Thread: 78 Trans Am getting some love

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Originally Posted by 53 Chevy5

Holy crap, the only thing I got from that was buy Holley Sniper It's a bit overwhelming, but I'll check some of those things out.

LOL! It's really not as hard as it sounds, it's just that you're not familiar with it.

I curse those fuel injection set ups, not because they don't work, just the opposite, they work to well and nobody's learning how to tune anymore. Curse, curse, curse!! TUNING IS FUN! Once you get over the fear...

Surging is usually lean, you really do not want it lean at WOT (very bad for the motor). Pull the plugs and take a look at the ring, porcelain tip and way down inside, the plugs tell all (post pictures). Right now we don't need to do any throttle chops, guys will tell you you need to do them to read the plugs, but for right now we just need to see generalities of the combustion. I have a plywood rack that holds my plugs (tip up) marked for each cylinder, you can do the same using cardboard to hold them (I'm a little anal), mark each cylinder so you can see what's happening in each cylinder.

Vacuum is too low for your cam, should be around 15hg, bringing initial timing up to 12-16° will help the vacuum but you're already over the top at 39° total. With that much total timing your surging may actually be detonation (really bad for the motor). Your motor will probably like 12-16° initial and 34 -36 total (36° max) and all in by 2200-2500rpm, but to do this you'll need to limit your mechanical advance to 18- 20° and change the springs (maybe weights too). 20-25° of vacuum advance is what we see in stock vacuum advance set ups, but it's too much for your motor, I would bring it down to 10° additional (15 max if it likes it).

For now (I know this is gonna sound oxymoron, but I'm trying to protect your motor), I would drop initial timing down 3-4 degrees bringing total down to a safer margin, then use manifold vacuum on your advance to bring the idle timing up (should get your vacuum up). See if it takes the WOT surging out, then work on tuning the carb, next the distributor. I put it in this order to keep your motor safe.

Get the total timing down to a safe place to prevent detonation, then tune the carb to get rid of too lean or rich conditions (error on the side of a little rich), once the carb is tuned, tune the distributor. You get this all done and you'll find you'll really need to HOLD ON, cause you will not believe the difference in power.

I will mess with the distributor springs right away. I thought the timing was crazy highl on everything too. I don't hear any pinging but you're right it still needs to come down.

Springs will NOT limit timing, only bring it in quicker (or later). PLEASE, follow the blueprint, I know it sounds counter intuitive, but it is safe for your motor. WOT with too much timing and/or too lean can destroy your motor.

Originally Posted by 36 sedan

Springs will NOT limit timing, only bring it in quicker (or later). PLEASE, follow the blueprint, I know it sounds counter intuitive, but it is safe for your motor. WOT with too much timing and/or too lean can destroy your motor.

Your right, I thought about that on my way to the shed, as late as my timing is advancing with rpm's I really should have lighter springs but need to stop the weights. But anyhow back to the order of things, here is a pic of #1 plug and I threw in a pic of the dist just in case

You're rich at idle, cruise looks close. Can't see WOT, it is way down inside the plug, sometimes you have to cut the plugs to get at it. Heat range is ok. May be using a little oil, check your PCV. The rust at the base of your plugs could be causing a bad connection, try loosening and tightening them couple times to make sure they have a good ground connection. May be time for new plugs.

cutting plugs.png

Doesn't look like your distributor has adjustable limit stops, there are some downloadable articles on line about how to modify your distributor.

Originally Posted by 36 sedan

You're rich at idle, cruise looks close. Can't see WOT, it is way down inside the plug, sometimes you have to cut the plugs to get at it. Heat range is ok. May be using a little oil, check your PCV. The rust at the base of your plugs could be causing a bad connection, try loosening and tightening them couple times to make sure they have a good ground connection. May be time for new plugs.

Attachment 72423

Doesn't look like your distributor has adjustable limit stops, there are some downloadable articles on line about how to modify your distributor.

36 sedan, that's the best picture diagram I've ever seen on reading plugs, and I'd never seen the part about WOT mixture being shown by the deepest part of the plug porcelain. Great information!

Thanks for your help so far with this , but I might take the easy and expensive way out. Tuning and dialing in engines is something I really do not enjoy doing and this is the only carbureted vehicle I have left. I think I might just go ahead and get the Holly Sniper injection for this thing and be done. I do want to thank everyone for the advice of saying the exhaust is not the problem, that saved me from wasting a crap ton of money. If I change my mind on the injection, I'll be asking more questions about carburetors that's for sure ��

Any time we can help my friend.
Sorry I scared you off, didn't mean to, sometimes I'm just a little too passionate.
Good luck..

Originally Posted by 36 sedan

Any time we can help my friend.
Sorry I scared you off, didn't mean to, sometimes I'm just a little too passionate.
Good luck..

Not too passionate, just like things done right and there's nothing wrong with that! On a side note just for curiosity sake I did back off the timing and took it for a ride, It couldn't get out of it's own way.

Originally Posted by 53 Chevy5

On a side note just for curiosity sake I did back off the timing and took it for a ride, It couldn't get out of it's own way.

That's OK, because now with the total timing down in the safe zone you can put the lighter springs in the distributor to bring the total timing in quicker, which will help until you can get the distributor stops installed and the carb sorted out.

Did it surging go away at WOT?

Originally Posted by 36 sedan

Did it surging go away at WOT?

No it did not, it was far far worse. I got the go ahead to spend the money for Sniper from the wife, but to do it correctly in the way that I want, I would be in at about 1,800 bucks conservatively. I'm having a hard time hitting the buy it now button. I asked about the sniper on a trans am page I belong to and anybody who has it loves it, but there was a guy who mentioned the Street Demon carburetor from Holley that he absolutely loves. I have done much much Google searching and YouTube searching and I have yet to find someone who does not love it. I can pick one of them up for $363 so I'll probably be in it right around 425 when it's all said and done. It's not that I'm against spending extra if I have to, but I don't know if I really have to.

I'm a real glutton for punishment, I run dual quads (2x4's). LOL

Remember, carburetors are completely mechanical, ALL carburetor need to be tuned to your motor. PERIOD. No carburetor comes out of the box completely ready to run on all motors. And all carburetors require tinkering to keep them at their best performance. While the Street Demon may run good on one motor there's no guarantee it will run out of the box good on your motor.

The only guarantee is, if it's tuned to your motor it will run great. The same goes for the distributor.