[DeTomaso] Carb hesitation on level ground at cruise

[Asa Jay Laughton]

Hi all,
I'm working with a PIM 427 Hammer (stroked Windsor) in a Pantera. This 
has a Demon carb on it.  I don't know what it has for jets.  I know it 
runs a little rich.

Here is my situation and in a bit of humility, am stumped at the 
moment.  Sam and I just took it out for a long test drive and it has 
problems on leverlk ground, no load, cruising mode.

It idles at about 800 rpm, a bit lumpy but starts right up cold, doesn't 
die, no choke (no choke on the Demon carb).
It revs easily and pulls away from a stop sign beautifully.
Under load, moderate throttle or foot to the floor, it runs great.
Off throttle, engine braking,  it runs fine, though it doesn't burbble 
like I would expect
Uphill great, downhill not so much (that cruise position of the foot on 
the go-pedal)
On level ground, 5th gear, holding cruise at 60 MPH at around 2,000 rpm, 
it hesitates, jerks, feels like it's misfiring.
Same when in say 4th, holding cruise at a higher rpm but no load either 
with go-pedal down, or engine braking
It does this hesitation at nearly any rpm from 1,500 to 3,500 only when 
holding cruise speed, not when accelerating (even mildly)

I'm thinking the problem is the idle mixture and speed settings. I'm 
thinking the throttle plates might be closed wee bit too much and idle 
mixture is compensating.  When the throttle is at off-idle, at cruise, 
the transfer ports aren't giving enough gas, or maybe it's air.  Trouble 
is there is no AF gauge on it, and my portable can only be stuffed in 
one of four exhaust tips.

<sigh>  so I'm asking for the collectives opinions, I know there are 
some good ones out there.  I figure I need to re-check timing, advance, 
and carb tune again.

Thoughts?
Thank you,
Asa  Jay

-- 
Asa Jay Laughton - W7TSC, MSgt, USAFR, Retired
Spokane County ARES-RACES-ACS EC/RO
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https://w7tsc.org
https://www.teampanteraracing.com