[DeTomaso] Intake Reversion

Wed May 1 20:46:39 EDT 2013

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
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