holley stumble on WOT - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 32 (permalink) Old Sep 6th, 09, 10:06 PM Thread Starter
Senior Tech
Ashlee and Andy
 
Join Date: Dec 2008
Location: Indiana
Posts: 178
holley stumble on WOT

I've spent a few days trying to get my motor to not have the WOT stumble, if I go from idle to wot it happens any other time it doesn't. with the hood open and blipping the throttle it seems like it wants to missfire engine shakes and then it'll get started again, idle mixture is set, 30cc accell pump shot, tried both the 26 and 32 numbered squirters.

At idle vacuum is around sixteen, the power valve is brand new and a 9.5, I also have an 8.5, timing is locked down to 8 deg initial.


My engine specs, 355 with vortec heads 9.5:1, 600 cfm holley
ap68 is offline  
Sponsored Links
Advertisement
 
post #2 of 32 (permalink) Old Sep 6th, 09, 10:37 PM
Senior Tech
Gary
 
Join Date: Mar 2009
Location: Auburn, CA
Posts: 439
Re: holley stumble on WOT

Make sure the "pump shot" is happening as soon as the throttle is cracked. If it isn't, you can change the pump cam profile by purchasing a kit for around $25. The blue cam cured my stumbling problems. Also, transition slot adjustment is critical too.

Gary
Gar's67 is offline  
post #3 of 32 (permalink) Old Sep 6th, 09, 11:23 PM Thread Starter
Senior Tech
Ashlee and Andy
 
Join Date: Dec 2008
Location: Indiana
Posts: 178
Re: holley stumble on WOT

I'll re adjust and check might need the bigger nozzle back on? and no kickdown cable installed
ap68 is offline  
 
post #4 of 32 (permalink) Old Sep 7th, 09, 07:14 AM
Senior Tech
 
Join Date: Apr 2008
Location: Illinois
Posts: 614
Re: holley stumble on WOT

What is the total timing set at? May need to play with distributor curve. Try 14 initial with 34-36 total all in by 3000 rpm.
markw is offline  
post #5 of 32 (permalink) Old Sep 7th, 09, 03:40 PM
Senior Tech
Ron
 
Join Date: Nov 2006
Location: North Channel Lake Huron
Posts: 3,934
Re: holley stumble on WOT

If it's not a vacuum problem and you have spark it's probably fuel delivery, anything from a pin hole in the gas line, insufficient gas line diameter, fuel pump, dirty filters, float level, jets or accelerator pumps ... etc

Z15CAM - There was a Viper in my Rear View
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

This was my 70 1/2 Z28

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Z15CAM is offline  
post #6 of 32 (permalink) Old Sep 7th, 09, 03:49 PM
Senior Tech
Todd
 
Join Date: Aug 2006
Location: Henderson, NV
Posts: 1,664
Re: holley stumble on WOT

With that much vaccum you may very well be introducing to much fuel with the accelerator pump. The reason a carburetor has an accelerator pump is to make up for that split second of lower vaccum when you open the venturis. I'd try a smaller squirter yet on both sides.
Vegas69 is offline  
post #7 of 32 (permalink) Old Sep 8th, 09, 07:05 PM Thread Starter
Senior Tech
Ashlee and Andy
 
Join Date: Dec 2008
Location: Indiana
Posts: 178
Re: holley stumble on WOT

well, here's my results so far, jetted carb down a little bit still just above the stock 66 jet size, have a slightly more aggressive accelerator cam in place. drove the car to work and back and had slightly better results, still had a stumble tho.

I've had a slightly annoying exhaust leak sound for the whole break in time that has been getting on my nerves, almost like a header leak, I ran a new exhaust on the car at work on saturday and did new header gaskets on monday. I still had an annoying header leak sound, I double checked the lash on the car a few weeks ago and only did the drivers side, passenger side had a loose valve when I just checked it.

I'm hoping this improves my performance a bit more
ap68 is offline  
post #8 of 32 (permalink) Old Sep 8th, 09, 07:24 PM
Gold Lifetime Member
Jim
 
jimbo68's Avatar
 
Join Date: Jul 2009
Location: California
Posts: 108
Garage
Re: holley stumble on WOT

As a general rule, the more the load that the engine see's off the line the more pump shot that is needed in rate and volume to cover the launch. Example: A car with a 3000 stall converter needs less fuel off the line then a car with a 1800 stall converter. In most cases a bog at WOT is caused by fuel starvation not flooding. I suggest try bigger nozzles and if needed place a 50cc pump on the primary side with a sharp nosed cam. This will ensure you get enough fuel for a WOT slam until the primary circuit kicks in. I used a pink cam in #2 position with large nozzles and this fixed my WOT issues. Good luck!
jimbo68 is offline  
post #9 of 32 (permalink) Old Sep 8th, 09, 07:31 PM
Gold Lifetime Member
Jim
 
jimbo68's Avatar
 
Join Date: Jul 2009
Location: California
Posts: 108
Garage
Re: holley stumble on WOT

Ap68, Funny as it sound spectre makes a very thick header gasket for cheap. My hookers super comps were also a problem at first. I actually ended up cutting in between each outlet to allow the header to seat better against the head then having one long solid piece. Do this as a last resort, but look for a thicker gauge gasket. Make sure to warm up the re-tighten again. Drive a while let it cool and re-tighten again. It may take 3 or 4 heat ups and torkings to get a good seal!
jimbo68 is offline  
post #10 of 32 (permalink) Old Sep 8th, 09, 07:40 PM Thread Starter
Senior Tech
Ashlee and Andy
 
Join Date: Dec 2008
Location: Indiana
Posts: 178
Re: holley stumble on WOT

funny thing is so far I'm settling for a pink cam in the number 2 position, I've got a number 36 (or 32, i don't remember which) nozzle on the car at the moment.

I'm just using the cheap mr. gasket header gaskets right now (work got me a good deal, $4 for the pair) they're not to thin probably 1/8" thick or so, sealed for now at least.
ap68 is offline  
post #11 of 32 (permalink) Old Sep 8th, 09, 10:33 PM
Senior Tech
Steiner
 
Join Date: Mar 2009
Location: Lyman, SC
Posts: 8,348
Re: holley stumble on WOT

Quote:
Originally Posted by markw View Post
What is the total timing set at? May need to play with distributor curve. Try 14 initial with 34-36 total all in by 3000 rpm.
I'll second what Mark said once you get the carb straightened out if that's the problem. Most weight sets and regular stops I've seen only have 20 degrees of advance with some of the brands like Summit only having 15 degrees. If yours are like most, with 8 degrees initial you're shorting yourself out of some power. I can't even get my car to start with less than 12 degrees initial for some reason, and run it at 14-16 for the timing advance to hit where I want it.

With more advance, you'll probably be able to back down on your idle screw as well.

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
500hp/538lbft

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

'69 Camaro Beater-SFT 327-M20-Moser 4.10-sold
'02 Z/28 vert-stock-sold and totaled
Steiner is offline  
post #12 of 32 (permalink) Old Sep 9th, 09, 07:02 PM Thread Starter
Senior Tech
Ashlee and Andy
 
Join Date: Dec 2008
Location: Indiana
Posts: 178
Re: holley stumble on WOT

well, I'm only idling at around 600 rpm in gear, 700 out of it. Well, little update around 2000 rpm, maybe more like 2250 rpm my air fuel gauge gets dangerously lean... like um, the lights went down to the red then went out, and the car began to surge and have a lean misfire.

I'm guessing this means I have to jet the carb up? this isn't accel shot related anymore is it?
ap68 is offline  
post #13 of 32 (permalink) Old Sep 9th, 09, 08:23 PM
Senior Tech
Todd
 
Join Date: Aug 2006
Location: Henderson, NV
Posts: 1,664
Re: holley stumble on WOT

Have you set the float levels? If it's a steady cruise and your float levels and fuel pressure is adequate, you need larger primary jets.
Vegas69 is offline  
post #14 of 32 (permalink) Old Sep 9th, 09, 08:33 PM Thread Starter
Senior Tech
Ashlee and Andy
 
Join Date: Dec 2008
Location: Indiana
Posts: 178
Re: holley stumble on WOT

alright that's what I was figuring, I reset float level, only got as far as pulling the sight plugs and rocking the car.

I'll pop in larger jets and see if that helps
ap68 is offline  
post #15 of 32 (permalink) Old Sep 9th, 09, 08:52 PM
Senior Tech
Todd
 
Join Date: Aug 2006
Location: Henderson, NV
Posts: 1,664
Re: holley stumble on WOT

Look for a vacuum leak as well.
Vegas69 is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Team Camaro Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.



Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome