Hood Scoop issues

SST159 · 09-10-2012, 12:03 PM

Anyone out there experience issues with air flow on hood scoops?
I changed my hood and scoop last fall and have been experiencing the motor popping during the run ever since.
Sometimes it occurs just on top end in the traps and sometimes at randam during the run. I pulled valve springs and they are good, plug wires are good, changed carb, changed fuel system (planned on doing that anyway). At one point I made a carb pan that sealed of most of the air with foam to the top of the scoop. That made improvements but still pops at random.
I tried taking the pan off totally and made a pass which it broke up so bad I had to abort the run. That tells me this issue pertains to the hood scoop and the way the air is hitting the carb. The only thing I did not try yet was an air filter which I would rather not use if I can avoid it. Any input or suggestions before I lose the rest of my hair?
Thanks in advance for your help.

FED 387 · 09-10-2012, 02:01 PM

sounds like its running out of air

Mark Schmidt · 09-10-2012, 02:43 PM

It's definitely going lean. If you don't have a computer, click it in the lights and pull a plug on the return road and richen it up if needed. A scoop makes a world of difference to a carburator.

Dave Steltz · 09-10-2012, 03:11 PM

Drew, with the Roadster I had some issues like this , especially when I went to the injection, go spend some money cheap guy, and get a UNI Filter...It made no change in power , but with straightening out the air flow made a world of difference...actually picked up a little MPH, vs air pans etc...
Same one that Ken and Tim run, check them out...

http://www.unifilter.com/online%20ca...utomotive.html

SST159 · 09-10-2012, 05:39 PM

I did not pull the plug deal because the EGT has been around 1350 which is not bad for my motor. I have gone up about 4 jet sizes over this race season and find no difference in performance. Perhaps I have gone the wrong way however the EGT was up in the 1400's until I increased the jet sizes.
Dave, (Dave Whoooo) I did look at Kenny's unifilter and actually thought the same thing but did not want to scar my cheap reputation and spend 170.00 on something that does not work. All kidding aside I am seriously thinking on buying one. Even if it does not fix the problem it cannot hurt to have an air filter. What I should do is make a pass without the hood on and see what that does.

nickh · 09-10-2012, 05:49 PM

Drew check your PM I am a UNI Dealer have them in stock. Questions call me 832-264-2478

Ed Sroka · 09-11-2012, 07:58 PM

I've performed CFD analysis on several scoop designs. Many with marginal results.

If you send me the details of the scoop, its position relative to the body/cage and let me know which scoop tray and carburetor you're using, I may be able to offer some feedback.

There are many concerns that exist here. It's likely a few scoop designs can cost in excess of 40 usable horsepower. The concerns with pressure and velocity begin externally and are exacerbated at the point of carburetor entry.

You can send a PM if you like.

I can provide information on the proper air filter choice as well.

SST159 · 09-12-2012, 11:04 PM

Ed,
Thanks for the help.
I will PM you with some info as soon as I can.
Thanks.

jmarkaudio · 09-17-2012, 03:04 PM

Try tying the vents together like the picture in the link. If the scoop upset the pressure at the bowl vents it can send it lean.

http://i287.photobucket.com/albums/l...udio/Flute.jpg

SST159 · 09-18-2012, 01:57 PM

yes, I did tie the vents together and it still pops. I am currently fabricating a full pan to totally seal off the scoop tight along with sealing off the open back of the scoop at the windsheild. hopefully I can get out to test next week. If that does not correct it then next step would be to try a filter. Problem is there are too many filter options to select from. What I cannot figure out is I see many racers run these hood scoops with no pan and wide open in the back and have no problems. Perhaps the air turbulance does not affect a dominator as it does the 4150. I think my car is pissed off at me for something. Bad enough when the wife gets pissed but when the race car does??? Thanks for the suggestions and still welcome any more if available.

09-10-2012, 12:03 PM	#1
SST159 Member Join Date: Jul 2005 Posts: 315 Likes: 5 Liked 20 Times in 16 Posts	Hood Scoop issues Anyone out there experience issues with air flow on hood scoops? I changed my hood and scoop last fall and have been experiencing the motor popping during the run ever since. Sometimes it occurs just on top end in the traps and sometimes at randam during the run. I pulled valve springs and they are good, plug wires are good, changed carb, changed fuel system (planned on doing that anyway). At one point I made a carb pan that sealed of most of the air with foam to the top of the scoop. That made improvements but still pops at random. I tried taking the pan off totally and made a pass which it broke up so bad I had to abort the run. That tells me this issue pertains to the hood scoop and the way the air is hitting the carb. The only thing I did not try yet was an air filter which I would rather not use if I can avoid it. Any input or suggestions before I lose the rest of my hair? Thanks in advance for your help. __________________ Drew Wonderly SST 159

09-10-2012, 02:01 PM	#2
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,416 Likes: 522 Liked 330 Times in 178 Posts	Re: Hood Scoop issues sounds like its running out of air

09-10-2012, 02:43 PM	#3
Mark Schmidt Member Join Date: Sep 2007 Posts: 273 Likes: 0 Liked 0 Times in 0 Posts	Re: Hood Scoop issues It's definitely going lean. If you don't have a computer, click it in the lights and pull a plug on the return road and richen it up if needed. A scoop makes a world of difference to a carburator. __________________ MDS Motorsports

09-10-2012, 03:11 PM	#4
Dave Steltz Member Join Date: Nov 2003 Posts: 323 Likes: 0 Liked 0 Times in 0 Posts	Re: Hood Scoop issues Drew, with the Roadster I had some issues like this , especially when I went to the injection, go spend some money cheap guy, and get a UNI Filter...It made no change in power , but with straightening out the air flow made a world of difference...actually picked up a little MPH, vs air pans etc... Same one that Ken and Tim run, check them out... http://www.unifilter.com/online%20ca...utomotive.html __________________ Dave Steltz 135G SG/SP/SST BIAECH Racing Team Last edited by Dave Steltz; 09-10-2012 at 03:12 PM. Reason: add url

09-10-2012, 05:39 PM	#5
SST159 Member Join Date: Jul 2005 Posts: 315 Likes: 5 Liked 20 Times in 16 Posts	Re: Hood Scoop issues I did not pull the plug deal because the EGT has been around 1350 which is not bad for my motor. I have gone up about 4 jet sizes over this race season and find no difference in performance. Perhaps I have gone the wrong way however the EGT was up in the 1400's until I increased the jet sizes. Dave, (Dave Whoooo) I did look at Kenny's unifilter and actually thought the same thing but did not want to scar my cheap reputation and spend 170.00 on something that does not work. All kidding aside I am seriously thinking on buying one. Even if it does not fix the problem it cannot hurt to have an air filter. What I should do is make a pass without the hood on and see what that does. __________________ Drew Wonderly SST 159

09-10-2012, 05:49 PM	#6
nickh Senior Member Join Date: Sep 2010 Location: Houston,Texas Posts: 819 Likes: 3,502 Liked 642 Times in 192 Posts	Re: Hood Scoop issues Drew check your PM I am a UNI Dealer have them in stock. Questions call me 832-264-2478

09-11-2012, 07:58 PM	#7
Ed Sroka Junior Member Join Date: Aug 2003 Location: Lake Zurich, IL Posts: 22 Likes: 0 Liked 1 Time in 1 Post	Re: Hood Scoop issues I've performed CFD analysis on several scoop designs. Many with marginal results. If you send me the details of the scoop, its position relative to the body/cage and let me know which scoop tray and carburetor you're using, I may be able to offer some feedback. There are many concerns that exist here. It's likely a few scoop designs can cost in excess of 40 usable horsepower. The concerns with pressure and velocity begin externally and are exacerbated at the point of carburetor entry. You can send a PM if you like. I can provide information on the proper air filter choice as well.

09-12-2012, 11:04 PM	#8
SST159 Member Join Date: Jul 2005 Posts: 315 Likes: 5 Liked 20 Times in 16 Posts	Re: Hood Scoop issues Ed, Thanks for the help. I will PM you with some info as soon as I can. Thanks. __________________ Drew Wonderly SST 159

09-17-2012, 03:04 PM	#9
jmarkaudio Junior Member Join Date: Apr 2008 Posts: 83 Likes: 0 Liked 0 Times in 0 Posts	Re: Hood Scoop issues Try tying the vents together like the picture in the link. If the scoop upset the pressure at the bowl vents it can send it lean. http://i287.photobucket.com/albums/l...udio/Flute.jpg

09-18-2012, 01:57 PM	#10
SST159 Member Join Date: Jul 2005 Posts: 315 Likes: 5 Liked 20 Times in 16 Posts	Re: Hood Scoop issues yes, I did tie the vents together and it still pops. I am currently fabricating a full pan to totally seal off the scoop tight along with sealing off the open back of the scoop at the windsheild. hopefully I can get out to test next week. If that does not correct it then next step would be to try a filter. Problem is there are too many filter options to select from. What I cannot figure out is I see many racers run these hood scoops with no pan and wide open in the back and have no problems. Perhaps the air turbulance does not affect a dominator as it does the 4150. I think my car is pissed off at me for something. Bad enough when the wife gets pissed but when the race car does??? Thanks for the suggestions and still welcome any more if available. __________________ Drew Wonderly SST 159