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

I need some help. I have a 327 Chevy with a Man a Fre intake and 4 Rochester 2G carbs. On the driver side we have good vacuum entering the carbs on the passenger side the 2 carbs have very weak air flow/suction. This makes it impossible to tune all 4 carbs to match. I'm guessing that I have a vacuum leak somewhere. The car is also puffing smoke from one of the exhaust pipes. I'm also wondering if the valves aren't adjusted correctly. Could too much lash cause smoking and poor vacuum? Engine was professionally rebuilt a couple years ago. After rebuild, the previous owner added the current intake and valve covers.

At this point we are thinking of pulling the intake and valve covers. I'm really wondering what it could be. Have y'all seen this before with other intakes or engines?

Thank you!

Nick

Sent from my Pixel 3a XL using The H.A.M.B. mobile app

 

Anyone have any ideas?

Sent from my Pixel 3a XL using The H.A.M.B. mobile app

 

sent you a "start conversation"

 

Do the old spray starting fluid around the edges of the manifold trick,and listen for sound changes to find a vacuum leak.Black smoke at the exhaust is fuel rich.You would likely smell this.Blue is oil being burned.IF the heads are milled enough the manifold may not seat tightly,and be sucking oil fumes ,or vacuum leaking.

 

I suspect , I take manifold leak at the head . Incorrect base gaskets , also . It sounds as if you have the correct base gaskets if two of the carbs are fine . Did you check for fit of the manifold to heads ? Somewhere through the years some one many have milled a touch from either of these and cause a slight mismatch in fit . And yes valve adjustment will effect vacuum . Very strange you have one bank adjusted correctly and one misadjusted . I have had the luck to look a four Deuce intake , does it have an open design under the carbs ? I guess my question is does each carb ONLY feed 2 cylinders ?

 

As as has been stated valve adjustments can effect vacuum, make sure they are correct first. Puffing smoke could be a vacuum leak into the lifter valley sucking oil on every intake cycle of one or mor cylinders...if your manifold has passages that tie all of the intake ports together in some manner remove the carbs.and you may see oil streaks where the cylinders have been " swapping spit" ....

 

I think that there's a previous thread on here about 4 carb manifolds, but it be man a fre exclusive. I think Moriarity has a one on his Vette, send him a pm.

 

Is there a PCV system and how is it plumbed? Looks like a pipe off the RF carb? Could be where your smoke is coming from...

 

^^^^^ Shouldn't it balance out as to vacuum at such a small loss?

But I agree that this isn't a manifold to run a pcv.

Or, is it a vacuum line to a automatic trans(?) and it isn't hooked up or a blown modulator valve ("smoke")???

 

First thing...with no air filters, you are asking for trouble..!

If you want to run a PCV system, then you NEED to tap into the balance tube...NOT one single carburetor. The PCV coming from a single carburetor, will somewhat obviously pulsate, rather than pull a smooth vacuum.
BUT...a PCV system is NOT the answer to a worn-smoking engine..! Fix the engine problems first.

I ran this setup on both a 327 and a 350 (same car) for many years on my daily driver years back. Once you learn the intricacies, they aren't any more trouble than most any other setup.

Mike

 

That's exactly what I was thinking!

Sent from my Pixel 3a XL using The H.A.M.B. mobile app

 

Yes. It's one of the earliest versions. Only 1 carb per 2 cylinders. Crazy hard to properly adjust.

Sent from my Pixel 3a XL using The H.A.M.B. mobile app

 

Here's my thoughts so far:
The passenger side bank of the intake is not sealed. Therefore oil and gases escaping thus loosing vacuum. This is only being observed at 4 cylinders so puffs of light smoke are intermittent from the exhaust. I think the unique cylinder/carb separation of the Man a Fre can result in one bank that is functional with good vacuum while the other is not.

I will also check the lash as well. This may also be another issue.

Also, the only black hose seen is for the Vaccum gauge. The only crankcase ventilation here is by passive flow. I don't have a road draft tube hooked up yet.

Thank you!

Nick

Sent from my Pixel 3a XL using The H.A.M.B. mobile app

 

@Moriarity must be sleeping in!

 

How are you measuring vacuum? The sizable balance port should make a large imbalance impossible. You may be chasing a red herring.
regards,
Phil

 

From your post I assume the engine was run with a different carb and intake and was OK. I would check the balances passages at an idle you would think they would equalize the vacuum. As old as that manifold is you might check if it has been milled.

 

I do need to check. I purchased the vehicle after it was set up. At idle there is an obvious vacuum loss.in the passenger side. You can feel it from the top of the carbs.

Nick

Sent from my Pixel 3a XL using The H.A.M.B. mobile app

 

The combination of low vacuum and smoking would make me think that the intake manifold gasket is leaking at the bottom of the intake ports on that side pulling in oil/vapor from that side. Like someone mentioned, the manifold may have been messed with over the years but hopefully it’s just a gasket that got displaced during installation.
You need to get the valves adjusted properly and the ignition timing set, it’s hard to troubleshoot these things when there’s a bunch of things out of whack. Are you using a Unisyn?


Sent from my iPad using The H.A.M.B. mobile app

 

If you are measuring at the dist advance ports in the carbs, all it's telling you is that the carbs are not synced. Those ports are covered by the throttle plates at idle and do not show manifold vacuum until they are open. A leaking gasket will not cause one bank to look low because they are all connected through the balance port. I would suggest you start with a careful carb setup and go from there.
Hope this helps,
Phil

 

Not the same intake but thru the same kind of experience on my 327 with a multi carb set up. The intake was pulling past the gasket on the bottom of the intake port...from the inside of the engine. The gasket had fallen apart. Then there was the process of getting the correct gasket to match the intake port to the head ports. There are many different variations in intake gaskets for a SBC...beware you get one that is proper for the combination of intake and head ports.
Also, look at your butterfly's to make sure they are seated against the venturi wall....no light past them when they are closed. You may have to file and lap.
Additionally, look to see that the accelerator pump linkage isn't bent improperly, holding the butterfly's from closing all the way. All four carbs have to close all the way or you will never synchronize them.

Also curious about idle circuits...but won't go there right now

Good luck

Sent from my XT1585 using The H.A.M.B. mobile app

 

Nic -

How did you start this project ? Did you just bolt on an unknown combination ? Is your ignition timing set to a modern value...close to 36 / 38 or so total ?

A MUST to start everything going in the right direction -
From 3 or 4 years of personal experience with the Man-a-Fre

1. The torquing of the "plate". Per Harold (the designer), it's not a manifold (by the dictionary he's right). This should be done carefully. The plate will move/warp around very easily as you tighten the fasteners. If not done carefully and evenly, the plate will leak.

2. Remove the carburetors.

3. Using drill bits, set all of the butterfly blades to the SAME drill bit diameter/gap. Get an average of the two "working" two carburetors, drill bit openings. Then set all four carburetors butterflys to the same opening. Probably, close to .008" or .010" dia.
Do NOT use a feeler gauge. That will give completely wrong information back.

4. Reinstall the four carburetors. During the tightening , pick a spot..! Set ALL four carburetors to the same location. That is, push them to the rear (or front !) of the hole vs screw diameter. It's a small difference...but it can make a big difference..!
Tighten all four.
Do not connect the linkage at this time.

5. The idle mixture screws should be adjusted to about 1/2 to 3/4 turns out, each. This may need another adjustment later.

6. Start the engine (NOT the car !). If the idle is a little high or low, don't worry, you'll fix that here.
Get your Uni-Syn gauge (you have one correct?) and slowly start adjusting the carburetors, idle speed.
Go slowly and do this step several times to make sure one carburetor isn't overpowering the others.

7. CAREFULLY...adjust and install the linkage so that all four open as close as you can get to the SAME time. Test several times.
DO NOT let the linkage move the throttle shaft as you secure the linkage to the carburetor.
Again, it works.

8. Repeat step #6 to make sure you didn't change anything as the linkage was installed.

9. After the engine is at full temperature, using your Uni-Syn gauge, make VERY small changes to the idle mixture screws. You are looking for a smooth idle and movement of the gauge. No up-down movement.

10. Attach your "air filters", and test drive.

Hate to say it, but if you need to adjust anything, you'll have to start at #6 and down all over again.

SMALL changes make a difference with this intake.

Mike

 

This mounted to a 4 barrel carb cover and adapted to a WCFB but it IS your friend.

 

I got it! We've tried but the two carbs on the passenger bank are two far out to even raise the ball at all. It's gotta be the intake.

Sent from my Pixel 3a XL using The H.A.M.B. mobile app

 

This seems like perfect advice. I've searched every post and site possible for this information. Thank you HAMB! I'm so happy and thankful for the help.

The car was purchased last fall as shown. It was said to just need proper tuning. We have spent several months and many hours tuning. The car has a relatively large cam. That hasn't made tuning easier. We have spoken many times with Larry at hotrodcarbs.com. He has helped us many times with great advice and parts.

Hopefully this thread will be helpful to others installing and using a Man a Fre for the first time.


Nick



Sent from my Pixel 3a XL using The H.A.M.B. mobile app

 

Poor vacuum on one bank plus some smoke from that bank make me think the manifold isn't well sealed on that bank. If the heads have been milled it affects the angle and height of the sealing surfaces relative to the manifold. You will need to pull it to see if that's the problem. However, if you know anyone who has access to to a smoke machine, you could smoke the bad side of the intake and see if the smoke comes out the crankcase. Conversely, you could smoke the crankcase and see if smoke comes out one or both of the carburetors.

 

Great point. We're gonna find something out next week! We're planning on getting together and working on it this Wednesday.

Sent from my Pixel 3a XL using The H.A.M.B. mobile app

 

Found this article in a old magazine that I was looking through last night ...don't know if there is any info that you can use or not .

Sent from my SM-T387V using The H.A.M.B. mobile app

 

I haven't seen this one before. Is there anything there about installing the system or tuning?

Thank you!

Sent from my Pixel 3a XL using The H.A.M.B. mobile app

 

Just what was in that article...found this ad in a 1964 hot rod magazine.
If I run across anything else I will post it.

Sent from my SM-T387V using The H.A.M.B. mobile app