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Carb for 320 vs 322


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Hi,

I have over this winter prepared and now finally installed a Stromberg carb, said to be for a -52 320 engine but upon arrival turning out to be for a 54-55 V8. After installation there is no problem in starting and letting the engine go on idling but as soon as you want to drive, the engine gets very rough and lacks any power. I have tried to clean out the carb as much as possible but with no succes. The air screws are to my knowledge adjusted correctly and I have not noticed any air leakages that will lean out the gas mix.

My theory to why it acts like this: could the fact be that a "long" 320 engine looses more gas on the way through the intake manifold to the outer cylinders than a "short" V8? By this I mean that the main jets are not as big as necessary for the 320, thereby the engine does not get enough of gas to run good. Or are all jets for a V8 comparable in every aspect to what a 320 needs?

Any aspects and advices are highly appreciated.

Mats

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I drove last week with my old Marvel carb, it´s a -38 engine, before the change and it acted like it always had, ie without any problems apart from being hard started when warm due to vaporisation. I will check the vacuum advance as well though.

On the other hand, I don´t think that the main jets on the new carb have been taken off as there is a need of a special tool. I am thinking of making such a tool and taking them and the discharge jets out for a cleaning.

I also noted when the carb was taken off the flange, two angled sticks from the flange up in the carb. Those I have not seen on any schematics so far, but they probably don´t affect the perfomance.

How do you know that you have the correct jets, as there are no markings on them?

Mats

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Mats - the 7-95 should work well on your 1938. Main metering jets should be 0.049 inch (1.25 millimeters). You should be able to measure this without removing the jets by gently inserting drill bits into the jet (from smaller to larger) until the next larger size cannot be inserted into the jet.

The special tool may be made by acquiring a piece of steel rod just SLIGHTLY smaller than the passageway for the jet. Now cut a slot in one end of the rod that is 0.2 inch (5.1 millimeters) wide. This may be done using an end mill; or if an end mill is not available, use a hacksaw and file. Cut the rod about 3 inches (76 millimeters) long, and drill a small hole in the other end. Insert a small rod through the small hole for a "T" handle. This should allow you to remove/reinstall the main metering jets.

Check to make certain that the accelerator pump check valve in the carburetor is not stuck. Also make certain that the float is working, and properly set. I believe that carb should have a "sight plug" on the side (not certain of this, as I don't have one at the shop to check). If so, fuel should just seep out of the hole when the float is properly set.

Jon.

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Jon,

thank you very much for your advices!

Now I know which size the jets should have and will check that.

I have had a thought of using a squared steel rod, similar to what you just propose, which is wide enough for a cutout of a slot for the jet but small enough to enter through the passages to the jets. Your information about the size of the jet is highly appreciated as it is hard to messure that.

I checked the float height after the first start and that was definetily too low, so I have adjusted the floats and have now the level so it just do not sipp out through the sight plug. I will raise it a little more as I know from earlier forum questions that the level is critical for a good perfomance.

I will keep the forum informed about the progress.

Mats

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Hi,

I have now been able to unscrew the main jets with the type of tool that you described and I have also managed to pull out the discharge jets. To say that they needed a cleaning is an understatement. Almost all of the small jet holes were plugged with some kind of white dried out gas.

Now a question. The shop manual states that it is important to make sure that the lead gaskets on the discharge jets are taken out from the carb body. One had the gasket on the jet itself while the other might still be in the body. But these gaskets can´t be replaced with new ones as they are not in any repair kits that I have. Can the old ones be used again?

Thanks for any help.

Mats

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Mats - the shop manual states to replace them because the odds are better for a good seal; that is NOT to say they cannot be re-used. Since you probably have no source for these, try re-using them.

Less expensive to at least try than ordering a custom kit from the USA.

Jon.

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I reassembled the carb, put it back in the car, started it and went for a drive, and......

WOW, what i difference!!

It now performs flawless with no problem whatsoever. Thanks to the information of the size of the tool and jets I could fix this. Now I will inform other people here about how to disassemble the carb totally. I am not sure that many have done this, probably more the usual thing of blowing it as clean as possible with air.

Mats

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