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I have today a MSD Atomic EFI and a MSD Distributor in place. This runs very well together. With my new highly tuned stroker engine (614hp) a Holley 750cfm 4150hp is foreseen.
Now I think about applying the Atomic EFI but with a fuel pump upgrade. This should support engines up to 625hp. So all good.
However I realised now that my camshaft is over the suitable limit of max 250 at .050“ duration with 253/261. The MSD tech support said not a good idea to go higher than 250. The setup is not made for this.

i think this has only to do with the insufficient vacuum produced by my sharp cam at idle which creates problems for the EFI. But increasing the idle will potentially overcome that issue, I believe. True or false?

Now I investigated the EFI market and found the MSD Atomic -2 upgrade. Goes up to 650hp has not the limitations on the camshaft as far as I can see. But the product interestingly is discontinued. Nevertheless it continues in a 1 to 1 fashion in the Holley Sniper-2 EFI.  Anyway my helping hands informed me about the severe issues with the Sniper-1 version especially with HF irritations due to bad alternators etc and the likes. So I was sceptical but learned that the Sniper-2 is not an upgrade to Sniper-1 but rather Atomic-2 has been transferred to Sniper-2 and hence is the stable MSD system in a new Holley housing. To be confirmed here?

In principal I am personally convinced about the manifold advantages from an EFI system but do you see also disadvantages over a Holley carby setup? Especially when the engine is highly tuned and requires a lot of air to perform?

Comments and advise appreciated.

Original Post

Be forewarned, I am no EFI expert.  I had a similar build done a couple years ago (636 bhp).  Dennis Quella had recommended we go with the Sniper 2 Terminator X.  But by that point, those were backlogged, and my builder got a FAST EZ instead.  Ultimately, we couldn't get it to work well for any length of time once we installed it in the car, it kept fouling O2 sensor and plugs, and the EZ is not laptop adjustable.  I know at least one P-car owner using a better FAST model that has worked well, but with more adjustability.  I know the Sniper 2 has a generally good reputation now.  I also know a member on here who had one installed/tuned by a performance shop, who has had many of the same troubles my system had.

I decided to swap out to a Holley DP chokeless (I'm in NC so that can work) carb custom set up and tuned by Chuck Nuytten out of Rockwall, TX.  He is well known for this, he will have you furnish all relevant engine specs and your performance/driving style needs and build accordingly.  I have nothing but positive things to say about this carb so far.  In my (generously long) phone conversation with Chuck on the front end, as I recall he said my issues were common and that the extremely limited O2 sensor placement option in Panteras can inherently create challenges.  My point is, if you were going to spend the money to "upgrade" to a Sniper 2, Chuck is another option, for less cost, easier installation, easier parts availability in a pinch, etc.  The only possible drawbacks I see would be some sacrifice of fuel economy, a little attention to the throttle on cold start, and a good mechanic friend of mine says Holley carbs can get sticky with periods of sitting unused.

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