[DeTomaso] Intake Reversion

[sean mundy]

Hey all, I recently had my new 408 Cleveland tuned and dyno'd at the shop.   438/411 hp/trq rearwheel.  
Very happy with the numbers but having some issues with how the motor runs. 
After driving it 50 miles I noticed at anywhere between 2-3k RPM 
in any gear there was a surging and hesitation in the engine.  
 I went back to the shop and we worked on the carb (750 Holley) 
by increasing the primary jets and adjusting the pump squirters.  
We put it back on the dyno and ran it several times.  The tech said he couldn't get 
good A/F numbers because the sensor placed in the tailpipe couldn't get past the 
baffling in the stock muffler.  It pulls very good in the top end but he noticed the
2-3k RPM surging and hesitation that I mentioned.
The tech told me that he thought since my vaccuum reading was so low (10-12 in) 
at low RPM that I was probably experiencing "reversion".   
He said that the lobe separation overlap on my cam specs were probably the cause 
of this and also a contributing factor was my single plane manifold.  Basically he made it
sound like I was stuck with what I got.
 
My cam specs are:
 
GROSS VALVE LIFT .617 .617 
DURATION @ .006 
TAPPET LIFT 286 300 
VALVE TIMING OPEN CLOSE 
@ .050 INT 10 46 
EXH 60 8 
SPECS FOR CAM INST. @ 108.0 CENTERLINE 
INT EXH 
DURATION @ .050 236.00 248.00 
LOBE LIFT .363 .363 
LOBE SEPARATION 112.0 
 
I've done some reading on the internet about reversion and it seems like a real thing.  
I read that installing a carb spacer designed to help eliminate the phenomen might work in my case. 
Wondering if anyone else has experience with this and what if any solution worked for you.  
Thanks, Sean