling with the hot idle speed, which seems to like 1500 rpm and doesn't like to go down.

The engine is well heaved under acceleration load, but it still bucks when creeping in traffic.

MikeM

Did you change the vacuum advance to full time as suggested above? That will help/eliminate that condition.

Also, 700 rpm idle speed is too low and can cause the bucking. Change the advance and set the idle to 750 and you should be in business if everything else is up to snuff.