Will be putting a tunnel ram setup on my 30 coupe this Winter. Using an Edelbrock TR1Y manifold and two Holley 600 with vacuum secondaries. Carbs are rebuilt with the following in them..Front jets 66, Power Valves 6.5, Squirter nozzles .025, vacuum pods connected together with hose. Will be going on a 355 big cam and roller rockers. Don't know much else on motor. It currently has 3 deuces on it and runs good. Turbo 350 transmission. Ford 9" but don't know ratio. Runs about 2900 rpm at 70 mph. The rear tires are P285/70R15. What I am looking for is if there are any obvious changes I should make to carbs before I mount them up. Just trying to save a little frustration at start. And yes I wanna do this!;0) Thanks for any help!!
I put a Weiand tunnel ram and twin 600 Holleys on my RPU. No advice to give really as I never ran it to the max at all, or set it up too well to run max power, roads were too screwed up where I lived. Couple of car guys, engine builders, I knew were a little surprised I had it idling so smoothly at 700rpm. It sure looked the part and ran well enough when I stood on it a bit occasionally.
I would check the list #on the carburetors and install jets and power valve and rear jets or metering plate to factory specs and start from there. If you have to make big changes to get hem close maybe there is something else wrong or they are just not correct for you combination. If you list the #s I may have the specs.
1972, Windsor, Ontario. George Fitzios' 427 side-oiler. Used gear driven secondaries, car was tuned to accel! Felt like a Saturn five launch.
You are going to have to get it running and see if it is rich, lean etc. Plan on tuning and more tuning to get them right. You will have to tune for idle , cruise, and full throttle.
Drive easy to begin with then work up to harder driving, freeway driving. Keep a close look on the (fresh) spark plugs at every step. The jet sizes and power valve you mention...are reasonable for single carburetor and small plenum. You have a much larger plenum now..! The squirter nozzles should be at least .031"'s to start. They'll need to fill a huge flat spot you'll have. The cam and cam rotation will need to be experimented with also. Think...more fuel. Actually...if there is a dyno shop near you...THAT's the best bet to get all the tuning done so the engine is happiest. Mike
I was told to expect zero low end power, no pull below 3000rpm, flat spots etc, but mine revved and took off far better than it ever did with a stock Chevy corvette manifold and a single 600 Edelbrock carb. Instant power as soon as I hit the throttle. The Edelbrock would just make it fall flat on its face if you stepped on it hard at low rpm. I only fitted the tunnel ram for the ‘bling’ factor, but I was very pleasantly surprised just how well it did run.
Saltflats' advice is sound. If possible, run each carb on a single 4 barrel engine 1st. Tune with a vacuum gauge individually, to get them closely matched. Of course, there are variables introduced with this method. But a good way to spot an issue with a particular carb, prior to running them as a pair. The ''poor man's flow bench''. Best wishes with it.
Thanks for the tips guys. Looks like I will see how they run when I finally get them on. I might change the squirters before hand since I have .025 in them now. Move on up to a .031. The carb number is and 1850. Will be back when running, but may not be till beginning of new year!
I built a tunnel ram manifold in about 1968 for my 331 hemi. Designed it in physics class in JC, Ran a Rochester 4-Jet carb. Zero bottom end for sure. The theory is they free up the system to one degree of freedom for the organ pipe pressure pulses that supercharge the cylinders at one designed engine RPM. They hurt performance at other speeds. The shorter the runner the higher the boost RPM. This design eliminates the spurious pressure pulses in a conventional manifold that result from flow through the carb, from other pulses coming from adjacent runners, etc., at the expense of good air velocity. In practice they look great but are pretty poor technology.
Yes, mine would take off like a scalded cat from crawling along at idle, to spinning rubber and howling tires, just by stamping on the throttle. The rumours about no power below 3k are just rumours.
Years back I had a 355 cid sbc in my coupe . Lots of cam and a 3500 stall. Two 500 eddys on a tunnel ram. After some extensive tuning this set up worked great. In town, very respectable manners, on the highway or at the track, she was a beast.
Holley 450cfm 2x4 tunnel ram carbs ran perfect on my 383 chevy. A/F meter said they were jetted perfect as they came. https://www.holley.com/products/fue...rburetors/tunnel_ram_carburetors/parts/0-9776
Go with 4.5 power valve, the 6.5 won't be fully closed and the engine will be 'false rich'; go with .028 squirters. You'll probably have to mess with the secondary vacuum springs, esp with a light car & cam. I'd invest in one of those kits for tuning the vacuum pots by removing just the top cover, the regular vacuum secondary pot has to be removed from the carb to take the top off, the kit provides a new top that you can access the spring without removing the pot. I suspect you'll need a light spring to open the secondaries.
Holley quick change spring kit # 20-73 is made for 2 x 4 Holley vacuum secondary carbs, it allows you the option to add a vacuum line to join both pods to equalize vacuum , insuring both carbs open secondaries equally when running same spring. With the big cam not making much vacuum at idle, lower the power valve number to about 1/2 of what your vacuum gauge reads at idle. example: 9 lbs vacuum = 4.5 pv Norb
Friend of mine had to do that, his secondaries were opening unevenly. Not sure if it makes any real big difference to performance, but for racing you want all the extra you can get. He had me hunkered down in the passenger seat watching them open as he ran down the 1/4 mile.....
Thanks for all the tips so far. Probably won't get on car for a few more weeks. Loots of good info, especially kit to put lighter springs in vacuum Hey Norb One quicky. When I get to checking vacuum, where do I check it at? From each carb at the base, or do I check at vacuum hole near top of the manifold? Thanks!
Hey Norb One quicky. When I get to checking vacuum, where do I check it at? From each carb at the base, or do I check at vacuum hole near top of the manifold? Thanks![/QUOTE] Yup, like Salty Said Ether carburetor at the base, or the vacuum hole near the top, should all read near the same vacuum for your test. What ever one is easiest to get to. If it is together, you might want bring it up to operating temp and do a baseline test to tell you what vacuum you cam is making now. Norb
tuning, tuning, tuning and understanding what the engine is doing to make changes. Long runners, small plenum, short runners large plenum? Long runners, large plenum use very small carburetors. This is for STREET driving....The reason people say they do not have any low end is because of a mis-matched combo....too big carb, short runners, large plenum and or the wrong power valve. ^ 2X, use a 4.5, 3.5 power valve to start , especially if you are using a "racing" cam. Bogging or hesitating?