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post #1 of (permalink) Old 04-14-2002, 12:14 PM
brendan
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TR, would you hold my hand?

Aaron, I could use some help.

Weight and Gearing
85 j10 longbed
t176
NP 208
Dana 44 (3.31 gears)
31" tires
turns roughly 2600 @ 55mph

Engine
258 block: 500 miles on .060 over rebuild
Crane 260H cam
4.0 head: new, stock 95 Model. Casting #7120.
rotating assembly balanced, crank balanced to 8000 rpm

Induction
stock 2bbl intake
mc 2100 1.21
7.5" power valve
autometer air/fuel gauge(20 led model)
Exhaust
stock yj to 2" pipe

Ignition
Stock distributor base. Vacuum advance is hooked to Ported Vacuum.
TR upgrade, tfi coil
stock motorcraft ignition unit
Timing set to 8* BTDC @ 1600 rpm w/vac advance isolated.

Driving habits
95 percent street (daily driver).
cruise at 2500-3200(50-85mph)
93 octane gas.


I am trying to get the fuel/air/spark curved right, and I am having a little trouble finding a baseline.

question #1: my vacuum behaves pretty much exactly like highfill's:

Idle: 16" steady
Steady 50mph on flat road, 4rth gear: 14"
Light acceleration and it was around 10".
Not much more throttle dropped it to below 5"(2.5-4").
Combine a hill with moderate throttle and vacuum went away completely.
Deceleration from upper revs I saw as high as 26", 27" maybe.

My local chrome valve cover store has a 4.5 holley power valve in stock. It appears to be compatible with the mc valve. Do you know if it is, in fact, compatible, and if so is it appropriate?

also, do you know offhand if holley jets are compatible with the motorcraft? I have yet to dig for the jets in the carb.



question #2: how reliable is an autometer ratio gauge? I ask because last night it read just above lean at idle, stoich. at cruise, lean on deceleration. I could not get it to read into the rich zone, even with repetitive goosings of the accelerator pump. this morning it is just above rich at idle, and richens up one or two steps at cruise, and leans out on deceleration, but never dips into the lean zone of the gauge. I realize that this gauge is only an estimation, but I am puzzled by its behavior.

If I try to tune the idle so it is close to lean, it stumbles from the lack of fuel. All i can figure is it was pouring last night and is starting to clear off today, so barometric pressure has risen and this has possibly affected the function of the gauge.

Now for an unexpected twist: I am completely anosmic. I cannot smell the difference between gasoline and 90W gear oil. I don't have the ability to just smell if the carb is rich, and so lack that baseline for tuning.



question #3: I cannot hear detonation in this new engine even with the advance turned way up.(I haven't tried to make it ping, but with all the fiddling haven't found it.) I have, however, found many misses in the tuning of system. should I assume that these misses are detonation, due either to a lean mix or timing advance?


I think that this is all I need to get close to tuned. Thanks a ton, Aaron, for your time and thanks highfill for the cut and paste stat sheet.

Brendan
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post #2 of (permalink) Old 04-14-2002, 12:33 PM
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Re: TR, would you hold my hand?

Hold your hand? I'm purdy sure TR don't swing that way! [img]images/icons/smile.gif[/img]
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post #3 of (permalink) Old 04-15-2002, 04:35 AM
 
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Re: TR, would you hold my hand?

I don't know about all that hand holding stuff....
I'm pretty much a homo-phob and proud of it!

Helping tune your vehicle is about as far as I'm willing to go!! [img]images/icons/tongue.gif[/img]
<hr>

*Timing set to 8* BTDC @ 1600 rpm w/vac advance isolated.*
*93 octane gas.*

1,600 RPM is a little high for an idle, don't you think?
With manual trans, you should be doing about 700 RPM for a curb idle.

Somewhere between 8 and 12 degrees BTDC is where I'd start and sneak up on all the timing I could before detonation.
Have you tried it with cheaper gas? No need to buy that expensive stuff if you can do just as well with 89 octane...
-----------------

*turns roughly 2600 @ 55mph*
*cruise at 2500-3200(50-85mph) *

Sounds like you aren't doing too bad on the final drive ratios.
You aren't working the engine to death, although I'd limit my extended runs above 3,000 RPM with stock cast iron connecting rods...
You should be safe to 4,000 to 4,500 with cast iron rods as long as you don't shock load the engine while you are up there. (IE: Don't rev it up and side step the clutch to do burnouts!)
-----------------

*Not much more throttle dropped it to below 5"(2.5-4").*

Sounds like you need a 5 or 5.5 power valve opening also.
Doesn't the 2100 have a two stage power valve? I'm not too familiar with farm truck carbs, but I seem to remember doing one a few years back that had a two stage power valve....
-----------------

*also, do you know offhand if holley jets are compatible with the motorcraft? I have yet to dig for the jets in the carb. *

The Motorcraft carbs that Holley built, the jets interchange, so will power valves, but I have NO IDEA what the Motorcraft part numbers mean when it comes to size...
------------------

*how reliable is an autometer ratio gauge?*

What is a 'Ratio Gauge'?
Do you mean a fuel ratio gauge, like an O2 sensor connected to a display head in the passenger compartment, or do you mean a vacuum gauge?

If I'm getting this correctly, you have the rich/ lean indicator, and you are wondering why you can't make it go into the rich area...

Here is a way, turn your idle mixture screws out some, but make sure you remember how much so you can put them back.

Also, you can jet the carb up, or close the choke blades most of the way while the engine is warm.
Both should affect the fuel/air mixture to the rich side...
-------------------

*I could not get it to read into the rich zone, even with repetitive goosings of the accelerator pump.*

The O2 sensor doesn't respond fast enough to read that very short time the accelerator pump shot lasts, and besides, with the throttle blades opening at the same time, you may never get much past balanced fuel/air ratio.

You have to remember, you are dealing with a carb that is set up to be very conservative, and to run on an engine that has to pass emissions standards. It's not like you have a racing only Holley right out of the box (IE: Jetted rich as hell).
It's going to be pretty close to 14.7 no matter what you do right now...

If you want to mess with the accelerator pump shot, (larger pump, larger discharge nozzles, longer discharge time, ect) you may see some rich side swings...

Sounds like your carb is pretty close to correct now, no detonation, no over lean, no over rich...
------------------

*Now for an unexpected twist: I am completely anosmic. I cannot smell the difference between gasoline and 90W gear oil. I don't have the ability to just smell if the carb is rich, and so lack that baseline for tuning.*

That sucks man! One of the greatest joys in life is the smell of burning rubber and sweet gas!

No matter what you have been told by the 'Old Mechanic Squad', you don't tune with your nose, you watch the plugs, and listen for detonation or lean misfire.
------------------

*question #3: I cannot hear detonation in this new engine even with the advance turned way up.(I haven't tried to make it ping, but with all the fiddling haven't found it.) I have, however, found many misses in the tuning of system. should I assume that these misses are detonation, due either to a lean mix or timing advance?*

There are a lot of reasons for misfires and dead misses...
Lean fuel mixture is one of them, so is improper rotor phasing when you turn the timing way up.
There is a long laundry list of things that cause misses....
Bad...
cap, rotor, coil, coil wire, plug wires, pickup coil, spark plug(s), module (especially if you have the stock one), and about a dozen or so wiring connectors that like to turn to green crap when no one is looking...
We can also include...
Rotor phasing, spark scatter, cross fire, multi-fire, ground fire, false triggers, ect...

All you can do is go back over the basics and use quality parts.

All in all I'd say you don't have too much of a problem.
You may want to richen up a little on the bottom end, and I'd give it about 12 degrees of initial timing (vacuum advance unhooked and carb line plugged).
I'd look into maybe being happy with the fact it runs pretty well (I know a crap load of 258 guys that would kill to run 85 MPH even down a mountain!) and only needs minor tuning.

Throw me some pretty close pictures of your engine bay, ignition system and carb, and I'll see if anything catches my eye...
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post #4 of (permalink) Old 04-17-2002, 06:29 PM
brendan
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Re: TR, would you hold my hand?

Clearly, I did need my hand held, because as I finished up the swap in the wee hours of the morning, I neglected to check that the port I had assumed was ported advance was, in fact, ported advance.(run on sentence)

In fact, this port draws no vacuum at all.

Why a port that draws no vacuum? why will people vote for Al Gore?

after finding a port with ported spark signal, the jeep is running much better. having a sense of smell might have clued me in.

I am pretty well on top of things now that I have vacuum advance. however:
1. The spec for the tuning the comp. controlled BBD 258s is base line timing 9*[email protected] Tearing off the pickup on the distributor, I found why. The 13/18* limit slots you are constantly pestered about are, on the 84 GWag dist, 6.75/7.75*. There is barely a slot there at all. I had it open right next to a 13/18* jobbie. So beware!-- engineers at work!

Now that I know why, I'll set my baseline at idle speed.


2. Retard timing 4 degrees from the point at which I hear detonation. If I am inside of this inaudible 4 degrees of detonation, will it still show on the plugs?


3. Announcement to whom it may concern: holley jets are not compatible w/ mc2100 BUT holley power valves are. I put one in last night, works perfectly, though it isn't really what I need.

4. I am going to a two stage power valve. I'm going to try a few, and looking in holley catalogs, I find "high flow" valves. Is there a significant advantage? Is'nt the flow limited by the flow rate of the main jet when the carb is in the power valve circuit?


Thanks a bunch for taking the time to pander to the idjits, Aaron.

yours straightly, Brendan
post #5 of (permalink) Old 04-17-2002, 10:52 PM
 
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Re: TR, would you hold my hand?

People voted for Al Gore because the only other choice was the sniveling, lying punk Bush...
Now that he's gutted the Freedom Of Information Act, made YOUR Medical Records public information, and stolen millions from the Enron employees, you see why I didn't favor the Bush punk for president...
(Interesting, the Bush family made money from Enron, and didn't loose 1 penny in the collapse...)
<hr>
Now, on to the other questions...

1. I don't 'Pester' anyone about anything.
I simply tell them what to check. If you don't want to check them, that's your choice.
(you can lead a horse to water, but he'll still sh*t on his heels...)
You found the problem with the timing computer distributor...
Why do you think I recommend the '79 distributor to everyone? (Full size advance slots....)

Set your timing at idle only if you have the long slots, and the timing computer disconnected... IE: Nutter Bypass....

2. If you can't hear the detonation, normally you won't find it on the plugs. Detonation has to be pretty severe to show up on the plugs using unleaded gasoline.
If you don't hear detonation, you probably won't have a lot of trouble with it.

When doing a custom tune, I recommend sneaking up on the timing until you have obvious detonation, then backing off until the detonation goes away, then backing off another 3 or 4 degrees and locking the distributor down.

3. I couldn't remember if the 2100 would use Holley jets or not, now I know...
As for the two stage power valve, they have their place, but I don't use them very often at all, and not very many people know how to tune using a 2 stage....

As for the 'High Flow' or 'Picture Window' power valves, you are NOT going to flow enough fuel to need them.
Just make sure you have the correct gasket for your power valve type.
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post #6 of (permalink) Old 04-18-2002, 07:24 PM
brendan
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Re: TR, would you hold my hand?

thanks a lot, TR. You misread number 1, I'm sure you have plenty to do besides pester folks you've never met.

I can understand why people voted for gore in the last election, what is weird to me is that he'll probably get elected to the presidency despite popping up on the news for four years saying some strange things. that is, if Tipper lets him run.

The same charisma that allows a man to go through life getting away with with being a sniveling, lying punk is the same charisma that will get him elected to office. This not a pattern that I can see ending anytime soon. McCain was who I wanted, but he lacks the vitality and charisma to reach the highest office. McCain vs Bradley battling for the presidency would have been such a great thing for the whole political clime of the country. It may have even raised the bar high enough that slicksters like Bush might never have been given the nomination again. The lowest common denominator is a real monkey wrench in the works of democracy. Anyway...

I'm thinking of drilling out a spare pair of jets I have because I can't seem to find a source for jets for the thing. How do I drill them without snapping the barely visible bits? High speed seems too high, and low speeds will put too much torque to the bit when it bites. I only get one guess. Any advice?

Last thing- I think that the accel. pumps for a holley will also work. I rebuilt one for a friend a few years back, and the diaphragm seems identical. I'll look into it.

Take it easy and thanks, brendan
post #7 of (permalink) Old 04-19-2002, 02:34 PM
 
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Re: TR, would you hold my hand?

John McCain with Colin L. Powell would have been my first choice, but the Bush camp smeared McCain so badly he didn't have a chance...
The guy spent years in a North Viet Nam prison camp while the Bush punk was hiding out in the Texas Air Guard (that daddy was senior advisor to), and the Bush spin doctors actually found a way to use that against him!
Only in America can being a war hero be used against you by a draft dodging punk!
That alone was enough for me to vote against Bush punk, not to mention the other 49,000 things...

I'd like to see Bush punk, Al liar- inventer of the internet, Dick (should have been indited with Nixon) Chaney &amp; Slick Willie hanging from the same tree, but that's my personal opinion...
<hr>
Let's have John McCain for president, Gen. Colin L. Powell for vice president, Gen. H. Norman Schwarzkopf chief of staff, and Bill Gates foreign trade secretary, now you can see how things will go...
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