I have a 69 302 factory original crossram/carb setup. Can someone give me the details on tuning these carbs. At low rpms and cold there is a popping in the exhaust. How do I get rid of this? Judging by the black inside the airhorns, these carbs also have been backfiring through the intake. Any help would be appreciated.

Me again... Can you give up some more details, condition of carbs, what cam, how much timing, stuff like that? You can get the factory carb info off the Holley web site, look for their carb list numbers section. Also check the Chassis Service Manual for tuning info, timing, carb settings etc. I don't think any Camaros rolled off the assembly line with a crossram so the CSM may not help. Improper timing can cause back sparking out the intake amoung other things, I would look there, possible a blown power valve as well. There are a couple guys that have experience with crossram carbs so be patient if they don't check in everyday it might be a bit before they see your post...

Not a good start. Im on here for one day and already got my first reprimand.

Not a good start. Im on here for one day and already got my first reprimand.

Nothing like a ticket to start the day!

Seriously, I have included a link to a vendor website with a crossram manual. Dont know a thing about it, but it may make for a good reference:

http://www.drclassic.com/catalog/Camaro/Air%20Cleaner/B00382.html

Cheers-

Rob

Oh common don't be that way! It wasn't intended as anything but help!! Damn some people anyway!!! :clonk:

Oh common don't be that way! It wasn't intended as anything but help!! Damn some people anyway!!! :clonk:

Tough crowd!

I would be interested to know if the book is any good, maybe cortezsilver will get one? I have a friend who is contemplating the 'ram- I am sure he will need all the help he can get, so I may grab a copy regardless. Sam Posey tested a 1968 Z-28 for Car and Driver back in the day. The car, equiped with crossram, 4.1:1 rear, ran 1/4 mile time of 13.77 @ 107.39 MPH. Otherwise in "stock" trim- now that's scootin' pretty good. Please keep us updated...

Rob

cortez you have not been reprimanded at all, where did you get that from? DjD gave you good info. that not many on this site are expert in the area of crossrams and it might take awhile for someone to have the expertise to be of help to you. That was very sound information and certainly not a reprimand.
If you had done something wrong, you would hear about it with a closed thread or deletion. Lighten up and enjoy the good folks that are here to help "if they can". Its all volunteer in here.

DJD was trying to help you understand how things work here. If you come off as snotty, you won't get much help from our members. Your choice.

That manual is not much good for tuning or jetting advice.
It says if you use dual 780 carbs, to use 72 jets all around. No other jetting recomendations. It does have info on the factory options that go with the manifold, including cams, air cleaners, hoods, oil pump, and various carbs used with the package.

Hey Guys, just kidding about the reprimand. Im pretty easy going Jim and dont have a chip on my shoulder as you might be suggesting. Its cool

DJD, I have been reading some of your post and replies. You are an asset to this site and I am sure alot of members here are happy that you are one of the moderators. I have been a member of the Lamborghini and Ferrari sites for several years and you would expect the mods there to be arrogant people but they are not. It takes very mature level headed leaders that are not judgemental, dont have a hall monitor demeanor and slow to get angry to do what you are doing the right way.

I know 2 guys that have their 69 Z28's set up and running great with the crossram. It's all in the jetting. I personally don't have my car running yet so I can't comment but I'll try to get in touch with them to get the combination they're running. In the meantime, what is your current engine combination? Stock cam or off-road cam? Headers or manifolds? Stock 3.73 gears?

I have a 69 302 factory original crossram/carb setup. Can someone give me the details on tuning these carbs. At low rpms and cold there is a popping in the exhaust. How do I get rid of this? Judging by the black inside the airhorns, these carbs also have been backfiring through the intake. Any help would be appreciated.

Hi,

When do the carbs backfire?? Is it on acceleration or during cruise?? I noticed you said it appears as though they have been backfiring by looking at their appearance, have you personally noticed any backfiring through the carbs at all??

What are the specs on your camshaft??

When do you notice the popping in the exhaust?? I know you said when it was cold, but is it when accelerating, cruising, idling, all of these??

Just trying to help

Thanks guys. It starts up and idles good when cold but a noticeable pop in the exhaust. Sounds like drivers side exhaust. Whem warm it goes away at idle but will do it when you first let off the clutch and slightly load the engine on take off. At lower rpms and cruising it does not pop but if you mash it it will backfire through the carbs as if it went lean. Stock cam that idles pretty smooth and headers. It has 4:11 gears.

When setting idle speed should both carbs be adjusted to the same butterfly opening?

Thanks guys. It starts up and idles good when cold but a noticeable pop in the exhaust. Sounds like drivers side exhaust. Whem warm it goes away at idle but will do it when you first let off the clutch and slightly load the engine on take off. At lower rpms and cruising it does not pop but if you mash it it will backfire through the carbs as if it went lean. Stock cam that idles pretty smooth and headers. It has 4:11 gears.

When setting idle speed should both carbs be adjusted to the same butterfly opening?

I did a search of the forums and got quite a few hits, one thread talking about A/F ratios, etc. May want to talk to Jerry MacNeish about Dist. set up? Here is one of the links:

http://www.camaros.net/forums/showthread.php?t=15454&highlight=crossram

That's a large manifold and when cold will have fuel dropping out of suspension and run lean, working with the chokes is about all you can do short of richening up the carb which will make it go too rich when the manifold finally heats up. I've had similar conditions working with four weber carbs on a SB chev.

That's a large manifold and when cold will have fuel dropping out of suspension and run lean, working with the chokes is about all you can do short of richening up the carb which will make it go too rich when the manifold finally heats up. I've had similar conditions working with four weber carbs on a SB chev.

Hmmmmmm....... no chokes on my carbs, but then again I don't have a real huge problem with puddling. Being in the Arizona climate does have its advantages.

I dont have chokes either. None of the original cross ram carbs had chokes or provisions for chokes. ZZ Mike, Do you have any tips?

As a matter of fact I'm working on a list for you :thumbsup:

I am just really paying attention to details before passing it along, since mine is a true '68 crossram, it has single squirter carbs and is really a different animal to tune when compared to the two-squirter carbs that the '69s had.

Bear with me, you'll have it in the next day or so. :D

Thanks ZZMIKE

Hi,

Just wanted to let you know that I haven't forgotten about the list, I have just been busy. Hopefully by this weekend I'll have it for you.