360 stroked to 408. Running issues.

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I know it's automatic, but did you accidentally "miss a shift" causing the engine to over-rev, - before it ran shitty ?
I'm thinking pushrod/rocker issue .
 
Maybe I misunderstood what you typed but did it sit for an extended period of time between when it last ran good, and now when it isn't running good?
My first guess at your issue is some sort of vacuum leak somewhere but old gas might not be helping. I was chasing ghosts in my car (still am) and some of them just disappeared as I finished off my tank with gas that was at least 4-6 months old and filled it up with fresh fuel.
 
I know it's automatic, but did you accidentally "miss a shift" causing the engine to over-rev, - before it ran shitty ?
I'm thinking pushrod/rocker issue .

no sir, has a rev limiter
Maybe I misunderstood what you typed but did it sit for an extended period of time between when it last ran good, and now when it isn't running good?
My first guess at your issue is some sort of vacuum leak somewhere but old gas might not be helping. I was chasing ghosts in my car (still am) and some of them just disappeared as I finished off my tank with gas that was at least 4-6 months old and filled it up with fresh fuel.

No it hasn’t been sitting
 
Hey guys,

I recently had boughten a 1972 demon 340 coupe. It has the blue print 408 stroker.
Keith black forged pistons
Hughes 4248S cam
Scat cast crank
Melling High volume oil pump
Aluminum edelbrock performer heads
Ceramic TTI headers with 3” TTI exhaust
Edelbrock air gap intake
Holley sniper efi.
It ran absolutely perfect when I bought it, insane throttle response tons of power. Now the issues are it’s having trouble meeting the target air fuel ratio on the controller. (Efi issues I know) and then when idleing the engine shakes bad. I have tried having the idle anywhere from 800-1000 to try and correct it and it still shakes bad. But settles down when cruising. Any one have any advice. Definatly scrapping the Holley sniper and getting a Holley 750 dbl as I can’t seem to figure out the afr issues with it. Holley tech seems to think it’s wiring but the thing is absolutely clean and have checked all wiring multiple times.
Jared when you say it settles down when your cruzing what’s the afr readings ? As mentioned try running the wizard again but usually when the afr spikes like that she’s taking in air from some where . Is the 02 got a bung or that crappy plate that Holley supply with the kit which you drill a hole in your exhaust and it’s clamped on ? .
 
Likely not the cause, but some of your plug wires look too cozy with the header pipes. Picture angle makes it look like they are resting on them.
 
Jared mine did similar to yours when I first set it up with timing control it would sound like it was running on 6 cylinders and when I would increase throttle it would pop and back fire and what I did find was my timing wasn’t increasing with rpm and staying on 16 degrees. How to check it is go into Home Screen than tuning , than monitor look down the bottom of the screen while increasing rpm see if your timing changes increases . I found mine for some reason wasn’t moving off 16 initial timing reran wizard and it came good.
 
Not related to your initial problem. Wires long enough?

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i am running the MSD ATOMIC on my 410 in Saskatoon. (same 1500 above sea level). and its been up and down the entire time that i've been running it. Most of my problems have been vacuum leak ( high idle) but i have had the shaking . hesitation, stumbling. rough idle as well. found that the throttle blades must be barely open so the air idle speed motor can have better control.1/8 turn max. dont know if this applies to other TBI systems but this was key to getting mine to run right.
 
i am running the MSD ATOMIC on my 410 in Saskatoon. (same 1500 above sea level). and its been up and down the entire time that i've been running it. Most of my problems have been vacuum leak ( high idle) but i have had the shaking . hesitation, stumbling. rough idle as well. found that the throttle blades must be barely open so the air idle speed motor can have better control.1/8 turn max. dont know if this applies to other TBI systems but this was key to getting mine to run right.

, makes sense. Will try
 
i am running the MSD ATOMIC on my 410 in Saskatoon. (same 1500 above sea level). and its been up and down the entire time that i've been running it. Most of my problems have been vacuum leak ( high idle) but i have had the shaking . hesitation, stumbling. rough idle as well. found that the throttle blades must be barely open so the air idle speed motor can have better control.1/8 turn max. dont know if this applies to other TBI systems but this was key to getting mine to run right.
On the sniper that’s the iac motor not sure if that’s the same as the Atomic . On the sniper it needs to be adjusted when the engine is hot between 2-8 it needs to be in that range in park or neutral . By turning it clockwise will lower it anti clockwise increasing but you need to keep an eye on the tps as if it goes off 0 you need to turn the engine off and restart which will reset the tps. Wait for 10-20 seconds before adjusting again. If you have an electric fan you want to do it before the fan kicks in as the iac will increase to compensate for the extra load .
 
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