Mild Built 340 Timing/tuning help?

[RustyRatRod]

Well, embarrassingly, no we just installed dot to dot. I suppose in hindsight we definitely should have degreed it.

No worries. Happens all the time. AT LEAST you KNOW what yall did. Here's the skinny on THAT. Unless it's degreed, you don't know "WHERE" the camshaft is, in relation to the cam card. I'm sure you understand that part. What can be worse is, it could be installed terribly retarded. I've seen 11-12 degrees retarded before in the past before I got one degreed, so it CAN BE a pretty big deal. Just food for thought.

 

[RustyRatRod]

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EDIT: This is our first engine build. If we sound like we're stupid, it's probably because we are! Lol. I continue to learn though.

It looks really NICE!

 

[PyePerformance]

It looks really NICE!

Thanks Rusty!
It took first place for A-Body Modified in the 2022 Muscle At The Strip judged car show competition here at Vegas motor speedway.
I think I will just tune it as best I can and run it and enjoy it for a few months until it cools down, then maybe pull it and swap out for some domed pistons, properly degree the cam, etc. Not too fun wrenching engines in solid 115 degree sunny days.

 

[RustyRatRod]

Thanks Rusty!
It took first place for A-Body Modified in the 2022 Muscle At The Strip judged car show competition here at Vegas motor speedway.
I think I will just tune it as best I can and run it and enjoy it for a few months until it cools down, then maybe pull it and swap out for some domed pistons, properly degree the cam, etc. Not too fun wrenching engines in solid 115 degree sunny days.

I think that's a fine plan. All that really matters is that you are happy with it.

 

[Gator]

Thanks for the replies! I'll attempt to address each one.

Sounds like the 110 is a no-go. We only ran it because some people were saying leaded is best. If unleaded 91/93 is okay, then fine by me!
In my HiPo 340 I am running a mix of 80/20 with 80 being 93 octane and the 20 being sunoco 110. I previously was running 50/50 but the cost was to high so when I switched to my current mix I noticed a big + in performance from when I was running 50/50 mix..



@RustyRatRod You are right on the money, as usual. They are the 4 eyebrow that are not zero deck. Heads are straight out of the box.(no machining)

@RustyRatRod I tested cold compression after we built the engine. All 8 were between 140-148psi.

I tested warm compression just now, (all plugs removed,) cylinders reading between 130-138psi (hopefully not cause for concern!)

@Garrett Ellison Yes, just running the Fel Pro blue head gasket 4.180 in, TRW below deck 4-eyebrow piston.

@Rat Bastid Thank you for bringing this up. Nobody told us about the circuit guard when we were talking to Summit's sales reps. I appreciate this and will order one asap.

I do have a slight doubt in trusting my compression tester. I may buy another to confirm the readings, although I presume this is accurate.

I should have also mentioned it's a 4 speed a833. Sounds like my compression ratio is lower than I had assumed. Are the warm compression test readings above any cause for concern?

Thanks again guys.

 

[Mattax]

Yes, I have had that issue of it running rich, idle and primary circuits. I do have a wideband o2 installed, I will probably be making a thread asking for help regarding that soon lol. I figured I would dial in proper timing before getting too deep into swapping PVs or rejetting, etc. Unless I am totally going about this ***-backward, in which case please advise!

its a good sequence in theory.
In reality tuning in the timing at idle ties in with tuning the fueling at idle.

See the link in my previous post about the transfer slots. While we can trim fuel mix at idle with the needle valves in the idle ports, we can't trim the off-idle that easily. Most driving at lower speeds is done with the throttles slightly open. Also, when the throttle is opened quickly from closed or nearly closed, the low speed speed system needs to respond quickly. That's why this is so important. If there is a dead spot, a or a hesitation when opening the throttle slowly, that will be a clue the idle wasn't tuned right. You can get away with this more with a manual transmission than with an auto. In neutral there is no load. One can run an engine ridiculously lean with no load. But engine output at idle is already pityful, especially on a high performance engine.
see this post and checkout the link to the desired AFR at different loads Timing Marks on the 273 [66 Barracuda]

Wideband can be a useful tool. It also has many people chasing meaningless numbers. Keep your eye on the goals, power and torque. The O2 data is just a reference to understand the impact of a change. It's extremely useful in determining if the AFR is flat and stable when making WOT runs at the dragstrip or on a dyno.

AFR readings

 

[Dale Davies]

Hello all!

I am new to the forums, but have been reading advice here for a couple years now. Time to finally post.

Me and my friends have built my father's '70 Swinger 340 engine, and now it is finally time for me to start tuning it. I am still fairly new to tuning older vehicles, although I have been studying and learning tons(quite a bit from you folks!) over the past few months. It runs well, I just need some advice on intitial/total timing(and timing curve) before I move onto tweaking the carb. Here's the engine:

340 .040" over
TRW pistons
Comp xtreme energy hydraulic flat tappet 224 @ 050
Eddy aluminum performer RPM heads
Eddy performer RPM Air gap aluminum intake
Mallory Unilite Distributor (mechanical advance, no vac)
Holley 800cfm DP
C/R is somewhere in the mid 9's:1 if I had to guess.
NGK BKr6e gapped @.035"
We run Sunoco 110 leaded.

I understand each engine is unique, but would anybody be able to possibly give me a "ballpark" answer to these questions?

1. Total timing. I have heard around 34-36* is recommended. Would that roughly apply to this mild built engine as well?
2. Mallory dist. springs -- what spring combo(timing curve) would be a good place to start?
   
3. What is the best way to determine initial adv?

Bonus points for a really dumb question. I have never personally heard engine ping, and I have read many times to pull as much advance as possible without pinging. What exactly is the noise I should be listening for, and would it only be under acceleration?

Anyways, thanks in advance, and forgive my stupidity!
- Steve

Let us start with ping, sounds like rattling marbles in a jar. Definately you want to steer clear of this. The 390 FE Ford even with the lower compression 2V engine would rattle about twice when stepping on it off a light. That is OK as it was not sustained. That rattling while driving will destroy the engine real quick.
Now what is the cause? Combustion in the cylinder under normal conditions is the burn of the air/fuel in the cylinder. This starts at the spark plug and progresses across the combustion chamber. Two things can cause ping or knock, both detrimental. One is preignition caused by a glowing hot spot in the cylinder from sharp edges or carbon. This lights the fuel early causing the cylinder pressure to rise quickly while the piston is still traveling up the bore. As the pressure rises the temperature in the cylinder rises quickly until the air/fuel reaches the temperature to auto ignite. This is like a diesel but the remaining air/fuel explodes like a hand grenade. This burns holes in the side of the piston crown, breaks pistons and hammers rod bearings out.
Too much ignition advance does similar in that that combustion pressure rise occurs too soon and ignites the remaining air/fuel. Proper ignition advance has the pressure rise maximum occur about 10° ATDC. By then the piston is starting to move down the bore. Static compression is part of affecting facturs. Dynamic compression is a bigger factor. A/F ratio and load which is a contributor to mixture density also affect the speed of combustion.
Concerning the Al heads and AirGap manifold; you do not have much heat transfer to the air/fuel mixture coming out of the carburetor. I hope by this time you have broken in your cam with breakin oil and have changed to an oil with 1,000ppm to 1,200ppm ZDDP to protect the cam. If you hook up your timing light, start the engine and point the light down the carb. You should just see the venturis. Slowly rev the engine and you will start to see droplets of fuel coming out of the carb into the booster venturis. With a dial back timing light you can see how the droplets break up as they drop further. With the AirGap style manifolds, they benefit from annular discharge boosters or "shear boosters". Holley has a few boosters they use. Straight boosters, downleg boosters and annular. The annular have a series of holes around the inside of the booster venturi which tends to break the fuel up into smaller droplets before entering the manifold. You will get better performance and economy with them. You can search shear boosters. Patented and available from the patent holder to install in your Holley.

 

[Dale Davies]

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EDIT: This is our first engine build. If we sound like we're stupid, it's probably because we are! Lol. I continue to learn though.

Not stupid. Not knowledgable, yet. Stupid can not learn while not knowledgable is changed by reading, listening and experience of doing.

 

[Dale Davies]

Yes, I have had that issue of it running rich, idle and primary circuits. I do have a wideband o2 installed, I will probably be making a thread asking for help regarding that soon lol. I figured I would dial in proper timing before getting too deep into swapping PVs or rejetting, etc. Unless I am totally going about this ***-backward, in which case please advise!

A/F ratio and timing somewhat related in tuning. The PV installed by Holley should be about right. It should not open while cruising at steady speed on level ground. It should only open as you require extra power. Rochester and Carter/Edelbrock carbs use metering rods to enrich the air/fuel as you open the throttle. You can change jets and the metering rods as required on them. Holley can not enrich this way from correct cruise jetting on the main jets. To get that required extra fuel they have a power valve that opens when the manifold vaccum drops. These have different opening ratings depending on the engine. Racers are at idle or full throttle much of the time so they block the power valve and jet for the wide open throttle. Do not do this for street as economy will be terrible.

 

[Rat Bastid]

A/F ratio and timing somewhat related in tuning. The PV installed by Holley should be about right. It should not open while cruising at steady speed on level ground. It should only open as you require extra power. Rochester and Carter/Edelbrock carbs use metering rods to enrich the air/fuel as you open the throttle. You can change jets and the metering rods as required on them. Holley can not enrich this way from correct cruise jetting on the main jets. To get that required extra fuel they have a power valve that opens when the manifold vaccum drops. These have different opening ratings depending on the engine. Racers are at idle or full throttle much of the time so they block the power valve and jet for the wide open throttle. Do not do this for street as economy will be terrible.

WTH? You can change the main jets on a Holley for cruise and change the power valve channel restriction for WOT. Two separate circuits and one doesn’t affect the other like the metering rod.

 

[Dale Davies]

Where do you have the problem Rat? Two different ways around one problem. Main jet for cruise and fuel enrichment for power. Just different methods to accomplish it.
With metering rods you have a hand full of different dimension rods and some jets. With the Holley you have jets, air bleeds, emulsion tubes and power valves.

 

[Rat Bastid]

Where do you have the problem Rat? Two different ways around one problem. Main jet for cruise and fuel enrichment for power. Just different methods to accomplish it.
With metering rods you have a hand full of different dimension rods and some jets. With the Holley you have jets, air bleeds, emulsion tubes and power valves.

Who said anything about emulsion? You were talking about the power enrichment circuit. My point is you can change the main jet and not affect power enrichment and vice versa.

Any time you have a metering rod going through a jet you change one you affect both. I learned this at 12 years old with dirt bike carbs.

 

[Bewy]

Changing the MJ on a Holley changes cruise AND power. Changing the PVCR only changes power enrichment.

 

[Dale Davies]

Who said anything about emulsion? You were talking about the power enrichment circuit. My point is you can change the main jet and not affect power enrichment and vice versa.

Any time you have a metering rod going through a jet you change one you affect both. I learned this at 12 years old with dirt bike carbs.

Well the main jet also affects wide open throttle. The idle screws also affect cruise A/F ratio. Emusion tubes? Just part of proper tuning a Holley. Some have replaceable tubes and some that came factory installed are fixed. All these components need to work together in getting a carb to function well. It is like making sure your beer is MT before pissing in the bottle. All about sequencing.

 

[Rat Bastid]

Changing the MJ on a Holley changes cruise AND power. Changing the PVCR only changes power enrichment.

Right.

 

[Rat Bastid]

Well the main jet also affects wide open throttle. The idle screws also affect cruise A/F ratio. Emusion tubes? Just part of proper tuning a Holley. Some have replaceable tubes and some that came factory installed are fixed. All these components need to work together in getting a carb to function well. It is like making sure your beer is MT before pissing in the bottle. All about sequencing.

On a Holley or clone, on the primary side when running a power valve you set cruise with the main jet and you do not touch it again unless you are trying to change the cruise A/F ratio. You do NOT touch the primary main jet to tune for WOT if you are using a power valve.

It you want to change the WOT A/F ratio you do that with the power valve channel restrictors.

I don’t know why people don’t understand you do not change the main jet for WOT. You don’t do that.

 

[TT5.9mag]

On a Holley or clone, on the primary side when running a power valve you set cruise with the main jet and you do not touch it again unless you are trying to change the cruise A/F ratio. You do NOT touch the primary main jet to tune for WOT if you are using a power valve.

It you want to change the WOT A/F ratio you do that with the power valve channel restrictors.

I don’t know why people don’t understand you do not change the main jet for WOT. You don’t do that.

Because most people like to hit the easy button and screw a jet in rather than drilling a set screw or replacing a pvcr, and wouldn’t have the knowledge to do it anyway. They make a huge global jet change instead of focusing the fuel where they need it. It’s laziness

 

[Mattax]

I don’t know why people don’t understand you do not change the main jet for WOT.

Technically true but people do it because its easier.
Also many times it worked out 'close enough' or even right on if they had cared to test (which most do not) the limits.
If its right on, then saves a ton of work.

edit> and what TT5 wrote as well.

 

[Dale Davies]

Who said anything about emulsion? You were talking about the power enrichment circuit. My point is you can change the main jet and not affect power enrichment and vice versa.

Any time you have a metering rod going through a jet you change one you affect both. I learned this at 12 years old with dirt bike carbs.

Rochester and Carter/Edelbrock can change cruise or power individually by metering rod diameter. If you find a metering rod with the same cruise dimension and a smaller power dimension, you enrich power without affecting the cruise A/F ratio. Changing the jet changes both.

 

[Dale Davies]

On a Holley or clone, on the primary side when running a power valve you set cruise with the main jet and you do not touch it again unless you are trying to change the cruise A/F ratio. You do NOT touch the primary main jet to tune for WOT if you are using a power valve.

It you want to change the WOT A/F ratio you do that with the power valve channel restrictors.

I don’t know why people don’t understand you do not change the main jet for WOT. You don’t do that.

Are you trying to educate me on something I know about and agree to a point with you on?

 

[Phreakish]

Are you trying to educate me on something I know about and agree to a point with you on?

I think the confusion is how it was stated in your first post about holley vs carter.
It read as if you were stating the holley could not separately tune WOT/cruise.

 

[Dale Davies]

I think the confusion is how it was stated in your first post about holley vs carter.
It read as if you were stating the holley could not separately tune WOT/cruise.

I think I clearly stated the MJ determines cruise A/F ratio and the PV is used for power enrichment.
Possibly the part about racers plugging the PV circuit and using the main jet richer. By this they remove a variable that could damage the engine should the PV fail to open. Street and race are separate situations. As I stated, a race engine is usually at idle or wide open with transition between generally for a brief time in the middle of a corner. Result is running a bit rich feathering the throttle through the corner until the apex is reached and the throttle is opened as possible.
Hope that clears that up.

 

[Phreakish]

I think I clearly stated the MJ determines cruise A/F ratio and the PV is used for power enrichment.

I agree, but can see how others might have mis-interpreted. I did at first.
From post #34: "Holley can not enrich this way" - you went on to clarify and explain, but the 'can not' could be interpreted as implying that the Carter can do something the Holley cannot. That isn't what you went on to say, but it leaves room for others to misread.

 

[Dale Davies]

I agree, but can see how others might have mis-interpreted. I did at first.
From post #34: "Holley can not enrich this way" - you went on to clarify and explain, but the 'can not' could be interpreted as implying that the Carter can do something the Holley cannot. That isn't what you went on to say, but it leaves room for others to misread.

Seems a matter of fully reading and not scimming over what you read. I can see where some could misinterpret.

 

[Rat Bastid]

Rochester and Carter/Edelbrock can change cruise or power individually by metering rod diameter. If you find a metering rod with the same cruise dimension and a smaller power dimension, you enrich power without affecting the cruise A/F ratio. Changing the jet changes both.

No ****. But what happens when you change just the main jet? Get it?