Projects Joe's American Graffiti Coupe with a Man A Fre (Milner Coupe Clone)

We've used it once to tune the carbs. We just need to fine tune them a bit now for better balance and idle.

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Use it every time ya tune

 

The uni syn will work fine on 3 of the carbs because of the even cylinder firing. But the 7-8 cylinder carb is different get 3 right then work with number 4.

 

Do you mean 5,7 cylinders firing in sequence and being fed by the same carb?


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Yes, I've heard about that issue. We're currently waiting to get back together. Hopefully it will not be too difficult now that the car is finally running strong. The idle is too high at about 1200 and it still is too rich.

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Yes. We think that is what the previous post was referring to. I've been told about that before.

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So, the rear carb on the drivers side needs to be leaner at idle and the main jets because you have a longer/ stronger signal on that carb? Just trying to get my head around this.

 

Those 2GC's came with a 100 different power piston assemblies as well and also 100 different bases depending on size of cam tuning could be a struggle they like engine vacuum. if your vac is low get some adapters and rum 97's reading your spark plugs and putting all the timing into it that she would like. and a cut down plastic cup and small piece of 1/4" rubber hose makes a great adapter for on top of the 2GC's for the sync.

 

I have seen " carb synchronizers" for 4- carb motorcycles would one of those be adaptable for use with automotive carbs ? I don't know why not ?

 

If you have fittings to hook them up it works great!

 

[QUOTE="Moriarity, post: 13512439, member: 218" I still think it is a huge mistake to eliminate the power valves and jet the carbs up. [/QUOTE]

Agree completely.

60 years ago, there were few tuning parts available for the Rochesters, and it MIGHT have made sense to block the power valves on a trailered drag car or trailered salt flats racer.

Spring kits for the power valve actuating valve ARE available today. I can see no reason to block the power valves today unless the car will be used ONLY as in paragraph one, OR a museum car that is never started.

Jon.

 

Probably would not work because of the balance tube, which will balance out the vacuum among the carbs. Motorcycles do not have a balance tube, so each carburetor has it's own unique vacuum, which is what those gauges operate on.

 

A carb synchronizer is simply a way of measuring above throttle blade vacuum , I don't understand why it wouldn't work with appropriate carb hats ????

 

I agree with your point. We were following the directions of others who have had success with the blocked power valves and bigger jets. I do know more now about the system. I have my doubts as well. I'm thankful that I saved the power valves and jets.

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Moriarity and others....

Y'all have been such a great help! Thank you for your shared expertise. What symptoms should I look for with the blocked power valves and 60 jets?

We were previously experiencing severe over fueling. That was blamed on the power valves not closing due to an absence of good vacuum at idle. This was said to result from the aggressive cam and engine build.

We have since discovered that the distributor and/or coil were not functioning properly. We now have outstanding throttle response without bogging down with rapid acceleration.

Hopefully soon we can better tune the set up as it is still running too rich at idle. It is also idling too high at this point. I'm looking for an idle around 900 RPM?. Would that be a good starting point?

Thank you so much!

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Absolutely!

When you install a aluminum intake, do the intake bolts need to be tightened again after the intake warms up? I would think aluminum would flex quite a bit. We are noticing a uniform amount of coolant seepage around the exterior of the intake. I thought it was just one spot before but it is wicking coolant very slowly around both sides. The only place that it is totally dry is the front and rear walls! Is this common with older intakes? Should I worry? I pulled a spark plug and it's dry.


Thank you!

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I'm still collecting rebuild parts, but I intend to use the power valves and jets as delivered. I hope to be at the tuning stage in a month. I definitely am going to the basement to look for info; my catalog/ storage system will not help the search. Thanks for your input.

 

I have a hunch that the flat ends of your manifold might be preventing the manifold to head gasket from completely sealing.

 

Very possible!

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Question before an answer. Do you have idle speed screws (not mixture) down as low as it can go and still run with out dying?

 

Have you placed a flat edge across the intake and heads?

 

I believe the vacuum reading is taken "below the throttle", or the engine side of the carburetor. Motorcycles do not have a manifold, the carbs are mounted directly to the cylinder head. The vacuum port for synchronizing the carbs on a multi carb engine are located on the cylinder head side of the throttle. For an example, see the image below of dual carb installation on a V-twin engine, and the vacuum ports location:


Though if you could connect the individual gauges to the above throttle blade vacuum source, you could use them that way. I don't believe Rochester 2G carbs have such a port.

 

No. We will be adjusting those next. As usual I'm jumping the gun due to my inexperience and worry.

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Yes. It looked relatively good to us.

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I think each of these carbs have a port on the rear. Our dash gauge is connected to the passanger front carb. We also have a hand held gauge to used as well. We tried it early in the process but could not get a solid reading. The needle was bouncing wildly. We attributed this to the cam. This was before changing the distributor and coil though.

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Those ports are below the throttle. Since the manifold uses a balance tube to balance vacuum those individual vacuum gauges won't work. You need to use the Unisync.

 

Nicholas,,

Please don’t take this wrong,,,,I don’t mean any disrespect .
I understand that you are really trying,,,and I appreciate the fact that you are inexperienced.
I am completely illiterate when it comes to these exact setups .
But I know one thing,,,,,,you have one of the smartest guys on here that has a lot of experience with these setups telling you what to do to fix it .
Please listen,,,,,Mark ,( Moriarity ),,,is on target with his tuning advice ,,,he knows these systems,,,,,probably learned through trial and error like the rest of us .
Through several posts he has explained to lean out the jets and use the power valves .
You are experiencing a rich condition,,,,,blocked power valves will cause that,,,,also rich jets .
Carb tuning 101 .

Tommy

 

This is 100% correct. The balance port insures that vacuum beneath the the throttle plates will always be the same regardless of whether or not the carbs are synced. A unisyn measures flow, not vacuum. It helps accomplish the same thing as setting the plates with a drill bit, but more accurately as you are actually syncing the flow. Concerns about the consecutive firing order on one carb are a red herring; it can and should be treated just like the others. I can't emphasize enough the importance of getting the basic setup correct before doing any actual tuning. If they are not synced you'll be chasing your tail with as much chance of catching it as a corgi. I also agree about the value of the power valves.
regards,
Phil

 

I totally agree. I'm doing my best to follow everything he has said. We have unfortunately been caught up fixing other issues that we found after blocking the power valves to fix the issues! So far we have:

Changed power valves
Replaced jets 3 times
Replaced accelerator pumps (not working)
Replaced idle mixture screws/springs (not working)
Added 3 missing idle speed screws and cams
Adjusted the sticking throttle linkage
Removed and resealed the carbs and intake
Finally found that the distributor and coil was not functioning properly and replaced them.

That's just some of the things that we have gotten into. We keep fixing things just to find more issues. I have 2 Uni-Syn tools. Up until now it couldn't be tuned with them at all. It was totally flooded. Now we're dealing with the Coronavirus issues just when I think it's getting better. I can't wait to really start getting the car tuned.

Unfortunately I don't have the skills or the confidence to do these things on my own. My friends are extremely talented car guys. They have their own way of getting the car fixed. My job is to take the wonderful information learned here and pass it on to my friends.

Thank you for your comments. You'll never offend me. To do that you would have to talk about my family. Please everyone, share your thoughts openly without fear....




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