old school tunnel ram and carbs question

[427TJ]

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fuel bowels

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I think you mean bowls . 'Bowels' are a part of the human anatomy, just below the belt loops and out back.

Seriously though, that is a fascinating essay on tunnel ram set-up. Makes me want another one. No wonder my 327 ran like s__t 25 years ago when I borrowed a buddy's setup! Too much carb (600's).

[JoeG]

Yeah---Weren't those Very times---

[Plowman]

I've come into this thread a little late, but wanted to add a few of my thoughts.

I've run several 1850 carbs with both tunnel and x-ram intakes. I've found that street driving required me to restrict the liquid line in the metering block. Since the 600 carb was factory tuned to provide idle- we'll say for 8 cyl. in this case, multiple carbs will then be very rich at idle- beyond the adjustment of the idle mixture screws. With this done, the 1850's can be tuned with conventional methods to run very well on the street. I'm willing to discuss this more if anyone is interested.

As for the vacuum secondaries, needing to be changed I’ll have to disagree. Although tunnel ram does lower the engine vacuum, the secondaries operate off of venturi vacuum. They are completely tunable on tunnel ram. I also think they help in making a tunnel ram engine more streetable because they only open X amount from the venture signal. Mechanical secondaries can give too much CFM too easily.

I actually like the look of sideways mounted carbs. When/If you remove the jet plate and add a secondary metering block to an 1850 carb (to allow standard jet changes) you can no longer mount the carbs inline. Sideways mounting also helps with fuel slosh.

Plugs do tend to foul with multiple carbs due to fuel puddling in the intake, but a vintage MSD 7A will remedy that. I’m sure any hot ignition system today would work as well- I just like the old MSD 7 before they went to the 7AL.

[musclcar]

when you say "restricting the liquid line " are you talking about lowering the fuel pressure down to control flooding by adding a pressure regulator ?? .also the secondaries will work correctly without the vacum line connecting them together

[whitetop]

The only other problem I don't like about running the carbs sideways is you have to cut an extra wide hole on the hood the clear the carbs and linkage. The extra large hole looks odd when the hood is closed (or open for that matter).
From your first thread it sounds like you want to make the car period correct. I would say only 5 out of every 100 street cars ran the carbs sideways. You can do what you want.

In terms of the vacuum secondaries There was a huge differnce when I ran the balance tube kit...for the better.

[Plowman]

Unfortunately, I was in the ER and just got released. I thought about this thread while I was in there and I'm glad to reply. The liquid line in the metering block is set up for 8 cylinders, so by having 2 1850s on there, there will be enough liquid to feed 16 cylinders. By restricting the metering blocks to only feed 4 cylinders each, you have 8 cylinders being fed and idle will not be super rich-very streetable.
The vacuum secondardies will work fine by themselves. They are adjustable by changing the springs in them.
If you have more questions, maybe I could post a picture of them.

[budnate]

a question..when we buy these so called matched tunnel ram holleys with the kit like from Summit are they not metered correctly..I was getting a good handle on this until the last few posts...

Thnx Bud

[427TJ]

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The only other problem I don't like about running the carbs sideways is you have to cut an extra wide hole on the hood the clear the carbs and linkage.

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Leave the hood off and chrome the hood hinges and springs. Then drive around with the hood hinges in the "open" position. Anyone remember that? A noisy gear drive adds to the impact. Suddenly it's 1979.

[whitetop]

Bud
The "matched" carbs from Summit/Jegs do not have anything special done to them. What Summit or Jegs mean by matched is they are the same part number ..and I'm being serious.

Plowman, I did not have to change the springs in my vacuum secondaries but in my friends street rod we did experiment with various springs. You mention you can run the vacuum secondaries by themselves(meaning without the vacuum balance kit). I found my car ran much better with the vacuum balance kit-because both secondaries open and close at the same time. I have yet to talk with someone who's engine ran worse with them. Of course everybodies setup is different...and some people just get lucky. I've talked to some people who took 450 holleys out of the box and they ran perfectly with no tuning whatsoever. Some people I talked with changed just about 3/4 of the components on the carbs and they still would not run right.

You talk about blocking metering plates etc to decrease fuel flow richness. I did that by running small 390's. I don't think my small 289 with metered down 600's would have run as good as the 390's.

[rat tuned]

has anyone ran a 6,000 rpm oval port big block with 450 holley's? it would seem to me that 900 cfm would still be plenty. i suppose the 1200 vacuum carbs would work as the carbs would deliver what the engine needed. i'm curious how my 454 oval port would respond as it has a 10" converter and 4.10 gears. i know i like the 450 carbs. mike