Throttle stop carb adjustment

EVIL CLOWN · 06-06-2021, 08:59 PM

Just looking for some advice running a 540 on a number 1 stop carb is set up for power been banging bearings due to destination I don’t have 02 or egt’s just wondering if anyone has advice on tuning it for stop was told that when you put a stop under it gets very lean it’s a 1250 carb I know everyone tells me it’s to big not the best combo any help will be appreciated thanks

Jeff Stout · 06-06-2021, 11:41 PM

Lack of proper quality fuel can promote hammering bearings to death.

Tom Goldman · 06-07-2021, 12:55 PM

Fuel and timing would be the first place to look . especially if you use a grid and pull timing out on the stop . cylinder pressure skyrockets up and can kill bearings [and cranks]. and yes that knowledge is from personal experience.
That said , the carb is way too big for a 540. again ,I speak from experience .
I've had 1050's 1150's 1250's on 1000hp 565's and found the 1050 to be the best all around for the Stinnett under carb stop I run.
All of the above carbs were from name shops and all ran lean when on the stop.
I recently put on a 1050 carb from ATM Innovations . It is the first carb to not go dead lean on the stop, pulls great off the stop with no lag in rpm gain and has a great fuel curve for the entire run. and I lost no MPH over the 1150.
Plus they were great people to deal with .

EVIL CLOWN · 06-07-2021, 09:44 PM

The carbs that I run are done by CFm and book very good carbs to big for stop racing irk very well off stop I know these guys don’t do stop carbs just looking to adjust what I have I run vp c 14 fuel trying to see if anyone knows when they go lean on the stop is what I’m thinking but what do I know need to put a 1050 on it in the future timing is 37 degrees and we don’t pull any timing out on the run motor runs 8.40s in 3080 lb car makes 1004 on dyno

Tom Goldman · 06-08-2021, 10:40 AM

Quote:

Originally Posted by EVIL CLOWN

The carbs that I run are done by CFm and book very good carbs to big for stop racing irk very well off stop I know these guys don’t do stop carbs just looking to adjust what I have I run vp c 14 fuel trying to see if anyone knows when they go lean on the stop is what I’m thinking but what do I know need to put a 1050 on it in the future timing is 37 degrees and we don’t pull any timing out on the run motor runs 8.40s in 3080 lb car makes 1004 on dyno

Without fuel data ,it's difficult to focus the cause ,or the time of detonation, If that is what is causing the bearing issue.
Are the spark plugs also showing signs of detonation? they should if the detonation is bad enough to cause bearing damage.
several carbs I've run have gone as lean as 15.3 AFR while on the stop ,running the same timing and fuel with 16 to 1 compression and conventional heads , not that any two engines want the same timing ,especially with your car weighing 700#'s more than mine.

EVIL CLOWN · 06-08-2021, 08:30 PM

The plugs are showing signs thanks fo your help probably going to run no stop until I get some o2 s going to call some carb guys this week that do carbs for stop racing don’t know if I will get anywhere then send me your carb or I can sell you one I’d like to put a stunner 1050 on it but not buying one now

Tom Goldman · 06-08-2021, 09:49 PM

Quote:

Originally Posted by EVIL CLOWN

The plugs are showing signs thanks fo your help probably going to run no stop until I get some o2 s going to call some carb guys this week that do carbs for stop racing don’t know if I will get anywhere then send me your carb or I can sell you one I’d like to put a stunner 1050 on it but not buying one now

Talk to the people at ATM. I'm sending them one of my QuickFuel 1150's to them to do.
Very good people to talk to, and they really do know throttle stop carbs.

Charlie Yannetti · 06-10-2021, 08:11 AM

I'm running a 1250 by DC Carbs on my 565, but I have a bit more HP than you, and my car is almost 1000 lbs lighter than yours.. I just don't have Tom's compression at 14.5 to 1.. on the stop my O2's get to about 13.9 to 14.1 or so.. I also changed from VP C-14+ to VP X-14 with positive results... no tuning changes, and picked up 1 MPH..

I have also been told by many that 1250 is un-necessary on my combination, and that a 1050 or 1150 would probably work better.. next test and tune, I'm going to back to back my 1250 with the renovated 1150 from my 522 motor.. bigger isn't always better, but some carb builders go by HP numbers.. at 1004 HP, I would say that 1250 is not for you, especially at 3000 lbs..

Running lean while on the stop is kinda the norm, but if you're banging bearings, and possibly hurting the crank, I'm not thinking that running lean for 2 to 3 seconds is your problem.. but that's just me..

06-06-2021, 08:59 PM	#1
EVIL CLOWN Junior Member Join Date: Jan 2009 Posts: 34 Likes: 0 Liked 1 Time in 1 Post	Throttle stop carb adjustment Just looking for some advice running a 540 on a number 1 stop carb is set up for power been banging bearings due to destination I don’t have 02 or egt’s just wondering if anyone has advice on tuning it for stop was told that when you put a stop under it gets very lean it’s a 1250 carb I know everyone tells me it’s to big not the best combo any help will be appreciated thanks

06-06-2021, 11:41 PM	#2
Jeff Stout VIP Member Join Date: Dec 2001 Location: phoenix Posts: 1,466 Likes: 59 Liked 703 Times in 280 Posts	Re: Throttle stop carb adjustment Lack of proper quality fuel can promote hammering bearings to death.

06-07-2021, 12:55 PM	#3
Tom Goldman VIP Member Join Date: Jan 2003 Location: Allentown,PA Posts: 2,454 Likes: 824 Liked 776 Times in 221 Posts	Re: Throttle stop carb adjustment Fuel and timing would be the first place to look . especially if you use a grid and pull timing out on the stop . cylinder pressure skyrockets up and can kill bearings [and cranks]. and yes that knowledge is from personal experience. That said , the carb is way too big for a 540. again ,I speak from experience . I've had 1050's 1150's 1250's on 1000hp 565's and found the 1050 to be the best all around for the Stinnett under carb stop I run. All of the above carbs were from name shops and all ran lean when on the stop. I recently put on a 1050 carb from ATM Innovations . It is the first carb to not go dead lean on the stop, pulls great off the stop with no lag in rpm gain and has a great fuel curve for the entire run. and I lost no MPH over the 1150. Plus they were great people to deal with . __________________ Tom Goldman 1500 SG , 1506 STK

06-07-2021, 09:44 PM	#4
EVIL CLOWN Junior Member Join Date: Jan 2009 Posts: 34 Likes: 0 Liked 1 Time in 1 Post	Re: Throttle stop carb adjustment The carbs that I run are done by CFm and book very good carbs to big for stop racing irk very well off stop I know these guys don’t do stop carbs just looking to adjust what I have I run vp c 14 fuel trying to see if anyone knows when they go lean on the stop is what I’m thinking but what do I know need to put a 1050 on it in the future timing is 37 degrees and we don’t pull any timing out on the run motor runs 8.40s in 3080 lb car makes 1004 on dyno

06-08-2021, 08:30 PM	#6
EVIL CLOWN Junior Member Join Date: Jan 2009 Posts: 34 Likes: 0 Liked 1 Time in 1 Post	Re: Throttle stop carb adjustment The plugs are showing signs thanks fo your help probably going to run no stop until I get some o2 s going to call some carb guys this week that do carbs for stop racing don’t know if I will get anywhere then send me your carb or I can sell you one I’d like to put a stunner 1050 on it but not buying one now

06-10-2021, 08:11 AM	#8
Charlie Yannetti Senior Member Join Date: Jan 2005 Location: Alpine, NJ Posts: 564 Likes: 184 Liked 185 Times in 81 Posts	Re: Throttle stop carb adjustment I'm running a 1250 by DC Carbs on my 565, but I have a bit more HP than you, and my car is almost 1000 lbs lighter than yours.. I just don't have Tom's compression at 14.5 to 1.. on the stop my O2's get to about 13.9 to 14.1 or so.. I also changed from VP C-14+ to VP X-14 with positive results... no tuning changes, and picked up 1 MPH.. I have also been told by many that 1250 is un-necessary on my combination, and that a 1050 or 1150 would probably work better.. next test and tune, I'm going to back to back my 1250 with the renovated 1150 from my 522 motor.. bigger isn't always better, but some carb builders go by HP numbers.. at 1004 HP, I would say that 1250 is not for you, especially at 3000 lbs.. Running lean while on the stop is kinda the norm, but if you're banging bearings, and possibly hurting the crank, I'm not thinking that running lean for 2 to 3 seconds is your problem.. but that's just me..