secondies modification

[buick83-T]

Was wondering what carb hangers and secondary rods should i use to run 15 psi after I have modifided the secondaries to fully open. I have a h,i,j,k and stock M hangers and for the rods I only have CV other than the stock CP and then CH. Should I just run the H hanger and CV rods which would be the richest or do I need to go richer than that? What flow should the carb be when fully opening the secondary AV. Also has anyone added a carb spacer(1") and it fit well being it sitting so high?

Thanks

 

[Ttype83]

I was running K hanger w/CS rods with 14 psi boost and opening only to 75%

You want to use a long rod(CV) the CP is a medium and the CH is a short...what this means is the longer power tip start power misture earlier...@ 70% of opening....

With a long rod hanger selection isn't as important.
Quoted from Roe's book (sort of)pg 152.
Jim

 

[Freddie's Buick]

Although I don't have a turbo powered 3.8, I've tried that combo on my Q-Jet. The 'CV' rod and 'H' hanger combo is very good.

I myself was lucky to find an 'F' hanger in a boneyard and I used Edelbrock's Rochester 'CK' rods. Much richer.... great combo too.

I also use 'Mr.Gasket's' 1'' phenolic Q-Jet spacer. It makes it so much easier to work on my carb when I have to, (more clearance).

On a turbo car I'd be careful though.....I would assume that there's not much clearance there to begin with.

As far as flow goes, most Q-Jets advertise a 750 CFM flow rate. Truth is most flow much less then that, (although they are capable of flowing the rated 750 CFM). In order to bring up the flow rate to it's max advertised rating, the secoundary air valve has to be modified to open a full 90 degrees.

 

[bakerlaw67]

Scavenging blasts from the past!

I'm going to get my extra carb rebuilt next week. I should do it myself but I want someone else to blame (I haven't rebuilt a carb since the late '80s and it was on a '76 AMC Hornet 1 bbl!)

Anyway, I intend to get this one made more "efficient" (more powerful) and I would like to know if there's a consensus on which combination of rods and hangers to use.

Is there anything else I should have done while they have it? Carb gasket tips? Install tips? (Is it worth $75)

I need the low down boys - and girl(s)

 

[b4black]

I would be very willing to bet that at 15 psi, you're knocking up a storm (and you won't here it). It knocks, then pulls timing, then it's slower than it was at 9 psi.

IMO, you must have some sort of knock gauge before upping the boost. Going with the richest rods and hangers will help some, but 15 psi is a lot to ask. Even at 9 psi, you'll be surprise at how much timing is being retarded and you'll never feel it relying on your butt alone.

At 9 psi, stock timing and stock rods, I still see some knock on 93 octane. I need to play with the BTM to see if I can get to 12 with acceptable knock. After that, I'm looking at water injection.

 

[bakerlaw67]

Originally posted by b4black
I would be very willing to bet that at 15 psi, you're knocking up a storm (and you won't here it). It knocks, then pulls timing, then it's slower than it was at 9 psi.

Did I miss something here? I got a VDO boost gauge from a buddy for free, and its installation is on the list well ahead of the putting on the rebuilt carb. I'm still running the non-adj actuator so I'm not really sure what you're talking about.

 

[b4black]

I was referring to the very first line of this thread.

Originally posted by buick83-T
Was wondering what carb hangers and secondary rods should i use to run 15 psi after I have modifided the secondaries to fully open.

When tuning a carb for WOT, you'll need something to tune against. Tuning against O2 or EGT is nearly impossible if the ECM is pulling timing. Tuning against knock is the coarse adjustment. Then, with no knock, you can fine tune against EGT.

 

[Ttype83]

Originally posted by buick83-T
after I have modifided the secondaries to fully open. What flow should the carb be when fully opening the secondary AV. Also has anyone added a carb spacer(1") and it fit well being it sitting so high?

Sorry just catch this, Did not have the secondaries open ant more than stock. A couple of have tried this, you only need around 400CFM for this setup, any more and it boggs out.
1" space should fix fine.
Jim