View Full Version : Dyno vs Demon

05-04-2012, 10:17 PM
Has anyone got any experience with Barry Grant Demon carbs? We were running the engine on the dyno to day when it developed a backfire through the carb. We switched carb and distributor/coil system. Smooth running. Put my distributor/coil back in with shop carb, smooth running. Dropped my demon back on and backfire again.
Tomorrow gonna pull carb apart clean and take back to dyno. Carb is new min hours. It did suffer the bad fuel issue though. Any suggestions with the carb would be appreciated.

05-04-2012, 10:30 PM
Guess your still workin out the kinks....Good luck.


05-05-2012, 08:48 AM
I agree with Mr Fixall. Check your float bowl adjustments. You also may need to adjust your accelerator pump to make sure you're getting a good pump shot when you give it gas. It also may be a bit lean. They are set up like a Holley and pretty simple to tune. Some Demons had issues with some metal shavings getting caught up in the small passages of the metering blocks from the machining process. I had that issue with mine right out of the box. You also may have blown the power valve with the backfire. I have a Speed Demon 650 with mechanical secondaries in my 61 Corvette. May be the best carb I have ever had. Once it's setup properly you may never need to fool with it again.

05-08-2012, 08:01 AM
also... which one do you have? I had a Mighty Marine Demon and loved it. Took minimal time to go through the setup process and it ran great. I loved the starting, after installing the BG and a new electric fuel pump it started like it had EFI.

I have heard of people having to clean out new ones though, and I'm sure the fuel didn't help. My guess is after you clean it you'll be good to go.

05-08-2012, 05:09 PM
Soon... A guy with a few of these convinced me.

http://ts1.mm.bing.net/images/thumbnail.aspx?q=4796658670634056&id=07022c4ed1e7923e1cbac828844a3b43 (http://www.donzi.net/images/view;_ylt=A0PDoYBbi6lPtiYARVWJzbkF;_ylu=X3oDMTBlMT Q4cGxyBHNlYwNzcgRzbGsDaW1n?back=http%3A%2F%2Fimage s.search.yahoo.com%2Fsearch%2Fimages%3Fp%3Dnhra%2B wallys%26fr%3Dchr-yie8%26fr2%3Dpiv-web%26tab%3Dorganic%26ri%3D46&w=182&h=400&imgurl=www.racesgmp.com%2Fskins%2Fuserfiles%2Fimag e%2FRandom%2520Site%2520Images%2FWally%2520Trophy. jpg&rurl=http%3A%2F%2Fwww.racesgmp.com%2Fschedule-dragstrip-detail.da%3Fid%3D53&size=32.8+KB&name=wally+up+for+grabs+the+nhra+king+of+the+track +championship+bonus+...&p=nhra+wallys&oid=c8c238413049557a007f8dabe7009773&fr2=piv-web&fr=chr-yie8&tt=wally%2Bup%2Bfor%2Bgrabs%2Bthe%2Bnhra%2Bking%2B of%2Bthe%2Btrack%2Bchampionship%2Bbonus%2B...&b=31&ni=96&no=46&ts=&tab=organic&sigr=11qvjkk1v&sigb=134s6oubd&sigi=12gjs32at&.crumb=9gCGqBq3ccS)

05-08-2012, 06:05 PM
What carb are you swapping the Barry Grant Demon for ?

Holley is OK, and the old performance standby~~~

But I prefer the Edelbrock Performer marine units built by Webber for Edelbrock.
It's basically an updated modern clone of the great old 1960-70s Carter AFB/AVS carbs.
These carbs have NO power valves to blow-out, they instead use piston operated main jet step-up enrichmen rods.
They also use a plunger pump with leather, or rubber pump cup washer~~~so also no rubber diaphram acceleration pump diaphrams to rot out.
The electric chokes are great also.
I had one on my 454 skiboat for 15 years with NO problem issues at all .

05-08-2012, 09:29 PM
+1 on the Edelbrock. Plug and play...

05-09-2012, 07:46 AM
Holley 650 HP. I got quite an education on carbs. Edelbrook and Holley almost played out the same. The Holley was there for purchase so I got it.