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66 Hemi jetting

AR67GTX

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Pulled of the carbs on my engine today to check how the are set up. Only pulled the top on the front carb before quitting for the day but didn’t find stock jets in it so probably need to make some changes, These are correct number 66 carbs and look to be in really nice shape.

I know the stock jetting specs but wanted to see if most owners are sticking with that or some slight modification. The engine seems pretty stock although I’m not sure what camshaft is in it - I suspect a later hydraulic one as it seems too quiet for solids.

I found .083 jets in 3 bores and a single .101 jet in the left secondary bore. Stock is .089 and .1065 so someone in the past has leaned it down. I’ll find out in the morning if this holds the same for the rear carb. My theory on ethanol fuel is that due to its less efficiency as compares to non-ethanol fuel, at least stock jetting or one size richer is generally good. Not sure that’s completely correct or valid but everyone has to have a theory. The car has seemed to idle rich (smelly) but now I wonder if it’s just too lean to burn efficiently.

Curious what other early Hemi owners are running for jets in stock engines - staying with stock jets or something else.
 
AR, I'd be interested in your Engine specs. Just getting started on a "stock" Hemi, 2x4 Street intake. I will keep eyes on your thread...
 
This maybe missing one jet size. Found 2nd one.
jet.JPG
jet1.JPG
 
What metering rods were in it?

That’s something else I’ve got to look at in the morning. Had to quit before I wanted to today. I’ll post what I find tomorrow.
 
AR, I'd be interested in your Engine specs. Just getting started on a "stock" Hemi, 2x4 Street intake. I will keep eyes on your thread...

I can’t really say much. I suspect stock pistons from running a bore camera in but with the center spark plug location it’s hard to get a perspective of pop up. Could be less than stock. Same with the cam - it has some rump rump at idle but idles down to 750 area just fine. I suspect a later hydraulic factory cam. Everything else looks stock.
 
When do jets affect the idle?

Yes too lean makes it smelly also. How do the plugs look?

what is the idle RPM?
How much idle vacuum does it have? That relates directly to the springs under the metering rod pistons.
 
Yes, good point. Idle mixtures adjusted to just short of lean roll off. Haven’t checked vacuum yet as guess I’ll have to cobble a hose to fit on the PVC nipple. Only other vacuum is ported. New plugs in it - old ones looked real old but dry black carbon. Really don’t think the car has run much for many years. I’ve been re-wiring it and replacing the heater core along with a bunch of other stuff so I haven’t had a chance to drive it more than a few miles. Waiting on bumpers and light buckets from plater still.
 
Fran, Where did you get that chart you posted? Be careful with the 67 info. The 4324/5 carbs were CAP carbs for CA emissions and the jetting of the rear carb is different then the 66,67 non cap carbs.

So here is my take after restoring some hemi carbs. Wisdom is richen them up because of today fuels, and move in the safe direction if a street car. Original meter rods hard to come by, jets can be found, BUT, you need to make sure you have the correct Venturi's in the carb especially primary. One of my carbs had Pontiac installed. Second, the air bleed go lean. From corrosion, varnish, etc... If they were properly restored or rebuilt the bleeds would be restored to factory spec. If not, the carb may have leaned out with age. So going rich on jets will also really go rich. The idle jet (brass tube in the venturi) also needs to be checked. It can go lean also. Many times the idle jet was modified, venturi tabs removed, etc.... So using the carter service data which has all the bleed info, etc... is mandatory in doing a carb right.

If running points your not as hot ignition wise and going with a hotter plug can also be helpful. Are you using exhaust heating and choke components. Choke working?
Did you actually measure those jet, or read a number? Also early numbers for the .089 are different then the later 389 jet.
 
I plan to blow out all the air bleeds with choke cleaner - the carbs look so clean I wasn’t planning to soak them. They don’t look professionally restored in that all the hardware is dulled down and not newly plated etc. The choke isn’t activating although all the tubing/housing is intact. That was one of the things I planned to get into. I’ll have time to look at the jets and rods closer today. Sounds like you believe as I do that with ethanol going a bit larger on jets is a good idea. I have the 66 Hemi FSM supplement which has some carb info in it.
 
Fran, Where did you get that chart you posted? Be careful with the 67 info. The 4324/5 carbs were CAP carbs for CA emissions and the jetting of the rear carb is different then the 66,67 non cap carbs.

So here is my take after restoring some hemi carbs. Wisdom is richen them up because of today fuels, and move in the safe direction if a street car. Original meter rods hard to come by, jets can be found, BUT, you need to make sure you have the correct Venturi's in the carb especially primary. One of my carbs had Pontiac installed. Second, the air bleed go lean. From corrosion, varnish, etc... If they were properly restored or rebuilt the bleeds would be restored to factory spec. If not, the carb may have leaned out with age. So going rich on jets will also really go rich. The idle jet (brass tube in the venturi) also needs to be checked. It can go lean also. Many times the idle jet was modified, venturi tabs removed, etc.... So using the carter service data which has all the bleed info, etc... is mandatory in doing a carb right.

If running points your not as hot ignition wise and going with a hotter plug can also be helpful. Are you using exhaust heating and choke components. Choke working?
Did you actually measure those jet, or read a number? Also early numbers for the .089 are different then the later 389 jet.
Think top from NHOA 30 years ago or NeHOA maybe? Thanks for info.
 
OK - looks like there has been some creative jetting and rod work in the carbs - here are my notes.

602882C1-7E42-4959-80E7-0DF9F383D4E1.jpeg


The jet sizes shown in () are from the 66 FSM supplement. The numbers next to them are what’s in the carb now - my memory after leaving the garage yesterday was bad - overall it’s jetted up a lot although the stagger doesn’t seem to follow the methodology in the FSM at all.

Rods look OK on the rear carb but don’t match on the front. FSM shows 16-136 rods on front.

The right secondary Venturi on the front carb (678) looks suspicious but not sure if it’s wrong or an issue.

I checked some of the jets with my pin drill set and they seem to be true dimension (401 jet measures .101”).

All the choke pieces seem to be there - it was just at a deactivated position. Only item I haven’t checked is if there is a spring under the piston - none in mine so I assume not.

I can’t provide any more info on the engine - it’s basically appears as a stock engine other than I suspect a factory hydraulic cam is in it. It’s certainly not a hot cam. No headers, has a dual point, 4-speed, no more than factory compression.

So, looks like I have a lot of Carter jets to find and maybe a couple of rods. Should I go with stock jet sizes (FSM) or go a couple thousands larger? Go with 16-136 rods up front and keep the 16-440 rods in the back?

Any recommendations where to find Carter jets. I’ve bought from Mikes Carburetors before and Woodruff is restoring theAFB for my 67 GTX right now but I’m not sure if he sells misc parts or not.

Mostly you see Edelbrock jets selling as a substitution and I have some of them but not sure it’s a good practice to use them in a Carter or not?
 
On my set and with our fuel here and altitude I kept the staggered jetting and went up about 5% on each corner. It's pretty hard to do evenly as you have to juggle needles as I recall. They ran really, really well though. I assume the intake manifold is still stock?
You have to do math to find the area of the jet orifice and the area of both portions of the needle. Sounds complicated but really isn't too bad.
 
Front Carb Jets

Pri Both 159 .089
Sec OP 159 .089
Sec PS 171 .1065
Low Spd Jet .035

Rear Carb Jets
Pri Both 159 .089
Sec OP 158 .082
Sec PS 175 .073^ Carter states this but FSM said .080
Low Spd Jet .035

Meter Rods
Front Both 136 .071x.061
Rear Both 440 .0665x.058

Your venturis are correct. The 678 does not have a secondary discharge port, a characteristic of hemi carbs. The 348 would, all part of distribution of fuel I am sure.
Is your intake cut open like the vanke mod? If not, I would go back to stock or as close as possible. Then tune from there. To do it right you need to use an o2 sensor and AF ratio meter.

Remember the front carb is high speed high throttle open only. Progressive linkage. So getting your rear carb dialed in for idle cruise. Since your jets do not have orig numbers they clearly were changed at some point. My L5 66 carbs had original jet numbers in them.
 
Thanks. The intake doesn’t have any machining between the bores - 4 round bores each. I didn’t have a small enough pin gage/bit for the low speed jet so I’ll have to assume it’s stock for now.

Any recommendations where to go for jets and rods?
 
Best choice is look for an old Carter Strip Kit if you can find one (or two). You can use new Edelbrock jets but their metering rod assortment isn't as thorough as the old Carters.
 
I’ve seen a few on eBay but the unopened ones are real pricey and the used ones are just a shot in the dark as to what’s still in them.
 
Front Carb Jets

Pri Both 159 .089
Sec OP 159 .089
Sec PS 171 .1065
Low Spd Jet .035

Rear Carb Jets
Pri Both 159 .089
Sec OP 158 .082
Sec PS 175 .073^ Carter states this but FSM said .080
Low Spd Jet .

.

Not sure I understand the secondary jet position terms OP and PS. I thought they might stand for operator side and passenger side respectively but that seems to be the reverse of the FSM which uses standard right and left from the drivers seat. Unless I screwed up my diagram somehow ??
 
Pump Side, Opposite Pump side. Pump being accelerator pump:D

I have a 10-201 kit new if you need one, can contact me via message.
 
Thanks all!

looks like I can order piece meal pretty much what I need from Mike’s Carburetor parts.

I can’t find the Carter 16-136 rods (.071/.061) anywhere. Mike’s lists an AFB rod available in what he carries with .070/.057. This would be a hair richer at cruise and a little richer yet under heavy throttle which should be Ok. QuadrajetParts.com has one measuring .070/.060 that would be a little closer but think I’ll stick with the one from Mike’s shop for simplicity. I don’t have any idea where these rods are sourced from.

I looked at some of the Carter strip kit contents and considering I need 5 - .089 jets and that they don’t contain any rods close to what I need, I don’t think they will work for me.
 
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