|
04-17-2017, 09:25 AM | #1 |
Senior Member
Join Date: Aug 2004
Location: Jacksonville, Florida
Posts: 803
Likes: 6
Liked 20 Times in 12 Posts
|
Qjet Question
I am having a problem with my Q-jet on my footbrake street car and I could use some advice on how to fix it. I have a nova street car with a sbc/t350 combo that I drive and bracket race. It has a stock valve body with a shift kit and I use a Q-jet. I leave at 16-1700 and it flashes to around 25-2800 and it shifts on its own if left in drive or second. It runs low 12's to high 11's. The problem that I have just started to experience is if I have caught someone early in the run and try to pedal the car it starts to slow down like you took your foot off the gas! But it is on the floor. On this particular run I pedaled once at about 1000' and lost .30sec,12mph and lost the rd! The engine makes a different noise like it is straining but still running but just not pulling. Any idea what this might be in the carb? Could the secondary flap close and get stuck in the closed position? Any idea what this is and how to fix it? I have not modified the linkages at all, and only have done the usual things to rebuild and set it up to run on the car and leave clean without a bog etc. Any advice would be appreciated. Thank you
|
04-17-2017, 09:46 AM | #2 |
Member
Join Date: May 2009
Posts: 171
Likes: 35
Liked 47 Times in 25 Posts
|
Re: Qjet Question
Choke mechanism allowing choke plate to pop shut and, in turn not allowing secondaries to open when back on the throttle?
|
04-17-2017, 10:31 AM | #3 |
Senior Member
Join Date: Sep 2016
Posts: 838
Likes: 148
Liked 276 Times in 151 Posts
|
Re: Qjet Question
Check the rear flap. Maybe hanging shut somehow.
|
04-22-2017, 12:43 AM | #4 |
Senior Member
Join Date: Aug 2004
Location: Jacksonville, Florida
Posts: 803
Likes: 6
Liked 20 Times in 12 Posts
|
Re: Qjet Question
Thank you all for the suggestions. The choke is wired open and it does not serve any function. I will look and see if somehow the secondary flap is getting caught on something. Please keep any suggestions coming. Thank You.
|
04-22-2017, 07:51 AM | #5 | |
Member
Join Date: Sep 2009
Location: Dresden On. Canada
Posts: 460
Likes: 0
Liked 0 Times in 0 Posts
|
Re: Qjet Question
Quote:
Got this from Doug Roe' s book Rochester carburation H.P. Books ...Trevor |
|
04-22-2017, 08:57 AM | #6 |
Senior Member
Join Date: Sep 2016
Posts: 838
Likes: 148
Liked 276 Times in 151 Posts
|
Re: Qjet Question
Is your linkage reworked to the secondaries or still factory stock. If still stock, could the rear throttle blades somehow stick closed when you pedal?
|
04-22-2017, 12:15 PM | #7 |
Veteran Member
Join Date: Mar 2002
Location: Miles From Nowhere
Posts: 7,414
Likes: 2,581
Liked 4,447 Times in 1,693 Posts
|
Re: Qjet Question
Not sure of the exact problem here, but I would say to look at each possibility.
Start with the sec. flapper, and make sure it doesn't come anywhere near the top opening. You can loosen the screws and shift the plates around a bit, and then re-tighten. Or, just file the casting a little bit, where ever it's close. Of course, you wouldn't want to do this on a S/SS carb. I'm sure you know this.
__________________
We are lucky we don't get as much Government as we pay for..... Will Rogers |
04-22-2017, 01:35 PM | #8 |
Senior Member
Join Date: Sep 2016
Posts: 838
Likes: 148
Liked 276 Times in 151 Posts
|
Re: Qjet Question
Just remembered this. I once had the split pin that secures the cam for the hanger walk out slightly and that interfered with the flap.
|
04-22-2017, 02:41 PM | #9 |
VIP Member
Join Date: Dec 2002
Location: Lower Dakota territory
Posts: 1,166
Likes: 1,016
Liked 762 Times in 226 Posts
|
Re: Qjet Question
What's the float level measurement? And fuel pressure?
__________________
"That'll never work....." |
04-22-2017, 07:30 PM | #10 |
Junior Member
Join Date: Dec 2008
Posts: 26
Likes: 0
Liked 1 Time in 1 Post
|
Re: Qjet Question
Had this problem approx. 30 years ago. What happens is that when you shut the secondary throttle at high vacuum the pressure across the throttle blades holds them in place when you try to open them again especially if the bores are a little oxidized and the actuating lever is NOT PINNED TO THE SHAFT. The fix is to pin the throttle shaft to the actuating lever; do not rely on the torsion spring to open the throttle. A $.10 rollpin is most common fix.
|
|
|