Hey all,

Just put a new to me Holley 4160 (1850-4, manual choke) on my truck (thanks grinnergetter!), with a Eddy performer 400 intake, did the swap about 2 weekends ago. It had the Autolite 2100 on there before, stock emissions equip.

I have a 400 4x4 4spd by the way, all stock. Only upgrades to the engine are the 4bbl, the intake and the proform hei dizzy.

The 4160 is jetted stock, (#66, stock metering plate), stock vacuum secondary springs, red cam on #1, etc, etc. It runs AH-MAZ-ING. This thing gets up and goes like a 3rd monkey trying to get on the ark.

Anywho, I can't get the dang thing to run below 900 when hot. I've done diagnosis, and I'll give you a background of the other parts.

Parts-
-Holley rebuild/renew kit, aed vac. diaphragm, holley brass floats, holley fuel pressure regulator, new airtex mech. fuel pump, completely replumbed from tank to carb.

I'll walk you through everything I did to make sure I didn't leave anything out.

Pulled the carb apart, only possible mistake hear is nicking the metering block trying to get the halves apart, but its only from the hole for the bowl capscrew to the locating lug hole.

Soaked the carb for a week in solvent, blew out the holes.

Rebuilt it using the new (blue) gaskets. Stock 66 jets, metering plate 134-9, 6.5 power valve. New brass floats.

Pulled old intake and carb off. Holy s*** that dern things gonna make me some money at the scrap yard.

New fel-pro full gasket, 1/16" bead around the holes and on the rubber pieces. Torque manifold bolts

Teflon tape on the stud that goes into the manifold, teflon on the plugs in the runners. New vacuum hoses everywhere. PCV, booster, vacuum advance, you name it, its got a new hose.

Put the carb on, ran it, adjusted floats and choke. Found out I needed new mech. fuel pump.

New fuel pump, adjusted to 5.5 on the fuel pressure regulator (I installed a summit gauge on one of the outputs)

Adjusted vacuum to get 20" (1.75 turns out total). Hot retorque of intake bolts.

So it runs great but I'm idling waaayyyyy to fast with the primary idle screw bottomed out. I think immediately its a vacuum leak, I mean I just put a new intake on. I check were it meets the heads, and at the base of the carb with the old carb cleaner and RPM rise trick. Then I pull the carb off, retorque the base plate screws and re adjust the secondary idle to specs, which was the exact same spot it was.

Pop it back on, still idling fast. Recheck the main suspects (head to intake, base plate). I also checked at the manual choke block off point, and the vac. secondary vacuum port, and pcv intake on the carb. Then I checked for a leak at vacuum advance. No leaks.

What.

So I check timing, I recently put a proform HEI unit on there. Base, 12*, 34* at idle with vacuum advance with full manifold vacuum. Maybe that's my problem, because when I disconnect vacuum advance it "idles" at like 415 RPMs. I know this engine can idle at 550 with no vacuum advance, I tried it.

So I ordered an adjustable vacuum advance canister. Popped it on, and also put a thicker base plate gasket on (didn't trust the cheap holley paper one).

Timing light, vacuum gauge, you know the drill. Start with my initial idle screw adjustments again, 1.5 turns out. Then I adjusted timing. Base still at 12*, but the vacuum advance I adjusted to 27* at idle, 1.75 total turns out on the idle screws = 20" Hg.

Took her for a ride, runs like a raped ape still (compared to what it used to be like). Part throttle cruise with a small increase in throttle ping is gone, awesome.

I get it home and watch the tach, and its still barely below a grand. What ze heck senor. This is with the idle speed screw backed all the way out too.

Should I take more vacuum advance out? Use ported spark vacuum? Lean out the idle? I'm running out of ideas, any input would be appreciated.

PS, sorry for the small novel

 

I believe vacuum advance should be run from ported vacuum...

 

I see lots of adjustments made to the air fuel idle mix screws... but nothing at all about the idle SPEED screws unless I missed it.. Did you back those out totally? Are you positive the throttle plates are actually closed? For a vacuum leak to keep an engine idling that high, you should hear it, IMO.

 

Been there, done that. Try this, buy,rent or what ever a 3/8 drive torque wrench in in./lbs. Install the hold down nuts and snug dowm progressively in a crisscross pattern (60-80 in./lbs.) I overtighten the carb throttle body and it would stick at a high idle.

 

devino-ported doesn't give you any advance at idle, only advance at cruise. IMO its an emissions era crutch

Psquare - yes, sorry, I thought I mentioned it. Primary idle is totally backed off, secondary is at the .020 open that holley calls for. Yeah, can't hear any vacuum leak. I can't stick a .0015 feeler gauge in there while its running, thats how closed the primaries are.

buck- check. I own a small army of torque wrenches, hold downs are at 65 in/lbs

 

are you sure the secondary butterflies are totally closed?

 

try disconnecting throttle linkage from carb and operate by hand as a test to confirm if primary side is not hanging open, if it corrects adjust throttle linkage

 

The purpose of vacuum advance is to allow the fuel more time to burn at higher RPM...manifold vacuum negates that purpose; there's no reason for vacuum advance at idle. If you're having trouble with it running on manifold vacuum, at least try ported.

 

Deeproots- double verified

Jeff- checked that with the carb on and off the truck, running and not running

Devino-i'll give it a shot when I get back by the truck. I was of the impression that you need more time to burn the richer and less atomized idle mixture as well.

 

Shameless bump

 

May have the same problem I am having...

The engine will start with high idle and run with high idle, secondary plates completely closed but still to much air passing through, I used a clean cloth and stuffed it into the secondary barrels to kill the air flow and the engine idled down to about 600 to 700 rpms and stabilized. as soon as I remove the cloth from the secondary barrels the engine dies back out.

Holley instructions say to close the secondary's all the way off and then back out 3/4 of a turn, but for some reason this makes no difference with mine.

I back the secondary's out just enough to see the transfer slot, tiny tiny amount of it showing, reinstalled and nothing changed, took carb back off and closed secondary off completely and reinstalled, same thing.

The mixture screws dont change anything at all until I turn them all the way in/closed and the engine fumbles. I backed them back to 1 1/2 out and still no change.

I am wondering if the secondary side can be disabled all together and just not use them, close them off and stop the air flow to them.

 

You have proven engine will idle properly with no vacuum advance hooked up. Timing is set to 12*BTDC base, good setting for most but try dropping to 10*. Vacuum ports on carb should be capped for this. Pulling the cap off the ported vacuum nipple should have no effect and no vacuum present. if there is, something is wrong in carb. Power valve should be a 6.5 and if engine has back fired during your process, replace it. Normal setup is ported vacuum. With these conditions met, hooking up the vacuum advance should have no effect on idle. I have my adjustable canister set to start kicking in at 4.5 hg using a vacuum pump gun.