63 R2 Avanti with auto trans stumbles. Need some good troubleshooting advice

[edpjr]

Just today my brother raised the pump rod connection up a notch. That definitely helped the performance some. But, it also stopped the car from downshifting to passing gear. So I'm wondering if the trans linkage/rods that we had previously set at the garage, now need to be readjusted too for consistency.

Regarding JDP's and your comments about the springs. That certainly seems to be a valid concern. Jon Meyer has sold me a few individual R2 Carb pieces (nozzle jet, etc.) that needed to be replaced. And, the parts in the T-Bow kit that JDP recommended were far superior to what was in the first carb kit I bought. Now we have a neoprene pump, new ball vlv, etc. We put on a new throttle kicker too.

It may not have a thing to do with anything, but several folks insisted that we should raise the timing about 4 degrees beyind the book spec of 24 degrees at 1600 RPM (where it is now).

Thanks for the continued technical info.

Well I have a little more insight now...you have a flat spot on part throttle acceleration would that be a fair description? I was thinking you are at full throttle and the engine bogs at 40 mph, recovers and you continue to accelerate until it loses power again at 80 mph.

If what you are feeling doesn't occur at full throttle then disregard all that I've said so far even though all of the above can occur it sounds like there is another issue.

JDP has you on the right track. The accel rods are pulled down by vaccuum and raise up as vacuum disappears momentarily as the carb opens to accelerate. You could have springs that are too weak keeping the rods from moving quickly or far enough to richen the mixture. Get an Edelbrock Tuning kit for the 600 CFM carbs 1406 style and experiment with stronger springs and maybe even a rod change. Easy to do and you don't have to remove the carb.

Even though your carb is rebuilt by a pro it still could require tuning. Even when the cars where new dealers had access to different rods and springs to cure driveability issues.

Stronger spring first and then if it helps but isn't perfect also do a rod change. If you get to that point you will need to mic the rod that's in there unless it's already been replaced with an Edelbrock piece because the originals weren't marked with the sizes like the new ones. There's a cross reference somewhere but it's just as easy to mic them. You want to go smaller on the thin end. The thick part of the rod sits in the jet at idle and at cruise and the thin part when accelerating or at full throttle. It's no big deal if you are a little smaller on the thick end also but avoid big changes like from 75 to 65.

ErnieR

[edpjr]

The bog at low speed and cutout above 70 mph is gone. My brother raised the pump rod connection up a notch and that definitely helped the performance. But, it also stopped the car from downshifting to 1st gear if you just punch it. It will downshift back to 2nd (passing gear) around 50 mph though. So I'm wondering if the trans linkage/rods that we had previously set at the garage, now need to be readjusted too for consistency? We also snaked the timing up a few degrees, and that helped more. Now, other than the failure to downshift to 1st when the pedal is floored on takeoff or at low speeds, the car is running smoothly and fast. Manually shifting works fine.

[41 Frank]

Moving the accellerator pump link one hole will not affect the linkage to the transmission at all.

[bige]

Regarding the timing, with my Mallory I tuned it so the centrifugal advance is only 10-12 degrees and run the static timing at 14 degrees at idle. The car definitely likes more initial timing but my engine is built with lower compression so it may be able to handle more than yours but don't be araid to experiment with more advance if the engine likes it and you have no detonation issues.

Sounds like all that's left is a minor adjustment on the trans linkage and you're good.

[edpjr]

Interesting. Do you have any ideas why the car won't downshift to low gear but will to passing gear?

Moving the accellerator pump link one hole will not affect the linkage to the transmission at all.

[Bob Langer]

Interesting. Do you have any ideas why the car won't downshift to low gear but will to passing gear?

Low gear is only available from the 1 position. In 2nd gear it will start in 2nd and remain there with no upshifts or downshifts. In D it will only downshift to 2nd gear.

[edpjr]

Well dang! Ya learn something new everyday. I guess I don't have any more of the problems originally associated with this post. Thanks again to all for the advice and help.

Low gear is only available from the 1 position. In 2nd gear it will start in 2nd and remain there with no upshifts or downshifts. In D it will only downshift to 2nd gear.

[edpjr]

As a followup, the car has been running like a screamer for awhile now. She has superb acceleration and I ran it up to about 100 mph last Fri nite easy as pie. It does want over 100 octane fuel. I've been using a mixture of 93, 100 and 110. I think the increased compression from the R1 heads with the blower combination give her a little extra horsepower. But, wow does she like to drink the fuel!