You need to find someone who knows how to setup the carbs and timing advance curve, also the gearing will need to match the combination.

I worked on one with two 390cfm holleys and it ran OK but on that combination the cam warranted drilling holes in the primary throttle blades to get a decent idle mixture.

If you list your total combination of engine parts, transmission, vehicle weight and rear gearing-I'm sure you'll get some good responses here on if the crossram will work and what needs to be done to get it tuned right. Bob

 

i run one of those things on one of my cars also. 2 500 cfm carbs is a LOT for a 327, i run two 390 hollys also, for a combined 780 cfm on a 350, that is even a lot. one big prolem with those manifolds they are really high rpm race manifolds of their day, as a result street manners suffer. each carb feeds all the cylinders on the opposite head. there is no provision for providing a balance between the two sides so you end up with two independent 4 cyl. manifolds fighting each other. it takes a genius to tune and if it ever gets there it isnt going to stay. my solution was to tie the two sides together with a balance tube, i drilled two holes in the plenems at the very front of the maniflold in front of each carb, tapped them for pipe fittings and screwed two 90 degree pipe to AN fittings into the two holes until they were pointing at each other. i used 3/8,-6 fittings, then i cut a piece of aeroquip -6 braided steel hose to the right length and screwed it all together. BANG!! ive got a balanced system that tunes a lot easier and stays longer and the earoquip actually looks quite nice and trick up there. you are working with bigger carbs on a smaller engine so you could try one at the back to but just the one worked well for me. your miss from 3700 up sounds maybe ignition related, if your guys couldnt get it tune ill bet some of the plugs are black by now.

 

Cross ram tuning

I believe both shops are qualified in tuning the set up but lack experience with this unusual set up. Engine specs. Bore 4.040, Stroke 3.250, Intake valves 2.02 Exhaust 1.6, 10.5 to 1 compression, cam hydraulic, cam specs at .50 lift, int lift @ valve .50in, Exh Lift @ valve .51, lobe center 114.0, valve overlap 11.0, int. duration 234.0, exhaust duration 244.0. I hope that makes sense. Trans is a 4 speed, 4.11 rear and the car weights 2,500. (should boogie).

 

Balancing cross ram

Thank you! Someone else had mentioned something similar to me in passing, but failed to give me details. I will seriously consider doing your modification. Any chance of getting a picture of yours? Any problems with air leaks where you tapped it?

 

no problems with air leaks. pipe tap in manifold, fitting come in pipe thread on one end and AN compression on the other. manifold has to come off to drill the holes, wrap a little teflon tape around the fitting and screw it in. no leaks-- it will be bulletproof. you were a little short on info on your setup, 2500lb. car, 4 speed, 4.11 gears is perfect for that setup. mine was mild 350, 4 speed, 4.56 gears, 2800 lbs full up and it was scary fast with that manifold. it would run mid to low 11s, mid 120s in the quarter. that mod will solve the idle, low speed light throttle problems better than anything else and doesnt affect high speed high power at all. this is not a fixall for every problem, you are still going to have to get the jetting correct for power. this fix takes a lot of the nightmare out of getting there. once you get i dialed in you will like it, i sure did!!!

 

OH, and when doing the mod run the tap in a little at a time and check the fit with the fitting. there is plenty of meat in the manifold, pipe taps are tapered and if you tap to deep the fitting will screw in to far--ideally you want the fittings to go in only as deep as the thickness of the manifold. this is NOT for any operational reasons, you want to keep the 90 degree fitting as high above the top of the manifold as possible to provide clearace to screw and tighten the AN braided hose fitting on the 90 adaptor.

 

Post deleted by author.

 

The cross ram is the only way to go in my book.
It's in the combination and tuning.
The early 302 Z 28's ran them without any problem.
I run one on my 434 sbc with two 650's that I rebuilt with annular boosters.
I Can put it down from an idle of 600 rpm without any problem.

 

old SMOKIE

CHECK OUT MY JOURNAL,http://www.hotrodders.com/forum/journal.php?action=view&journalid=18944&page=5&perpage=5&reverse=1 i HAD A 1959 VETTE 375 HP 202 HEADS ,4SP, EDEILBROCK VINTAGE CROSS RAM TWO 500 CFM CARBS AND IT RAN WELL.THEN OVER THE YEARS IT STARTED TO SMOKE ON THE LEFT BANK ,IT WAS A MANIFOLD LEAK THE BOLTS ARE HARD TO GET TO IN THE CENTER,USE A CROWS FOOT SOCKET ,EXTENTIONS AND SWIVEL,AND TAKE YOUR TIME,AND GET THE TORQUE TO THE BOLT.ALSO CHECK TO SEE IF THE MANIFOLD WAS DECKED OR IF THE HEADS WERE DECKED YOU COULD HAVE THE WRONG ANGLE OF THE DANGLE!!

 

That is what I was suspecting. It sounds like you had the EXACT same problem as me including the same side. I am ready to pull it off and get it trued by a machine shop; just in case.

On a side note; an out of town buddy was just in the garage looking the the intake and noticed my clear fuel filters never fill completely and the electric pump never shuts off or seams to reach a maximum pressure, even with they on and engine not running. Looks like I might have a fuel issue too. Hence the lack of performance.

Thanks for your input.

 

It sounds like a intake gasket is bad.
After a few years they tend to squeeze out and split causing it to suck oil & air and give poor response from a vacuum leak inside the motor, can cause a backfire from being lean.
Ive had this happen to me on different intakes thru the years.
The mounting bolts are easier to get at with the valve cover's removed.
Don't use chrome bolts as they tend to loosen up, they are junk for holding torque. Use a little Permatex #2 on the bolts for sealing. :thumbup:
My setup can be seen here, http://community.webshots.com/user/1bad80100

 

1Bad 80

Nice car,I had the same manifold,great bottom end torque for a tunnel ram and awsome top end performance