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Tunnel ram help

Posted By: Harley

Tunnel ram help - 11/18/10 07:38 PM

I have a tunnel ram with 2 Holley 750 DP carbs on my 505 inch motor. I put a set of spark plugs in and took the car out and drove it all day. The car ran okay for the most part, it dose not idle very well in gear. Anyway I pulled the plugs and noticed that the front of the motor
(plugs 1,2,3 & 4) are running lean and the back plugs are running rich. The carbs are set up exactly the same. When the motor is warm I turn in the mixture screws in until the motor stumbles and then I back them out ½ turn. What would cause this? Is this common? Should I just back out the mixture screws some more on the front carb and turn them in on the back?
Thanks.
Posted By: Guitar Jones

Re: Tunnel ram help - 11/18/10 08:53 PM

Need more info, is this a brand new set up or was it used. Has it been on your engine for awhile?

What I'm getting at is it sounds like the carbs may not be the same or they could be dirty, the float levels may be off, so many possibilities.
Posted By: DJVCuda

Re: Tunnel ram help - 11/18/10 08:55 PM

what type of linkage? is there flex?

What about the idle setup - they have to be the same - so how are you setting the idle?
Posted By: Harley

Re: Tunnel ram help - 11/18/10 10:04 PM

Quote:

Need more info, is this a brand new set up or was it used. Has it been on your engine for awhile?

What I'm getting at is it sounds like the carbs may not be the same or they could be dirty, the float levels may be off, so many possibilities.


The carbs have been on for a while. They are 750dp list # 6109. I had water issues in the past and replaced the old gas tank. I also had to take the carbs apart and clean all the [Edited by Moparts - Family Friendly Site - Keep it clean] out of them. The float levels are fine. They sit sideways on a Weiand hi-ram intake.
Posted By: Harley

Re: Tunnel ram help - 11/18/10 10:08 PM

Quote:

what type of linkage? is there flex?

What about the idle setup - they have to be the same - so how are you setting the idle?


The linkage seems to be fine. They both have 1 ½ turns out on the idle mixture screws.
Posted By: Harley

Re: Tunnel ram help - 11/18/10 10:16 PM

What I mean about the idle being bad is the motor idles at 1100 rpm in park, and when you put it in gear it drops to 900rpm and starts to fall from there. I have to drive with 2 feet. The timing is locked. It makes about 7 inches of vacuums in park. I forgot to mention it has a flat tappet solid cam in it .613 lift 278@.050.
Posted By: Brandon70cuda

Re: Tunnel ram help - 11/18/10 10:29 PM

Sounds a bit like a vacuum leak. Would explain the front being lean and the idle. Carb base gasket leaking maybe?
Posted By: Harley

Re: Tunnel ram help - 11/18/10 10:47 PM

What’s the best way to check for a vacuum leak?
Posted By: mac56

Re: Tunnel ram help - 11/18/10 10:52 PM

Quote:

What’s the best way to check for a vacuum leak?


Spray wd-40 any where you suspect a leak. The engine will pick up rpm as it is sucked in and burnt.
Posted By: polyspheric

Re: Tunnel ram help - 11/18/10 11:42 PM

The timing is locked
Mistake #1.
Where are the throttle disc vs. transition holes at idle?
PV, Y/N?
Do you have a balance tube between the front and rear float bowls?
Posted By: Ari440

Re: Tunnel ram help - 11/19/10 12:04 AM

I would look into the back carb ,see if its dumping fuel in or it has an issue

block the two outer air holes on the top see if the carb reacts to it
Posted By: Harley

Re: Tunnel ram help - 11/19/10 12:48 AM

Quote:

The timing is locked
Mistake #1.
Where are the throttle disc vs. transition holes at idle?
PV, Y/N?
Do you have a balance tube between the front and rear float bowls?


The throttle blades are not close to the transfer slot. I have no p/v. Why is locked timing a mistake?
Posted By: Harley

Re: Tunnel ram help - 11/19/10 12:52 AM

Quote:

I would look into the back carb ,see if its dumping fuel in or it has an issue

block the two outer air holes on the top see if the carb reacts to it


No it is not dumping any fuel, the floats are set correctly. And the motor dose slow down when blocking the air bleeds.
Posted By: VanishPt

Re: Tunnel ram help - 11/19/10 01:07 AM

try switching the carbs and run them for a while . See if the problem follows the carb.
Posted By: mac56

Re: Tunnel ram help - 11/19/10 01:19 AM

Quote:

try switching the carbs and run them for a while . See if the problem follows the carb.


Very good idea in my opinion.
Posted By: Ari440

Re: Tunnel ram help - 11/19/10 01:42 AM

Quote:

Quote:

try switching the carbs and run them for a while . See if the problem follows the carb.


Very good idea in my opinion.





I see two new metering plates in your future !

one of them is running rough
Posted By: Harley

Re: Tunnel ram help - 11/19/10 02:06 AM

That is a very good idea. I will switch them up on Sunday.
Posted By: Cab_Burge

Re: Tunnel ram help - 11/19/10 04:12 AM

When you have both carbs off look at all four sets of butterflys on the throttle shafts, use a feeler gauge to see if there opened the same(front and rear on both carbs.) on the idle circuits, if not adjust them so they are BTW, di dyou buy those carbs new or used? If used look at the idle and high speeds bleeds as well as the idel fuel restrictors in the metering blocks The RPM drop sounds good but it may be loading up aftet idling a small amount of time in gear
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