The Ford Barn

quinn-grant · 02-10-2019, 05:16 PM

I'm hoping someone can give me some suggestions with my latest Teapot issue.

Rebuilt the carb using a Mike's Carbs kit, and everything seemed to go well (although whoever designed those secondary down-tubes was a sadist!). Car started right up, however I now have a massive flat-spot in acceleration.
Car will rev from 600RPM to about 1000 using 1/4 pedal. However from there, no increase in revs until I get to over 2/3 pedal, at which point the engine will rev all the way up as normal (same when manually manipulating the linkage).

Suspecting the accelerator pump, I watched near the main booster venturis as I moved the linkage. I'm seeing strong fuel squirt for about 1/3 - 1/2 pump travel, and then nothing for the rest of the way down.

I can only guess that the accelerator pump plunger is pulling up fuel half way, and then air the rest of the way. Although, if I'm at 1/2 throttle, shouldn't the engine rev up eventually to an appropriate RPM, pump-squirt or not? Thanks in advance for any suggestions!
-Matt

scicala · 02-10-2019, 06:34 PM

If your car didn't have that condition before you rebuilt the carb, I agree it should be a carb issue. The 4000 teapot Holley carbs are difficult to work on and especially get right.
If you mean both accel pump nozzles give a steady stream for 1/3 to 1/2 of the throttle lever travel, that would be a good shot since the pump only goes down that far, then bottoms out in the pump bore. Carbs normally backfire if the accel pump isn't up to snuff, which makes it a little tough to understand. If the pump squirt is just weak, maybe there is an issue with the pump check ball in the bottom of the pump bore not being in there if the round wire clip wasn't installed when put back together. If so, most of the fuel would go back to the bowl instead of out of the nozzles. Maybe a bad seat for the check ball too. Also possibly a pump piston problem. Tough to diagnose without being there.
This is all considering your ignition system is up to snuff too.

Sal

quinn-grant · 02-11-2019, 06:56 PM

Sal, Thank you for the reply!
I did not have this condition before the rebuild, so It's likely I dorked something up. Both accel nozzles give a strong stream for about 1/3 linkage travel, right into the boost venturis. If you're saying that's normal, then I clearly need to look elsewhere. Makes sense, else why would the pump piston have a spring!
I think the main clue is that I get no increase in RPM at all between 1/3 and 2/3 linkage travel. Even without the accelerator pump, shouldn't the RPMs increase linearly with the butterfly valve, just not as immediately?
Thank you again for the advice!
-Matt

scicala · 02-11-2019, 10:19 PM

Quinn, yes, it's very strange that the engine won't accelerate at all when between 1/3 and 2/3 throttle. Also kind of tells me it's not really a lean condition, or it seems like it would backfire out of the carb. Don't know what to tell you without being there, other than recheck your work and all of the channels in the carburetor.

Sal

fiddy6 · 02-12-2019, 04:27 AM

What is the choke doing through all this?

I reassembled my teapot recently and had issues with the choke not opening properly.

packrat5 · 02-13-2019, 01:08 PM

Sponsored Links (Register now to hide all advertisements)

Do you have the pump arm in the recommended position?

quinn-grant · 02-13-2019, 07:38 PM

Good news is I've pretty much fixed the problem. The detailed solution is very complicated, but the short answer is: I'm a knuckle-head.
Turns out the accel pump is just fine. I sat in the car watching the entire linkage as I pushed on the accelerator pedal just to see what was happening. Turns out the throttle rod never moved -- it was just sliding immediately up the kickdown slot without pulling on the carb linkage. Only when it topped out in the kickdown slot was it forcibly pulled back, explaining why no RPM increase until over 1/2 pedal travel.
Then I did something crazy -- I followed the instructions on how to set the throttle rod length/position! With a phillips screwdriver through the linkage guide holes, the throttle rod stuck out a good 1/2" past the hole in the carb linkage. Not sure how, but fixing that made all the difference. The kickdown spring now holds the throttle rod in the down position for as long as it is supposed to. Next job is to fix the choke as you suggest, fiddy6, as it is clearly way off!
Thank you all for your patience with this newb!
-Matt

scicala · 02-13-2019, 09:41 PM

Thanks for posting what you found.

Sal

miker98038 · 02-13-2019, 10:37 PM

Well, if you just joined the knuckle head club, especially on the kick down linkage, you’re 52 years behind me. And I’m still re upping my membership on a regular basis. Thanks for following thru on the solution.

fiddy6 · 02-17-2019, 01:52 AM

The choke issue I had was when I reassembled it. When cold it stayed completely closed until full throttle. Letting off the throttle would slam it shut. I'd have to pull the air cleaner off and pull the choke cam forward to open it a little... it would start then and operate normally as it warmed up.

02-10-2019, 05:16 PM	#1
quinn-grant Junior Member Join Date: Jun 2018 Location: CO Springs, CO Posts: 7	More fun with Holley 4000 Teapot! I'm hoping someone can give me some suggestions with my latest Teapot issue. Rebuilt the carb using a Mike's Carbs kit, and everything seemed to go well (although whoever designed those secondary down-tubes was a sadist!). Car started right up, however I now have a massive flat-spot in acceleration. Car will rev from 600RPM to about 1000 using 1/4 pedal. However from there, no increase in revs until I get to over 2/3 pedal, at which point the engine will rev all the way up as normal (same when manually manipulating the linkage). Suspecting the accelerator pump, I watched near the main booster venturis as I moved the linkage. I'm seeing strong fuel squirt for about 1/3 - 1/2 pump travel, and then nothing for the rest of the way down. I can only guess that the accelerator pump plunger is pulling up fuel half way, and then air the rest of the way. Although, if I'm at 1/2 throttle, shouldn't the engine rev up eventually to an appropriate RPM, pump-squirt or not? Thanks in advance for any suggestions! -Matt

02-10-2019, 06:34 PM	#2
scicala Senior Member Join Date: Jun 2010 Location: Detroit suburb, MI Posts: 3,706	Re: More fun with Holley 4000 Teapot! If your car didn't have that condition before you rebuilt the carb, I agree it should be a carb issue. The 4000 teapot Holley carbs are difficult to work on and especially get right. If you mean both accel pump nozzles give a steady stream for 1/3 to 1/2 of the throttle lever travel, that would be a good shot since the pump only goes down that far, then bottoms out in the pump bore. Carbs normally backfire if the accel pump isn't up to snuff, which makes it a little tough to understand. If the pump squirt is just weak, maybe there is an issue with the pump check ball in the bottom of the pump bore not being in there if the round wire clip wasn't installed when put back together. If so, most of the fuel would go back to the bowl instead of out of the nozzles. Maybe a bad seat for the check ball too. Also possibly a pump piston problem. Tough to diagnose without being there. This is all considering your ignition system is up to snuff too. Sal

02-11-2019, 06:56 PM	#3
quinn-grant Junior Member Join Date: Jun 2018 Location: CO Springs, CO Posts: 7	Re: More fun with Holley 4000 Teapot! Sal, Thank you for the reply! I did not have this condition before the rebuild, so It's likely I dorked something up. Both accel nozzles give a strong stream for about 1/3 linkage travel, right into the boost venturis. If you're saying that's normal, then I clearly need to look elsewhere. Makes sense, else why would the pump piston have a spring! I think the main clue is that I get no increase in RPM at all between 1/3 and 2/3 linkage travel. Even without the accelerator pump, shouldn't the RPMs increase linearly with the butterfly valve, just not as immediately? Thank you again for the advice! -Matt

02-11-2019, 10:19 PM	#4
scicala Senior Member Join Date: Jun 2010 Location: Detroit suburb, MI Posts: 3,706	Re: More fun with Holley 4000 Teapot! Quinn, yes, it's very strange that the engine won't accelerate at all when between 1/3 and 2/3 throttle. Also kind of tells me it's not really a lean condition, or it seems like it would backfire out of the carb. Don't know what to tell you without being there, other than recheck your work and all of the channels in the carburetor. Sal

02-12-2019, 04:27 AM	#5
fiddy6 Member Join Date: Jul 2018 Posts: 97	Re: More fun with Holley 4000 Teapot! What is the choke doing through all this? I reassembled my teapot recently and had issues with the choke not opening properly.

02-13-2019, 01:08 PM	#6
packrat5 BANNED Join Date: Mar 2015 Location: Wisconsin Posts: 301	Re: More fun with Holley 4000 Teapot! Sponsored Links (Register now to hide all advertisements) Do you have the pump arm in the recommended position?

02-13-2019, 07:38 PM	#7
quinn-grant Junior Member Join Date: Jun 2018 Location: CO Springs, CO Posts: 7	Re: More fun with Holley 4000 Teapot! Good news is I've pretty much fixed the problem. The detailed solution is very complicated, but the short answer is: I'm a knuckle-head. Turns out the accel pump is just fine. I sat in the car watching the entire linkage as I pushed on the accelerator pedal just to see what was happening. Turns out the throttle rod never moved -- it was just sliding immediately up the kickdown slot without pulling on the carb linkage. Only when it topped out in the kickdown slot was it forcibly pulled back, explaining why no RPM increase until over 1/2 pedal travel. Then I did something crazy -- I followed the instructions on how to set the throttle rod length/position! With a phillips screwdriver through the linkage guide holes, the throttle rod stuck out a good 1/2" past the hole in the carb linkage. Not sure how, but fixing that made all the difference. The kickdown spring now holds the throttle rod in the down position for as long as it is supposed to. Next job is to fix the choke as you suggest, fiddy6, as it is clearly way off! Thank you all for your patience with this newb! -Matt

02-13-2019, 09:41 PM	#8
scicala Senior Member Join Date: Jun 2010 Location: Detroit suburb, MI Posts: 3,706	Re: More fun with Holley 4000 Teapot! Thanks for posting what you found. Sal

02-13-2019, 10:37 PM	#9
miker98038 Senior Member Join Date: Mar 2013 Location: Kent, WA. Tucson, AZ Posts: 1,397	Re: More fun with Holley 4000 Teapot! Well, if you just joined the knuckle head club, especially on the kick down linkage, you’re 52 years behind me. And I’m still re upping my membership on a regular basis. Thanks for following thru on the solution.

02-17-2019, 01:52 AM	#10
fiddy6 Member Join Date: Jul 2018 Posts: 97	Re: More fun with Holley 4000 Teapot! The choke issue I had was when I reassembled it. When cold it stayed completely closed until full throttle. Letting off the throttle would slam it shut. I'd have to pull the air cleaner off and pull the choke cam forward to open it a little... it would start then and operate normally as it warmed up.