Holley 4160 tips

[74newman]

I am trying to tune my holley 4160 and am curious what everyone else is running. I live at 3500 feet and wheel uip to about 7000-8000 occasionally. I have a 302 with stock heads and etc.. mild RV cam, Headers. I am not sure what jets are in there right now, but it is running a bit rich and stumbles a little bit off idle. What jets and metering block should I run for this setup?

I should have asked this in the Tech section, Mods can you move please?

 

[oleguy74]

what is the # on the air horn? it will be like 80452. your # might be diff.i would leave secondary plate be for now and re-jet primary.power valve will be the next thing.also accelerator pump.i went with a 2.5 power valve and 2 sizes on the main jets.

 

[CDHUNTER]

I agree with the Oleguy. Jets first to handle the rich. If jets aren't helping much definitely look at the powervalve setting to make sure it isn't opening early and causing the rich condition. Normally I'd look at the pump setup for the stumble next. There are two tuning options squirter size and cam adjustments. Cheap and quick test is to move the cam position to another hole to see if it clears up the stumble. If not try a squirter based on black smoke or not. If there is smoke go with a smaller squirter. Just the opposite for no smoke.

 

[broncnaz]

Welcome
More than likely a #28 or #31 squirter will cure your stumble I believe the 1850 comes with a #25. Usually the stock power valve is fine I believe its 6.5 shouldnt need to change it unless your manifold vaccum is very low which it shouldnt be with a RV cam.
Check your plugs after a high speed run to make sure you are running rich. If they are black there rich if tan or grey your good if white your lean. Stock jets are usually #64 might try 62 or 60's always go with 2 jet sizes from what you have as 1 size is hardly noticeable. The stock jetting in the 1850 is usaully very close to what a 302 needs.
One other thing related to tuning and running rich is your timing usually 10-12 degrees initial timing is good for 302's. Sometimes 8-10 is better and gives a cleaner idle, also if running a stock dist they really need a better timing curve which requires changing the advance springs(aftermarket kits are sold) it will help get the most out of you engine.

 

[oleguy74]

you could even go to a 4.5 powervalve .that might work too.i just like the 2.5 my self mainly at 6000 + alt ,vacume drops off prety fast when you have to accelerate on long pulls.

 

[broncnaz]

My take/understanding on the powervalve is that you want it to start working higher in the vacuum range before you lose power/vaccum. To size your powervalve you need to check vaccum at cruising speed then go down 1 1/2 -2 in of vaccum and get the power valve thats the closest. Most stock 302's should be able to pull more than 10in of vaccum at cruising speed. You want the power valve to kick in just when the vaccum starts to drop on that long pull.
That said I run a 6.5 power valve while I probably should run a 8.5 but big tires and high gearing make the vaccum drop quick when I hit a hill so I usually pull about 5-6in on hills so its about right.
Basically the power valve allows you to run smaller main jetting and adds jetting when needed(during dops in vaccum). If your pulling low vaccum at cruise rpms either your cam is big or your gearing is ill suited for your engine.
While you can lean out a engine with a lower opening power valve you may actually have a opening thats to low and it never opens and leans out the engine to much when more fuel is needed. In turn then your probably running jets that are way bigger than they need to be just to keep it from being to lean.

 

[oleguy74]

well!power valves work on a loss of vac.example when you are under load ,a 6.5hg power valve will open around 6-7 hg of vac.this is manifold vac.when throttles open,manifold vac goes down,venturi vac goes up.venturi vac is what operates vac advance,or ported vac.an increase in altitude affects manifold vac.as it drops faster than at sea level.a 4.5 wuold be a better power valve for 74newmann than a 6.5 that it probably came with.

 

[broncnaz]

Like I said it all depends on what vacuum your engine actually pulls. Many stock or near stock engines can pull over 15in of vaccum while cruising and about 18-20 at idle. I understand elevation has a effect as I run at high elevations often but I can still pull about 10in of vacuum while cruising I pull about 15 at idle. I suggest installing a vaccum gauge and driving as normal and see what vaccum your pulling during normal driving then pick a power valve that opens about 2in below that. This will help power output. Just putting in a real low opening power valve can cause the engine to loose more power before the extra fuel gets there. Its also just a shot in the dark otherwise.

 

[oleguy74]

that is why i said a 4.5 would be better.also i run a 2.5 and no problems that i can tell.i go 6500-8500 feet.runs better than the 6.5 it came with.broncnaz!did you move ?thought you lived closer to pheonix?

 

[broncnaz]

Yeah I used to live in Tucson. actually I still about the same distance from phoenix. I just retired and have a new job lined up here in my old home town. Finally out of the city and more time to spend on my broncos.

 

[oleguy74]

great!!!good to have another retired guy out there.been retired 4 years now.you have a lot of good info.thats how we get things ironed out.lot of fun.

 

[ugly74]

my driving range is between 5,500-10,000 feet, and I run a 6.5 power valve. It seems to work just fine, since my vac gauge says I'm still at 12 inches of vacuum on level ground, at 70 mph. but I'm thinkin of dropping to a 2.5 pwr valve, just to see how it acts.

 

[oleguy74]

the main reason i went to a 2.5 is beacause off-roading is diff than just cruesing down the hi-way.i found at those altitudes of and on gas on hard climbs is where you see the diff.