Tuning a 489 cu in Gen II Crossram Hemi for the street

[jobenz]

Morning, can anyone help me with smoothing out my 489 Crossram Hemi, 675 HP to run better at lower rpm?? Just had the 770 carbs rebuilt by Ray Barton as he said that would be the problem, but it wasn't. Just installed a Tremec TKX 600 with a lower 1st gear, that didn't help either. Timing is set at 32. Anything else I should try to do would help as I do not want to sell my car. Thanks in advance.
My cam is a hyd roller, valve lift, int .573. exh 555 @.050 11.0 compression, aluminum stage 5 heads, TTI headers, Holley 3116 770 carbs.

 

[j-c-c-62]

EFI and use the carbs as throttle bodies?
I should have asked how radical is your cam?

 

[ruffcut]

Yes, camshaft is the first thing that comes to mind. More info would be helpful .

 

[Fran Blacker]

Morning, can anyone help me with smoothing out my 489 Crossram Hemi, 675 HP to run better at lower rpm?? Just had the 770 carbs rebuilt by Ray Barton as he said that would be the problem, but it wasn't. Just installed a Tremec TKX 600 with a lower 1st gear, that didn't help either. Timing is set at 32. Anything else I should try to do would help as I do not want to sell my car. Thanks in advance.

Here's a thread for you. So anybody try a wideband O2 on a crossrammed Hemi yet?

 

[Geoff 2]

A cross ram has a HUGE amount of air [ plenum ] volume in it. It is never going to run great at low rpms because it is not a low rpm intake. The huge ports in Hemi heads do not help either....

 

[67_satellite]

Morning, can anyone help me with smoothing out my 489 Crossram Hemi, 675 HP to run better at lower rpm?? Just had the 770 carbs rebuilt by Ray Barton as he said that would be the problem, but it wasn't. Just installed a Tremec TKX 600 with a lower 1st gear, that didn't help either. Timing is set at 32. Anything else I should try to do would help as I do not want to sell my car. Thanks in advance.
My cam is a hyd roller, valve lift, int .573. exh 555 @.050 11.0 compression, aluminum stage 5 heads, TTI headers, Holley 3116 770 carbs.

If you had enough carb. trouble to need to send them off for Professional help, you may have fouled the spark plugs beyond saving, try a fresh set now that the carbs are "fixed".

 

[autoxcuda]

Try a fuel pressure regulator if you don’t already have one. And try turning the pressure down.

The 1850 style carbs for sure don't like the pressure. And when coasting to a long stop the carbs bowl would fill too high. Don't know about the 770's. But worth the try.

 

[autoxcuda]

<snip>
My cam is a hyd roller, valve lift, int .573. exh 555 @.050 11.0 compression, aluminum stage 5 heads, TTI headers, Holley 3116 770 carbs.

intake lift: .573
exhaust lift: .555
duration @ .050: ?
lobe separation: ?

My buddy built a 472 auto and 528 4-speed with cross ram 68 super stock clones. What made them reliable on the street was not getting too aggressive with the cam.

 

[68-500]

Whats your initial timing and where is the vacuum advance hooked to manifold or ported?

 

[Fran Blacker]

Ran mine for about5 years. Hope you look through the thread I posted.

 

[66 Cornpicker]

I started with the same carbs you have and Dave at Woodruff built me a set that was a little bit smaller and we picked up 58 HP on the dyno and I drive it every day I can. They perform excellent, call him, mine was a 446ci Max Wedge manifold and made 660+ HP and over 600TQ on pump gas with a roller cam

 

[Rebelrouser]

I have done max wedge crossrams and with a little fiddling they work well. You did not list the duration of the cam, which is the most important factor in drivability tuning. But if you can't do it yourself, in my opinion sending a carb off will not get the job done no matter how good the carb guy is. You have to have a vacuum gauge, be able to read plugs or O2 sensors to get it right and that means driving the car and tuning as you go. Plus you need a selection of jets, power valves, metered drill bits etc.

 

[jobenz]

intake lift: .573
exhaust lift: .555
duration @ .050: ?
lobe separation: ?

My buddy built a 472 auto and 528 4-speed with cross ram 68 super stock clones. What made them reliable on the street was not getting too aggressive with the cam.

average duration @.050 intake ,250 exhaust .262 lobe separation 108 116