Carb help, Holley 390 or 470TA

[drawk]

No emissions junk on the motor, I have sprayed everything with carb cleaner and propane. I can't find it, if its there maybe stuck lifter or sticking valve too.


My dizzy has two vac points on it as well so I don't know quite which one I have.

 

[gutthans]

Yep, well if you've sprayed things down w/o result, then a late valve could be to blame...slightly worn cam lobe, pushrod wear, stem wear...who knows? But if it runs and you can get a decent idle...drive it until it breaks something.

You could pull the dizzy and make sure everything is smooth and there's no problem with the gear teeth or shaft...but unless it looks really bad I'd leave it alone because other things will be aging soon too.

 

[Jaya]

I got the new choke cap and took it for a drive. Grey spring for the secondaries paper clip didn't move but I put it on funky as well so I will try again. No bog and the throttle response is great. So here's the specs so far.


AMC 258 i6 / 4.2l with clifford 6=8 intake and hedman header with stock dizzy and petronix module holley 470cfm truck avenger
10*btdc


Holley is set as follows

.031 discharge nozzle
.050 jets main and secondaries
8.5 power valve
800rpm idle on manifold vacuum
19.5" hg of vacuum at idle

I will check spark plug color and reply with the results

Hi drawk and all,

Just read this thread last night and ...this is great ... I mean really great .. I've been waiting for this kind of thread for quite some times.

I also running Holley TA 470 & offenhauser intake in my AMC 258 i6 / 4.2l I6 with Crane H-272-2 cam and a Summit blue printed HEI distributor + MSD HEAT HEI module & in cap MSD coil and a set of Magnecor KV85 race wire.

This setup has been for 3+ years and so far has been great .. except for the MPG ... not too bad but I am very happy if it can be improved as its a daily driven in addition to an off road jeep.

I only encounter problems during the initial install ... its due to stock intake and bad lifters ... I replace the intake with offenhauser which dramatically improve low end torque and solve the hesitation issue ...

During trying to get rid of a tick - tick - tick sound ... we found out that we need an adjustable push rod and also found out that the COMP CAM lifters I've been using is not opening far enough ... and finally some of them failed causing a rough idle and backfires ... similar like having a vacuum leak.

On the fuel burning side ... after I re-jet the primary to 54 .. I never get a black exhaust or spark plug ... colour is grey ... or a bit darker grey after driving on highway (the secondary is still on 57 jet size).

I did ask Holley support for their expert advise ...hoping they might keep some similar setup in their database... they only replied that I have to experiment it myself ...same engine different situation/condition.

So I will try to get the same jet size and discharge nozzle with 6.5 power valve and replace the secondary spring with the medium ... hope everything works for me too

Appreciate the great thread very much .. thank you.:driving:

 

[gutthans]

Drawk, oince you are happy with the general performance...it'll be time to tune for mileage. That will require jet changes...figure a rough 4% change in flow between numbers. Listen for lean pops in the exhaust during shifts or while decelerating in gear. Plug color should be between slightly red/brown to ash gray. Good Luck!

In a few cases, you can go even leaner by playing with the shooter nozzle size and the pump cam color BUT...it is a pain, and every time you do a shooter change you risk losing one of those durn tiny washers into the intake (A 12" length of coat hanger wire with a slight bend at the end makes a great removal/installation tool for that shooter!).

 

[Jaya]

Hi gutthans,

I have tried .047 jet on the primary ... performance no good ... however that was when I still on the stock intake.

Do you think I should try it again before getting .050 jet size ... is .047 to lean ? I read your setup is using .050 jet with the 390 holley ?.

Thanks gutthans

 

[gutthans]

.047 is too lean. The lowest I could go on the 390 was .048 without problems, so I would say .049 or .050 would be a great start place for the 470.

Sart your tuning with either an .050 or a .051 set of jets. Get your ignition set at stock settings that you want to run (8* - 12* static timing with your idle at 750 - 800 rpm...now start the process of road testing and tweaking the shooter size and the accelerator pump.

For a complete write-up of the Holley tuning process you can go to www.holley.com and download their tuning instructions under the technical tab on the main screen. There will be one that's included with new carbs for initial installation, and a performance tuning sheet with a how-to do the on-engine tune process.

Just remember, after every change you make...adjust the idle speed back to spec with the screw on the carb...don't alter the distributor or jets or anything else to compensate, or you will ruin your tuning progress.

 

[drawk]

I played with the vacuum secondary springs a little and over all Im really happy with the mileage. Overall I think I have a great fit. I am working on a new problem now of a engine tick. So I did a atf flush and my oil change with MMO and some lucas engine break in for the extra zinc. Im using 15w40 Rotella for oil but it still ticks. Louder under load and at higher rpms. From the sound of it I'm thinking its a rocker bridge or a pivot so I will pull the valve cover this weekend and take a look. Im not thinking its the lifters but i could be wrong.
Other than that the CJ5 runs great and I have no hesitation or bog and it still has pretty good power. 20PSI oil pressure on the factory gauge. Once I get the speedometer to read right I will post some real world MPG for everyone

 

[gutthans]

Good luck with that tick, they all do it.

The AMC 258 i6 / 4.2l /4.0 is non-adjustable and is well known for slop in the valve train. You will find a .020 difference in any stock set of pushrods, for instance. However, the tolerances are pretty wide so the AMC design doesn't care. Guess they figured who's going to notice offroad?

You can quiet this down (assuming you don't have a bad lifter) by doing 2 VERY different things:

1. Buy slightly longer pushrods (Comp Cam has an .050 longer one for Jeep, OR you can look for other stock rods that are .010 - .030, like Oldsmobile ones)

2. Install YellaTerra roller rockers (yes, Harland - Sharp makes Jeep rockers...BUT you must cut the head and install Crane 5/16 to 3/8 studs to mount those first) Yella is a direct bolt-in to the head as it sits.

 

[drawk]

I was thinking check the bridges and pivots first. Its super loud sometime and then from nowhere seems to go away or at least quiet down so its not so noticeable. i know with lifters the just keep going. When I pull the valve cover this weekend I will report bad what I find.

 

[Jaya]

The tick tick sound also happen to my truck and solve after using an adjustable pushrod ... I purchase a used sets from a friend .... Its an isky brand.

Engine sounds great now .. Almost like stock ...

 

[Jaya]

Hi drawk & gutthans,

I have installed those changes in my 470 TA .51 jets prim & secondary, 6.5 PV, mid spring for secondary vacuum and an autometer vacuum gauge. I also install a 2 in spacer with groove from Transmission dapt.

The .031 squiter is not applicable to me .. I did try to install it but it fail when accelerate causing backfires ...

So far performance wise is remarkable .... Surprisingly exceed the original setup with .54 and .57 jets .... Do you think the 2 in torque spacer contribute something or the mild soring secondary ? .. I am planning to check if the vacuum sec did open at certain rpm ... If it open to soon.

On the MPG .... I have not see any improvement ... Maybe is there but just a little .. I am planning to review this for a week or two and replace back the vacuum sec spring back with the heavier one.

The vacuum meter shows 15 hg at idle ... 20 hg when cruising and 8 hg at passing other vehicle ... It will go lower on heavy acceleration and reach 1 momentarily if throttle is floored.

Regards,

 

[drawk]

Hi drawk & gutthans,

I have installed those changes in my 470 TA .51 jets prim & secondary, 6.5 PV, mid spring for secondary vacuum and an autometer vacuum gauge. I also install a 2 in spacer with groove from Transmission dapt.

The .031 squiter is not applicable to me .. I did try to install it but it fail when accelerate causing backfires ...

So far performance wise is remarkable .... Surprisingly exceed the original setup with .54 and .57 jets .... Do you think the 2 in torque spacer contribute something or the mild soring secondary ? .. I am planning to check if the vacuum sec did open at certain rpm ... If it open to soon.

On the MPG .... I have not see any improvement ... Maybe is there but just a little .. I am planning to review this for a week or two and replace back the vacuum sec spring back with the heavier one.

The vacuum meter shows 15 hg at idle ... 20 hg when cruising and 8 hg at passing other vehicle ... It will go lower on heavy acceleration and reach 1 momentarily if throttle is floored.

Regards,

Theres a couple questions I guess we need to figure out first.

15" at idle is a little low but that depends on the cam too. Is the cam stock
What do you have it timed at?
What ignition system are you running. Team rush, MSD, Stock etc..
Were you missing either the top or lower washer when you installed the .031 discharge nozzle
Why did you install a spacer? boiling in the float?
What intake do you have? Clifford or Offy?
Whats your elevation where your running the jeep. Mine is at sea level.
Do you have the secondary spring kit? Try between the black and the plain springs.
Any other mods to the engine… head work, cam, pistons, rockers or anything else that affects air/ fuel mixture or flow?
Did you set the front and rear float settings. I had to lower mine because I was puddling on the primaries. MPG went up

This is all I can think of right now.

 

[gutthans]

Hi drawk & gutthans,

I have installed those changes in my 470 TA .51 jets prim & secondary, 6.5 PV, mid spring for secondary vacuum and an autometer vacuum gauge. I also install a 2 in spacer with groove from Transmission dapt.

The .031 squiter is not applicable to me .. I did try to install it but it fail when accelerate causing backfires ...

So far performance wise is remarkable .... Surprisingly exceed the original setup with .54 and .57 jets .... Do you think the 2 in torque spacer contribute something or the mild soring secondary ? .. I am planning to check if the vacuum sec did open at certain rpm ... If it open to soon.

On the MPG .... I have not see any improvement ... Maybe is there but just a little .. I am planning to review this for a week or two and replace back the vacuum sec spring back with the heavier one.

The vacuum meter shows 15 hg at idle ... 20 hg when cruising and 8 hg at passing other vehicle ... It will go lower on heavy acceleration and reach 1 momentarily if throttle is floored.

Regards,

You won't need the .031 squirter. The AMC 258 i6 / 4.2l /4.0 DOES NOT DRAW ENOUGH VOLUME for that to be effective IMHO. The .025 or .028 will be a better choice.

Yes, as I mentioned the 6.5 PV keeps gas out of daily driving until you really floor it, that's because your vacuum will hang around 11 - 15 until freeway ramps or passing (then 7 - 8" Hg).

The .050 - .052 jets are the way to go on the 470 TA, as the 54 and up are just TOO LARGE for a AMC 258 i6 / 4.2l (unless you drag race it or pull with a really radical cam. You should be pretty close to ideal...just remember, you DOPN't want the secondaries to open below 2800 - 3000rpm...otherwise, you'll be sucking gas at cruise on the highway.

 

[Jaya]

Theres a couple questions I guess we need to figure out first.

15" at idle is a little low but that depends on the cam too. Is the cam stock
What do you have it timed at?
What ignition system are you running. Team rush, MSD, Stock etc..
Were you missing either the top or lower washer when you installed the .031 discharge nozzle
Why did you install a spacer? boiling in the float?
What intake do you have? Clifford or Offy?
Whats your elevation where your running the jeep. Mine is at sea level.
Do you have the secondary spring kit? Try between the black and the plain springs.
Any other mods to the engine… head work, cam, pistons, rockers or anything else that affects air/ fuel mixture or flow?
Did you set the front and rear float settings. I had to lower mine because I was puddling on the primaries. MPG went up

This is all I can think of right now.

Hi drawk,

The cam is Crane Cams H272-2 advert duration 272/284. Its timed as per recommendation .. I'll check the detail.

The ignition is summitracing blue printed hei dist with MSD HEAT HEI module and coil, magnecor spark cable and autolite spark plugs.
The ignition timing is set at 10 deg ... But i also set the vacuum advance spring to loose. The vacuum line hooked up to the carb timed spark port.

The .031 discharge nozzle was properly installed.

My intake is offy dual plane, it needs spacer to create some space between the carb throttle linkage and the intake and to reduce heat transfer ... Mine is tropical country ... Hot at all time .. 30 deg celc the whole year.
Originally it was 1 in spacer ... But i was tempted to try a thicker one especially the one with groove in each hole.

I am also at sea level.

I dont have the secondary vacuum spring kit ... Just have the black and the plain ... I am using the plain now.

I remember setting the primary float level once. I will check both of tgem again and set them low.

Other mods ... Comp double valve spring .. Engine block bored at .040 when it was rebuild.

I am using 6-1 header ... Local made ...

Thank you drawk, really appreciate your thoughts.

Regards,

 

[drawk]

The Offy intake should get better milage than my clifford. I would try what gutthans said and try a smaller discharge and try picking up the secondary spring kit. It saves multiple trips to the parts store. The only other things I can think of is float level and spark plug gap. Read you spark plugs too. They have a wealth of information and they can determine exactly what you need.

 

[Jaya]

The Offy intake should get better milage than my clifford. I would try what gutthans said and try a smaller discharge and try picking up the secondary spring kit. It saves multiple trips to the parts store. The only other things I can think of is float level and spark plug gap. Read you spark plugs too. They have a wealth of information and they can determine exactly what you need.

I will try to re install the .031 discharge 1st ... If succeeded then I will get the .025 ..

BTW this is the cam spec ...

Crane Cams 753941 H-272-2 Hydraulic Flat Tappet Camshaft AMC 199 AMC 258 i6 / 4.2l I6 64-05 Good low and midrange torque, Good idle, daily usageand off road, towing, performance and fuel efficiency, 2600 - 3000 cruise RPM, 8.75 to 10.5 compression ratio advised.
Part Number: 753941
Grind Number: H-272-2
RPM Power Range: 1800-5400
Duration Intake @.050": 216
Duration Exhaust @.050": 228
Advertised Duration Intake : 272
Advertised Duration Exhaust: 284
Lobe Separation: 112
Valve Lash Intake: 0
Valve Lash Exhaust: 0
Gross Valve Lift Intake: 0.484
Gross Valve Lift Exhaust: 0.512

Thanks both of you

 

[gutthans]

Was re-reading this and thought about the backfire you said you had with the .031 the first time you ran it...One of the tuning problems people have is changing more than 1 thing at a time before road testing. The smartest, although slowest, way of tuning is to do it (road-test) after each mod you make...no matter how simple it seems.

I'm not sure why you are considering going back to the .031 but make sure that with each squirter you try, you road test from a dead stop, and then from a 20-30 mph roll. THEN change the cam screw to the other hole, do it all over BEFORE you decide the squirter is wrong for the setup...

The reason has to do with both the fuel curve on the cam and the delivery rate of the squirter. You have to test them out in combinations to find one that will have punch off the crawl and not bog while driving...IF, after those four trials the motor bogs or backfires from a dead stop or bogs in the roling midrange and none of those combinations work...you now know the squirter is wrong.

 

[Jaya]

Was re-reading this and thought about the backfire you said you had with the .031 the first time you ran it...One of the tuning problems people have is changing more than 1 thing at a time before road testing. The smartest, although slowest, way of tuning is to do it (road-test) after each mod you make...no matter how simple it seems.

I'm not sure why you are considering going back to the .031 but make sure that with each squirter you try, you road test from a dead stop, and then from a 20-30 mph roll. THEN change the cam screw to the other hole, do it all over BEFORE you decide the squirter is wrong for the setup...

The reason has to do with both the fuel curve on the cam and the delivery rate of the squirter. You have to test them out in combinations to find one that will have punch off the crawl and not bog while driving...IF, after those four trials the motor bogs or backfires from a dead stop or bogs in the roling midrange and none of those combinations work...you now know the squirter is wrong.

Hi gutthans,

When I was installing the .031 squirter it backfires right after I press the throttle pedal ... It never had the chance to test drive it.

I am planning to test it once again along with changing the cam ... My application differs than yours in camshaft and the 2" carb spacer ... Its affecting fuel delivery.

After taking the jeep round town for few days ... Yes, I can see significant changes in MPG. Much more efficient, especially after adjusting the A/F mixture screw.

I am getting the .049 jets and the spring kit vac secondary ... So I decide to give a try on lower jets because the .051 jets did not have any impact on performance .. Its getting better actually ..

Any target on MPG to achieve .... ?

Regards,

 

[gutthans]

I happen to have a 1" spacer (phenolic) under the carb...mine however is the 4-hole type. So basically I extended the venture length before the flow sees the plenum area of the manifold.

You probably didn't need to road test the .031 with the immediate backfire, if that was the cause of course...but absent an immediate problem, road testing is the next step.

I have run as low as 48 jets, but I found a lean pop would occur when slowing down in traffic, and went back up to the 51's. That seemed to be the nicest fit with the .025 shooter installed.

Target Well, If you're a sane driver...18 should be in reach, possibly 20 mpg if you can let go of the top end of the cam and promise never to drive over 55. If you want a free boost, lose the clutch fan and get a Puller electric fan setup...you may get 1-2 mpg just from that.

 

[Jaya]

Hi gutthans,

If can reach 18 mpg ... Thats a very good result .... The .049 jets and summit spring kit were just arrived ... I think I will have to try it since I bought it already.

I am not comfortable running without a clutch ... I have one 16" electric already in front for the A/C condenser ... Decided to keep the stock fan setup just in case.

Will update the result.

Thanks gutthans.