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Old 10-09-2012, 09:07 PM
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ggevaert ggevaert is offline
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t-slot setup


Well, the other thread was supposed to stick to just distributor type questions (re: mechanical and vacuum) and this one about holley type stuff but there is some overlap going on.

Anyway, that's why I'm here and asking questions, some items I'm fairly familiar with but others are new hat.

My cam is a Comp Cams 450 lift, 224 duration, 206 lobe centre. I had it running good at 800 idle with just primary screw adjustments but when I looked at the t-slot after pulling off the carb it was pretty large (didn't measure or write it down as I was going to go through the 0.020" setup procedure anyway). I will, for the record, reset the secondary to closed, adjust the idle with the primaries to 850 and then pull the carb and read the t-slot size.

The part I was trying to understand was the proper order of things when modifying a holley and then, in turn, doing each of these to ensure you have a properly running engine. I do understand there is some level of going back and forth but there must be some items that have to be done in order to get them correct. For example, you would never setup a holley until your timing is good.

Here is the list I have sofar of steps and the order they should be done in.
1. Get the timing fixed and correct
2. Verify that you have 4-7 psi of fuel pressure; ensure it is NOT higher than 7.5 psi as that can cause severe fuel control problems
a. If too high then install a fuel regulator and set to proper psi at 6.5 psi
b. If not enough then you need to replace the tank intake, pump and all the lines as they could be clogged.
c. At high rpm or WOT fuel pressure should not drop below 3.0 psi; if it does you need a higher volume fuel pump.
d. Ensure that the fuel filter is the large one and does not come close to heat or in contact with the engine itself. A large filter can transmit a lot of heat to the fuel.
3. Ensure you use a large 14"x3" open element air cleaner; it will offer very little resistance to air flow, thereby not causing the fuel to go leaner. All Holley carbs are initially calibrated using this type of air cleaner.
4. Check for manifold-to-head and manifold-to-carb vacuum leaks
5. Take out the Carb and take it apart. Write down:
a. Jet sizes
b. Actuation point of the power valve
c. Size of the accelerator pump squirter
6. Get the floats right
a. Primary with the level just barely below the sight plug, secondary the fuel level about .050" below the sight plug
i. My carb (Holley 600 w/vacuum secondaries) does not have adjustable so must leave as is
7. Make sure venturi butterflies and the choke plate open fully
8. Set the transfer slot as per procedure below
9. Set Idle mixture as per procedure below
10. Check off-idle circuit (tip-in) as per procedure below
11. Set your power valves as well as your PVCR’s as per procedure below
12. Set your jets as per procedure below
13. Tune your secondary’s
14. Set your accelerator pump
15. Set your fast idle setup (for when choke is on)

Where it says 'as per procedure below' I then have detailed steps (with pics) on how to do that from what I have learned (both from reading and by experimentation). I did read a lot of articles from reputable companies like Holley (which has a whole technical library) to car magazine articles and where I found corroboration then I put that in my procedure. If you want to read it let me know and I'll upload it for you to see.

Sooo, long story short, when I set the primaries to 0.020 and the secondaries to 0.020 then my idle was at 2200 with the fast idle off so then i adjusted the secondaries to give me an idle of 1050. I think I was closing them off slowly, can't recall right now.

It sounds like my next steps now are:
- close down secondaries and run engine to see what happens with tslot on primary set only at 0.020"

BTW, my idle air screws are currently reset to 1.5 turns; when I tried to work them before I did my t-slot adjustment they did nothing. no increase or decrease in vacuum until I stalled the engine going all the way closed so I left them and started at the t-slot procedure.

Sorry for the long email

Last edited by ggevaert; 10-09-2012 at 09:16 PM.
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