Carter TQ - VERY rich at WOT...how to troubleshoot?

[M_Body_Coupe]

I'm running a Carter TQ 9801 (Aftermarket with the attached electric choke) carburetor on my 408 stroker.

Having been working with the TQ carbs for many many years now, right down to installing adjustable air bleeds, etc...I would say I am fairly proficient with these carbs...however this issue I have ran into has me stumped and it may very well be the simplest of things that I'm actually overlooking, and perhaps not even caused by the carb itself!

So here is the combiantion:
1) W2 408 Stroker: Victor W2 intake, TQ on the spreadbore to squarebore adapter plate
2) Carb itself is setup exactly as the original OEM config: 0.095 primary jet, 0.137 secondary, 2110 rods, the ONLY difference is that I drilled air bypass holes in my primary throttle blades to help with the idle situation (Comp Cams 292 hydraulic roller cam, 240/248 @0.050"), which gets me a healthy 10" vacuum signal at 900 RPM, idle mix screws are out 3.4 turns, so I'm good there
3) The Carter mechanical Strip pump (M6902) is what is feeding the carb, that passes through a Holley pressure adjuster (12-803)
4) 16" drop base air cleaner, using K&N filter, I have about 1.5" of free space above the TQ vent tubes

I tune using Innovate O2 setup (LM-1 and LMA-3 AuxBox), which does give me a nice readout of AFR throughout the throttle opening and matching RPM ranges.

...and here is my problem: at WOT (either from rolling start, or at cruise) my AFR goes to a pig-rich 9.5-10 level!!!

I went back through all my tuning logs and as best as I can tell I started to run into this issue when I built the W2 motor...but several things changed at that time, such as: intake combo, fuel pump combo, etc, etc...so I have too many pieces moving to be able to peg this down to one change that's the culprit.

In that sense I went back to 'square one' so to speak: work one thing at a time until I get to "something".

1) adjusted the secondary air door opening (went super wide) but that made no difference...LOL, heck if anything my AFR dipped into the low 9s this time...I figured the extra opening actually caused even more fuel to be pulled

2) I disconnected the secondaries and re-did the test just on primaries: I expected a nice & clean AFR here, but oh boy was I wrong: still pig rich!!!
- not sure what to make of that though b/c perhaps by design the primaries itself may very well expect the extra AIR volume through the secondaries and so it could very well be that they will show RICH on their own (heck, I've never had the need to try this before so I really do not know what the baseline is)

3) I tested the phenolic fuel body to see if I have a fuel leak under the primary jet well, but all seems to be good here, no leak

So the only thing that remains is to tune down the Holley fuel pressure adjuster, force it to about 4-5 PSI and see if that make a difference because it could be that the extra fuel pressure the Carter Strip fuel pump (rated at 6-7.5 PSI) is putting out, as compared to the previous Carter Street pump (M6270, rated at 6 PSI) I was running, is forcing the fuel inlet valve off of the seat and simply flooding the carb at WOT.

This might make sense seeing as the converter flash is about 4000-4200 RPM and at that level the Carter Strip pump should be putting out pretty much all the pressure it has.

Outside of this, the last couple of times I headed out to troubleshoot I noted that at WOT and buzzing right up to 6500 my vacuum signal never drops below 5", in fact it actually seems to climb as I've seen it go to 6.5" right as I shift when the Tach light goes off (which is set to 6200). This is unlike anything I've seen before and suggests a massive restriction somewhere...but where??? Or is this simply the result of all that extra fuel NOT getting burned and the engine effectively choking itself off???

Needless to say, when I spotted this I made sure that the Diaphgram Connector Rod is adjusted correctly and during a WOT throttle blip I see the secondary air door swing open...so that seems to be working fine as there are no mechanical obstructions.

Alright, many things here...but what else am I missing???

Thanks as always!

 

[ch1ll]

I'm not carb expert much less a TQ expert. Did you take a good look at your accelerator pump? Is it squirting too much fuel? Other than that, is the spread bore to square bore adapter a choking point? Specificly what intake manifold are you using?

 

[M_Body_Coupe]

I'm not carb expert much less a TQ expert. Did you take a good look at your accelerator pump? Is it squirting too much fuel? Other than that, is the spread bore to square bore adapter a choking point? Specificly what intake manifold are you using?

Good points!

YES, the accelerator pump setting is good, as in: per the OEM specs, so no higher, no lower than what is the be expected.

I will say this, the 'pig rich' AFR I'm talking about is not just a spike, it continues until I let off the pedal...so there is a very real fuel feed issue, or lack of air feed.

Regarding the intake manifold: so with my previous motor (which was a 360) I ran both the Performer RPM (dual) as well as the Strip Dominator (single) intakes, which both required the adapter plate. In both cases the idle=>WOT AFR rations were within the range I was expecting to see. In fact I was able to tune things very well at that point in time.

Now my W2 stroker motor is using the Edelbrock 2920 W2 single plane intake.

 

[M_Body_Coupe]

...So the only thing that remains is to tune down the Holley fuel pressure adjuster, force it to about 4-5 PSI and see if that make a difference because it could be that the extra fuel pressure the Carter Strip fuel pump (rated at 6-7.5 PSI) is putting out, as compared to the previous Carter Street pump (M6270, rated at 6 PSI) I was running, is forcing the fuel inlet valve off of the seat and simply flooding the carb at WOT...

Well, while that was a quick check (fuel pressure adjuster set to 5 PSI), it still netted me the same end result: 9.1-9.4 AFR at WOT. Otherwise, the AFR ranges are fine throughout.

 

[Professor Fate]

I'm sure you've checked and rechecked this, but-
Brass or plastic floats?
Partially flooded brass or partially saturated plastic floats will allow the inlet valves to pop open at a lot less than 5 psi... possibly contributing to your rich condition at WOT.

 

[ch1ll]

I could see why you would be reluctant to modify a w2 intake for a spread bore carb.

 

[RustyRatRod]

Have you checked the position of the secondary air door at WOT? If the tang is bent so the air door isn't opening enough, that can cause your problem. Much the same as closing the choke plate.

 

[M_Body_Coupe]

I'm sure you've checked and rechecked this, but-
Brass or plastic floats?
Partially flooded brass or partially saturated plastic floats will allow the inlet valves to pop open at a lot less than 5 psi... possibly contributing to your rich condition at WOT.

Plastic floats, set to 29/32...but seeing as I've just about exhausted all external troubleshooting I'm going to hit that next: take the carb apart, all new gaskets and will check the floats.

Last time I checked them to make sure they are still good. Both were <8g spec and balanced accordingly on the bench, meaning: you lay the float flat, tip it up on the needle side and the float should stay up and not come back down flat to the bench top.

 

[1MeanA]

Try a stock fuel pump to rule out high pressure. How well do those Holley regulators really work?

 

[M_Body_Coupe]

I could see why you would be reluctant to modify a w2 intake for a spread bore carb.

You know...I did consider doing this because there is just enough room to actually contour the intake's carb mounting flange to the spreadbore carburetor base, and that's without there being any potential gasket issues.

But yeah, I chickened out...although I have been thinking this may be worth a try as I would like to run a taller air filter (right now I'm using K&N E-3024R, which is 3.5" high).

 

[M_Body_Coupe]

Have you checked the position of the secondary air door at WOT? If the tang is bent so the air door isn't opening enough, that can cause your problem. Much the same as closing the choke plate.

So by default I had this set to 0.5" as measured between the primary airhorn housing and the leading contour of the air valve. (check)

Then I opened it up some more thinking maybe I simply wasn't getting enough air flow to match the fuel that was being pulled. This time I widened that to 0.550"...but that just seemed to net me a richer AFR....ugh??? lol

 

[M_Body_Coupe]

Try a stock fuel pump to rule out high pressure. How well do those Holley regulators really work?

Could be...but I will say this: I have a fuel pressure gauge attached and it reads a pretty steady 5 PSI throughout various RPMs...even buzzing this thing up keeps the reading steady.

I will mess with the carb first before I try the fuel pump replacement...just lazy enough to want to avoid all that work again!

 

[RustyRatRod]

So by default I had this set to 0.5" as measured between the primary airhorn housing and the leading contour of the air valve. (check)

Then I opened it up some more thinking maybe I simply wasn't getting enough air flow to match the fuel that was being pulled. This time I widened that to 0.550"...but that just seemed to net me a richer AFR....ugh??? lol

It may possibly work backwards from what I suspected. I assumed the more the door opened, the more air. Which makes sense. BUT, it may pull in more fuel as well. So, just for kicks, try limiting the amount the door opens more and see what you get.

 

[ch1ll]

My Holley strip dominator was cast for spreadbore, but not W2.

Your air filter is 13-14" diameter, right? I can understand the desire to add more filter height, but not at the reduction of height by using a lower rise intake and you don't have to. There is a solution, it's called a hood scoop.

 

[TT5.9mag]

You’re pulling 5”-6” of vacuum at wide open throttle? That’s a very serious restriction and is representative of closing the choke flap and so is the very rich afr. As a test, can you remove the TQ and adapter and put a different carb in place just to try?

 

[MobileCustoms]

I'd be tempted to mount a gopro and light right over the carb and make a good pull to see how the throttle openings are behaving during a hard run. Might shed some light or might just be a stupid video.

 

[M_Body_Coupe]

You’re pulling 5”-6” of vacuum at wide open throttle? That’s a very serious restriction and is representative of closing the choke flap and so is the very rich afr. As a test, can you remove the TQ and adapter and put a different carb in place just to try?

YES: 5" and steadily rising as the RPMs pick up...I'm floored because I have a VAC gauge mounted on my dash and I typically watch this and it NEVER does that...and yet at some point in time it started and now that's consistently what I'm seeing.

So here is the thing: Carter TQs is the ONLY thing I have!!! lol

...but yeah, I do have some other TQ options, as in these are known working carbs, one is a NOS 9801 piece actually that's pretty much the same thing I'm running right now but short of the drilled air bypass holes in the primary throttle plates.

I am inclined to think that it is not the adapter that's causing the problem only because I have ran this very same combo on multiple setups prior to the W2 stroker build and have never experienced this rich AFR issue.

For what it's worth: I cleaned up the K&N air filter, drying right now, will re-oil and re-test...but I only put about 5K miles on that setup, albeit over like 3 yrs...still, that should not be causing the issue I'm seeing.

EDIT
====
You know, if it is the choke flap there is an easy way to sort that out: remove the linkage and re-test...without the mechanical link there should be absolutely NOTHING causing the primary choke valve to close.

 

[M_Body_Coupe]

I'd be tempted to mount a gopro and light right over the carb and make a good pull to see how the throttle openings are behaving during a hard run. Might shed some light or might just be a stupid video.

Ha ha...oh man, what is it they say: "great minds think alike"...yes??? LOL

I dusted off my trusty Hero3, re-charged and just need to get a slightly longer air cleaner stud so that I can precisely position that little rascal right over the secondaries...but you bet, absolutely on my TO-DO list!!!

 

[TT5.9mag]

Is there any way the throttle butterfly’s are hitting the adapter and not opening all the way?

The more powerful, bigger cubic inch engine will draw harder on a carb (more signal) than a lesser hp smaller engine so it’s no surprise the tune up is off. But it sure sounds to me like you e got something hangin up somewhere. I’d be throwing zip ties or wire or coat hangers or anything else at the choke and air valve to hold stuff open for a test.

 

[M_Body_Coupe]

Is there any way the throttle butterfly’s are hitting the adapter and not opening all the way?

Definitely NO...I checked this over several times, on both primary and secondary side. This also included having a helper go through the full idle=>WOT pedal sweep, no restrictions were observed.

The more powerful, bigger cubic inch engine will draw harder on a carb (more signal) than a lesser hp smaller engine so it’s no surprise the tune up is off. But it sure sounds to me like you e got something hangin up somewhere. I’d be throwing zip ties or wire or coat hangers or anything else at the choke and air valve to hold stuff open for a test.

Something else changed and as best as I can recall this took place AFTER I had done my initial few runs on the new W2 motor. I say this because I watched the AFRs carefully, along with the VAC signal (both logged on my LM1 & LMA-3 AuxBox setup) as I was worried about running into a problem wetting the cylinder walls and ruining the new ring break in...but there was no issue there.

I just read and re-read my Carter Technical books over the past couple of hours.

Some additional takeaways:
1) Rule out improper fuel bowl venting, if this is not working (either the vent is not opening up enough, or the purge to the canister is wrong) that may cause pressure build up within the fuel bowl which will force extra fuel out causing rich condition

2) Rule out gasket issues: this is my tuning carb so it's been ON and OFF repeatedly, and there is always a chance I may have either broken through a gasket somewhere, or perhaps flattened something which is now causing an internal signal leak

3) Following a gasket change and re-test, if the issue is still there I will strip out the choke linkage and run w/o a choke valve on the primary side. If there are any mechanical issues that are causing this issue they should be just about completely ruled out by this approach I would think

 

[Bewy]

Congrats on using the best 4bbl ever made!
Got 600 hp on the dyno with a 440 & TQ recently, street driver, 900 rpm idle.

The 5" of vac is the clue. Too high:
- make sure the secs are fully opening. Choke slightly on keep secs from opening.
- some times the air valve dashpot linkage can bind, especially if it has been ' adjusted'. I would disconnect it & test without it. You will likely get a slight bog, but at least you will know.
- make sure the sec air bleeds are not blocked. All of the 6XXX models I have come across have 039-040 bleeds; later 9XXX models had 029 bleeds. I enlarge to 039. They run harder.
- control sec operation with the AV spring. The factory 1 1/4 turns is too soft, 1.5-2 turns is better.
- if you have bigger n/seats, you have to lower the float level, because bigger n/seats raises the fuel level.
- the o rings in the main body near the pri jets. If they leak, you get a rich mixture...very rich. I NEVER use the factory rings, a poor design. I use ordinary fuel resistant 5/16" o rings, 1/16" thick.
- the plastic pods under the main body. If they leak AND the gasket is not breached, you get a clean idle but very rich off idle; that is because fuel fills the cavity in the alum base & it acts as a 'reservoir'. If the gasket is cracked/broken between the pod & the t/bore, fuel will flow continually into the bore direct from the fuel bowl. Any question about the integrity of the pods, I would re-epoxy them.

 

[M_Body_Coupe]

Congrats on using the best 4bbl ever made!
Got 600 hp on the dyno with a 440 & TQ recently, street driver, 900 rpm idle.

NICE!!!

I figured the 9801, despite the small 1-3/8" primary size, would be a great fit for my stroker motor which spends about 99% of it's time handling street "chores".

For '***** & giggles' I have the CS-4846SA Comp all boxed up and will eventually try it...but seeing as that is a race carb I just never seem to find the time to go through it, set it all up to just try it out.

The 5" of vac is the clue. Too high:
- make sure the secs are fully opening. Choke slightly on keep secs from opening.
- some times the air valve dashpot linkage can bind, especially if it has been ' adjusted'. I would disconnect it & test without it. You will likely get a slight bog, but at least you will know.

OK, I think my plan to disconnect the primary choke plate linkage will cover the 1st part and disconnecting the dasphot will remove that from the mix as well, good call sir!

Further re: dashpot. I have it set per the 9801 specs, it visually works when I blip the throttle and when testing with the vacuum hand pump (as in: it keeps the vacuum - so no leak - and once that's removed it releases the pot in the allotted timing - which escapes me at the moment).

- make sure the sec air bleeds are not blocked. All of the 6XXX models I have come across have 039-040 bleeds; later 9XXX models had 029 bleeds. I enlarge to 039. They run harder.
- control sec operation with the AV spring. The factory 1 1/4 turns is too soft, 1.5-2 turns is better.

Carb is always pressured air blown through each time I touch it. One of the first things I did so far was to see if the air bleeds were obstructed in some way, the matching drill sized passed through w/o any problems, so I think I should be fine, but of course that's hard to guarantee w/o pulling the carb apart.

Re: secondary bleed sizes. Hmm, the measured sizing I noted on this 9801 carb is: 0.039", so I think that's already in the ballpark. I assume by saying "later 9XXX models" you perhaps meant the factory stuff? To be honest I can't quite tell just how 'different' the 9800 series (Aftermarket) carbs really are. There are some obvious differences, but otherwise the basics circuits are all the same...

Agreed on the AV spring, but I will say this: with my 4K stall converter and the 4.10 gearing I have consistently been able to run with literally just 1 turn...which all my previous experience dictated would be nearly impossible. Still, I tightened this back to 2 turns (and the 9801 specs call for that anyways) just to rule that out.

- if you have bigger n/seats, you have to lower the float level, because bigger n/seats raises the fuel level.

YES, I am using 25P-1103, which is just a single step up to 0.110" size. Seeing as I have never noted the need to drop the floats further, what do you recommend? Right now the stock setting which I am using is 29/32.

I really question the need to change the float setting because the orifice size only controls the volume that will pass through during specific time period (assuming the same fuel inlet pressure). This simply means that the bowl will re-fill faster but ONLY up to the level determined by the float setting...so if that stays at 29/32 it means the bowl gets back to that 29/32 fuel level faster. You get my thinking?

- the o rings in the main body near the pri jets. If they leak, you get a rich mixture...very rich. I NEVER use the factory rings, a poor design. I use ordinary fuel resistant 5/16" o rings, 1/16" thick.

Seeing as over the years I've amassed a pretty good assortment of parts, I have been using the X-style rings, which were a later model year change to the original O-ring. Some of the kits did actually have a yet-another-style which just looks like a square thick O-ring....but definitely NOT round or X-shaped.

If all the other non-invasive changes fail to produce the desired outcome I'll eventually pull the carb open and will replace these.

- the plastic pods under the main body. If they leak AND the gasket is not breached, you get a clean idle but very rich off idle; that is because fuel fills the cavity in the alum base & it acts as a 'reservoir'. If the gasket is cracked/broken between the pod & the t/bore, fuel will flow continually into the bore direct from the fuel bowl. Any question about the integrity of the pods, I would re-epoxy them.

So in a sense I suppose I've always had great luck with this. Never had to replace one yet, but like they say "first time for everything"...

I think I am OK because my AFR reads nice until I go WOT, meaning: I get a decent 14.3-7 highway cruise, around town I'm between 13.7-14.2 but when called upon to give it a bit more gas (but NOT WOT) I'll dip into the high 12s, so that's about right where I would want to be...maybe a little richer off-idle would be nice, which I had when using the smaller 0.040" idle circuit air bleeds, but which went leaner moving back to the 0.054" that's the OEM setup (which was to be expected).

 

[TT5.9mag]

Congrats on using the best 4bbl ever made!

We know you’re a TQ connoisseur and you brought a LOT of good diagnostic information to this thread (thanks for that) but you discount your own statements by starting with this sentence.

Got 600 hp on the dyno with a 440 & TQ recently, street driver, 900 rpm idle.

Can you share more on this? Specs on the engine? Video of the dyno runs?

 

[Bewy]

TT5,
[1] I do not have a video of the pull, the owner saw it & relayed it to me. Tq curve was very flat.
[2] It has a 6000 series 850 TQ on it, choke removed, extensive mods to the secs. Steve Dulcich of Chrys renown claims these flow over 900 cfm....with the choke in place.
[3] M1 4500 intake, no spacer, street car, so it needs to fit under the hood with an a/cleaner. I was able to drill the carb base to fit the intake directly, but the AV dashpot needed modification. I made a turtle for the plenum floor.
[4] TF 240 heads, ports untouched.
[5] Comp sol roller custom grind, 248/248 @ 050, 106 LSA.
[6] Comp steel rockers
[7] Headers, 2.5" full exh system
[8] 10.5 CR
[9] Idles at 900 rpm, has enough vac for the brake booster.
[10] idles with 43* of timing.
[11] Ign is Chinese HEI module & Mopar dist, NGK 5 plugs, believe we set gap at 060. E core coil, engine was taken to 5650 rpm & HP was still climbing slightly.
[12] Forget which forum in the past 10 days, Chrys stroker & Comp Series TQ made 700 hp...

 

[Bewy]

M-body,
I would get a new AV dashpot. Originals are decades old & rubber goes hard with age.
I use 0.110 n/seats in perf engines & reduce the float level to 1". If you increase fuel pressure or n/seat size, it raises the fuel level which should be reset. The link below is for AFB/AVS carbs, but you can see the effect. The external adj float level is one good feature of Holley carbs.
If the AV link rod has been bent, it can sometimes bind in the AV slot opening. So check that out.
The Mopar Perf book recommends the sec WOT angle of 81* for dual plane & 88* for single plane. That is how I set them.
I have never had to use anything but the outside hole in the acc pump lever for least amount of pump shot on any Carter 4 bbl. That is how good the metering system is.