Gents I thought I would give you some thoughts on carburetor repair and maintenance based upon what I have done/recently seen fixing this simple unit on the bench and truck.
Maxim one remember many perceived carburetor faults are NOT fueling problems at all but those caused directly by ignition related issues or something mechanical like tight valve clearances, plugged air filter/suction hoses/external filter in poor condition. Before adjusting the instruments check the state of the engine and the timing/ign components etc.
With the plenum cover lifted off the carburetors prop it open with a screwdriver propped in the dip stick tube. Do a visual with the engine off.
Anything loose--like the carburetor bodies on the bases.
The accelerator pump links in good order. Over adjusted links won't allow you get adjust a to good idle. Generally the link should be located closest to the fulcrum point
Take a look at the top covers. The cross tube drilling is blanked off by external blanking discs. Have any of these blown out by "spit back". With these drillings open the carburetor response will be seriously affected.The rear unit is harder to observe so use a mirror to glance at the rear.
Is there any loss of fuel? The most common one is hose leakage/banjo bolt leaking, followed by a slow flood out of the spindle bosses in the bases.The loss of fuel is in most cases is due to internal flooding and the leakage is seen coming out of the spindles. Simply put the fuel is welling on the butterflies and running out of the clearance spaces.
Remove the accelerator link ball joints and do a test lift on the spindles. Excessive wear will cause stumbling, poor response, and inabilities to control idleing/control. This also applies to the accelerator pump arms as well!
For now.. If it all looks good, start the engine and warm it up. While it is in warm up take the time to look into the throats. Are fuel droplets cascading down the venturies at idle? A sure case of flooding.
What are the throats like? Is there dirt in the venturies. A sure case of dirt in the bowls so over the long period causing erosion of jets.(more of that later).
Are the choke plates leaking, A cheapo gasket and removal of two screws etc can easily fix it. A leak at this point will affect operation.
Are all the return springs in place, and for now is the bell crank arrangement on number three valve cover in good order?
Bye Bye for now
Dennis
Carburetor woes
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lindenengineering
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Carburetor woes
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lindenengineering
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Douwe
Hold your hosses with those wrenches; have several more episodes to add!
Best regards & Merry Christmas to you and Ann and the wee one.
PS Guys
Douwe & his wife must have the cutest "7 monthish old" little boy I have seen in a while he's got a beguiling smile. Marvelous!
D
Hold your hosses with those wrenches; have several more episodes to add!
Best regards & Merry Christmas to you and Ann and the wee one.
PS Guys
Douwe & his wife must have the cutest "7 monthish old" little boy I have seen in a while he's got a beguiling smile. Marvelous!
D
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lindenengineering
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Well guys I thought I would post a another info tip line on carburetors now that the Christmas alcoholic haze has passed and the crazy holiday at the shop has passed into a mad dashed memory!
The last thread left me mentioning the need to lift the plenum cover off the carburetors to check for flooding. At this stage I am assuming there is no flooding but the thing runs like crap!
The first thing I always do is first check for a 'click" on each solenoid to verify operation. That's with the ignition on by the way!
If that's ok look at the linkage to do a balance. You will need one of those snail style balancer units SAV sells. At idle the reading should be 9.75. That's not indicative of anything significant its just that is the best reading I often get for a balanced idle. If its out of whack adjust it to get a synchronized reading. That's best achieved by prying off the front upper throttle ball joint setting the idle screws on BOTH instruments and then adjusting the ball joint to drop onto the throttle arm WITHOUT altering the readings on either carburetor. Look for wear on the ball joints and loose ball pillars on each carburetor accelerator arm.
Now one thing will become paramount, the engine will either race at this setting or stall. Stall means a weak mixture, racing a rich one. Turn in each mixture screw evenly by the same amount on each instrument to achieve an idle of 950r/m. If the thing improves run in each mixture screw until it bottoms, then back it out the SAME you turned it in. Do the same for each idle mixture screw making sure they are all the same "backed out". If the thing still sounds a bit "off" move the idle mixture screw in a "hair" in either direction to achieve the best possible idle.
More to come, missus has called it's dinner mustn't miss that!
Dennis
The last thread left me mentioning the need to lift the plenum cover off the carburetors to check for flooding. At this stage I am assuming there is no flooding but the thing runs like crap!
The first thing I always do is first check for a 'click" on each solenoid to verify operation. That's with the ignition on by the way!
If that's ok look at the linkage to do a balance. You will need one of those snail style balancer units SAV sells. At idle the reading should be 9.75. That's not indicative of anything significant its just that is the best reading I often get for a balanced idle. If its out of whack adjust it to get a synchronized reading. That's best achieved by prying off the front upper throttle ball joint setting the idle screws on BOTH instruments and then adjusting the ball joint to drop onto the throttle arm WITHOUT altering the readings on either carburetor. Look for wear on the ball joints and loose ball pillars on each carburetor accelerator arm.
Now one thing will become paramount, the engine will either race at this setting or stall. Stall means a weak mixture, racing a rich one. Turn in each mixture screw evenly by the same amount on each instrument to achieve an idle of 950r/m. If the thing improves run in each mixture screw until it bottoms, then back it out the SAME you turned it in. Do the same for each idle mixture screw making sure they are all the same "backed out". If the thing still sounds a bit "off" move the idle mixture screw in a "hair" in either direction to achieve the best possible idle.
More to come, missus has called it's dinner mustn't miss that!
Dennis
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lindenengineering
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So you had a go at synchronizing and things are still not working right.
So before you go tearing into the carburetors consider the aspects of the truck that could affect the way it runs.
Obviously the more tools you have the more achievable the results can be. I would highly recommend at this stage an infrared heat gun to measure exhaust temps, not expensive but a real diagnostic aid to measure heat generation on each cylinder short of grasping each header pipe and guessing the temp balance----Ouch!
If the thing runs rough shoot and record the temperatures, when running hot at idle expect to see around 350 to 450 dg F on each pipe. See a dramatic difference, that's the cylinder giving the trouble. Easy eh!
Its always good to have some parts on hand, I would recommend some inlet runner to carburetor base gaskets, some manifold to head gaskets (4 minimum), some throttle ball joints, and the return springs that you see on the carburetors and throttle link bell crank.
Here are a few areas around the carburetor that need to be considered.
Jets can be blocked by debris, the aftermarket accelerator pistons seals are made of leather that fragment over time, bits of leather have been known to plug a jet. These are easy to remove and blow out.
On the left side of the engine is the vacuum hose for the brakes. It does rot over time and create a vaccum leak into the engine causing nos 1&2 cylinders to run rough. If you suspect a leak, disconnect the hose and plug it with a short length of 1/2" hose and a bolt, See if the engine running improves, obviously the hose is defective. Replace it with Napa 1/2" multipurpose hose (red in colour) . don't use heater hose, it will collapse under depression and affect brake assist.
Want to get aggresive, remove the carburetors and set aside. take a look at the base gaskets, now junk, you can discard them but take a look at their condition for fragmentation. they can affect the way the engine runs
if leaking.
Now lift the tin covers to expose the cooling capsule interior, and a bridge pipe to balance both manifolds.This must be in good condition and not loose to ensure smooth engine operation.
NOW. Important. Take a look at the link between both manifolds that supports the plenum holder eye pin bolt. It does have a tendency to rip a chunk out of a manifold runner causing a monster leak and impossibility to control half the engine properly. Again the heat gun will show you that.
If all that looks kosher, grasp the runners and look for any looseness. They do have a habit of cracking at the bases causing air leaks. Also if your truck has been a "heavy back spitter" when cold it may have blown out the manifold to heat paper gasket causing yet another air leak.
If all that looks good and you start to slap it back together but take the opportunity to clean out the cooling fins with detergent and a hose. Plugging the manifold ports of course with rags. The back two cylinders are often piled high with dirt accumulation.
Well that shoulds be enough for now. Plenty to get at this weekend if you are bored with all that Christmas time off.
Bye Bye
Dennis
So before you go tearing into the carburetors consider the aspects of the truck that could affect the way it runs.
Obviously the more tools you have the more achievable the results can be. I would highly recommend at this stage an infrared heat gun to measure exhaust temps, not expensive but a real diagnostic aid to measure heat generation on each cylinder short of grasping each header pipe and guessing the temp balance----Ouch!
If the thing runs rough shoot and record the temperatures, when running hot at idle expect to see around 350 to 450 dg F on each pipe. See a dramatic difference, that's the cylinder giving the trouble. Easy eh!
Its always good to have some parts on hand, I would recommend some inlet runner to carburetor base gaskets, some manifold to head gaskets (4 minimum), some throttle ball joints, and the return springs that you see on the carburetors and throttle link bell crank.
Here are a few areas around the carburetor that need to be considered.
Jets can be blocked by debris, the aftermarket accelerator pistons seals are made of leather that fragment over time, bits of leather have been known to plug a jet. These are easy to remove and blow out.
On the left side of the engine is the vacuum hose for the brakes. It does rot over time and create a vaccum leak into the engine causing nos 1&2 cylinders to run rough. If you suspect a leak, disconnect the hose and plug it with a short length of 1/2" hose and a bolt, See if the engine running improves, obviously the hose is defective. Replace it with Napa 1/2" multipurpose hose (red in colour) . don't use heater hose, it will collapse under depression and affect brake assist.
Want to get aggresive, remove the carburetors and set aside. take a look at the base gaskets, now junk, you can discard them but take a look at their condition for fragmentation. they can affect the way the engine runs
if leaking.
Now lift the tin covers to expose the cooling capsule interior, and a bridge pipe to balance both manifolds.This must be in good condition and not loose to ensure smooth engine operation.
NOW. Important. Take a look at the link between both manifolds that supports the plenum holder eye pin bolt. It does have a tendency to rip a chunk out of a manifold runner causing a monster leak and impossibility to control half the engine properly. Again the heat gun will show you that.
If all that looks kosher, grasp the runners and look for any looseness. They do have a habit of cracking at the bases causing air leaks. Also if your truck has been a "heavy back spitter" when cold it may have blown out the manifold to heat paper gasket causing yet another air leak.
If all that looks good and you start to slap it back together but take the opportunity to clean out the cooling fins with detergent and a hose. Plugging the manifold ports of course with rags. The back two cylinders are often piled high with dirt accumulation.
Well that shoulds be enough for now. Plenty to get at this weekend if you are bored with all that Christmas time off.
Bye Bye
Dennis
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McCall Pinz
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Dennis,
Thanks for the detailed instructions. I'm hanging on every word and have some questions.
Both of my carbs have brass throttle shafts with about .5mm of play measured along the shaft and a slight amount of play "up and down" within the bore. Reading previous posts, this play is excessive and I should order the steel shafts from SAV. The bases do not have O-rings in them, but there is a square-profiled groove that could fit an O-ring on each side of the base. Is this where the throttle shaft seals go or does a groove need to be machined?
Also, the Goatwerks rebuild photos show intake manifold insulation which mine does not have. Is this common? It seems like a good idea for anyone that lives in snow country.
Thanks in advance
Thanks for the detailed instructions. I'm hanging on every word and have some questions.
Both of my carbs have brass throttle shafts with about .5mm of play measured along the shaft and a slight amount of play "up and down" within the bore. Reading previous posts, this play is excessive and I should order the steel shafts from SAV. The bases do not have O-rings in them, but there is a square-profiled groove that could fit an O-ring on each side of the base. Is this where the throttle shaft seals go or does a groove need to be machined?
Also, the Goatwerks rebuild photos show intake manifold insulation which mine does not have. Is this common? It seems like a good idea for anyone that lives in snow country.
Thanks in advance
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lindenengineering
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McCall.
Ah Ha! Brass spindles and grooves to accept seals, 1st generation unit with a seal inclusion. Meant to be sacrificial shafts you will probably find the base spindle bores in acceptable condition to insert replacement steel shafts from SAV with negligable "lift" present after assembly. Well that's my experience anyway.
As for the seals you should be able to find what you need from a seal stockist in your area. Take the body and new shaft with you for sizing. prelube the seals with silicon grease to ensure longevity.
There is a mix out there some having insulation, some not. I think it is a good idea to retain it as in certain conditions it prevents freeze up on the runner (manifold tubes). rermeber the pinz engine is running on a full cool so and heat retention should aid even running.
Dennis
Ah Ha! Brass spindles and grooves to accept seals, 1st generation unit with a seal inclusion. Meant to be sacrificial shafts you will probably find the base spindle bores in acceptable condition to insert replacement steel shafts from SAV with negligable "lift" present after assembly. Well that's my experience anyway.
As for the seals you should be able to find what you need from a seal stockist in your area. Take the body and new shaft with you for sizing. prelube the seals with silicon grease to ensure longevity.
There is a mix out there some having insulation, some not. I think it is a good idea to retain it as in certain conditions it prevents freeze up on the runner (manifold tubes). rermeber the pinz engine is running on a full cool so and heat retention should aid even running.
Dennis
OOOps no customer bashing now
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lindenengineering
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Gents here's the last of this.
Remember most of the carburetor woes you think are fueling issues are in fact ignition related. Even skilled trades folk are often thrown by these problems. The maxim is don't condemn the carburetors without considering the ignition system first.
The heat gun if you buy one, will help you isolate a dead cylinder that is caused by ignition failure, plug, wire, cap etc. Its as easy a sliding under the truck and shooting a header.
The distributer on this machine is highly prone to wear. A replacement shaft assy is easy to replace and can make a huge difference to how the vehicle will perform.
A much overlooked item are valve clearances. I have often had a frustrated customer in my shop who has done everything right but overlooked the valves. If you don't know how to check them get someone to show you how.
Lastly of course there are the electrical systems that support the whole function of the truck. Breakers, wiring to the cut off switches, and the ballast resistor in front of the coil can all give you major problems in driveability.
Besty of luck with those carbies.
Over & out Dennis
Remember most of the carburetor woes you think are fueling issues are in fact ignition related. Even skilled trades folk are often thrown by these problems. The maxim is don't condemn the carburetors without considering the ignition system first.
The heat gun if you buy one, will help you isolate a dead cylinder that is caused by ignition failure, plug, wire, cap etc. Its as easy a sliding under the truck and shooting a header.
The distributer on this machine is highly prone to wear. A replacement shaft assy is easy to replace and can make a huge difference to how the vehicle will perform.
A much overlooked item are valve clearances. I have often had a frustrated customer in my shop who has done everything right but overlooked the valves. If you don't know how to check them get someone to show you how.
Lastly of course there are the electrical systems that support the whole function of the truck. Breakers, wiring to the cut off switches, and the ballast resistor in front of the coil can all give you major problems in driveability.
Besty of luck with those carbies.
Over & out Dennis
OOOps no customer bashing now