Hemi cross ram idle tuning

[68 HEMI GTS]

mine was a little bit of a battle at first with the surging in gear. we had it pretty good, when i switched cams it totally went away. with your carbs facing out instead of in i gotta wonder if that plays into it at all.

my pops did me up a set of 850 holley's for mine. i've been playing with these a little, runs real strong. just have a slight distribution problem im trying to get iron'd out. hope to run it at monster mopar with the 850's, feels like she has a little to gain.

 

[2059]

mine was a little bit of a battle at first with the surging in gear. we had it pretty good, when i switched cams it totally went away. with your carbs facing out instead of in i gotta wonder if that plays into it at all.

my pops did me up a set of 850 holley's for mine. i've been playing with these a little, runs real strong. just have a slight distribution problem im trying to get iron'd out. hope to run it at monster mopar with the 850's, feels like she has a little to gain.

Never really thought about it. every AFB set up i've seen has been this way... good luck at MM.

 

[Hemirunner]

The number 1 plug is looking the best, but the dark deposits on the porcelain indicate that it's still rich. The dark black around the base is the idle mixture and it's too black and thick, which means rich. I'm guessing with GR4 plugs that you don't have much static compression in that thing. Idling (especially if it's too rich) carbons the plugs up so it's hard to get a good read on the WOT part of it, but I'd take some fuel out everywhere. Did you take the cover off the step up pistons and watch them at idle? You want them to stay down and not bounce at idle.

 

[2059]

The number 1 plug is looking the best, but the dark deposits on the porcelain indicate that it's still rich. The dark black around the base is the idle mixture and it's too black and thick, which means rich. I'm guessing with GR4 plugs that you don't have much static compression in that thing. Idling (especially if it's too rich) carbons the plugs up so it's hard to get a good read on the WOT part of it, but I'd take some fuel out everywhere. Did you take the cover off the step up pistons and watch them at idle? You want them to stay down and not bounce at idle.

I didn't mention it in the prev. post but after I got the engine to idle without oscillation, I was able to more accurately set the idle mixture screws. just as a point of reference both screws on both carbs leveled out at ~1.5 to 1.75 turns. Before they were set ~2.5ish. I'm gonna run these for a bit and then check them.

I didnt check the step-up pistons but that's a good point. One of the tuning points mentioned in the Edlebrock manual was the behavior of the pistons and spring strength. That will be the next step. I did check for vacuum leaks around the carbs, throttle shaft, base, etc... and didn't find any.

 

[tanglewoodHemis]

Well I took today off and yesterday my cross ram setup came from ray Barton. I only used the return springs and brackets. If anybody wants to buy the bell crank, linkage rods and cable bracket pm me. Anyway, checked for leaks, set the flow, reset the mixture screws and reset the timing. Idles right around 1050-1100.

Couple pictures and a vid link.

 

[tanglewoodHemis]

How did you solve your idle problem on the cross-ram manifold?

 

[6PKRTSE]

I have an old Magnesium cross ram Hemi intake that has about an inch thick of orange high temp silicon adhesive applied underneath it. I bet it adds 10 lbs of weight to the manifold. I am assuming an old super stock trick to keep cool?