Thread: 78 Trans Am getting some love

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Bump the secondaries up one and it should pull better at higher rpm (that's where the secondaries work).

Is the 13-14 at just off idle (low speed cruise) and the 15-16 at high cruise? Where is the accelerator pump set?

The 13-14 is at cruising speed and it will climb going up a slight hill or just giving it a little gas. It comes right back down again when you give it a little more gas. I don't notice anything except for the gauge climbing.Cruise rpms are 2500-2700. I had the pump on the slow hole and I have it back in the center one now, is that used during cruise? I got a pic of a very white plug. It was just starting to brown a bit at the tip, can't see it well in the pics.

Originally Posted by 53 Chevy5

The 13-14 is at cruising speed and it will climb going up a slight hill or just giving it a little gas. I don't notice anything except for the gauge climbing.Cruise rpms are 2500-2700. I had the pump on the slow hole and I have it back in the center one now, is that used during cruise?

Accelerator pump is not active at steady cruise, but should come in as you give it gas. Moving it up a notch should stop the lean out as you give it a little gas, other wise cruise it great.

Originally Posted by 53 Chevy5

I got a pic of a very white plug. It was just starting to brown a bit at the tip, can't see it well in the pics.

Plug looks a little lean at idle (I like to see a full ring of color around the face), give it 1/8 turn more open on the idle mixture screws. Plug looks too hot, needs a colder plug.

What is your total timing set at?

I have my total timing set at 34°

I think we got it running good for now. I went back to the 58/44 rods and that seem to help with the leaning out going up a hill, not perfect yet but better. I bumped the timing up to 36 total, and it's running it about 13.5 Cruise and the step up is 12.5 ish. It's hard to tell I swear it changes every night. I did replace my fuel pump because last time I drained the carburetor I had to crank forever to get it to fill up again. I checked and sure enough the diaphragm was leaking, but it was holding 6 psi . Maybe it was getting worse as it warmed up down the road and that possibly accounted for some changes to. The only thing I might change is the secondary orifice to a size up, but I'm not sure if I'm going to do that right away or just drive it. Anyhow thanks for everybody's help on this thing, especially 36 Sedan! , it's running better than it ever has since I've owned it. I'll pull the plugs again after he is driven more and look at the burn pattern too. If there's one thing I've learned, I now can laugh inside now when somebody says yeah I threw on a 750 and now it runs awesome! It maybe does, but without tuning it you're just throwing darts with your eyes closed.

I've stayed out of this 'cause to many cooks... you know?
But, now is when you watch and record the output from your A/F gauge. wait for a minimum of 3 readings on different days to decide on a change.

If you make a change and the air is different the next day, you could actually decide to un-do changes that were for the better!
This is the major drawback to a carb, it's dependent on so many things that change daily / hourly etc. Now that your in good shape, watch / wait and see which way the readings are working before you decide on change.

FWIW, My point oh 2, etc etc etc.. yada yada yada.. imho... if 36 tells you different, do what he says! nod nod wink wink..

34-40 as always you give good advice.

Once the carb is dialed that is exactly how to use the gauge. Right now we are at that point once (and it’s abig once) the plug’s reflect the AFR readings. At present his plugs read too hot, needed to be cooled a step or two, then we’ll start seeing a true representation of what’s happening inside the cylinders.

We’ve come a long way from where it was to where it needs to be, the finish line is in sight.

And the big moral to this story is “All carburetors Benefit from being tuned.”

Would tightening the gap on the plugs cool them down? It's a brand new set of Autolight plugs, and I gapped them them to 60 per what the sticker said on the radiator support, but now I read that and they knocked it down to 45 for specs. I thought 60 seemed kind of wide. The reason why my timing is at 36 now is because I adjusted the vacuum advance up 2° with the distributor forgetting that I had an adjustable vacuum advance lol. I will bring that back down to 34 to help cool things off as well. It's been about 90° with 70% humidity here lately, I'm curious to what the AFR readings will be when the outside temp and humidity go down.

Tuning a motor usually requires several sets of plugs, the cost of plugs is relatively cheap compared to the cost of hiring a tuner. I'm proud of you, you have gained the knowledge and confidence to do it yourself! My only charge is that you pass it on to others so they too can learn and have fun!

The gap won't change the heat range of the plug, that's determined by the porcelain inside the plug and how fast it transfers the heat to the plug base, usually shorter porcelain is a cooler plug. The strap and threads on your plug show too much heat, performance will benefit from a cooler plug.

Set plug gap at .035, usually high performance motors like a tighter gap (even with HEI). 36° total timing is ok if the motor likes it (some head designs don't), 2° can make a difference as long as it doesn't ping.

Ignore all the tuning specs on the radiator, those are factory recommendations and you are way beyond that now. Keep a log of all changes and their results for future references.

AND most of all, ENJOY!!

It's very cool to see the bird out from it's death sentence, I mean staycation. That was a long read but very good that you were able to get it tuned in with good help from members here. Reading this thread made me question my choices on my 40. But hopefully 2020 is the year to get immobile rides mobile?

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Originally Posted by 40FordDeluxe

It's very cool to see the bird out from it's death sentence, I mean staycation. That was a long read but very good that you were able to get it tuned in with good help from members here. Reading this thread made me question my choices on my 40. But hopefully 2020 is the year to get immobile rides mobile?

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Death sentence in the garage? That poor car has seen more 3 digit speeds, smoke rolling, and getting beaten like a red head step child that it's seen in years, It's begging to get back in the garage In all reality my end goal for the car is a LSX with a 6 speed swap, I just can't get it out of my head I'm trying tuning it but once again it got stuck on the side burner till Rita gets its tow package and a clean bill of health for the Black Hills trip ( not to mention all the other to-do lists around the place )

Just my point oh two, but if you do go the LS route, just get a holley terminator setup from the get go and party time.

Sorry 36, I feel kind of bad about this because of all the advice and help you gave on on tuning a carb, but I did the unthinkable, I bought Holley Sniper for the T/A. It all started when I found a new Pontiac Sniper distributor for the cheap on swap, then I thought I might as well buy the rest of it too. I'm hoping to get it put on this winter and have my dyno guy tune it in on the dyno for $400, I guess he's pretty good at it. The more you dig into it, there is a lot more tuning on these that is available if you want to put in the effort.

No worries, I had fun with you in the journey! EFI definitely has advantages in performance and motor life, I've considered it myself. LOL
Keep us posted on how it does.

Have a nice Holley for sale if you need one