Weber Bit o' Buckin' Question

[ARCHINSTL]

Well - for those who have installed a Weber...
The car accelerates OK with the Weber...

However - and I'm using the term pretty loosely - I'm getting a bit of bucking/surging/stuttering when slightly decelerating but kinda still pressing the accelerator. This is not a great description, I know.
Example: Driving at 30 on level ground and moving the foot back on the pedal just a tiny bit so you are going maybe 29 - and there is a very slight bucking/surging/stuttering. This also happens at 40 or 35 or any - pick your speed.
It also occurs when slightly decelerating going down a slight decline - as in "not wanting the officer to nab you for going 32 in a 30 MPH zone..."

I finally got the "lean drop method" dialed in - but maybe not?
Odd, too, is that the idle has been at 800 RPM, but today is at 1000, without me touching anything.
Have I explained this adequately? Anyone else experience this?
I still have until Jan. 30th to call RedLine for free answers.
Tom M.

[scouttster]

Bucking, jostling, a shimmy'ing surge and de-surge when you let off the gas.. I experience this with my stock carb. I was told its probably a vacuum leak. I will change out the gaskets, but I'm not sure if this going to correct anything. ( from what I have read on here) Does it happen when the car is cold or only after the car warms up and comes up to temp? Maybe answering that question may help putting you on the right path to correcting the issue. Good Luck and thanks for reply help you have offered over the last few weeks.

[ARCHINSTL]

As to having a vac leak - I'd swear that there is none.
Before I installed the Weber, in my final fight with the Aisan, I had replaced all vac hoses, tested each emissions component, retorqued the manifold and carb bolts,and tested all joints with carb spray - and could discover no vac leaks.

When I installed the Weber, all vac hoses were disconnected. The only one retained was from the manifold "gas filter" to the UPPER front distributor port (the dizzy's back upper port was plugged). The Weber carb base vac ran to the lower dizzy port.
The Weber's base and adaptor were "emery-clothed" to give a smooth surface. Permatex gasket cement was used in addition to the installation gaskets. The phenolic plate was retained for PCV attachment and was also installed with new gaskets and sealant.
The second gas filter port was plugged, as were the five outlets on the TVSV. The EGR port on the manifold is blocked with a plate and two gaskets with sealant.

Observed fuel pressure is running 2.0 to 2.5 psi - although that is kinda unknown while actually driving - could this be too low? Although I dunno how this could affect a part-throttle situation; in "acceleration mode," whether mild or gonzo, nothing amiss is noted.

I have not noticed it when the car is cold - as in the first mile or two; it occurs seemingly only when warm.
It is not dramatic - but pretty annoying.
Tom M.

[gatemaster]

according to racetep the weber is supposed to run best with 4 PSI fuel pressure.

Webers work best at approx 4 psi of fuel pressure (Not 2 psi like many of the older books stated.) and you need Volume not Pressure to keep the float bowl full.

read the rest here: http://www.racetep.com/webfuelspark.html#webfuel

[ARCHINSTL]

Hmmm...well, I guess I'll try to raise the pressure using the regulator - although I think I tried that when I installed it all, and never got above what I have now. The fuel pump was new just before the carb installation, so it should be putting out whatever the max for the pump is (7 psi?).
The Weber carb source in NY states specifically that various Toyota mech pumps put out too high of a pressure and the Holley 12-804 regulator must be used - which I did.
I realize that you bought the Carter electric pump (not yet installed ?), but the $95+ is a bit beyond me at the moment...and since apparently no other Weber owner here had installed one, I figured it was not essential. Incidentally, when you DO install it, PLEASE do a writeup - none exists here (include the wiring hookup, too!).
Thanks!
Tom M.
P.S. The advance is the same as stock - no change; 5 degrees and 13 degrees.

[splatterdog]

You might want to play with timing. For the vacuum advance I used the supplied port on the carb to the advance nipple that provides the largest increase in timing. I forget which one it was....

As far as fuel supply, I think the mech pump is just fine. I've cruised 85mph with pedal to spare now. No signs of starvation that I have seen. I also like the low cost/ standing up while replacing it type part that it is. Mech pumps are often more reliable than elec from my observations too.

Larger alternator might become a necessity depending on your current electrical demands as well switching. Adds at least 5-7 amps draw

How many turns out did you land on with the idle mixture screw? If i remember right if you are 2.5 turns out you need a bigger primary idle jet. Since this is happening at just off idle it could be mixture related as well. They are super easy to replace. A 50 primary idle jet worked better for me than the 45 that came with it.

I also can only hit 2.5 psi, even with the regulator pegged. I keep my screw adjusted right at the point I see it start to drop pressure, so I know it's doing something.

[ARCHINSTL]

Well - as to the vac to the distributor - I initially had the manifold vac hooked to the UPPER front dist vac port and the carb vac source to the LOWER dist port (the rear upper port was plugged/formerly to the HAC). The manifold source ran through the OE check valve, too. This seemed the most logical, as it was the closest to the OE vac line setup; this was my reasoning, anyway.
Then in attempting to fix the high idle (before I noticed that the bell crank didn't move enough due to tight cable), I plugged the carb vac source to the LOWER dist port and ran the advance just off the manifold to the UPPER (keith is apparently the only one who did this routing, but I dunno whether to the dist upper or lower port).
Then I fixed the high idle, but left the (second) vac setup.
I don't recall if the stuttering was there before I fixed the high idle (and redid the lean drop).
Guess I'll plug the manifold vac source to the UPPER dist port and try only the carb source to the LOWER dist port...report back Tuesday.

As to the idle mixture screw - I think it's out at slightly over 2 turns - pretty positive it's less than 2 1/2. I think I'll do the vac rerouting before messing with the lean drop again.

Incidentally, I do have my doubts on the claim from RedLine that whichever jets come in the Tercel kit are perfect; I recall asking if they are correct for STL's altitude and without hesitation they said they were - didn't even ask about what STL's altitude is.
Tom M.

[gatemaster]

I use a regulator in the mean time set at 4 psi until I get the carter installed. not happening in this weather. The jets that came with my weber were not the right ones.

[ARCHINSTL]

OK - RE the timing - look at my revised vac routing notes in posts preceding - due to advancing senescence, I forgot which I had hooked to what...
Sorry...
Tom M.

[Mattel]

Hi Tom,
My Weber was put on by a pro who specializes in these sort of modifications and I am still running the OG mech fuel pump. I too notice that the accelerator is pretty sensitive at first. I'm not sure if my driving has modified itself or the cables and springs have settled in a little to reduce the bucking and surging that you mention. I do notice a lot better torque through the mid range and the economy is defiantly helping the weber slowly pay itself off.

[gatemaster]

Mine works with the mechanical also. I bought the Carter electric mostly because I get bad vapor lock during the summer. Mostly after a 20 to 30 minute hot soak.

[ARCHINSTL]

Well, here is a follow-up...maybe not the definitive one, but a follow-up nevertheless:
I reconnected the vac port at the bottom right of the Weber to the lower port of the dist.
I left the manifold gas filter source hooked to the upper front dist port (through the OE check valve).
This is how I had the conversion set up originally; it seemed closest to the OE setup.
It ran just fine - no bucking, etc.
Note that "bucking" is a kinda strong term, but the best I could come up with.
When it warms up a bit outside, I will remove the check valve to see if that makes a difference. I will also try sourcing the dist vac from the carb base only (to the front top port, blocking the lower port). I presume this is how others have done it?
So - I presume the carb vac port is a stronger source for vac, and it "overpowered" the manifold source?
Tom M.
EDIT 012809:
I just realized that the connections outlined above are exactly the OE way that CA and Canadian cars are set up, including the position of the check valve.
So - I guess I'll just leave it alone. Any other opinions?

[splatterdog]

The carb vacuum port is "ported vacuum". Meaning- it comes from above the throttle plate.

I didn't use any of the old vacuum system other than the little single steel pipe that goes from carb to dist.