Hi all. I have an Edelbrock X-C8 cross-ram that I would like to install on my 55 Chevy. This is a street machine and not a race car. It has a 383, Dart 1 heads, lumpy Racer Brown cam, BW T-10, 3:08 rear. Have a pair of Edelbrock 1904 carbs for it also. In an earlier post, I received some excellent advice from forum members. This includes the suggestion that I install a crossover tube or tubes in a pair of carb spacers, to make this mid to high RPM manifold more streetable. This made a lot of sense to me. However, I have several remaining questions: -Should the spacers be made of aluminum, or phenolic? -Would two 1-1/2” crossover tubes joining the carb spacers likely be enough? -I have read that backfiring can be a problem with this type of manifold. Would installing backfire valves in each spacer be a good idea? Thank you all in advance for any advice you may give me.
I'd use rectangle aluminum tube, lain on its side, spanning between aluminum 1-1/2" or 2" spacers under each carb. TIG welded, you can leave it as-welded or grind smooth, your choice, but I would radius the inside lip on each end. Be prepared to also have to alter the booster cluster to bigger pump nozzle size. There is a calculator for determining recommended total plenum volume for a given combination, but I cannot recall where I've seen it. Might have been over at the Speed-Talk engine forum. If you wanted to be creative, I would also try orienting the spacers so the carbs can be mounted sideways, with each carb facing inward towards each other, with the secondary's to the outboard. Linkage will be a little project, maybe weld a mount pad on the top side of the plenum tube?
Maybe some HAMB members will post pictures of how they approached the problem. I would, but I held out for a M/T crossram that has the balance tube cast in. The old 6x2 log manifolds often came with 3/4”-1” ID ******s cast in for balance tubes so I would start small and work up. Having the carburetors side by side makes it easier. I guess I would get a couple aluminum 2” tall carb spacers and drill and tap each for two heater hose fittings (1/2”pipe to 3/4” hose, 3/4p to 3/4 if you can find them). Aluminum is easy to drill and you can weld on it if need be. You might consider a 1/4” Bakelite spacer under each 2” spacer just for heat control but that’s probably overkill. That’s what I would do, but like I posted on your other thread, back in the 70s my old Edelbrock crossram ran ok without adding anything - it was my daily driver. Get it running and see if it’s as bad as everyone else thinks it is. Start with the basics and work up.
Eric and Bob, Thank you very much for your advice. I appreciate it. Time to check my underhood clearance and order some parts. Take care!
Curious why you would have the carburetors with the primaries to the inside. The 409 that I'm working on with the M/T crossram I was planning on having the primaries to the outside like Mopar had back in the days. I have to edit this as I went back and looking at my pictures I do have the primaries to the inside.
Not sure how much it would help you, but Engine Masters (David Freiburger) did an episode comparing a cross ram to a tunnel ram on an engine dyno. You can search for it in YouTube. Thay didn't do the balance tube that you are pursuing but maybe some of the testing they did could give you some insight to what you can expect.
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