Blower issue, part two

[GT63]

I'm still trying to figure out this blower. I finally got the correct instructions from Barry Grant after a good tongue lashing from me about sending the regular manual with the blower carbs. BG is useless when it comes to support. These blower carbs have a 1/16 NPT port under the primary bowl that is for sending a vacuum signal to the power valves. So I had to find two 1/16" NPT male to hose barb fittings. Nobody in town had them and I tried everybody including Stuart Hose in Lewisville, TX. I finally found two -3 AN male to 1/16" NPT male fittings and one of the hose barb fittings at a speed shop over in Fort Worth, so after some trial and error I got the vacuum line hooked up to the vacuum assisted power valves. I also re-curved the distributor so it is now 18 degrees all in at 2500, which is what MSD, Dyers and BDS recommended. I spent most of the afternoon trying to get it to idle. I've re-read both of my supercharger books and the Demon tuning books to make sure I was on the right track. I can get it to idle at around 1000 RPM with no lope, but as soon as I try to get it down below 1000 RPM it starts to surge. I've got the idle mixture screws on both sides of the carbs screwed out about 1 full turn. The timing is pretty close to 16 degrees. It seems to like having the vacuum advance hook up, so I have it connected for now. I think its about 2 to 4 degrees more advance. I'm not sure what to do now. I've got almost 20 Hg of vacuum when it idles at 1000 RPM. I noticed that my AHC coated zoomies were turning dark near the flange while I was trying to find the sweet spot. The temp gauge never went past 180 though. Im thinking about moving it from the back of the manifold to the front near the thermostat.
No matter what I try I cant get it to idle down without the blower lopesurge.
Any Ideas?

 

[RPM]

How much initial timing are you running at idle? I had a very simalar problem with mine, the headers were getting dark at the flanges. The guy that does the headers said this was from late ignition timimg. So I bumped the timing up from 8 to 18 and it made a world of difference in the way the engine runs. A LOT more low end power. This gives me a total timing of about 38 degrees. I use the MSD boost retard box and take out 1 degree for each lb of boost. Most of the time we are not going to see boost, probably less than 1% of the driving time will you see any boost. :funmeter2:

 

[GT63]

How much initial timing are you running at idle? I had a very simalar problem with mine, the headers were getting dark at the flanges. The guy that does the headers said this was from late ignition timimg. So I bumped the timing up from 8 to 18 and it made a world of difference in the way the engine runs. A LOT more low end power. This gives me a total timing of about 38 degrees. I use the MSD boost retard box and take out 1 degree for each lb of boost. Most of the time we are not going to see boost, probably less than 1% of the driving time will you see any boost. :funmeter2:

As best as I can tell initial timing is at 16 or 18 degrees. My MSD 6a iginition is giving my timing light fits. If I set the timing light on 0 I get an initial timing of 60 degrees, If I set it to 60, then I get an initial timing of 16 or 18 degrees. I'm guessing the multiple discharge is causing it to read incorrectly.

The engine starts right up so I know the timing is real close and I have max vacuum (18-19 Hg) where it is right now.

It still wants to die if I rap the throttle.

 

[Lee_in_KC]

I'm guessing the multiple discharge is causing it to read incorrectly.

Grant, I went through three timing lights trying to overcome the MSD effect. Finally sprung for one of MSD's lights, guaranteed to work with their ignitions. Works as advertised, but a little spendy.

I might have told you this before, but I have my 6-71 SBC set at 18 initial, 34 total, all in by 2800. It idles at about 800 with just a slight cam lope. I think I told you I can tune out the surge with the idle mixtures, although it ends up idling awfully rich.

 

[GT63]

Well I think I finally found the sweet spot. I've got 18 degrees initial with 18 degrees in the distributor all in at 28003000 for a total of 36. It still idles at 1000 RPM but it's smooth with only a little lope after it starts then it evens out in a few seconds. I'm gonna take it for spin a little later and see how she repsonds. It still wants to die if I rap it real quick. It starts real quick and sounds pretty good. Left idling for awhile and the temp went to 200 then came back down to 180 and seems to hover between 180 and 185.

 

[GT63]

Sent an email to BG. I gave then all the specifics I could and asked then about the engine trying to die when I open quickly open and close the butterflys (rap the throttle). They want to me to remove the carbs and check the butterfly opening from the bottom and make sure it's no more than .020 .

Edlebrocks are looking better day by day.

 

[RPM]

I have a BG on my other car. It is a POS!!!!

On the blower car I have Edelbrocks, followed their set up for a blower and it was right on the money.

 

[GT63]

I have a BG on my other car. It is a POS!!!!

On the blower car I have Edelbrocks, followed their set up for a blower and it was right on the money.

I was talking to the owner of a local Speedshop this past weekend while trying to find the fittings and he told me he won't sell BG unless the customer insists on them. He's found all kinds of things wrong with their carbs. He had one of their triple shooter kits he was installing for a customer and couldn't get it to run. Said he took apart the carbs and the center one wasn't drilled correctly in the metering plates. He told me BG support was useless too. Then he wished me luck with my set-up. :rofl:

If this last little adjustment doesn't help, the Demons will go on ebay and I'll switch to Edelbrocks.