Race Hemi crossram carb tuning

[Phillip marvetz]

I'm getting the crossram set up ready to go and need to know about setting the Holley carbs up. Any tricks I should know? I'm at sea level most of the time. I'm using one of the new MP intakes. I have one of the Mopar books but it is a little old.

[Shawn Blair]

You going Super Stock racing now? I don"t recall ever seeing anything about tuning the newer Mopar manifold, the old specs might be a place to start and hopefully somebody who's ran one will chime in

[rickyr]

Originally Posted by Phillip marvetz

I'm getting the crossram set up ready to go and need to know about setting the Holley carbs up. Any tricks I should know? I'm at sea level most of the time. I'm using one of the new MP intakes. I have one of the Mopar books but it is a little old.

Are you using carbs LIST # 4235 & 4236?
If so they came with 80 pri jets and a 6.5 Power valve
You can either see how much vacuum you have @ idle (in gear if auto trans)
Then divide that # by 2 ( cut vacuum reading in 1/2)
for a power valve size
Or race only you can block off the power valve and go up to 86 pri jets
After either one of these are done
then all you can do is read spark plugs to see if you need to go up or down on the jets
if plugs are white go up 2 jet #'s if black go down 2 jet #'s
do this until they are tan to brown.
then if you go up in elevation, you will need to go down one jet # for every 2000ft
Thanks Ricky Holley tech service

[Phillip marvetz]

Originally Posted by Shawn Blair

You going Super Stock racing now? I don"t recall ever seeing anything about tuning the newer Mopar manifold, the old specs might be a place to start and hopefully somebody who's ran one will chime in

The crossram is legal in IHRA. Dave seems to think the old crossrams are tuned differently than the new MP ones, Just looking for somebody that has played with one of these lately.

[Phillip marvetz]

Originally Posted by rickyr

Are you using carbs LIST # 4235 & 4236?
If so they came with 80 pri jets and a 6.5 Power valve
You can either see how much vacuum you have @ idle (in gear if auto trans)
Then divide that # by 2 ( cut vacuum reading in 1/2)
for a power valve size
Or race only you can block off the power valve and go up to 86 pri jets
After either one of these are done
then all you can do is read spark plugs to see if you need to go up or down on the jets
if plugs are white go up 2 jet #'s if black go down 2 jet #'s
do this until they are tan to brown.
then if you go up in elevation, you will need to go down one jet # for every 2000ft
Thanks Ricky Holley tech service

Yes those are the carbs. Race only. What about the secondary metering plates? Do the new manifolds need different tuning than the originals or the rat rosters?

[rickyr]

Originally Posted by Phillip marvetz

Yes those are the carbs. Race only. What about the secondary metering plates? Do the new manifolds need different tuning than the originals or the rat rosters?

The new intake should not need any different tuning.
For the sec. plates the stock ones will be = to about a 86 jet,
there are not any plates offered any larger than that
So if you cannot get it dialed in with the pri. jets all you can do is drill
the bottom holes .002” to .003” at a time.
but at wide open throttle it is running off of the Pri. and sec.,
so any change to the pri. will also help the sec.
you also might want to install the white springs in the sec. Dia.
to make them open quicker
they came with a plain spring
the spring kit is part # 20-13
you will need it 2 times
I hope this helps
Thanks Ricky R. Holley tech service

[Dinsdale]

Hmmm.. That seems like a lot of jet. Hemi's must be hard on gas!

[Alan Roehrich]

Phillip, Clark Holroyd has special metering plates for the back of your carburetors, they're called "Holroyd's Hemi Plates". If you don't know how to reach Clark, I can hook you up. And he'll know as much about setting up your carburetors as anyone.

[Phillip marvetz]

O.k, that helps.
I had spoke with Dave Wren about this also and he felt that each style of manifold wanted different jetting. Some like to be jetted square and some like to be staggered, he hadn't used one these manifolds though to give a me a base line. So I guess my real question is should I leave the factory staggered jetting in place or not.

[Dyno]

Quick Fuel and Jones offers a secondary metering plate that works well. 86 jets sounds to be on the big size, 82-83 works well. Dyno