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First drive post head work
https://slantsix.org/forum/viewtopic.php?t=34831		 Page 2 of 2
Author:  Aggressive Ted [ Tue Apr 14, 2009 1:13 pm ]
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With my E254 cam it will idle fine between 16 and 20 degrees initial. After allot of experimenting I like the feel at 16 and left it there. The idle will be faster and can become rougher the higher you go.
As an example: at 5 to 10 degrees it sound like a clock, steady as can be.

Bill your engine will probably settle down after awhile. You may have a slight vacuum leak somewhere.
Author:  66aCUDA [ Wed Apr 15, 2009 6:04 am ]
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Bill
IF its that cam?? I agreed with Ted that you may have a leak somewhere. Was the cam Degreed when you put it back together? Im a little distracted right now let me come back to this.
Frank
Author:  Doctor Dodge [ Wed Apr 15, 2009 9:07 am ]
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Great work... now the "fine tuning" starts. 8)

Where is the valve lash set? (did I miss that info. above :? :oops: )
Loosen the lash as far as you can with-out a lot of ticking, try for at least .018 Int. and .022 Ex. and more if you can get it.
That will bring the vacuum reading up and help the idle quality.

As for the distributor recurve, do your final valve lash adjustment first, get everything else set and then find the initial advance setting that it "likes" best... including hot restarts. (12 - 14 initial??)
Build the rest of the curve from there, so you end up with 30-32 degrees total. For a street car, a "staged" curve is best (light & heavy spring) with the light spring doing all the work, except for the last 4-6 degrees.
DD
Author:  wjajr [ Wed Apr 15, 2009 6:02 pm ]
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Hi Doc, thanks for chiming in.

Lash is .010" & .020" which I did not previously list. My thought was to get as close as possible with standard lash, than as a last resort start backing it off. I would like to use as much of the cam as I can, and it dose tick when loose. Before the head work I had backed off 0.002" intake & exhaust per your instructions last spring.

I have discovered that my Holley 4160's idle circuit is a bit out of tune. I'm currently correcting that deficiency now that I better understand how it is designed to function. Once idle mixture screws do their job, and the engine will idle properly, I'll back off the lash if needed.

I'm getting close, tonight It will now idle at 900 rpm with a steady vacuum.

A nerd question for you:

I understand when backing off the lash one is accentually changing the specifications of the camshaft in that the duration is shortened, and lift is reduced. Will this adjustment in lash translate into more torque at a lower rpm?
Author:  Aggressive Ted [ Thu Apr 16, 2009 10:31 am ]
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Bill,
Quote:
I understand when backing off the lash one is accentually changing the specifications of the camshaft in that the duration is shortened, and lift is reduced. Will this adjustment in lash translate into more torque at a lower rpm?
I asked Doc that question a few years ago when I was setting up my engine. The answer he gave me was yes.
It seems to settle down the idle and provides more torque off idle. With a posi you will be able to spin the tires allot easier and right off idle. It makes a big difference. Vacuum will also be higher and mileage is better providing you don't drive too aggressively. :D
Author:  wjajr [ Thu Apr 16, 2009 1:55 pm ]
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Doc & Ted,

Holley 4160, 51 jet, 3.5 poewr valve.

I have taken your advice turned my engine into a ticker by opening up intake to 0.015", and exhaust to 0.022" as predicted vacuum came up 2 inches at rpm range 950 to 2500. Idle is no smother, and now I have kick-back when engine is shut down, and aggressively goes into gear from N or P. The off line spunk feels better at this setting.

Before slacking off the lash I had some idle screw adjustment at 1000 to 800 rpm when throttle plates were drilled 1/8". Flat spot during light acceleration 1500 to 2200 rpm had all but disappeared, still there under moderate acceleration, and no kick-back when shutting down engine. When I closed the idle air bleed on the secondary's with fingers, idle rpm picked up I thought this may indicate a lean condition, so I soldered the 1/8" holes re-drilled to 7/46" to lessen the lean condition.

Now with the slacking of the lash, 7/64" hole, throttle plate fully closed idle screws are out 2 1/2 turns to give smoothest idle @ 1000 rpm. which ain't very smooth. Flat spot is pronounced light & moderate acceleration. By increasing vacuum, have I once again leaned out the idle mixture, and need to reduce the drill hole more?

I need to get this thing to go into gear with out a slam, idle stopped in gear with out stalling and needing feathering of throttle, and wanting to aggressively creep at any rpm over 950.
Author:  GENT [ Thu Apr 16, 2009 2:16 pm ]
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Sounds like a vaccum leak somewhere.As soon as you can drop the idle it will no longer slam into gear.
Author:  terrylittlejohn [ Thu Apr 16, 2009 3:48 pm ]
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if this cam is only 254deg dur, it should idle at 650rpm with no problem.you have a lean condition, ignition timing or an electical problem with volts to coil.
Author:  wjajr [ Fri Apr 17, 2009 4:44 am ]
Post subject: 
Quote:
Quote:
Quote:
Aggressive Ted
With my E254 cam it will idle fine between 16 and 20 degrees initial.
66aCUDA
Bill
IF its that cam??
GENT
if this cam is only 254deg dur, it should idle at 650rpm with no problem.
I don't think I have any vacuum leaks other than the controlled ones from the drill holes. All new gaskets, studs, nuts, and fresh machined surfaces, all torqued properly.

Cam specifications are unknown to me, and I was unable to degree it when the head was off. I did measure the lift while head was off the block as 0.292" x 1.5 = 0.438". My machinest listend to it run and said the cam sounded rather radical for what that is worth.

This engine never liked to idle under 1000 rpm before head work. Any rpm under 950 vacuum gage needle becomes quite jumpy to +/- 5", at 1000 it sits steady at 10" with backed off lash. Now I can bottom out throttle plates with the 7/64 drill holes, and have idle adjustment between 1 3/4 & 2 1/4 turns out. Previously I had to have throttle plates unseated to the point of exposing the vacuum advance feed hole, and about .060" of idle transfer slots showing to idle at 1000. This over powered the idle mixture adjustment rendering them useless, produced a pronounced flat spot during light & moderate acceleration.

A 4160 question:
The main air bleed passages on this carburetor are plugged, no air hole, looks as if it came from the factory that way. Is this how 4160's are built?
Author:  68barracuda [ Fri Apr 17, 2009 10:15 am ]
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mine is quite open...the air bleed just above the boosters correct?
Author:  wjajr [ Fri Apr 17, 2009 11:19 am ]
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68barracuda:
Quote:
mine is quite open...the air bleed just above the boosters correct?
The four air bleeds in the secondary side are open, only the two idle air bleeds are open in the primary side on my unit.
Author:  ceej [ Fri Apr 17, 2009 11:46 am ]
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Did you set your secondary idle screw?

It is on the oposite side of the throttle shaft from the lever. I found that the factory setting was pretty close, but there may be a slight discrepancy in how much it needs to be open on the slant.

If you are not getting good effect from the mixture screws, open the secondary just a tiny bit and try again. If your having to close the primary plates, and are way past the transfer slots, close it down a tiny bit.

Hope that helps!

CJ
Author:  wjajr [ Fri Apr 17, 2009 11:56 am ]
Post subject: 
Me quoting me:
Quote:
I don't think I have any vacuum leaks other than the controlled ones from the drill holes. All new gaskets, studs, nuts, and fresh machined surfaces, all torque properly.
Poppycock there torque breath!!!!

I have pulled out the last of my hair this morning over this runability issue. Suddenly sun rose over Marblehead, or bald head I had not checked the base of the carburetor for flatness... There it was, all four eyes bent forming a nice inverted bowl shaped bottom. The damn thing was sucking so much air from all four sides that a whole can of carburetor cleaner sprayed one side at a time would not change idle speed.

After some elbow action with a big flat mill bastard file I got her flat, bolted it back on the intake and fired the engine up. Set timing to ~+16* per Aggressive Ted, idle set at ~850 rpm dropping to 650 in gear with quite a lope after a bit of fiddling around. It has a little rpm lope up & down when idling of about 75 rpms, can't get that stopped yet.

Filled the tank, than took a 30 mile test drive getting stuck behind a 10 under jerk for a while, and than an "at the limit" poke for the first 12 miles. The car ran smoothly, not particularly spunky, the gas gage hardly moved, a welcome sight for a change. Got to a back road for the burn out test: failed miserably, however she will redline from a stop if a little sand is on the pavement and not move far forward. On the way back I had a chance to wind her past 3100 rpm on level ground. At 3200 rpm this car becomes a beast at half throttle pulling real hard almost as if the were a turbo under the hood spooling up!

For now, enough with the carb, on to the rear end & transmission...
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