Mild Built 340 Timing/tuning help?

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PyePerformance

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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! :D
- Steve
 
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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? Good place to start 32 and go from there.
  2. Mallory dist. springs -- what spring combo(timing curve) would be a good place to start? I would start advancing around 1100-1200
  3. What is the best way to determine initial adv? By ear really see where it likes without kicking back during start.
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? Kind of like marbels in a can hard to describe.

Anyways, thanks in advance, and forgive my stupidity! :D Hey we all were at one time!

Hope it helps.
 
PyePerformance said:
We run Sunoco 110 leaded.
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PyePerformance said:
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.
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Running straight 110 octane leaded on an engine with mid 9:1 compression and the closed chamber Edelbrock heads is probably a waste. I don’t see any reason your engine shouldn’t run on 93 octane. Case in point is a 391/318 stroker running 11.2:1 on 93 octane with the same XE274 cam and Edelbrock top end. It ran best on 22 degrees initial with 32 degrees total timing with mechanical advance only, but it was in an obscenely heavy truck.
 
100 octane is a waste, not probably. You may even get away with 87. Case in point, my sons 360 is at 10.5-1 with Edelbrock heads and runs on 87 with a smaller cam. (A smaller cams tends to build more cylinder pressure requiring a higher octane.)

Ping … like marbles is a good answer but I’d add that there being violently bounced around until the make a sound like a rattle.
 
I agree about the 110 octane leaded. It could even be costing some power. Certainly costing money!

If you really want some insight as to what octane to run, do a compression test on it and see where those numbers are. That's not an end all be all, but will certainly give you an idea. If you do it, post the numbers up so we can advise further.
 
Because here's the thing. There are only TWO pistons for the 340. One is the 71 dna prior that has positive deck height and two eyebrows. Those were rated at 10.2:1 from the factory, but always blueprinted around 9.5. Then there was the 72 and 73 pistons which were rated at 8.5:1 and were actually lower. MOST builds get the 4 eyebrow flat tops that do not come up to zero deck. So taking that into consideration, you in all likelihood, have an 8-8.5:1 engine, UNLESS the heads have been milled a good bit, OR you have the earlier 2 eyebrow flat tops with two eyebrows. I put my money on your engine being in the 8.5 range. Once you run a compression test, we'll know.
 
For the initial, this will put you in ballpark.
Distributor starting point for a curve
I'm going to guess something around 18* BTC at 850 rpm when you get it worked it in.

To determine the best for your combination, you will have to iternatively make changes and then readjust and check for max power at that idle.
Your goal is the lowest rpm it will idle with power.
Power is proven by putting it into gear with the least drop in rpm (automatic), a little more difficult to prove with manual transmission but same concept.
For a given initial this means adjusting the mix screws and and reducing the idle speed screw. Be sure the transfer slots stay in their operating range. (.020 to .035 transfer slot showing below the primary throttles). see this post for illustration and explanation Setting Throttle to Transfer slots

Then adjust the initial timing a couple degrees and go throughthe process again to see if you can improve the power or idle speed.

To do this ^^^^ There must be enough spring tension on the distributor weights that the timing isn't advancing at the idle speed you are working with. This was the one downside of the DirectConnection race distributors. They were already advancing at idle rpms. Back in the day, for drag racing, they were willing to accept that. The trade off was easy hot starting. (Races can not be won if you can't pull to the starting line)

Since you are not using vac advance, an advance curve similar to those used in the Direct Connection tach drive race distributors will be fine.
see these posts
Performance timing

and a Mallory distributor on a distributor machine showing why Direct Connection and others built in a long slow mechanical advance in the mid to high rpms/.
School Me On Distributor Performance
 
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I have a similar build. 30 over 340, 10.2/1 with the comp cams X285HL air gap with 2.02 J heads. Run 91 all day long, most of the time I run non ethanol 91. Timing is set at 16 base, 35 all in at 2800. When I get my poop in a group, I have ported Eddy rpm’s and air gap on the shelf with will bring it up to 11.5 - 1. Still going to run pump gas…0

110 at over 10 bucks a gallon in a waste, granted I do like the smell of race gas. My brother runs the vintage Cosworth BDA 1600 race engine in the mid 12-1 range but those things are spinning 10k rpm. Race gas in the pressure washer works well
 
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Do you know if the TRW pistons are above deck? Also, what head gasket are you running? Even with the 64 cc Edelbrock chambers, if it's the low compression 340 pistons that are below deck and you're running a 4.18 bore Felpro gasket that 8.5:1 compression or less is a good possibility.
 
Agree with above, the 110 is costing you money and likely power. Run pump gas. A good general baseline to start at is 32 total with one light spring and one medium spring in the distributor. That should get your all in around 3000 and and not be to fast that it pings. Tune from there. You have to limit the mechanical curve to run higher initial numbers, which your engine will probably need to get the transfer slots synced up.
 
Since most of everything is covered I’ll add this. DO NOT EVEN HOOK A BATTERY UP TO THAT ENGINE UNTIL YOU BUY THE CIRCUIT GUARD THAT GOES IN-LINE WITH THAT DISTRIBUTOR. PERIOD.

That Unilite will outlast ANY ignition and work very well doing IF you follow these two rules.

1. Always use the in-line circuit guard. Always. It filters out “dirty” power from the alternator. That is one of the thinks that will kill the module. It also stops bad grounds and shorts from killing the module.

2. Never and by never I mean NEVER EVER hook a battery charger up to you battery with the Unilite plugged in. Ever. That’s one reason why it comes with a simple plug. If you have to charge the battery then unplug it and charge it up. And never jump start the car. Again, unplug the Unilite, let the battery charge on the jumper cables and then plug it back in and start the car.

Following those two simple rules will ensure you never get stuck somewhere because the module took a crap on you. If the module fails it’s because of one of those two reasons.

Just an FYI to save you some time, money and frustration.
 
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!


RustyRatRod said:
Because here's the thing. There are only TWO pistons for the 340. One is the 71 dna prior that has positive deck height and two eyebrows. Those were rated at 10.2:1 from the factory, but always blueprinted around 9.5. Then there was the 72 and 73 pistons which were rated at 8.5:1 and were actually lower. MOST builds get the 4 eyebrow flat tops that do not come up to zero deck. So taking that into consideration, you in all likelihood, have an 8-8.5:1 engine, UNLESS the heads have been milled a good bit, OR you have the earlier 2 eyebrow flat tops with two eyebrows. I put my money on your engine being in the 8.5 range. Once you run a compression test, we'll know.
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@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.
 
PyePerformance said:
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!




@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.
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Was the camshaft degreed in or just stabbed dot to dot?
 
Or me, Lolol! Plugging the numbers into the dynamic compression ratio calculator shows between 8.7 to 9:1 compression at 2000 feet of altitude (depending on what part of LV you’re in). That’s if the cam is installed where it’s supposed to be (106 ICL) with the intake closing at 60 degrees ABDC. I think your cranking compression is acceptable, but it wouldn’t surprise me if you had advanced the cam a little. Any idea how far below deck the pistons are? No doubt that could be tuned to run on 87 junk gas or 89 mid grade without issues.
 
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Scody21 said:
No worries. Taking smack as we like seeing engine photos… Otherwise it didn’t happen…
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View attachment 1715962158

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.
 
ping sounds like your rods are hitting the pan. And it usually happens at low RPM when you lug it, ie 3rd gear doing 20 and you mash it. Your either gonna lug it or you going to spin them. Spinning is prefered!
 
pishta said:
ping sounds like your rods are hitting the pan. And it usually happens at low RPM when you lug it, ie 3rd gear doing 20 and you mash it. Your either gonna lug it or you going to spin them. Spinning is prefered!
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Thank you! Based off that, apparently I have not had any issues with pinging then, lol.
 
It's almost impossible to add enough timing to a 9:1 or less engine on 110 leaded to make it ping! I will say you've got your mixture in a happy place. If it's at all rich in the low to mid circuits with the BKR6E plugs they fuel foul pretty quickly. We discovered that when re-setting the float height and air bleeds on a pretty well used carburetor with the 392 stroker.
 
Garrett Ellison said:
It's almost impossible to add enough timing to a 9:1 or less engine on 110 leaded to make it ping! I will say you've got your mixture in a happy place. If it's at all rich in the low to mid circuits with the BKR6E plugs they fuel foul pretty quickly. We discovered that when re-setting the float height and air bleeds on a pretty well used carburetor with the 392 stroker.
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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! :D
 
PyePerformance said:
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!)
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At those cranking pressures I'd bet that thing would run on the cheapest gas you can find.

For reference, my 9.6:1 (measured) 340 cranks 170 psi w/ 230* @.050" camshaft. I run 24* initial and 34 total. It runs great on 91 with no detonation.

I'd give it as much initial timing as it wants - provided it doesn't buck the starter when warmed up.
 
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