oamhmad

iTrader: (1)

I'm running a 600 CFM Holley 4160 vacuum secondary carb on a Goodwrench 350.

I noticed a bog on WOT and confirmed an extremely lean mixture around 17 via a wide band gauge. This was with the black (heaviest spring). I've used every single spring from heaviest to lightest and still have a bog and lean mixture at WOT. The only difference the lighter springs made, was the secondaries opened farther and the afr went full lean sooner.

How do Iget the secondaries from going lean on WOT? Help!

pancherj

This is the problem with the vacuum actuated Holley. You only get a pump shot into the primary side. On a double pumper, you get a pump shot into both sides. You can slow down the secondary opening (decrease performance) and/or increase the pump shot into the primary side. You may need to play with the pump cams too. Make sure the primary pump circuit is functioining correctly. You should get a shot of gas with the slightest move of the throttle.

Damon

Is this a momentary bog and then it gets up and goes or does it go lean and stay lean no matter how long you keep your foot down?

sofakingdom

iTrader: (1)

Check your gaskets carefully. Make sure they're the right ones, not upside-down, etc.

Consider a 4150 conversion kit.

I'm perosnallly not a big fan of the 4160.

oamhmad

iTrader: (1)

No it is not momentary. It goes lean and stays lean as the RPM's climb. It actually pulls harder if I do not go WOT and only use 3/4 throttle or so.

Update: I wired the secondaries shut and no more lean bog! It pulls all the way through the RPM range at WOT around 13-14 AFR.

Put the heaviest spring back in and the bog cam back. What's going on here? I don't think the carb is over sized for the engine, so why am i not able to use all 4 barrels?

InfernalVortex

iTrader: (4)

A 4150 is a double pumper, yes? I thought there was nothing you could do to convert a vacuum secondary to a mechanical secondary completely? Something about no squirters on the secondary side on the 4160 carburetors?

oamhmad

iTrader: (1)

Here are some pictures of the secondary side gaskets. I'm pretty sure they are on the right way. They're a little worn looking but still seal well.

spicyskater

set primary jets first ,then calculate proper power valve number for ur engine ,then u need to set accelerator pump nozle size...and last u set the spring for vacuum secondary

oamhmad

iTrader: (1)

Already done. I'm running 63 jets. At steady cruise, 45 mph, the afr is 13-13.5. All 8 plugs are a nice tan color after immediately shutting down the motor on the side of the road.

Had a slight hesitation at idle tip in. Discovered accelerator linkage had play. Adjusted linkage and no more hesitation.

Was getting backfires while accelerating beyond highway cruise speeds in high gear. Noticed lean AFR. Increased power valve from 6.5 to 10.5. No more back fires.

Verified with vacuum gauge that vacuum tends to remain higher than 12" HG while driving around or very mild acceleration.

Now if only I could get the vacuum secondaries dialed in...

Damon

You're just running dead-lean on the secondary side for some reason. I'd take it apart, clean out all the passages, make sure the float is set properly (and make sure the inlet valve is not plugged or obstructed) and check the size of the holes on the bottom lip of the metering plate. Those are the secondary "jets" in a 4160. Possible the plate is not the right one or they are plugged up with goo or.... who knows.

BTW- the metering plate number has NOTHING to do with how big the metering holes are. A Holley 600 vac sec List #1850 should use a #9 plate, which has metering restrictions that are equivalent to a #64 jet (and are close to .064" diameter, but can vary slightly).

Here's the complete x-referece of Plate number to equivalent jet size:

Plate # / Jet #
3/56
4/59
5/63
6/69
7/53
8/64
9/64
10/65
11/72
12/73
13/63
14/85
15/82
16/64
17/69
18/63
19/69
20/69
21/75
22/65
23/64
24/72
25/77
26/79
27/79
28/65
29/75
30/64
31/74
32/59
33/64
34/53
35/69
36/64
37/69
38/71
39/69
40/59
41/69
42/94
43/71
44/74
45/79
46/75
47/78
50/79
53/65
54/82
55/78

oamhmad

iTrader: (1)

I'm running a #8 plate. From your chart looks like it is the correct jet size (#64) for a 600cfm 4160.

I checked the passages with compressed air and wd40. Looks like everything is clean and all the passages are open.

oamhmad

iTrader: (1)

Ok so I bought and installed the 4160-4150 secondary metering block conversion and installed #79 jets in it. The car is still lean at WOT! I'm using the heaviest spring in the vacuum canister.

pancherj

It looks like the one remaining unknown are the boosters on the secondary side. Have your verified fuel flow coming out of the boosters?

bestracing

Yea That is what I'm thinking as well.

Running a 63 on the primary side and 79 on the secondary side means something just isn't right. I have never seen a carb staggered that much between primary and secondary jets.

How much valve overlap do you have in your cam? Are your A/F readings from a wide band sensor? Any leaks in the header flange? I'm wondering if your A/F readings are accurate or not as well.

Also I'm use to seeing the primary a little higher on jet size as well like somewhere around 68 but this was on a car with a '73 corvette motor.

Have you tried a 68 jet on the primary?

novaderrik

[cough]quadrajet[/cough]

FtrSpeedy

Fuel pressure?

oamhmad

iTrader: (1)

Yes I have. When I had the fuel bowl and metering plate removed, I squirted some wd-40 through a straw into the holes on the secondary side of the carb's main body and verified that the WD-40 was indeed coming out of the secondary boosters.

oamhmad

iTrader: (1)

I'm running a GoodWrench replacement crate 350. Cam specs are miserable, (.383''/.401'' and 112° lobe separation).

Yes they are. It's an Autometer Wideband gauge. I have shorty headers. The O2 sensor is mounted right above the collector on the driver side.

No leaks any more. I used to have a leak at the header mounting flange and could hear a loud ticking. I replaced the exhaust gasket and it fixed the leak and sound. I doubt any of the welds are leaking, I would probably hear it if they were.

I'm pretty certain the A/F readings are accurate. For example, whenever I feel a lean bog I can verify a lean reading on the gauge. Tuning the mixture needles using the vacuum gauge method gives me pretty close to 14 AFR readings on the gauge. During mild acceleration I can watch the gauge go lean until the vacuum drops enough for the power valve to open and then the gauge registers richer AFR, etc. Not really sure how else I could verify its accuracy.

No, but I have some 65 jets that I'm going to try tomorrow.

redneckjoe

make sure your air bleeds arent plugged up.

oamhmad

iTrader: (1)

Nooooo!!! People have been tuning Holleys for years without widebands with great success, or so I hear. I have a wideband. This shouldn't be too difficult.

oamhmad

iTrader: (1)

be

LOL, nothing better to do on a Friday night than TGO? Me neither,

I'm using a Holley 1850/4160 vacuum secondary carb. I don't think it has air bleeds?

redneckjoe

LOL, i guess your right.
i used the adjustable vacuum secondary on my 4160. it runs like fuel injection. you must have something plugged up, im thinking.
yup, nothing better to do, cant sleep, LOL. good call.

five7kid

iTrader: (14)

No.

4160 has a metering plate, 4150 has a metering block with replaceable jets. Has nothing to do with the secondary type (mechanical or vacuum).

If it stays lean and never gets to stoic, you've got a fuel metering/delivery problem.

five7kid

iTrader: (14)

Yes, it does. They may not be replaceable, but they are there. Look at redneckjoe's photo - those 4 small holes in a line at the back of the venturi are the air bleeds. 2 are for idle, two are for the main circuit.

BTW, if they're plugged, you won't go lean.

oamhmad

iTrader: (1)

I checked the air bleeds. They seem to be clear. I was able to get wd40 to squirt out of them by spraying it into one of the holes on the secondary side of the main body.

I also replaced the #63 jet on the primary side with #65 jets. It's running a little richer at cruise, but still goes lean at WOT!

I'm really stumped, I think I've tried everything:

I replaced the secondary metering block with a metering plate and jetted up the secondaries to #73, didn't work.

I bought a spring kit and am running the stiffest (black spring), didn't work.

I raised the float level in the secondary bowl, didn't work.

I checked for fuel flow through the secondaries, they flow ok.

Note that I can go to WOT without going lean on the primaries only by wiring the secondaries shut. I'm completely at a loss here.

FtrSpeedy

Lack of fuel pressure/supply will cause those same issues.

five7kid

iTrader: (14)

Obviously you have a problem with the secondaries only. Jetting up the primaries isn't going to help.

I assume when you said you raised the float level in the secondaries that you confirmed at that time that the secondary bowl actually has fuel in it. True?

It sounds like something stupid simple like main fuel passages plugged in some fashion or another.

oamhmad

iTrader: (1)

Yes it did have fuel in it.

About the fuel pressure, I'm running a high volume mechanical fuel pump. I've checked the fuel pressure while cranking the motor, it's 7 PSI. Even if the pressure is too low, don't the fuel bowls hold enough fuel to go WOT for at least a couple of seconds before running dry?

oamhmad

iTrader: (1)

Problem solved!!!

The secondaries were clogged. I basically emptied out an entire can of compressed air into the passages on the secondary side. You should have seen the crud that came out! I guess the Wd-40 I was using earlier was not enough pressure to clean it out.

I can now go WOT and the AFR stays at a healthy 13.1-13.5. However, there is a still a momentary bog that I can feel as well as see on the wide-band as the rpms climb beyond a certain point. Then I can feel the secondaries kick in and the AFR drops to around 13. I can appreciate now why people use double pumpers.

bestracing

Now you can play with the springs I'd start with the silver to get the secondaries to open at the right RPM for you. Also you might need to back down on the secondary jets as well, 68 to 70, and see what you get.

Damon

Glad you got it fixed.

For future reference, you clean carbs with CARB CLEANER. Never ever ever use an oil like WD40. Not only will it not clean typical carb schmutz, it will attract NEW schmutz to accumulate and stick everywhere the oil touches, like all oils do.

Carbs require NO OIL ANYWHERE. They run DRY- metal on metal. Always.

oamhmad

iTrader: (1)

Thanks that's good to know. Never knew Wd-40 could mess up a carb.