Crossram and exhaust manifolds anyone?????

[aaronz28]

i am going to put the crossram on my Z, but would really like to keep the manifolds and smog on...

I put the repop Z28 headers on this week and even with the 30-30 and single 4bbl, the car runs a 1000% stronger from 2000 on up to 7000.

it will actually burn the tires off the car from 4000rpm on up....

but not only did I install headers,  I pulled the chambered exhaust off and went with a 2.5 mandrel bent system and crossover tube....

is anyone running the crossram with manifolds with good results?  We see alot of the cars in photos with them on, but i've never actually spoken to anyone who runs the crossram 140cam and manifolds - regardless of exhaust system.

any info from somone who has experince with this setup would be greatly appreciated.

thanks

Aaron

[jdv69z]

I've always read that this is a high RPM setup only; NOT recommended for street driving; If y the car is for street driving I'd steer away from the crossram.

Jimmy V.

[zzmike]

I agree.  If you are not comfortable with keeping the car above 3,000 RPM to have any usable power, it is probably not the choice you want to make.  BTW, I have never had manifolds on my car to see how it would act, but I have to run cut-outs behind the headers to keep it happy, anyway.  For this reason, I doubt manifolds would be a good choice.

[aaronz28]

Do you guys have real experiance with the crossram?

Wayne Guinn has stated to me several times that the crossram is what the 302 is designed for and in both of his books, there are dyno sheets showing more peak torque and more peak HP across the entire rpm range. In his opinion it is a very streetable intake and equally streetable to the 30-30 cam and 4bbl intake... (IF USING HEADERS although his books show several pix with the crossram and cast manifolds.)

I've seen several photos of cars with this manifold and the exhaust manifolds and I'm trying to determine how well it runs in that situation.

My car woke up a ton when i went to headers, but i also changed from the Chambered exhaust to an almost no backpressure 2.5 inch mandrel best system with a crossover, so I'm not sure how much of the "waking up" was a result of the headers, or the entire exhaust system.

 
I'm not concerned at all about running it above 3000 rpm... thats where it loves to be now anyway...
with a wide ratio and 4.10 gears.... low end isn't really an issue even for a 30-30 cammed 302.

[zzmike]

I have very real experience with the crossram.  I have a Z/28 that has worn one since 1968.  That is why I gave you the advice that I did.  You don't have to take it, that is your perogative.  Have a great day.

[hotrod68]

It's like going to a pie-eating contest constipated--why take in more than you can get rid of? The ugly, restrictive manifolds choke a crossram (or any other) setup at high rpm. Those things were designed to run on real Trans-Am racers with open headers. Admittedly, a crossram setup looks trick, but manifolds would make it even more sluggish at low rpm and strangle it on top-end. And invest in a lot of AC46S plugs if you mostly drive it around town! The sheer plenum volume gas-washes the cylinders at any kind of low rpm with even a moderately high overlap cam like the 30-30. It takes a LOT of tuning to make a crossram run right on the street. My 2 cents and good luck! 

[grandseahawk]

I have a 302 with the GM cross ram. Dyno  (on the stand) results just came in at 466HP @7400RPM  and 404 ft/pds in the 5K range. This was with somwhat restrictive exhaust. Doug's Headers are on now @ 1, 3/8"  The motor is "built." We could have put a hotter cam in for more HP, but "driveablility would have gone down."

I'll post the net HP and torque when the motor is in the car and I'm able to take it to Bottle Blown for a true  "rear wheel HP" dyno. And, I'll post it's "drivablility."

Rock On...

[zzmike]

I have a 302 with the GM cross ram. Dyno (on the stand)  Doug's Headers are on now @ 1, 3/8"

1 3/8" is an awfully small primary.  Are you sure they're not 1 3/4" ??

[jdv69z]

I'd be curious as to torque/HP at off idle to 3000 RPM range. This is where you will live on the street. I have owned a car that has to be revved up to get usable torque to pull off the line, and it's not much fun to drive on the street.

Jimmy V.

[grandseahawk]

Oops, my bad...yes, 1 3/4" headers, not 1  3/8".

I'll post low RPM results shortly...

Rock On...

[crossram]

I also had a 69 Camaro with the off road cam and headers and a factory crossram set up. You need to seriously consider how you are going to drive the vehicle prior to adding the intake. You are going to be flooding that engine, not that that is a bad thing, and yes that is what it was intended for. However taking off from a stop especially when the engine is cold, can be difficult to say the least. Originally these cars had no choke plates, so proper warm up is required before they will function well. I say this as after I installed the crossram on my car, I ended up driving it less. It is a nice set up for racing, difficult for street, especially low rpm. Best of luck with your choice.

[plumL78]

I have a factory crossram , 140 cam, headers. on my 302 and I drive it anywhere any time and it runs great. I've put about 16K in five years.  I haven't touched a screw on it in two years. I'll change the plugs and tweak it  this winter and they go for about two years too. As for having stock manifolds why would you. Once you bolt the crossram on you aren't stock any longer any way not to mention how its going to run with manifolds.

[JKZ27]

Aaron, do you think a close ratio trans could help your driveability?


John- (No crossram experience)

[plumL78]

The close ratio doesn't have the low gear you need. Gearing is a big key and chevy didn't make any that really work for the crossram. Mine has custom gears in the muncie  tranny. 296 1st, 220  2nd , 159 3rd. I wouldn't go any higher. After all the gearing you still need to play with the carbs. and timing to make it streetable

[jdv69z]

Hello pluml78,

Just curious - what rear axle ratio are you using?

Jimmy V.