79 Mustang lean as a bean

From one of your old threads you have a Holley list # 7159 450 cfm carburetor that had # 59 jets as original equipment. It also had an 8.5 power jet in it.

Right now you have a 6.5 in yours, see the picture in your other thread.

59 mains have a .058" hole

That's not a typo, you'd expect 59 mains to have a .059 hole but they don't

Here's a Holley main jet chart

Your size should be stamped on the jet itself but sometimes old ones are tough to read since it's small and stamped on the end.

Sometimes you'll see the stamping on the side of one of the hexes

You're right though, can't tell much from your picture but if you think you're lean go up a few jet sizes and put in an 8.5 power jet

Question, am I correct in saying the carb is a 4160? You're right that the carb says 7159 but I'm under the impression that it's of the 4160 family of Holley carbs?

I'm going to go ahead and order up that 8.5 power valve and a few jet sizes between what I have (the 59) and probably 70 and see what everything looks like.

Thanks again Keno!

Yes it's a 4160. The list # is 7159

The list number if you look that up will give you the specifics for that carburetor.

I need to go out again and do plugs at different loads. You're right about the soot ring, but I still feel as if I need to go a step or two colder with my plugs. This was a fresh plug on a WOT run. Almost no idle time except to confirm oil pressure.

Ford 302 Commander
10:1 compression
GT40p heads
8.5 power valve (stock)
#65 main jets (#59 stock)

(The picture of the band did not turn out, only this picture)

Springs not weights but, even the standard springs are hard to find. What's your base timing set at? What octane gas are you running?

Here's a picture from your other thread

Those slots in the advance plate that the pins on the weights ride in limit your total advance.

Your's is made of nylon and those slots should give you around 34 to 36 degrees total advance if you initial is set at 10

Like Tim said you can bend the tabs that the spring ends hook to and affect the rate of advance but not the total advance unless you bend the tab enough to really stiffen things up and prevent the weights from hitting the stop..

Doing that is pretty much a crap shoot and probably won't have good results

What's your timing curve look like now.

You say you had 10 initial in the other thread, so what's your total at say 4000 rpm.

Better yet, what is the advance at 1000,2000,3000,4000 rpm

Most people have a hard time getting full advance from that distributor because of the big stiff spring but I guess you're not having that problem.

Why don't you just back the initial off and see how things run as a starting point ?

In 1979, probably about 8.3 to 8.5 to 1 or so,

Bore diameter: 4.030in
Stroke: 3in
Cylinder head volume: 57cc
Piston dome volume: +2.7cc
Deck clearance: .01in
Compressed head gasket thickness: .040in (Roughly, this number came from Fel-Pro)

I rebuilt the engine, put new pistons in with GT40p heads, resurfaced the heads, decked the block, CC'ed the heads and came up with about 10:1 compression ratio. This is why I'm messing with carb jetting, plug heat, and timing.

Somebody earlier mentioned octane rating, it's difficult to find above 91 octane here so I've been running 91. Typically on a street SBF build, you don't want to run above 10.5:1 on this fuel if you want to keep it mostly hassle free from detonation, I keep tripping over tuning though because I'm not used to this type of control and I haven't had to read plugs in at least 10 years. I'm very much used to running a wideband anymore. Honestly, it's like I'm pulling my hair out half the time, and loving all of this the other half.

I'll eventually go up to a 600 but it probably wont be this season unless something happens. When I get a 600 I'm also going to end up porting the heads, gasket matching the exhaust, a little more aggressive cam, running a different prop and so on; but that's more research for a different day.

Right now I finally found my old books and notes on reading spark plugs, but I'm probably going to be in for a new spark plug inspection light, which is fine because I'm going to have to cut these plugs first anyway.

Tomorrow I'm going to gap some new plugs, take it back out to the lake again and make a few more test runs and actually come back with usable data. I'll get my timing set out there first, then get a run to check to see what my fuel looks like, after I get fuel dialed in I'll play with the spark plug heat range. I just want to make it safe for now.

Tim and KENO are spot on, best heed

As been said, I would also further encourage reducing the span on the distributor asap, so your not tempted to run too much total advance just to get back the strong off-idle and launch 10btdc provides.

Total advance will have to be reduced if the compression is as high as you say, due to the faster moving flame front and faster peak pressure developed.

To only way do do both, is to reduce the mech advance span, and weights /springs is not equivalent..

Also, a colder plug has to be considered for the right reasons. To make it look like its not lean, is not the right reason. Predetonation, may be one, but the timing has to be spot on and eliminated firstly.
Think of the plug asyour gauge, once one goes changing gauges, things get blurry very quickly.
Something has to be held constant, till the method and evidence is sound.

This thing must sound good with domes and flat-decked.

Or consider a rear metering block conversion kit (uses replaceable jets instead of the fixed plate. I'd still go 600cfm to start with, though. Makes tuning much easier.

summit racing has secondary metering blocks to convert a 4160 to a 4150.    I think you're playing with fire to run too lean like this, detonation could ruin all the work that you have just done to make what sounds like a nice motor.   Jody had some $25 cores a few weeks ago, and sounds like Tim has some he is willing to sell.    That and a carb kit is going to be much cheaper than a motor rebuild if you have a detonation problem or too hot of a burn. you might even have some lookers for that 450 CFM to offset the cost of the core/kit

Kook

Here's something I put in another thread yesterday but it pertains to you too

It's power valve info and it'll tell you something about when your power valve opens and closes

A lot of people aren't gonna want to believe what I'm about to say, but if that's the case they can verify some readings for themselves.

You always hear that boats run under constant load and then when a power valve discussion pops up, somebody will say that when you punch it from a dead stop, vacuum goes to zero and quickly recovers.

It don't happen that way though

If you give it full throttle vacuum drops to zero and stays there till you back off the throttle.

If you run the boat at a steady 4000 rpm's vacuum stays steady, it never recovers to a higher vacuum till you back off the throttle.

Same thing at any RPM in a boat that's operating under a constant load.

Here are some representative numbers on a good running 351 that I wrote down a couple of years ago and verified again with a quick boat ride tonight

Full throttle     zero

4000 rpm        2.5 inches vacuum

3000 rpm        7 inches

2000 rpm        9.5 inches

1000 rpm in gear   13 inches

idling in neutral 20 inches

This particular boat has a 6.5 power valve so it's open whenever the boat is going over about 3300 rpm

All these numbers can vary some from what I have depending on engine loading, hull efficiency etc but they'll be steady at whatever reading you have till you move the throttle. It's the concept we're after here. And remember it ain't a car.

Like I said, it's bound to lead to some discussion, but you can check it for yourself easily enough.

You can hook into your PCV line to measure vacuum and use enough hose to get the gauge out where you can see it.

So Kook You'll figure out that your power valve is open a lot of the time adding fuel to the engine. Sounds like you went to an 8.5 so any time your vacuum is less than 8.5 it's gonna open and stay open till you back off the throttle.

Just bought a brand new 450 cfm Holley with a 8.5 in it. Is it possible only the 600's have the 2.5 ? Wonder how they determined a 450 needs a 8.5 and not the 600 too?

Gary S wrote: Just bought a brand new 450 cfm Holley with a 8.5 in it. Is it possible only the 600's have the 2.5 ? Wonder how they determined a 450 needs a 8.5 and not the 600 too?

Hi Gary

I dug through some carburetor list numbers and found 7 450 cfm marine carburetors with different list numbers and they all had 8.5 power valves as standard equipment. I'm sure there must be more than 7 but that's what I came up with doing a quick check

I suppose somebody at Holley knows, but since it's really just an auxiliary main jet that opens and closes at a certain vacuum setpoint, it must have been part of their calibration process. It puts the fuel in through the power valve channel restrictions in the metering block and they have different sizes in different metering blocks for calibration purposes.And those PVCR holes come in plenty of different sizes in different metering blocks

I figure I'm not saying anything you didn't already know though.

That doesn't really answer your question or our curiosity though