Six pack tuning help needed, please

1/4 turn out on the end carb mixture screws won't be enough. going to 2 1/2 turns on the center carb means your trying to make up for the ends not being rich enough. the center carbs have an idle restriction tube in the main well. the idle orifice isn't large enough and the idle air bleeds are a little big. so, you'll need to make up for that on the end carbs. there's a possible cure for this but i'll save that for later. are you guys using some aftermarket jet plates in the end carbs? do the black bushing first and if need be go to lighter springs. total advance will need to come in around 2000rpm, maybe sooner, with an automatic. something to keep in mind; the carbs can never be properly adjusted until the ignition is correct.

Yes He is using the promax plates. Has a blue and silver spring on the advance. So we should go with 2 silver springs & black bushing, correct? We are using the method of covering the air bleeds on the top outside to check the outers. We tried turning them in from a 1/4 but would idle up when covering the bleed. Do we need the 3.5 power valve?
Thanks

did you check to see if the plates are interfering with the floats? i bought a set of quick fuels for a set of carbs, gave them a good look, and tossed them in the carb box and forgot about them. wasn't happy with the way they are installed or the fuel supply channels. try the two lightest springs with the black bushing before you go back at the power valve. covering the idle air bleeds is how i set the end carbs , but i'm pretty sure a 1/4 turn won't get it once the ignition curve is set up. the ignition curve should be the primary focus. until thats corrected adjusting the carbs will be like a dog chasing it's tail.

And my understanding on checking the correctness of the power valve is to drive around and see how the vacuum reads while driving normal. Need a long hose hooked to the vacuum gauge so it reaches inside the car and someone can watch it as you drive around.

But I just read the Holley bulletin, and I forgot I guess you can check it with the car merely idling in gear.

OK we will try to get the ignition dialed in tonight and see what happens. Had to go get bushing & springs today.

OK so we got the timing reset with the 2 silver springs & black bushing. It's now 18 initial & 35 all in at about 2100 rpm.
We retuned the carbs but not to big of a change. Outers went to between 1/4-3/8 & center stayed pretty close to the same also at 2 1/2

I had problems tuning the set on my TA and it was these adjustment screws under the lead plugs that were out of whack.
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Yes, that's what we're working on.

RS23VOA said:

I had problems tuning the set on my TA and it was these adjustment screws under the lead plugs that were out of whack.
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Those screws were only out of whack if you made prior engine modifications !

I bought a car that didn't run. The plugs were out when I got it and after taking the carbs off and on until I rounded the fuel line fittings off I finally figured it out.

Well I gotta say a huge thanks to Lew!!! We finally got the bird running really well now. Timing is such a big deal, I see that now. Got the initial at 16, 34 all in at 2100 rpm. It now idles glass smooth @ 850 with 12-13 vac. & 10-9 in gear at idle. Shuts off with out dieseling or use of the idle solenoid. Revs and returns to idle as it should. We are at 1 1/4 on the center carb & 1/2 on the outers. I feel there is yet some more to gain but he is super pumped. The car has never been this good since the motor was instaled. Thanks again Lew, you da Man!

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I gotta add that I originally thought his cam was a little big, but after retuning it I see it is just about perfect for what I was looking for for mine. BTW heres some pictures of Jeff's car.


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Now we just need some dry streets for a road test!

Once again, Lew, you come to the rescue with great advice. Thanks for sharing.

when you guys get a chance start doing some fuel delivery checks. do some WOT fuel pressure tests and definitely go after the vapor separator.

Will do. We may close up the .070 holes in the outters to see if that further helps the tuneup. It's raining here but we'll get a road test soon.

69 GTX said:

Well I gotta say a huge thanks to Lew!!! We finally got the bird running really well now. Timing is such a big deal, I see that now. Got the initial at 16, 34 all in at 2100 rpm. It now idles glass smooth @ 850 with 12-13 vac. & 10-9 in gear at idle. Shuts off with out dieseling or use of the idle solenoid. Revs and returns to idle as it should. We are at 1 1/4 on the center carb & 1/2 on the outers. I feel there is yet some more to gain but he is super pumped. The car has never been this good since the motor was instaled. Thanks again Lew, you da Man!

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View attachment 252535I gotta add that I originally thought his cam was a little big, but after retuning it I see it is just about perfect for what I was looking for for mine. BTW heres some pictures of Jeff's car.
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Now we just need some dry streets for a road test!

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what cylinder heads are on the engine? what pistons?

They are stock 906's & and Diamond 11:1 dome pistons.

He has been running 75% 93 premium & 25% 100 low lead. With the timing now at 34 (was 38) all in I'm looking forward to see if he can get away with just 93.

i seriously doubt 93 with that much compression and no quench. i've had trouble with 9.5 no quench and 93 octane. the engine in my r/t is 9.3:1 with quench and it's really finicky on tune up and gas. something to keep in mind is carbon build up. just .010" of carbon on the piston and chambers will raise the compression ratio 1/2 point. he'll easily be in the 11:1+ range with some drive time. this is why i prefer to start off with a more conservative compression ratio.

Do either one of your engine combos have aluminuim heads. I've read that it will allow you to run 1/2 to a full point higher compression. Also read an interesting article that said for every 25 degrees of rise or drop on your intake charge was good for 1 point of octane rating. What is the average corrected altitude where you live during the summer?

good questions but i think the answers might be a little subjective. one engine i have does have alum heads and good cooling. it has 9:75:1 comp with clean chambers and piston tops, good quench, has a longer duration cam than the iron head engine and seems to be comfortable with 93 octane, i figure with some carbon build-up it'll be in the 10.25-10.5 range.

the other engine is iron head, 9.3:1 with clean chambers and pistons, not ideal cooling, shorter cam and it's fussy about good gas. obviously this isn't an apples to apples comparison between the two.

my altitude is 800ft above sea level.

are you looking for a loophole in the "laws of detonation",...lol. we all do, but there's just a point where pump gas won't support certain levels of pressure no matter what we try. i've read a lot about detonation in internal combustion engines and never found any concrete info stating that "one" thing is the culprit. it can be a multi-layer destructive problem and no engine can be made detonation proof. otherwise you can break an anvil if you try hard enough.

i used to do some shooting some years back. i always reloaded my ammo and used the manuals to help me pick a load with the correct propellant and components. i had to always keep in mind not to use a propellant that burned too fast. this would give too much pressure too soon in the burn process and break parts. detonation in an internal combustion engine is basically the same too much pressure too soon in the burn cycle. we can't vary the "propellant" (pump gas) for a slower burn but we can take the variables out that lead to making too much pressure too early in the burn cycle. variables can be combustion chamber design, plug location, type of fuel, engine cooling, ignition timing, atmosphere, combustion chamber contaminates, to a degree head material. so what i do is try to take all these variables to task and eliminate as much as i can to build as much resistance to detonation as i can. i don't knowingly push the limits.

what i've noticed thru the years reading and listening to people they are always willing to push the limits for a few extra horses. this is a short term strategy; you will pay the piper. long term; build as much resistance as is possible. i'd gladly give up 10 horsepower for reliability and a thicker wallet.