I checked the linkage multiple times, it is not binding.
I'll test for intake leak next.

Idling up high, running hot and dieseling when you shut it off sounds like vacuum leak.

I do not have any experience with the Predator carbs but that could be your problem to.

quote:

Originally posted by truckman:

The biggest problem came when I got back to the pits. The motor would not idle down, stayed at 2500 or so, temp was right around 210 which is normal for an LS.
When I tried to kill it, it dieseled a ton before stopping.
At this point I've spent a lot of time tweaking the Predator carb and it may be time to give it up.
I'm looking for a Holley or something I can run one time to see if that's my problem.

If I remember correctly from so long ago, it seems there were many who had idle problems with those carbs. Among many other things. In any event it is adding another unnecessary variable that a normal carburetor should take away.

After I check for vacuum leaks, I'll try to borrow a normal 4 barrel to try. If that works, I know what my next step is.

On the plus side, the car went straight, would've been a pretty good run if not for my bad reaction.

Practice makes perfect. Ther's no such thing as too much seat time.

Update. I dumped the Predator, got a Holley Ultra, 4-barrel double pumper.
Starts and idles MUCH MUCH better.
I have a stumble at initial throttle hit, found the nozzles were in opposite of how they should be, 31 front 28 back. Reversed those and it got a little better. Also the spring on the forward accelerator arm was collapsing instead of pushing the arm down. A couple washers increased the tension and now I get a good squirt of fuel. I moved the cam screws to position 2.
I still have the stumble so I'm getting bigger nozzles. Can't run this Saturday and it looks like rain Sunday so may have to wait a week to see how it does.

quote:

Originally posted by truckman:
Update. I dumped the Predator, got a Holley Ultra, 4-barrel double pumper.
Starts and idles MUCH MUCH better.
I have a stumble at initial throttle hit, found the nozzles were in opposite of how they should be, 31 front 28 back. Reversed those and it got a little better. Also the spring on the forward accelerator arm was collapsing instead of pushing the arm down. A couple washers increased the tension and now I get a good squirt of fuel. I moved the cam screws to position 2.
I still have the stumble so I'm getting bigger nozzles. Can't run this Saturday and it looks like rain Sunday so may have to wait a week to see how it does.

On the carb blow out the air bleeds with carb cleaner. When you blow them out you are looking and listening for them to flow though cleanly.
Verify float level, if it is low then it is leaner. If it still stumbles, open up your idle mixture some and see if that helps. If it does then continue adding more fuel with nozzles.

quote:

Originally posted by truckman:
Update. I dumped the Predator, got a Holley Ultra, 4-barrel double pumper.
Starts and idles MUCH MUCH better.
I have a stumble at initial throttle hit, found the nozzles were in opposite of how they should be, 31 front 28 back. Reversed those and it got a little better. Also the spring on the forward accelerator arm was collapsing instead of pushing the arm down. A couple washers increased the tension and now I get a good squirt of fuel. I moved the cam screws to position 2.
I still have the stumble so I'm getting bigger nozzles. Can't run this Saturday and it looks like rain Sunday so may have to wait a week to see how it does.

It would be helpful if you provided the size of the carburetor & if it's new or used?

Don't rule out power valve to help with the issue.

2BKING

quote:

Originally posted by truckman:
Update. I dumped the Predator, got a Holley Ultra, 4-barrel double pumper.
Starts and idles MUCH MUCH better.
I have a stumble at initial throttle hit, found the nozzles were in opposite of how they should be, 31 front 28 back. Reversed those and it got a little better. Also the spring on the forward accelerator arm was collapsing instead of pushing the arm down. A couple washers increased the tension and now I get a good squirt of fuel. I moved the cam screws to position 2.
I still have the stumble so I'm getting bigger nozzles. Can't run this Saturday and it looks like rain Sunday so may have to wait a week to see how it does.

Glad to hear you have things heading in the right direction. If you do need different size nozzles I would suggest looking into the new style from BLP. They have two exit holes on each side that squirt at different angles. One toward the booster and one lower. I started using them and they work really well. I was able to decrease the size of nozzle on my alcohol carb.

https://blp.com/product/billet...p-discharge-nozzles/

quote:

Originally posted by Curly1:

quote:

Originally posted by truckman:
Update. I dumped the Predator, got a Holley Ultra, 4-barrel double pumper.
Starts and idles MUCH MUCH better.
I have a stumble at initial throttle hit, found the nozzles were in opposite of how they should be, 31 front 28 back. Reversed those and it got a little better. Also the spring on the forward accelerator arm was collapsing instead of pushing the arm down. A couple washers increased the tension and now I get a good squirt of fuel. I moved the cam screws to position 2.
I still have the stumble so I'm getting bigger nozzles. Can't run this Saturday and it looks like rain Sunday so may have to wait a week to see how it does.

On the carb blow out the air bleeds with carb cleaner. When you blow them out you are looking and listening for them to flow though cleanly.
Verify float level, if it is low then it is leaner. If it still stumbles, open up your idle mixture some and see if that helps. If it does then continue adding more fuel with nozzles.

Good idea, I'll do that.

quote:

Originally posted by B KING:

quote:

Originally posted by truckman:
Update. I dumped the Predator, got a Holley Ultra, 4-barrel double pumper.
Starts and idles MUCH MUCH better.
I have a stumble at initial throttle hit, found the nozzles were in opposite of how they should be, 31 front 28 back. Reversed those and it got a little better. Also the spring on the forward accelerator arm was collapsing instead of pushing the arm down. A couple washers increased the tension and now I get a good squirt of fuel. I moved the cam screws to position 2.
I still have the stumble so I'm getting bigger nozzles. Can't run this Saturday and it looks like rain Sunday so may have to wait a week to see how it does.

It would be helpful if you provided the size of the carburetor & if it's new or used?

Don't rule out power valve to help with the issue.

2BKING

Sorry 750. Lightly used, allegedly it was too big for the first motor it was on and too small for the second motor.

quote:

Originally posted by CURTIS REED:

quote:

Originally posted by truckman:
Update. I dumped the Predator, got a Holley Ultra, 4-barrel double pumper.
Starts and idles MUCH MUCH better.
I have a stumble at initial throttle hit, found the nozzles were in opposite of how they should be, 31 front 28 back. Reversed those and it got a little better. Also the spring on the forward accelerator arm was collapsing instead of pushing the arm down. A couple washers increased the tension and now I get a good squirt of fuel. I moved the cam screws to position 2.
I still have the stumble so I'm getting bigger nozzles. Can't run this Saturday and it looks like rain Sunday so may have to wait a week to see how it does.

Glad to hear you have things heading in the right direction. If you do need different size nozzles I would suggest looking into the new style from BLP. They have two exit holes on each side that squirt at different angles. One toward the booster and one lower. I started using them and they work really well. I was able to decrease the size of nozzle on my alcohol carb.

https://blp.com/product/billet...p-discharge-nozzles/

Those are pretty cool, i may have to get some.

If you have the carburetor off take a look at the transfer slots, the butterfly of the carb should have them squared. If the front is open too far and the back is completely closed adjust the backs. It's common for the idle to be turned high to compensate for a cam and the primarys are running on the transition circuit. This will cause a bog or hesitation. Also understand how the accelerator pump springs work and why they are there. There is an adjustment procedure and if you make them too tight you can rupture the diaphram. Larger squirters can help but I've had to change the pump cams also to cure a bog on a footbrake car. Again if you change the cam you have to re-adjust the spring length on the arms of the acc. pump.

Carb is on but takes only a minute to remove. I will check the slots, thank you for that info.
I used a small flat washer and a small lock washer to get more tension on the spring, I'll remove the lock washer, in case it's too much. Or just replace the spring. Trouble is there's no speed shops locally anymore so anything like that I need has to be ordered online and wait, or drive 3 hours to Summit.
I need to replace the fuel bowl gaskets, and I have a minor fuel leak on the secondary acc. pump.
I may have to replace that diaphragm.
Not a footbrake car, has transbrake. I think I said that I moved the cam screws to the #2 hole, I know there's different colored cams, with different profiles, I might end up adjusting those.
I've been doing as much research as I can but getting advice from people who've done it is really valuable.
Thank you.

If you're transbraking the acc. pump just has to get you on the 2 step. The springs on the arms are made to collapse a little, that is how the system works. Have someone hold the throttle wide open. While it's wide open push down on the little lever that the spring pushes on and using a feeler gauge you should have .015 clearance. Adjust the bolts in the center of the spring to set the clearance. Just from experience when tightening anything on a Holley style carb be careful about pulling the threads. It's simple to helicoil the threads for the bowls but the squirters are a different story.it turns into machine shop work.

OK, next installment;
I've got the carb tuned pretty well using a vacuum guage, still a little stumble off idle but as stated it doesn't really affect launch.
Got to run the whole day at the local track, here's results.
1st run;
1.02 reaction
1.80 60'
7.65 et
84.69 mph.
Flubbed the burnout, pulled up to the lights late, other car left and I had to wait for the next run.

2nd run;
.64 reaction
1.87 60'
7.58 et
90.53 mph.
a bit better, felt good.

3rd run;
.52 reaction
1.89 60'
7.50 et
93.79 mph
The car seemed to be running good, no high idle on return as before, and cooled with electric water pump and fan pretty fast.

4th run;
This was the start of the Gamblers, I posted a 7.48 which I now know was too low. first round and I ended up against one of the best guys there with a 5.40 dial.
.52 reaction to a .53
1.91 60' to a 1.19
7.55 et to a 5.44
101.52 to a 110.83
lost by .011
I felt pretty good about being that close.

Bought back in and redlighted by .55, I should have won that race, he was .11 off dial in (8.04), I was only off .07. (7.48)
.456 reaction to a .687
1.89 60' to a 1.87
7.55 et to a 8.15
93.13 to a 85.42.

On advice from another racer I was deep staging, that seemed to help, but maybe I got a little too deep on that last run.

So all in all I learned a lot, didn't break anything or crash.

I did get the car on the scales and evened out the weight as close as I could by adding weight to the right rear, about 735 each side, but I'm 775 on the fronts, I would like to get rid of some of that.

A new friend offered to video me and the car lifts a little in the front but seems to stay pretty flat in back. I'm not sure if I can figure out how to post the video but I'll try.

I did have some problems with the burnout, I think I need to bleed the front brakes.

If you have any stumble it will kill your reaction times. Usually if it stumbles or spits it is lean, add more fuel. I would start by just fattening up idle mixture to give you an idea if it is rich or lean. If fattening it up helps then larger squirter nozzles and work with plastic squirter cams then lean idle mixture back down some. Too rich it will be a little sluggish but usually problem is lean off idle. Also off idle stumble could be float level a little low. One other thing any time you have a carb issue first thing I always do is blow out all of the air bleeds with carb cleaner until you can see and hear that they are open.

When you get all of that stumble out then your reaction times and 60 foot times should get better and more consistent. Your 60 foot times were from 1.80 to 1.91 way too much and that effects ET all way down the track. With that much 60 variance are you sure you are not spinning?

As for Deep staging I never do that because say if you have 10 inches of roll out and you bump in 8 inches one time and 3 the next time then you can never be consistent. I always shallow stage and barely light up the bulb. Then if reaction time is slow I add RPM and tire pressure.

For right now I would not even worry about reaction times. If it was me I would shallow stage same every time to try to be consistent (what ever it is) and then try to get car working. Once you have car consistent you can start working on getting reaction times lower.

Bracket racing is all about consistency and predicting what car will do in weather and track conditions. So first things first I want the driver and car to do same thing run after run then you start making improvements as needed. And each of those changes should have predictable results.

Thanks. I'm up to a 37 nozzle in the front, I had to put the 35 in the back because that's the next biggest I had. I don't have any other cams right now but it's a red one in there.
The motor is a mild 6.0 LS with a Summit stage 2 cam and Wiseco pistons.
Car is a Camaro with a 4 link, 'glide, 5:23 gears, at about 3k#.
Running a MSD 6014 on the truck HO setting.
Vacuum shows about 13-14.
Ethanol free 90 octane gas.
Should I add octane booster, switch to 93 octane, or find some VP fuel?
Float level is right in the middle of the sight glass.
It's a t-brake car so I'm launching after the acc pump circuit, I assumed that would be ok, but I still need to work on it.
I did clear the bleeds.
The video shows very little tire slippage, running 13.5 psi.

What size rear slicks? if they are 10.5's then 13.5 is a good pressure to start from. You say you 4 linked the car and with slicks and your 60' times there shouldn't be any inconsistency from traction on a prepped track.
If deep staging just take small bumps to turn the top bulb off, same technique as shallow staging. Your 60'times seem to indicate inconsistent staging depth. Also pay attention to engine temp pulling out, after burnout and staging. Big inconsistency in MPH.