258 not happy with the Holley.

[mitchelllogic]

Right?!!!

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I even have my spare selected if the old one breaks.....

Can't wait to be asked what the dickel on my Jeep is for!

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[R717]

Guys don't forget usually 2bbl carbs and 4 bbl carbs are rated on different depression/vacuum levels, so its not apples to apples comparing the cfm ratings.

Check your ignition first for troubleshooting. Ive never seen the water cup trick but best idle will often be too much static advance. Listen for pinging under heavy load.

When you had the holley apart did you true-up the metering blocks? If they arent true it can cause all sorts of issues. Unfortunately this affects old ones and new ones for various reasons.

You should be able to find a manual choke kit and just run a cable as an alternative to the elec choke

 

[mitchelllogic]

Good point on the static advance. I failed to mention what to listen for.
Thanks


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[MDPJeep]

Have to disagree with you.
4 barrel eidelbrock 525cfm (1403) on a 1" riser works like a charm on a AMC 258 i6 / 4.2l if you set it up right.
5 years on mine. Easy rebuilds.

It put the fun back in my ride.



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Well, I'm glad I read your post ! I would have never thought the AMC 258 i6 / 4.2l " would have enough CFM to get a 4 barrel working properly.

 

[JeeperChris]

Well, I'm glad I read your post ! I would have never thought the AMC 258 i6 / 4.2l " would have enough CFM to get a 4 barrel working properly.

Some things to consider:

Using 80-85 % as the engines volumetric efficiency a AMC 258 i6 / 4.2l inch engine will use 371 CFM. At 100% VE the AMC 258 i6 / 4.2l would use 447 CFM. - calculated at 6000 RPM maximum.

A 4-barrel 525 CFM vacuum secondary carb will have approximately 260 CFM on the primaries and secondaries. It will basically be running on a 2-barrel and only using the secondaries when needed and because they will be vacuum opened they will only open for what the engine will need. A mechanical secondary carb would be overkill, but not a vacuum secondary carb.

The Motocraft 2150 and Autolite 2100 2-barrel carbs came in different CFM ratings all the way down to 190 CFM so it's possible to find a 2-barrel that will have a more exact CFM for the top performance of the engine. The 4-barrel on the other hand will allow the primaries to be smaller and give better lower RPM performance before needing extra CFM at top performance.

Also of note is the intake manifold that mitchelllogic is using. That Offenhauser is engineered to have an extremely good flow on the primaries - they are separated from the secondaries until the runners reach the head.

 

[gr8dain]

That sounded like a lot of science there.[emoji12]

I had a AMC 258 i6 / 4.2l with an offy intake and a holley 4bbl for about 8 years. Mine ran very well. I could have rebuilt and cleaned the carb, but never did. Then I pulled it and installed a sniper 4bbl kit. Loved that a lot.

Unfortunately I did something to the motor and am pulling it to put in a 4.0.

I just came to say the 4bbl may have been more than needed for the AMC 258 i6 / 4.2l , but it worked fine. 11mpg, but it ran well.

 

[mitchelllogic]

No arguments here. If your after "smiles per mile", want instant gratification when you hit the gas, and are after that "hopped up" sound, then you are looking at a total system upgrade (Then hop on the crazy train. It's fun). More of a hot rod mentality really. "Because you can" is the litmus test.

This path started with a rebuild, cyl bore .30 over, mild cam, headers, split intake 3+3, dual exhaust and upsized pipes, flow through mufflers, re-jet, needles, seats, upgrade the ignition system, high vibration coil and an MSD (don't forget offroad spring set up in the carb), new floats, and lots of tinkering to get it just right. I love it. Makes me smile. Growls nice. Loves touring gas stations.

Could get away with a 2 barrel for sure. Makes way more sense too! I get that.

Now if I could just ram more air down the throat.........

I think you are understanding my disease.

That said I do have to admit:

After years of carb tuning for weather changes I am getting lazy, and frugal, so I'm headed toward EFI (probably, ok maybe, alright not just yet but maybe next year.....). Check back in a year or two.

I do hope I can keep the rest of the setup if I go EFI but don't think my intake will play nice with the smarts in the EFI parts.

I know my setup is not for most. But I love it!

Maybe don't follow me.

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[mitchelllogic]

Some things to consider:



Using 80-85 % as the engines volumetric efficiency a AMC 258 i6 / 4.2l inch engine will use 371 CFM. At 100% VE the AMC 258 i6 / 4.2l would use 447 CFM. - calculated at 6000 RPM maximum.



A 4-barrel 525 CFM vacuum secondary carb will have approximately 260 CFM on the primaries and secondaries. It will basically be running on a 2-barrel and only using the secondaries when needed and because they will be vacuum opened they will only open for what the engine will need. A mechanical secondary carb would be overkill, but not a vacuum secondary carb.



The Motocraft 2150 and Autolite 2100 2-barrel carbs came in different CFM ratings all the way down to 190 CFM so it's possible to find a 2-barrel that will have a more exact CFM for the top performance of the engine. The 4-barrel on the other hand will allow the primaries to be smaller and give better lower RPM performance before needing extra CFM at top performance.



Also of note is the intake manifold that mitchelllogic is using. That Offenhauser is engineered to have an extremely good flow on the primaries - they are separated from the secondaries until the runners reach the head.

Exactly!
Responds well on the bottom end with light pedal (2-Barrel) and wakes up with your foot in it (on 4).

If you jump on the pedal you run out of your first three gears pretty quick. 4th gets you to highway speeds, 5th is rarely used.

My problem at the moment is a lack of power in my AX15s "Overdrive or 5th gear". 4th gear at 4k rpm is the end of responsiveness. 90km/hr+ is where the issue is. Getting to 120km/hr takes patience.
I do need to figure that out.

Wasn't as noticable on the T-5 (then again keep in mind the new setup smashed that T-5 like I was crushing a pop can so....theres that.)

Anyway. Glad it stimulated this conversation!


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[Belizean]

Hey mitchellogic what the heck is km/hr ? Not very easy to figure out mpg.

 

[mitchelllogic]

Hey mitchellogic what the heck is km/hr ? Not very easy to figure out mpg.

100kmh = 64mph ish
120kmh = 75mph ish

We buy gas in litres at about a .95 cents a litre.
Or 3.60 CAD a gallon ($2.75 USD?)

I can't convert MPG to SPM (smiles per mile) though.....calculator just kicks back 5318008.

[emoji847]

Ahhh 80s LCD humour. Such a child.

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[Belizean]

Actually I knew those conversions from driving back and forth to the southern boarder of Mexico in the early 70s. I was just messing with you. I have to admit I never was good with the litre though. Glad I'm not having to pay for that expensive Great White North oil. Only paying $ 1.96 yesterday

 

[LanceMaster]

Set a cup of water on your fender.
Check your park brake is on.
Shift the Transfer Case to neutral.
Block your tires.
Start your rig.
Observe the ripple pattern in the cup.
Stop the engine.
Mark your current distributor alignment by scribing a line on the base of the distributor and engine.
Loosen the distributor hold down bolt but leave some resistance on it so the distributor doesn't flop around.
Get a friend to start the engine while you hold the distributor in place.
Slowly, very very very slowly start rotating the distributor in small increments while you watch the ripple pattern in the cup.
If it gets worse (choppy or uneven rings) STOP and rotate back then the other direction.
You will find a "sweet spot" where it sounds right but the ripple pattern, once even and low ripples, will get you spot on. Tighten it. (Carefully as it's hot now).
I haven't used a light for a tune in years.
(Different story if you had removed and replaced your distributor).

Be careful with a running engine. Hot parts, poor insulation on old plug wires, an un-guarded fan, shifter slip, all can cause severe injury or death.


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Never heard this one before. Does beer work, or does it have to be water...?

 

[Belizean]

Never heard this one before. Does beer work, or does it have to be water...?

I'm thinking a cup of water first thing, then when running just right, very nice single malt scotch, the beer might get to warm in the beginning

 

[mitchelllogic]

Actually I knew those conversions from driving back and forth to the southern boarder of Mexico in the early 70s. I was just messing with you. I have to admit I never was good with the litre though. Glad I'm not having to pay for that expensive Great White North oil. Only paying $ 1.96 yesterday

Warm weather, cheap gas, and a Jeep? I am starting to think I should come visit.....and stay. Jeep and I just made it through a week of 40 below weather!


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[mitchelllogic]

I'm thinking a cup of water first thing, then when running just right, very nice single malt scotch, the beer might get to warm in the beginning

You sir may arm chair in my garage!

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[Belizean]

Warm weather, cheap gas, and a Jeep? I am starting to think I should come visit.....and stay. Jeep and I just made it through a week of 40 below weather!


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Yeah I don't know how you handle that cold, but then you would probably say the same about here in July & August. The a/c runs probably 50 minutes an hour.

 

[mitchelllogic]

Yeah I don't know how you handle that cold, but then you would probably say the same about here in July & August. The a/c runs probably 50 minutes an hour.

Might be able to handle a visit in spring or fall but I would melt and die in your summer. Went to Vegas one summer and just laid out on the hotel A/C. Seriously thought I was going to have brain damage from the heat. I didn't know a person could sweat like that. A Brita water filter in the flesh. Don't understand how you do it.

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