Summerfun

......Running 16 at idle and 14,5 + any other time

Jetting time.

Maine Vette

What's your setup? How difficult was the install?

Summerfun

I have a NGK powerdex AFX.
BBC 540 ci. with Vortech centrifugal supercharger, side exhaust, Holley4150 pro series Carb 1000cfm, MSD 6AL. NGK BCPR7EIX Iridium plugs into Dart Pro 1 345cc rect port open chamber aluminum heads

Welded the bung into the passenger side collector, connected the wires and that was all.

This thing has about 20 feet of wire for some reason.

I think I may be needing the Lars papers soon

lostpatrolman

Wow, that is extremely lean. Especially for a blown engine.

windsoreight

Would it be better to get a reading form both sides of the motor? I am getting ready to supercharge my small block and would like to be able to check both sides. Or does it matter?

Summerfun

It should be pretty close both sides unless there is an internal failure of sorts.


......and to lostpatrolman, lean, yes

GrandSportC3

Wow, that's lean! You will need to go up at least 4 jet sizes on primary and secondary side as a starting point!

MotorHead

I would play with the idle mixture screws first before jetting, that will bring your idle A/F down and also your cruise/light load A/F

norvalwilhelm

Look at this post. There are lots of links to some great articles on air fuel ratios and gages. A worthwhile post to look at.
http://www.digitalcorvettes.com/foru...ad.php?t=58020

norvalwilhelm

Look at this link. It is from the above link
http://www.mummbrothers.com/SRF_Stuf...e/Air_Fuel.htm

norvalwilhelm

I agree with motorhead. I run a blown bigblock and this spring I had to up my jetting working up 5 sizes to get the motor to run right but I dropped 4 mpg. Then I got the idea that maybe the motor which was idleing very lean would like a richer idle and a leaner top end.
I ended up richening the idle and that made low rpm cruising alot better and I was able to drop 7 seven sizes in the main jet, regain my lost 4 mpg and yet the motor runs better then ever.
Good point motorhead.

Simmo

Can you post pictures please centrifugal and bigblock is tight. What brackets?

gerry72

You have an exhaust leak that's introducing air into the exhaust. The car would be undriveable, if it could run at all, with that lean of an A/F ratio especially at idle.

Summerfun

I'll have new pics over the weekend.

I read the posts and played with the idle circuits.
She now idles and cruises below 2000 rpm's reading 13-14A/F

I also changed the squirters to 36 in front and 50 in the back
....used to be 31 and 36

For now I decided to leave the jets as she reads 12,5-14 under load at different rpm's

Lars was kind enough to e-mail me his papers on the Holley and on the BG......my spare carb is a Race Demon 975, so I may compare the 4150 pro series Holley 1000cfm to the BG carb.

....lots of playing for the weekend

Any and all input appreciated.
Thanks for those who already posted and thanks in anticipation to those who will. The info is great to widen ones spectrum of thoughts

Summerfun

Ran into a different problem today....

When I cruise in sixth gear and decide to go faster at some point I hit a brick wall.....around 4000 rpm I think (I was watching the road).

This only happens in sixth gear. Suddenly it feels like the engine just shuts down as I get deeper into the gas. It literally puts me forward into the seat. I get out of the gas, pump it, it backfires and keeps going. I kept driving without any trouble at lower rpm's

I did it a second time, and when I hit 'the wall' I got onto the gas harder. Suddenly it blew 'steam' and some fibers out of the supercharger intake filter. ......it would seem that it backfired through the carb is the only sense that I can make out of it.

This must mean that either
1)My timing is off
or
2)The carb jets are too big and overcompensating for rpm's that come up slower in sixth gear ??

I'm using an MSD master timing retard that is set a 2.....retarding timing 2 degrees for every 1000 rpm's. The timing is set at 36 degrees at 3000 rpm's.

I will set the button to 1 and if that doesn't work I will change the jets to smaller ones.

My reasoning somehow feels flawed to me.......

big_G

I thing you are losing your fuel supply at full throttle. Gauge time...

Summerfun

I have a Barry Grant 220GPH electric fuel pump with a regulator set at 7psi. Should never run that thing dry!!!

big_G

Are you running a blow-thru carb.?...Is the fuel pressure regulator boost-referenced?

Summerfun

Vortech carb box with carb inside.....yes

Hmmm, the regulator is an old unit that I used before with a prior mechanical fuel pump before I changed to the BG electric pump.
I presumed that the BG will keep pressure at 7psi all the time and I would not need higher pressure under boost.

Anyway I do have an Aeromotive boost reference regulator that I will install to see if it makes a difference.

big_G

Your fuel pump will need to have a capacity of (max. boost + 5 to 7 psi). The regulator will compensate (add) fuel pressure 1 to 1 ratio to off-set the boost, which is trying to off-set the fuel pressure in the fuel bowls.