flames at idle?

blown sbc. BV leak 78% 5lb check 1800rpm 20amp mag. set at 33* checked TDC pointer., running VP M5 fuel. at ilde it pops and flames at idle. bring it off ilde and it stops?? pipes are not overly wet eather. seems like it will pick a bank eather left or right at a tiime, then sometimes both..after a burnout at night it looks like its on 95%.

 

Our injected sbc does the same thing, never a huge flame but always somthing at idle.

 

I'm jealous!

at night, my blown sbc will pop about 6" of fire out every once in a while. Sorta cool!

 

When I've had this its either a lean BV or my timing retards at idle, like too much cam end play or too much gear clearence.

 

I got wicked flames by accidentally using solid core spark plug wires....won't try that again as we also burned a hole in the carpet under the car....ya might wanna make sure you have resistor style wires...

 

Do you have a MSD mag?

 

Had the same issue with my blown bbc. Turns out it seems to have been a combp of a cam retarded too much and weak valve springs (not enough seat pressure). If your leakdown is right and everything else is normal then what you are seeing is combustion in the pipes or it still happening in the bore when the exhaust valve opens. Maybe it's not completing combustion before the ex. valve opens?

 

Flames

I would say the M5 could be a factor, late timing or water in fuel , Blower motors need 99.9% alky..IMO
Mark..

 

yes its a msd pro mag 20 with the 8106 points box. springs on the seat are 360lb. checked cam. its dead on with the cam card. it has done this with the crank trigger or off the mag...it allmost sounds like its opening the valve as its still buning,its got a pop to it for sure! at night its a 2 foot flame out the zoomies...other than a lean BV the only thing i can come up with is put some more timing in it? motor was ran with a mag 44 and was told never go past 35* but got a pro 20 when got the motor, hear of ppl sayin that with a mag44 they have to take timming out...if that true if goin backwards wouldnt you have to put timing back in?? just thinking outloud here....motor was ran dry no water for 2 min. in the shop. and the head temp was 165-175* thanks for the help

 

we had that happen a few weeks ago and changing the points box fixed it. if you have a spare, I'd suggest giving it a try

edit: If it was me, I wouldn't add any more timing. You may not be at the top end of how much timing you can handle, but you're nowhere near low enough to be putting flames out of the pipes (IMO)

 

i had that happen it looks cool but the motor was way fat and not enough timing

 

I'm surprised. Don't any of you guys do color tuning? What's that you ask?

Settle back, true story.
Way back before personal computers, data loggers and flow benches Disco was king and my first blown 8-71 alky digger had hat nozzles only. I could tell the cylinder balance was a little off and tended to chase my tail on it by conventional means.

Inspiration....or desperation struck one night. We took the car to the furthest extremes of the track where it was pitch black.. Turned the idle down a touch, backed the timing down a shade and fattened up the barrel valve. Got the flame deal going and it seemed obvious by the flames that there might be something to this insanity.
I kept changing nozzles up, down and around until I had all eight flames the same height and color.

Beside using up 25 gallons of alky what was it worth? 1.6 tenths, 3 mph.

Ya gotta love night racing.

Dave Koehler
http://www.koehlerinjection.com

 

2 things... barrel valve...and timing...