Just picked up an Offy crossram intake and really want to run this on my hot rod...Need help on deciding upon proper engine combination (carbs, cam, heads, compression ratio as well as rear gears...) I've read that a very mild cam is more desirable over a wild one in order to keep a strong vacuum signal to draw the fuel in...My idea of mild may be different than yours...so some numbers on that are needed!! Street/street hotrod..weighs about 2500lbs wet...weekend warrior..so I don't mind hard to handle I'm pretty much "open" to engine component suggestions to use this intake....I have a 350 4 bolt standard bore block to start with..pair of "993" 76cc 1.94/1.50 valve heads, flatops. No need to use those heads other than they are here and fresh, same with the pistons. Also need to decide on rear gears as well....30" tall tires and using a worked over powerglide w/brake. No converter at this time-didn't want to buy until I know whats going on with the engine! ..take suggestions on that as well!! Thanks as always!
Not familiar with how tunnel/cross ram behaves, especially on a mild low compression motor, but small vacuum secondary carbs and a somewhat healthy cam (about 230?@ .050) to let you better take advantage of the intakes power band along with a 2800 or better stall speed seems to make sense to me. I'm ***uming you are using it primarily for looks? An intake with shorter runners would probably make more power and have better throttle response on a 9:1 350 with stock heads. And like I said, never tried one myself but this ought to get the ball rolling anyways.
There's a guy on here named RodShop57 who runs a cross-ram on a 327...might give him a shout. And here's a recent thread: http://www.jalopyjournal.com/forum/showthread.php?p=6038547#post6038547
I would recommend using what GM used on the 302. Two 600 cfm Double Pumpers, the most important thing would be making sure the primaries are opposite of each other for better driveability. One carb facing fwd the other reverse. Another key is upgrading to 50cc acc pumps. ( too much plenum volume for 30cc). Whichever way you decide to cam it, I'm ***uming not soild? make sure you have the correct Vac/hg on your power valves. I have always drilled my primary ****erflies when running hot cams with multiple carbs, ( helps to prevent fowling and also helps idle characteristics). You will need I feel a minimum of 10.1 to keep the engine "snappy". I would probably not drop below 110 degree lobe center on the cam. With the 30" tall sneakers I would probably go with a minimum of 3.89's in the rear, don't forget those tires will take some gear out of it. Hope this helps a little. I have 30" tires and run about 3100rpm at around 70mph, with my 3.89's. I can still pull hard off the line cause of my Big Blocks torque, but I can also still enjoy it on the hwy without it screaming.
Years ago, one of the big magazines did an intake shoot out. They said the problem with the crossram was a reversion problem. They tried building reversion dams inside the manifold but it was little help. My friend tried it on a BBC 427 with a healthy cam, reversion dams and all. He ended up taking it off and using inline quads. At idle, you could see a fine mist above each carb. I suspect the manifold was designed for high rpm application as in trans am.
Thanks everyone for the input!! The more I'm learning about these the more I'm questioning using it!!! I just love the look, and a 60's drag them is what I'm going after...ohhhh decisions, decisions, decisions!!
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