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Discussion Starter #1
I'm working on a 78 Firebird that has a Pontiac 400. The motor I would say is basically stock, except for a mild cam, Torker II intake and a Holley 600. Don't know much details about the motor.

The carb was leaking gas, so I rebuilt it and found that it was missing the secondary metering body plate, so I found one and installed it.

The car always had a rich smell, so I checked the vacuum signal and I was getting 14", so the 6.5 power valve should be ok. I set the idle mixture screws up to read the highest vacuum signal and they are both a 1/2 turn out. The main jets are 66's or 65's.

Float levels are good as well.

If I go down on main jet size, will that help with the richness?

I checked the plugs and they have a brownish tint to them, but didn't look to bad.

Any thoughts?

thanks
 

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Is it only at low speed that you seem to be rich? Screws only 1/2 turn out is awful low. As long as your timing is good, and basing it on the really low mixture adjustment that would lead me to beleive you are getting some uncontrolled fuel. Could be IFR have some gunk in them, ruptured PV or leaking PV gasket, warped metering block allowing fuel into vacuum chamber for PV..
Changing your main jet should not affect low speed or idle at all.
When you say there was no metering plate, was it just missing the steel shim?
 

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Discussion Starter #3
The steel shim was missing and I put in a new one, the metering plate was there. The power valve is new, all new gaskets, needle and seat assembly, everything. The only thing I didn't check or replace was the squirter.

Float levels are adjusted right below the site.

The car is rich all the time.

When I replaced those cork gaskets at the idle mixture screws, I turned them in all the way and back out 1-1/2 turns. I start the car, let it warm up, check my vacuum gauge and it was about 13", so as I turned in the mixture screws, the vacuum signal increase and the motor smooth out and I got my best vacuum reading, which was 14" with the mixture screws turned in, with only a half turn to go on both sides.

To me that doesn't seem right but it's at the highest vacuum signal adjusted like that.
 

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Just another data point, but I have the same engine that I put into a '73 Firebird body, I swapped to a 1969 pre-emissions Pontiac intake, and a '73 Pontiac Quadrajet carb. With that combo and an OEM blueprint cam (the 335hp 400 ci version) it ran mid-13's at over 3800 lbs. The Q-jets are more complicated to tune, but once you get it working well then it runs and idles great.
 

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Well you are either getting unmetered fuel or are going to have to play with air bleeds. I have had original metering blocks warp and not seal causing all kinds of havoc. Drain the carb good and pull the primary block out, check for fuel behind the power valve in the vacuum chamber. If you have fuel there I would check your block, gasket, valve etc.. really good. If it is good and dry, make sure that your air bleeds are clear, dont take much to restrict them and make things really fat.
 

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Discussion Starter #7
I think my next steps are to check and make sure the air bleeds are clean and open and then double check the secondary idle speed and make sure the transfer slots are not exposed to much.

How hard is it to drill the air bleeds larger?
 

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That intake that you are using isn't helping either,if the combo is that mild it would be better with a dual plane intake.If that is a typical Holley 600 vac secondary ,they always run rich,you would probably be better off with a good Q-jet.
 

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It really is not that hard, but take your time and make LITTLE adjustments if you end up down that road. Make sure if you need to drill them that you blow the ports out really good after, dont want any little filings in the air bleed port. Again, before you start drilling check to be sure the block is sealing to body properly and that the air ports are clear.
 

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Discussion Starter #10
If you saw this car, it was like someone just threw parts on this motor just to sell it. I would like to see him get rid of that Torker II and just use a Performer intake.
 

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I think my next steps are to check and make sure the air bleeds are clean and open and then double check the secondary idle speed and make sure the transfer slots are not exposed to much.

How hard is it to drill the air bleeds larger?

transfer slots..good point and make sure the secondary ( i call it the Z bar) is holding the secondary's closed.
 

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LOL. Yea I have never been a fan of the old Torker II, but I suppose back in its day it was ok. Of course if you get him to anny up to a better intake, might as well grab a good 750 VS carb, then a little converter, then a gear swap, then some head work etc.... LOL
 

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Discussion Starter #13
Again, before you start drilling check to be sure the block is sealing to body properly and that the air ports are clear.
Sorry, forgot to mention, when I pulled the main metering block off, it was dry. The weird thing was, when I pulled off the secondary metering body, the plate was missing for that, so I had to go find one.
I'm going to check and make sure they are clear, first.
 

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Discussion Starter #14 (Edited)
LOL. Yea I have never been a fan of the old Torker II, but I suppose back in its day it was ok. Of course if you get him to anny up to a better intake, might as well grab a good 750 VS carb, then a little converter, then a gear swap, then some head work etc.... LOL
I does have a set of 4.11's in it and from the way it shifts, I'm sure there is a shift kit in it. I wanted him to buy a new carb but then he saw that a rebuild kit was only $25 so he went that way. I tired!!!
I'd like to see him get a new intake but I doubt it.

The more I think about it, when I looked at the secondary idle adjustment, from what I read, your to run the screw up in, until it touches the stop and then go a quarter turn more. Does that sound right? If so, it comes to mind that the screw was not even touching the stop and maybe not enough of the transfer slots are being exsposed.

Would this cause a problem?
 

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The more I think about it, when I looked at the secondary idle adjustment, from what I read, your to run the screw up in, until it touches the stop and then go a quarter turn more. Does that sound right? If so, it comes to mind that the screw was not even touching the stop and maybe not enough of the transfer slots are being exsposed.

Would this cause a problem?[/QUOTE]

Are you sure the rear throttle plates are closing all the way> Is this a vac or mech? Either way if the rear plates are hanging open some that could be giving you problems.
 

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I know what he's talking about ..the secondary "stop" yes adjust it so the plates are just off the throttle plate it will keep them from sticking.....but if the "bar is not bent to keep them closed at idle it will pull them open while running.
 

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Discussion Starter #18
Yes this is a 600 vac secondary.

Here is what's confusing me now, why isn't that diaphragm lever or stop, resting on the diaphragm adjusting screw?

Could that lever be bent?

The "Z" bar that you are referring to is the small linkage that connects the secondary to the throttle arm, correct?

If worse comes to worse, I have a second base assembly that I can swap this one out with.

Here is something else, I removed the electric choke because it was not all there. Is there a cam or something I need to now take off or make an adjustment, because that is gone?
 

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remove the link (z bar) adjust the secondary stop till plates just touch the bores of the throttle plate, then turn small set screw a bit till plates are just off (hold it up to light and look for light shining through) done.
replace link and bend it till it just keeps the plates closed at set idle...

if you readjust the idle (higher) you'll need to do this again.
after that readjust the pump arm...15 thousand and WOT.......should be set to go.
 

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Ok, gotta ask. Is the spring in the vacuum diaphram? the diaphram rod should hold the secondarys closed against the stop screw. As soon as you are off idle, cruising etc the z-bar is no longer in contact but the diaphram should hold them closed until there is demand for the secondarys. ^^^ is correct, the stop screw should be set only enough to keep the throttle blades from sticking in the plate.
 
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