Thread: 78 Trans Am getting some love

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Originally Posted by 53 Chevy5

We're back to timing on the T/A I got the Hyperspark and Sniper installed so I can mess with the timing with a keyboard now. I'm finding out my engine likes to ping pretty easy while I'm trying to mimic my mechanical & vacuum curve. My question is on a mechanical dist, if the mechanical advance it at maxed out at 34 with the weights, does the vacuum advance it 10 or so deg above that if the vacuum is available at cruising speeds?

The weights and vacuum diaphragm both move the same plate, so once you max out you're done. At cruise I would think your weights wouldn't be maxed out, so vacuum could give you more timing, but only to your 34 degree limit.

Roger you took 2 sentences to explain what I gave up on after half a page LOL.

Basically your just trying to dial in your total and insuring it doesn't come in too quickly.


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That's what I was thinking. I'm going to have to change the parameters on the table to represent that better. Thanks.

Seth, the vacuum advance really only works "Around town"... it keeps timing earlier during lower rpm, as you raise rpm the vacuum does less and less, higher rpm's are then controlled by the centrifugal weights. When folks say "All in by some number", it means that there is no advance left to give. So if you max the advance at say 2500 rpm, there won't be any more timing input until the rpm's come back down.. say like 2400... General rule of thumb for max advance is to keep it at 30 degrees total. Then once you're sure the combo of air/fuel is good -then move up the total to 32 then 34 if all is working well. You may never reach those top 2 settings as pre-ignition and detonation are easy to induce.

The hyperspark has a offset setting you put in to mimic vacuum advance but it seems to raise the all in timing too much. If it's all controlled with a computer I'm not sure why I can't put in 10 for crank timing 22 at idle and ramp it up to 30ish at 2700 and call it a good start. If you can see the numbers in my chart you can see where I get into trouble. If you look at the very top line of my chart, those are my base values, and the rest is what happens after I add plus 20 of vacuum advance.

My msd does the same thing. 10 for crank and at idle should be fine, then let the controls dial it all in by 2500. I have mine set so the "vacuum" setting only works from idle to 15 or 16 hundred rpm... and Vacuum Advance is used at lower rpm, NOT above say 1600.. then it's all centrifugal. You can actually "lock out" the advance I believe. ( I know mine can) After starting, I can have it go to 30 degrees and just stay there. That helps with easy starts and takes all the guessing out of the way.

got the Sniper on my T/A tuned today.I no longer watch the fuel guage drop while I drive and it runs way better than it did before. It is a pretty mild engine build so it only had 275 hp and 350 lbs of torque but thats still about 75 hp more than factory lol. its pretty sad that the most powerful car I have ever owned is Rita or my 13 Impala, they both have 300 hp Here's a video of the dyno.
https://photos.google.com/photo/AF1Q...Psu-ua_ZvBHrfE

I got a "404" error.. any one else?

I’m enjoying following this thread Seth……I suspect it will end up saving me some confusion down the road.

I did what you warned me about though, and read some more on the forums and yeah more

The current one I have is in regards to the intake. One guy seemed to be disappointed in performance of the Sniper and he diagnosed it down to using a dual plane intake with a plenum divider. He changed over to single plane intake and is apparently much happier.

As I recall the intake you’re using is a dual plane with divider (stock intake (?) ). I realize you are still dialing it in but I was wondering what your take on single vs dual plane intake with the Snipers is. Seems somebody put a dual plane with divider on the last engine he built


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Originally Posted by 34_40

I got a "404" error.. any one else?

Yep, Google says the link to the photos isn't linked.

You try this link. https://youtu.be/O6IXyVC1AYI

Mike, I read the same thing about the dual planes so I just cut out the center divider on my stock Pontiac one. I was told the Pontiac intake flows better than the Edelbrock .

that link works.. Thanks. Good looking car too.

My nephew asked if he could take my T/A to prom and of course I said sure. He had a lot of fun and I think he put more miles on than I have since the Sniper install

Does he need to wash it before it comes back? Wink Wink... LOL Good on you Boss.

Originally Posted by 53 Chevy5

My nephew asked if he could take my T/A to prom and of course I said sure. He had a lot of fun and I think he put more miles on than I have since the Sniper install

Did the boys go stag, or was the photo before they picked up their dates?