‘72 400 Jet Size
- Thread starter Xlratr
- Start date
1970FuryConv
Old Man with a Hat
I see #65 in 1972 FSM. .065 drill which I believe converts to .065"
Thanks! I've been googling stuff for hours. I understand the carb number is a R6368A (according to the manual). I can find the R6368 in an online parts diagram (without the A suffix) and that seems to show a #65 on the pump side and a #63 on the choke side. Sound plausible? The #65 matches what you said! I don't know if the "A" suffix makes any difference.
I'd like to know before dismantling so I can get parts ready.
I'd like to know before dismantling so I can get parts ready.
Staggered jet sizes on a 2bbl seems a bit strange to me. What issues are you having with the carb?
I'd go for "65" jets on both sides, personally.
The "A" after the number has to do with the variation of the particular carb part number. Sometimes this relates to adustments and other times to some other items which the orig carb did not have. In this case, I suspect the "A" means the original version.
Take care,
CBODY67
I'd go for "65" jets on both sides, personally.
The "A" after the number has to do with the variation of the particular carb part number. Sometimes this relates to adustments and other times to some other items which the orig carb did not have. In this case, I suspect the "A" means the original version.
Take care,
CBODY67
Thanks! The issue I have is that when I get on the gas quickly, it'll stumble for a second, like it has no fuel. This is something new, just since she came out of winter "sleep". Last year the response was crisp. I'm guessing the fuel has gummed something up over winter, maybe the accelerator pump? I thought I'd go in there and give it a good clean and put new jets in while I'm at it. Who knows how old they are?
I've found several references to staggered jets in 2 Barrels online, and also in some videos. Although in the videos they then go on to say "but in this one they're identical" (without mentioning the size). In the Holley diagram I found on the CarbsUnlimited website I can also see staggered jet sizes (65 and 63).
I think I'll go ahead and order a jet board so I'll have everything I need when I get in there. But your advice on the #65 is valuable. I know now approx where I should be.
At the last vehicle inspection the inspector fortunately turned a blind eye to the emissions result. And the exhaust tip is certainly pretty black :-(. I'm thinking about going one size down on the main jets. Any thoughts on that? I live at sea level with a summer temperature of around 70 degrees, so pretty standard.
But before I do anything, and along the lines of "if you think it's fuel, it's probably ignition", I'll put in new points, rotor, cap and condenser, just to rule that out. I've seen specs to set the 400 2bbl to 5 degrees advance and other recommendations that all 400s be set to 10 degrees. Any thoughts on that?
Sorry for all the questions!
I've found several references to staggered jets in 2 Barrels online, and also in some videos. Although in the videos they then go on to say "but in this one they're identical" (without mentioning the size). In the Holley diagram I found on the CarbsUnlimited website I can also see staggered jet sizes (65 and 63).
I think I'll go ahead and order a jet board so I'll have everything I need when I get in there. But your advice on the #65 is valuable. I know now approx where I should be.
At the last vehicle inspection the inspector fortunately turned a blind eye to the emissions result. And the exhaust tip is certainly pretty black :-(. I'm thinking about going one size down on the main jets. Any thoughts on that? I live at sea level with a summer temperature of around 70 degrees, so pretty standard.
But before I do anything, and along the lines of "if you think it's fuel, it's probably ignition", I'll put in new points, rotor, cap and condenser, just to rule that out. I've seen specs to set the 400 2bbl to 5 degrees advance and other recommendations that all 400s be set to 10 degrees. Any thoughts on that?
Sorry for all the questions!
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Look on the emissions label on the core support near the radiator. I believe that our '72 Newport Royal 400 2bbl had a base setting of 7.5 degrees BTDC, plus or minus 2.5 degrees BTDC, which means you can set it at 5 degrees on the low side or 10 degrees on the top side. Seems like I set it at 10 degrees BTDC at hot base idle in "P" no a/c running.
Main jets don't wear out, so getting new ones is not really necessary, other than to standardize them at 65s.
The idle flat spot can easily be the accel pump and nothing else. PROVIDED that the hot base idle speed is correct, with the mixture screws adjusted correctly for "lean best idle". Unleaded fuel will result in a black exhaust pipe inside surface, but not sooty, which could indicate a rich mixture or one not getting fired-off enough. What do the spark plugs look like (check a couple of the easy ones!)? In many states, once a vehicle gets past a certain age, emissions are not checked, which leaves only the safety check items, by observation. IF the car was actually missing, that might be a different story. OEM production spark plug was Champion J-13Y for that year 400 2bbl, gapped at .035".
There is a known issue with Holley 2210-family 2bbls that results from the air cleaner nut being over-torqued for a long period of time. Result is that the gasket between the float bowl and carb throttle bores does not seal as it should. Which also means the vac channel to the power valve loses vacuum, so the carb is on "power enrichment" all of the time. The prior Stromberg WWC3 on our '66 Newport 383 2bbl had this issue, too. So, look for the gasket indention on that float bowl gasket when you take the carb apart.
Enjoy!
CBODY67
Main jets don't wear out, so getting new ones is not really necessary, other than to standardize them at 65s.
The idle flat spot can easily be the accel pump and nothing else. PROVIDED that the hot base idle speed is correct, with the mixture screws adjusted correctly for "lean best idle". Unleaded fuel will result in a black exhaust pipe inside surface, but not sooty, which could indicate a rich mixture or one not getting fired-off enough. What do the spark plugs look like (check a couple of the easy ones!)? In many states, once a vehicle gets past a certain age, emissions are not checked, which leaves only the safety check items, by observation. IF the car was actually missing, that might be a different story. OEM production spark plug was Champion J-13Y for that year 400 2bbl, gapped at .035".
There is a known issue with Holley 2210-family 2bbls that results from the air cleaner nut being over-torqued for a long period of time. Result is that the gasket between the float bowl and carb throttle bores does not seal as it should. Which also means the vac channel to the power valve loses vacuum, so the carb is on "power enrichment" all of the time. The prior Stromberg WWC3 on our '66 Newport 383 2bbl had this issue, too. So, look for the gasket indention on that float bowl gasket when you take the carb apart.
Enjoy!
CBODY67
1970FuryConv
Old Man with a Hat
I also agree with the accelerator pump being the problem. I have read about staggered nozzles. 63 and 65 would not be out of the question as original. Also some Carter carburetors have more than one position at which you can attach the rod that moves the accelerator pump lever. If you move the rod to the inmost position, i.e. the position closest to the carburetor housing, you get the largest squirt from the accelerator pump. I have rebuilt carburetors before, they still didn't perform right, I moved the rod to that inmost position, and they were just fine. Sometimes older engines need a bigger squirt to get going.
Every time you choose one of the other slots in the accel pump arm, you also have to re-adjust the bowl vent valve, as it runs off of the end of that accel pump linkage.
I have tried the different slots in the accel pump adjustment (Stromberg WWC3 on the '66 Newport 383 2bbl, Holley 2210 which I replaced it with, AFB on the '67 Newport 383 4bbl, and AVS on the '70 Monaco 383 4bbl) and ended up back in the middle slot on each one.
Just my experiences,
CBODY67
I have tried the different slots in the accel pump adjustment (Stromberg WWC3 on the '66 Newport 383 2bbl, Holley 2210 which I replaced it with, AFB on the '67 Newport 383 4bbl, and AVS on the '70 Monaco 383 4bbl) and ended up back in the middle slot on each one.
Just my experiences,
CBODY67
As the stumble is a new phenomena I'm assuming that the basic accelerator pump settings are ok. I hope I just need to clean the respective ports. But I've considered to move it to a different slot if all else fails. If my rebuild kit arrives on time I may be able to get into it this weekend.
I see that the rebuild kit contains a new power valve. Do you think that will have the correct vacuum rating for the 400? Are there different rated power valves for the 2210?
I see that the rebuild kit contains a new power valve. Do you think that will have the correct vacuum rating for the 400? Are there different rated power valves for the 2210?
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I also don't think it's the issue, I just don't want to replace the existing power valve with one out of the rebuild kit if there's a risk that it may have the wrong vacuum rating. I'll start off with just cleaning and replace as few parts as possible to keep the number of variables low.
Thanks again for your help!
Thanks again for your help!
You might desire to look at the carb illustration to see how the Hollety 2210 power valve is configured and what runs it.
Manifold vac goes up the rear wall of the float bowl until it gets to where the air horn completes the vac circuit to the power valve, which is part of the air horn casting. The "valve" itself is in the bottom of the fuel bowl. The plunger is attached to the air horn casting, with a resistance spring around its plunger/rod. When the vac drops below a certain level (probably about 5.5"Hg as the 4bbls are), then the spring will causes the plunger to extend and push down on the valve and cause it to open and flow more fuel. Nothing iike the Holley 4bbls, but similar to many other 2bbls (other than Holley 2300s).
The power valve is not something which should have a real "wear life" or fail with age, I suspect. No need to replace it as a part of a carb rebuild, either. Just replace the gaskets, the accel pump cup, and clean things up. BUT do check that rear area of the float bowl gasket (between the float bowl and throttle bores) for evidence of contact. No or little contact means the power valve vac is being bled-off and the power valve plunger is extended, so the carb is in "power enrichment mode" all of the time. Usually no more than 12mpg, city or highway, at best, back then. And in cold weather operation, when the choke valve closes enough, it can cause fuel to be pulled out of the float bowl and into the throttle bores, which means VERY rich operation until things warm up and the choke is no longer operational. Been there, done that.
What causes the air horn casting to warp? Too much torque on the air cleaner wing nut, over time. Same reason the Stromberg WWC3s had the same issue. In the earlier times (with the earlier air cleaners), it was common to tighten down the air cleaner wing nut to ensure the air cleaner top was firmly against the air filter element. For good measure. But that also exerted an upward pull on the wing nut stud, which warped the air horn. It should not have been necessary to do that with the 1970s-style air cleaner with the bottom and top, but it apparently still happened. Chrysler issued a "Bridge Kit" to address the issue on the Holley 2210-family carbs. And it worked. Finding one of those kits now is worse than hens' teeth, I suspect, but can be somewhat replacated with careful carb air horn screw torque, possibly, while also using two air horn gaskets stacked together.
My gut suspicion is that a "kit" in the carb will not really fix anything. Other than you get to take the carb apart for inspection and pump cup replacement. And to clean the air bleeds and such with solvent, on the venturi cluster and such. Then you'll also know what condition everything's in, too. DO ensure that the vac choke pull-off is not failing, too. Similar with the vac advance can. Be sure to have a verified straight edge handy to check the bottom of the air horn casting, too.
Just some thoughts and experiences,
CBODY67
Manifold vac goes up the rear wall of the float bowl until it gets to where the air horn completes the vac circuit to the power valve, which is part of the air horn casting. The "valve" itself is in the bottom of the fuel bowl. The plunger is attached to the air horn casting, with a resistance spring around its plunger/rod. When the vac drops below a certain level (probably about 5.5"Hg as the 4bbls are), then the spring will causes the plunger to extend and push down on the valve and cause it to open and flow more fuel. Nothing iike the Holley 4bbls, but similar to many other 2bbls (other than Holley 2300s).
The power valve is not something which should have a real "wear life" or fail with age, I suspect. No need to replace it as a part of a carb rebuild, either. Just replace the gaskets, the accel pump cup, and clean things up. BUT do check that rear area of the float bowl gasket (between the float bowl and throttle bores) for evidence of contact. No or little contact means the power valve vac is being bled-off and the power valve plunger is extended, so the carb is in "power enrichment mode" all of the time. Usually no more than 12mpg, city or highway, at best, back then. And in cold weather operation, when the choke valve closes enough, it can cause fuel to be pulled out of the float bowl and into the throttle bores, which means VERY rich operation until things warm up and the choke is no longer operational. Been there, done that.
What causes the air horn casting to warp? Too much torque on the air cleaner wing nut, over time. Same reason the Stromberg WWC3s had the same issue. In the earlier times (with the earlier air cleaners), it was common to tighten down the air cleaner wing nut to ensure the air cleaner top was firmly against the air filter element. For good measure. But that also exerted an upward pull on the wing nut stud, which warped the air horn. It should not have been necessary to do that with the 1970s-style air cleaner with the bottom and top, but it apparently still happened. Chrysler issued a "Bridge Kit" to address the issue on the Holley 2210-family carbs. And it worked. Finding one of those kits now is worse than hens' teeth, I suspect, but can be somewhat replacated with careful carb air horn screw torque, possibly, while also using two air horn gaskets stacked together.
My gut suspicion is that a "kit" in the carb will not really fix anything. Other than you get to take the carb apart for inspection and pump cup replacement. And to clean the air bleeds and such with solvent, on the venturi cluster and such. Then you'll also know what condition everything's in, too. DO ensure that the vac choke pull-off is not failing, too. Similar with the vac advance can. Be sure to have a verified straight edge handy to check the bottom of the air horn casting, too.
Just some thoughts and experiences,
CBODY67
Great information. Thanks!
The part description of the power valve in the diagram for the R6368 is "56-6" so I assume that it is rated at 5.6"Hg.
My rebuild kit has arrived and a power valve is included. It is stamped with a number 25, so I don't know what that means. If the old valve looks to be in good shape I'll probably leave it in.
The part description of the power valve in the diagram for the R6368 is "56-6" so I assume that it is rated at 5.6"Hg.
My rebuild kit has arrived and a power valve is included. It is stamped with a number 25, so I don't know what that means. If the old valve looks to be in good shape I'll probably leave it in.
The Holley 2210-family power valves are NOT rated in "Hg as there is NO vacuum going to them. I suspect there might be some flow specs, but we do not know what that might be.
The vacuum calibration is in the spring around the plunger in the power valve piston that is attached to the bottom of the air horn casting.
In some cases, Holley used a two-stage power valve in the 4bbls, which allegedly allowed them to calibrate the cruise mixture one jet size smaller. On those two-stage valves, the first stage of enrichment happened at 10" Hg with the second stage happening (the main stage) at 5.5" Hg.
Otherwise, any markings are for "production ID" and specs, which will NOT be anyhere but at the manufacturer/vendor.
Enjoy!
CBODY67
The vacuum calibration is in the spring around the plunger in the power valve piston that is attached to the bottom of the air horn casting.
In some cases, Holley used a two-stage power valve in the 4bbls, which allegedly allowed them to calibrate the cruise mixture one jet size smaller. On those two-stage valves, the first stage of enrichment happened at 10" Hg with the second stage happening (the main stage) at 5.5" Hg.
Otherwise, any markings are for "production ID" and specs, which will NOT be anyhere but at the manufacturer/vendor.
Enjoy!
CBODY67
OK, the results are in!
Before I started, I checked the ignition timing. It was exactly 10 degrees so I guess my harmonic balancer is where it should be.
I replaced all the ignition parts and timed it with both a strobe and a vacuum gauge. The further I increased the advance the higher the vacuum got, way off the scale on the timing tab. So I think there's lots of room to go higher there. I backed it off and set it at 12 to 13 degrees.
Then I took the carb off and took it apart. (I've looked at so many drawings and videos, it seemed like I'd done it a dozen times before
.)
I was surprised to see the accelerator pump in the top slot (Edit: which in my understanding is primarily for manual cars?).
Both the jets were #65.
I cleaned everything the best I could with carburetor cleaner and ran brushes through the holes. Then I put everything in an ultrasonic bath.
I adjusted the float height slightly, and replaced the power valve and needle/seat. I kept the #65 jets. I put a new cup on the accelerator pump.
I put the accelerator pump linkage in the second slot.
Put everything back together and took her for a drive this morning.
Runs fantastic, no hesitation at all and she really gets going when you step on it. Feels like 20HP more! I'm happy.
Thanks for all your input!!
Oh, one more thing. When I did the final adjustment to the idle at the side of the road, the odometer read 01972! Must be an omen!
Before I started, I checked the ignition timing. It was exactly 10 degrees so I guess my harmonic balancer is where it should be.
I replaced all the ignition parts and timed it with both a strobe and a vacuum gauge. The further I increased the advance the higher the vacuum got, way off the scale on the timing tab. So I think there's lots of room to go higher there. I backed it off and set it at 12 to 13 degrees.
Then I took the carb off and took it apart. (I've looked at so many drawings and videos, it seemed like I'd done it a dozen times before
.)I was surprised to see the accelerator pump in the top slot (Edit: which in my understanding is primarily for manual cars?).
Both the jets were #65.
I cleaned everything the best I could with carburetor cleaner and ran brushes through the holes. Then I put everything in an ultrasonic bath.
I adjusted the float height slightly, and replaced the power valve and needle/seat. I kept the #65 jets. I put a new cup on the accelerator pump.
I put the accelerator pump linkage in the second slot.
Put everything back together and took her for a drive this morning.
Runs fantastic, no hesitation at all and she really gets going when you step on it. Feels like 20HP more! I'm happy.
Thanks for all your input!!
Oh, one more thing. When I did the final adjustment to the idle at the side of the road, the odometer read 01972! Must be an omen!
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1970FuryConv
Old Man with a Hat
Congrats. I'm glad the test drive was gratifying. Time to celebrate!
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