Thread: Tune a Fresh 454

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Hello people,
Just got my 454 running (mild, 9.37:1, 770 vac, small oval, 213/219@.050, .515/.530) and with the help of a friend we did the following:

1) Timing; disconnected and plugged vac adv, then set timing for highest vac reading and backed off (retarded) 1". Couldnt get it to go down 2" so that left us sitting at about 19" (resultant timing was about 17-18* initial)

2) Mixture; adjusted mixture screws for highest vacuum reading at idle (in gear, 500rpm) and they were pretty much dead on (factory setting). Any adjustment eather direction and the vacuum drops along with idle quality.

It starts/runs just fine except for my blackened spark plugs and a slight hesitation off idle. So I am thinking that I need to go up one heat range on the plugs (currently R44T) and try adjusting the pump shot for the hesitation.

Your thoughts are encouraged. Thanks.

btw: I have not road tested it yet, driveway tuning only.

Just a couple of thoughts, I am no expert, so hopefully someone else will chime in.
When you road test it you may be able to determine if you need more or less timing. Put a load on it and see if you have any pinging. If so, retard it a little, if you don't ping, maybe you can advance it a little. (unless you start experiencing hot start problems, then you probably have gone too far advanced)
Also, sitting in the driveway and noticing a stumble is different from driving it and having a stumble. again load vs no load. I am kinda holley ignorant, so I may be talking out of my azz here.

Now, about those heads, I think you should have done a bowl blend and a gasket match..........then call it good.

Worry about the plugs after you get the timing set where it should be, if that 770 is new, it is probably adjusted pretty close to where it should be, but maybe one of the holley gurus here will help to explain how to tweak and tune it.

I have heard your load/no load method in reference to getting a good read on the spark plugs. But I dont see how it applies to the stumble off idle. If it does it in my driveway, I think it would do it on the street too. Only one way to find out though !

for your second comment (?)...I dont see how that relates to anything.

From what we saw, it looks like it is right on as far as the mixture goes unless I can be told otherwise. I was thinking also (not good when I think sometimes) that my plugs might be black because of the idle time? Maybe they havent gotten hot enough to burn off the carbon?? Just guessing here...

I would not try reading you plugs yet if you have not road tested yet. I am sure I will get smacked for saying this but I have never had any luck with AC plugs, I believe Champion RV15YC4 plug will burn cleaner and give better start up. Holley carbs most generally will run on the rich side out of the box but I would get an excellerator pump cam kit and start adjusting and test there first.

I'm not a huge fan of reading plugs on a motor you re breaking in. Let her break in a little. Right now it seems rich, that's OK as long as she ain't washing the cylinders down too much. How is your ignition? A good high V ignition will do wonders for idle. Especially an MSD ignition. Is this an old rebuilt carb? Sometimes they just don't work out; get a new one.

Something to consider I hope .............

Kitz

Everything is brand new. I'll run it a bit like you said and maybe change brands of spark plug. Once it heats up it idles nice and smooth.

Thanks for the input guys!