[DeTomaso] Intake Reversion

Sean seanmundy at hotmail.com
Wed May 1 21:49:51 EDT 2013


We briefly checked for leaks but I will do as you suggest.  Thanks for the feedback!!!

Sent from my iPhone

On May 1, 2013, at 5:46 PM, "michael at michaelshortt.com" <michaelsavga at gmail.com> wrote:

> Have you thoroughly soaked the carb spacer and intake to head seam while the engine was running with carb cleaner?  I once had a hard to find vaccum leak that caused similar conditions with an impossible to adjust idle and wild running fluctuations based on engine temps.
> 
> Michael Shortt
> 
> On May 1, 2013 6:08 PM, "sean mundy" <seanmundy at hotmail.com> wrote:
>> 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
>> _______________________________________________
>> 
>> Detomaso Forum Managed by POCA
>> 
>> DeTomaso mailing list
>> DeTomaso at poca.com
>> http://poca.com/mailman/listinfo/detomaso



More information about the DeTomaso mailing list