Hemi Magnesium Cross Ram Concern...

[SSing]

Application Nostalgia ´68 SS Race Hemi.
You sometimes hear stories how these intake "blow up" but how much of a problem was it really.
I acquired this magnesium intake in the early 70-ties and it would be ashame if something happened to it now, just because of me being negligent.
Never got a chance to run it than, so have no experance of it.
Anyone here that do have experience with this intake and can give me a few advise.

 

[gkent]

They blew up if fuel puddled in the bottom of them. There was the same issue with the "rat roaster" hemi intakes. Was it a common occurance - not really. If you pumped the living daylights out of the carb trying to start the car then yeah, you'll likely have an issue!

 

[nitro_rat]

I can see how it might happen with each carb being in the center with the intake ports at each end. Lots of plenum floor there for fuel to puddle on. "Race car" ignition/starter switch will prevent puddling at start up. Get 'er spinning before pumping the pedal to prime and then flip on the ignition to start. I would think that minimizing idle time would be the other best prevention. Maybe buff down the OD of all the core plugs so they're not too tight of a fit and install them with a wipe of permatex? Hopefully they'll blow out instead of damaging the manifold if there is a bang...

 

[dvw]

I blew up a modified Mag cross ram in a friends A990 car. The issue that caused it was a exhaust valve that had a adjuster come loose. The pushrod fell out so the valve couldn't open. When the intake opened with some throttle applied, BOOM. It happened in the pits at Milan. Blew one of the carbs hard enough against the hood that one of the vent pierced the hood scoop like a paper punch. It was hanging on the scoop when the hood was opened. The entire lid was gone. This is not a normal occurance. Just like the modern Indy 440-25 crossrams, it can happen with a backfire during starting. been there as well. Holding the throttle open is the best practice. Along with pumping the throttle a few times and allowing the fuel to evaporate prior to starting. With this method never an issue.
Doug

 

[Rebelrouser]

I don't know about the old original hemi crossrams, but I never had a maxwedge cross ram backfire and blow up. However, the Indy cross rams for maxwedges are kind of like bombs, seen several of them explode, I hear the secret is to hold the throttle at 1/2 when starting and you have no problems. Buddy of mine caught his car on fire when the indy manifold went off. I think some guys even went as far as to weld in a blow off panel like a blower manifold has.

 

[Fran Blacker]

Don't run NO2 ! Nitro_rat covered it. Had a few sneezes on mine but nothing bad. Street driver for a few years.

 

[MWbirdLOVER70]

WOW, these are some crazy **** stories on non NO2 bottle fed babies. Never seen it on straight gas cars but from what I’m reading it happens and will keep me more alert. Thanks for the share brothers

 

[6PKRTSE]

I have a factory magnesium Hemi cross ram modified by Barton. I have never had any issues with it.

 

[rickseeman]

Rat Roasters blow up. You see nearly as many used ones with a cracked top as you see without. They say Chrysler bathtubs could blow up. But I've never seen a mag xram blow up so I don't think you have to worry.

 

[Fran Blacker]

Application Nostalgia ´68 SS Race Hemi.
You sometimes hear stories how these intake "blow up" but how much of a problem was it really.
I acquired this magnesium intake in the early 70-ties and it would be ashame if something happened to it now, just because of me being negligent.
Never got a chance to run it than, so have no experance of it.
Anyone here that do have experience with this intake and can give me a few advise.
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View attachment 1968856

One thing when you install your crossram the gasket will compress. You'll need to torque the bolts several times until you have to slightly over torque the bolts to get then to break loose. Some make fun of the way I do it by torque 12 times over 3 days. I re-torque them periodically, like if the car sat for a month or 2.