Crossram questions

raceu4her · #1 (**permalink**) 03-22-2007, 07:57 PM

I bought this manifold last year and havent put it on yet. Its going on my 289in my 65 comet. the carbs are 450cfm. Im wondering what you guys think would be a good for a cam and heads. Its going to be a street car but id like to get the most out of it i can. Im going to have 4.56 and a c4. I like a really rough idle and would like to stay solid lifter. any info would help. thanks guys

bubbagump · #2 (**permalink**) 03-22-2007, 09:32 PM

I can't offer cam or any other recommendations. First I would like to congratulate you on securing possibly one of the rarest intake manifold ever made for a SBF. Did you acquire the special distributor too. Or you could go distributorless.
I was interested in these a while back. Then I started running searches on the Smokey Yunick version for a SBC. The low speed torque is nonexistant. Power doesn't come on 'til 4000 r's. They are considered to be unstreetable.
So, I guess you could match the r's too that with the camshaft, say a Z303 and try that.
GL.

Tongue Pirate · #3 (**permalink**) 03-22-2007, 09:52 PM

I'm no expert on crossrams but I would guess that with 900cfm of vacuum secondary carbs your gonna need quite a bit of the ol' RPMs to get much use out of the 2nd half of the carbs. Maybe someone can give a rebuttal of more experience or carb education

raceu4her · #4 (**permalink**) 03-22-2007, 11:04 PM

i was thinking the 450s are to big. maybe 390s?? I dont have the distributor but there is one on the market i found that will work. compression is 10.5 to 1. I should also put any information anyone has on this would help me out a ton, how many were made, what year its from, ect. I know nothing about it other than it looks cool, its NOS and i think it will fit under my hood without having to cut anything. Im trying to keep my comet somewhat b/fx style

olddog · #5 (**permalink**) 03-23-2007, 03:56 PM

At 10800 rpm and 100% VE (not likely) a 289 would suck in 900 CFM.
At a more realistic 80% VE your looking at 13,500 rpm.
You need the smallest carbs you can find, in my opinion.

Tongue Pirate · #6 (**permalink**) 03-23-2007, 04:04 PM

That's kinda where I was headed with my thinking. I wasn't sure if a Cross Ram such as the one pictured would create any sort of situation to where an increase in vacuum might pull the secondaries open. I am fairly familiar with Carbs & manifolds but really haven't run any manifold similar to the one pictured.

Jim Vander Wal · #7 (**permalink**) 03-23-2007, 06:07 PM

I'll pipe in on the crossram style manifold and in particular the Smoke Ram SY1 from Edlebrock on a '69 Z/28 302 in a '67 Vette. 700 double pumper, stock Z/28 solid cam, 11:1, angle-port fuelie heads, 1 3/4" headers, 4-speed, 3.23 gears 3,150 pounds. Just to set the stage.

The coolest combination I have ever run. 7,000 rpm and more, good bottom end power and worked all through the rpm curve from about 2,500 and up.

If I could run this style manifold on my SB 427 I would in a heartbeat. Size the carbs properly and ROCK. Would be way cool.

If it fit on a 9.5" deck height 351 I'd tell you how horrible it would be and offer to buy it just to take it off your hands.

Run it with the right carbs and enjoy.

Jim 1855

FIA-ERA · #8 (**permalink**) 03-23-2007, 07:43 PM

Hey if your interested in some help contact me via PM. I have a friend that has vast knowledge of these intakes. He is willing to lend some info. I remember this same type thread last year. He can get you in the direction you want. Let me know. Matt

bubbagump · #9 (**permalink**) 03-24-2007, 06:32 AM

A flat ram is an underhood version of a Tunnel Ram. The dream is volumetric efficiency will go over 100 percent with the tuned length runner. I would keep the carbs that are on it and use them initially.

Commander · #10 (**permalink**) 03-24-2007, 07:37 AM

what does the inside of the plenum look like

is it separated down the middle...two halves, or all open inside

if all open, then carbs too big, if divided, then only one primary set feeding half the engine...gets you into weber-think...one throttle body per cylinder instead of all venturi available for all cylinders like a 4v intake.

what'll wake that intake, and the engine it's attached to, up, is displacement. bore and stroke the bejebus out of it.

Anthony · #11 (**permalink**) 03-24-2007, 08:52 AM

Quote:

Originally Posted by bubbagump

A flat ram is an underhood version of a Tunnel Ram. The dream is volumetric efficiency will go over 100 percent with the tuned length runner.

that's the idea with weber carbs, tuned runner length. But with webers, you'll probably get better/even fuel distribution. Some of these aftermarket cross rams don't get good fuel distribution, and may not make the power you think they should make. On a dyno, you can test each cylinder to see what A:F ratio each cylinder is getting. If they are off, then you can make alterations to the inside of the intake to get even distribution. Alot of work. I've heard that the Edelbrock and M/T FE cross rams are not that great for making power because of this, although they look impressive.

Commander · #12 (**permalink**) 03-24-2007, 09:13 AM

Quote:

Originally Posted by Anthony

that's the idea with weber carbs, tuned runner length. But with webers, you'll probably get better/even fuel distribution. Some of these aftermarket cross rams don't get good fuel distribution, and may not make the power you think they should make. On a dyno, you can test each cylinder to see what A:F ratio each cylinder is getting. If they are off, then you can make alterations to the inside of the intake to get even distribution. Alot of work. I've heard that the Edelbrock and M/T FE cross rams are not that great for making power because of this, although they look impressive.

there are 'ways' of dealing with fuel distribution problems in old style manifolds, some available way back when, some which are only now available to the common man, which is why he may want to get a new top plate made and get hold of a 'bad man' inline carb...