Help sorting out new GT/CA car.

bert powell · 08-04-2010, 10:07 PM

I have a GT/CA 84 camaro 402/340 that I just finished. Having trouble with it leaving the line. It runs 6.30s in the 1/8 with 4.10s 330ft. The issue is the 60 ft, can't get better than a 1.39. It should be low 1.30s in this heat. The engine made good power on the dyno and it seems to run fine past the 60 ft. I have more 4 link in it that it should required and have removed the limiters. It picks the front end up ~ 1 ft but with the setup should stand straight up. I sent the converter back to ATI and they loosened it up some but no difference. I have tried two different carb that we dynoed with. The thing I have noticed is on my playback tach the motor jumps to ~5400-5600 rpm and bounces ~200 rpm then takes off past the stall speed of 6200. I can't feel this in the car but it shows up on each run. The carbs have as large a pump shot you can get, could this be causing the stumble? It has been close to 100 degrees with a DA ~3000ft. Could it be going rich for a instant due to the pump shot? I have the spark plug boot on the vent. Would like to try the stock baffle on the secondaries but do not have one. Could the trans be doing this? Let me know your thoughts, would like to solve this before having to rering the motor, lol. I think it will run decent once I get this .010 in 60 ft. Thanks!

Alan Roehrich · 08-04-2010, 10:21 PM

Are you staging at a high idle and then flat footing it?

If so, can you try staging at WOT on a two step at around 2500-3000?

bert powell · 08-04-2010, 10:33 PM

Footbraking- tried 3000rpm and even 4000rpm. Do not have a 2 step currently, always heard they had there own set of issues to setup. Wanted to sort car out footbraking and then try a 2 step.

Alan Roehrich · 08-04-2010, 11:11 PM

I'm not saying it will solve the problem if you leave off of a two step.

Here's what I'm looking at. The carburetor is a Q-Jet, correct? If so, then this applies. If you are at WOT on a two step, there will be no pump shot, and you will have very little vacuum, so if the carburetor still has a power piston, spring, and metering rods on the primary side, they should be all the way up, or nearly all the way up, so the power circuit is already working. Some cars even get the secondary air door open on the two step, some don't.

So, leaving on a two step may allow the carburetor to function in the simplest way possible. If it happens to help the situation, it gives you a few things to look at. The same applies if it makes the problem worse. And if it changes nothing, you may want to look elsewhere.

bert powell · 08-05-2010, 08:18 AM

Will hook up the 2 step and try. I have another carb I am going to try first. Thanks!

08-04-2010, 10:07 PM	#1
bert powell Member Join Date: Jul 2002 Posts: 241 Likes: 35 Liked 33 Times in 11 Posts	Help sorting out new GT/CA car. I have a GT/CA 84 camaro 402/340 that I just finished. Having trouble with it leaving the line. It runs 6.30s in the 1/8 with 4.10s 330ft. The issue is the 60 ft, can't get better than a 1.39. It should be low 1.30s in this heat. The engine made good power on the dyno and it seems to run fine past the 60 ft. I have more 4 link in it that it should required and have removed the limiters. It picks the front end up ~ 1 ft but with the setup should stand straight up. I sent the converter back to ATI and they loosened it up some but no difference. I have tried two different carb that we dynoed with. The thing I have noticed is on my playback tach the motor jumps to ~5400-5600 rpm and bounces ~200 rpm then takes off past the stall speed of 6200. I can't feel this in the car but it shows up on each run. The carbs have as large a pump shot you can get, could this be causing the stumble? It has been close to 100 degrees with a DA ~3000ft. Could it be going rich for a instant due to the pump shot? I have the spark plug boot on the vent. Would like to try the stock baffle on the secondaries but do not have one. Could the trans be doing this? Let me know your thoughts, would like to solve this before having to rering the motor, lol. I think it will run decent once I get this .010 in 60 ft. Thanks!

08-04-2010, 10:21 PM	#2
Alan Roehrich VIP Member Join Date: May 2006 Location: Murfreesboro TN Posts: 4,930 Likes: 1,003 Liked 1,079 Times in 282 Posts	Re: Help sorting out new GT/CA car. Are you staging at a high idle and then flat footing it? If so, can you try staging at WOT on a two step at around 2500-3000? __________________ Alan Roehrich 212A G/S

08-04-2010, 10:33 PM	#3
bert powell Member Join Date: Jul 2002 Posts: 241 Likes: 35 Liked 33 Times in 11 Posts	Re: Help sorting out new GT/CA car. Footbraking- tried 3000rpm and even 4000rpm. Do not have a 2 step currently, always heard they had there own set of issues to setup. Wanted to sort car out footbraking and then try a 2 step.

08-04-2010, 11:11 PM	#4
Alan Roehrich VIP Member Join Date: May 2006 Location: Murfreesboro TN Posts: 4,930 Likes: 1,003 Liked 1,079 Times in 282 Posts	Re: Help sorting out new GT/CA car. I'm not saying it will solve the problem if you leave off of a two step. Here's what I'm looking at. The carburetor is a Q-Jet, correct? If so, then this applies. If you are at WOT on a two step, there will be no pump shot, and you will have very little vacuum, so if the carburetor still has a power piston, spring, and metering rods on the primary side, they should be all the way up, or nearly all the way up, so the power circuit is already working. Some cars even get the secondary air door open on the two step, some don't. So, leaving on a two step may allow the carburetor to function in the simplest way possible. If it happens to help the situation, it gives you a few things to look at. The same applies if it makes the problem worse. And if it changes nothing, you may want to look elsewhere. __________________ Alan Roehrich 212A G/S

08-05-2010, 08:18 AM	#5
bert powell Member Join Date: Jul 2002 Posts: 241 Likes: 35 Liked 33 Times in 11 Posts	Re: Help sorting out new GT/CA car. Will hook up the 2 step and try. I have another carb I am going to try first. Thanks!