340 Static Compression Numbers and Test Procedure

[92b]

The more I (we) dig at this the more unknowns we are finding guiding me closer to pulling this puppy.

The pistons are 0.30 from the bore scope readout. nmn9 what are you thinking regarding comparison of the TRW piston weight to the stock ones? I read on a other forum the weight is 735 for an 0.030 over TRW.

Hang in there, you're getting close.

 

[nm9stheham]

The more I (we) dig at this the more unknowns we are finding guiding me closer to pulling this puppy.

The pistons are 0.30 from the bore scope readout. nmn9 what are you thinking regarding comparison of the TRW piston weight to the stock ones? I read on a other forum the weight is 735 for an 0.030 over TRW.

Well that is pretty close. I have 719 grams for the stock 340 piston alone, plus the pin is another 154 grams, and I suspect the TRW pin+piston are about the same.

So if the stock rods were used, then the bobweight will be the same or close to stock. If the stock cast crank was used, then it ought to be close to the factory balance tolerance..... which was rather loose compared to what hot-rodders allow, but obviously it will survive.

So IMHO, time to carefully check over the TC for weights. Take pix. 92b's pix of the Magnum flexplate is a good illustration of weight sizes. It has the big weight on one side for the intentional external imbalance, and then a couple of smaller weights for fine-tuning it in. A neutral balance TC may have small ones so don't let those fool you. The 340 external weight will not be as large as the 360/5.9L external weight.

BTW, is it possible to fit your camera probe up into the oil pan drain hole and get pix of the crank and rods? IDK if you have a flexible probe or what....

 

[340inabbody]

Well that is pretty close. I have 719 grams for the stock 340 piston alone, plus the pin is another 154 grams, and I suspect the TRW pin+piston are about the same.

So if the stock rods were used, then the bobweight will be the same or close to stock. If the stock cast crank was used, then it ought to be close to the factory balance tolerance..... which was rather loose compared to what hot-rodders allow, but obviously it will survive.

So IMHO, time to carefully check over the TC for weights. Take pix. 92b's pix of the Magnum flexplate is a good illustration of weight sizes. It has the big weight on one side for the intentional external imbalance, and then a couple of smaller weights for fine-tuning it in. A neutral balance TC may have small ones so don't let those fool you. The 340 external weight will not be as large as the 360/5.9L external weight.

BTW, is it possible to fit your camera probe up into the oil pan drain hole and get pix of the crank and rods? IDK if you have a flexible probe or what....

Thanks again nm9! Ok so if I understand your thinking the rotating mass might be close to the original mass indicating that it might be running ( a 1973 set up) a cast crank which was externally balanced. This is my hunch too but means the HB was totally wrong as I had suspected not only the timing mark in the wrong place which was obvious but it was set up for an internally balanced set up. Also the Torque Converter balance needs to be confirmed through visual inspection.

Correct me if I am wrong here.

Now you brought up a great idea my bore scope IS flexible AND thin and should easily snake up through the oil drain plug! What a great idea. I might be able to find a parting line to capture on the counter weight.

 

[92b]

Thanks again nm9! Ok so if I understand your thinking the rotating mass might be close to the original mass indicating that it might be running ( a 1973 set up) a cast crank which was externally balanced. This is my hunch too but means the HB was totally wrong as I had suspected not only the timing mark in the wrong place which was obvious but it was set up for an internally balanced set up. Also the Torque Converter balance needs to be confirmed through visual inspection.

Correct me if I am wrong here.

Now you brought up a great idea my bore scope IS flexible AND thin and should easily snake up through the oil drain plug! What a great idea. I might be able to find a parting line to capture on the counter weight.

Also look at the counter weights for heavy metal added to the crank.

 

[nm9stheham]

Thanks again nm9! Ok so if I understand your thinking the rotating mass might be close to the original mass indicating that it might be running ( a 1973 set up) a cast crank which was externally balanced. This is my hunch too but means the HB was totally wrong as I had suspected not only the timing mark in the wrong place which was obvious but it was set up for an internally balanced set up. Also the Torque Converter balance needs to be confirmed through visual inspection.

Correct me if I am wrong here.

Now you brought up a great idea my bore scope IS flexible AND thin and should easily snake up through the oil drain plug! What a great idea. I might be able to find a parting line to capture on the counter weight.

Mostly correct. The bobweights (which are the rotating + reciprocating mass equivalents of each pair of pistons and rods) are the same for the early and later 340's from what I know. These same bobweight piston/rod assemblies would have been used for both cranks, forged and cast. (There is one factor I have to research in this matter but don't have time right now. Maybe later today...)

So the crank could have been swapped from cast to forged and then the correct damper and TC would be the neutral balanced ones.

Yes, check the TC weight visually.

 

[340inabbody]

Well it looks like the TQ is set up for an internally balanced engine.

 

[340inabbody]

Ok n order to try to answer the question of a cast crank or not. I also tried to capture the back end of the crank by the flexplate connection. I was hoping to find a parting line in the ring but I didn’t see one.

 

[340inabbody]

Well rather depressed as I tried and one last method to determine if this crank is cast or not. I tried using my bore scope up into the oil pan. While a great idea the windage tray makes it very difficult and there is enough residual oil to foul up The camera tip...... Now I know how the GI doctor feels after a bad colonoscopy .....

 

[yellow rose]

Well rather depressed as I tried and one last method to determine if this crank is cast or not. I tried using my bore scope up into the oil pan. While a great idea the windage tray makes it very difficult and there is enough residual oil to foul up The camera tip...... Now I know how the GI doctor feels after a bad colonoscopy .....

View attachment 1715468725

I seriously doubt anyone would be silly enough to internally balance an OE cast crank. I know I probably wouldn't do it, even if the customer wanted it.

It would be an incredible waste of money. I can find better places to spend money than to internally balance a crank like that, especially if they already had a damper and torque converter.

But, I've been doing this long enough to know that stranger things happen. But I doubt this is a cast crank.

BTW, back in the day I've seen engines balanced with a weighted damper on the front just for the claimed better dampening characteristics.

 

[340inabbody]

I seriously doubt anyone would be silly enough to internally balance an OE cast crank. I know I probably wouldn't do it, even if the customer wanted it.

It would be an incredible waste of money. I can find better places to spend money than to internally balance a crank like that, especially if they already had a damper and torque converter.

But, I've been doing this long enough to know that stranger things happen. But I doubt this is a cast crank.

BTW, back in the day I've seen engines balanced with a weighted damper on the front just for the claimed better dampening characteristics.

Hey YR I don’t think I am implying that this is a balanced cast crank as I have no clue as to what it is. I agree a balance job on a cast unit makes no sense and I doubt any machine shop would even do this.
Just trying to figure out how best to continue if I don’t know what it is. The previous guy who worked on this set up had no brains whatsoever so I am not convinced that it was set up correctly. I guess I have to pull the oil pan to get a better look at the crank to make a determination if its forged (internally balanced) or cast (externally balanced).

 

[yellow rose]

Hey YR I don’t think I am implying that this is a balanced cast crank as I have no clue as to what it is. I agree a balance job on a cast unit makes no sense and I doubt any machine shop would even do this.
Just trying to figure out how best to continue if I don’t know what it is. The previous guy who worked on this set up had no brains whatsoever so I am not convinced that it was set up correctly. I guess I have to pull the oil pan to get a better look at the crank to make a determination if its forged (internally balanced) or cast (externally balanced).

I get what you are doing and dang sure don't blame you.

If it was me (I'm not into doing more work than needed...the wife says I'm lazy) I'd rather pull the timing cover. You should be able to roll the crank around and see the parting line on it.

That's way less work than pulling the pan. Unless the engine is out. This is a long thread and I get confused.

 

[92b]

Well rather depressed as I tried and one last method to determine if this crank is cast or not. I tried using my bore scope up into the oil pan. While a great idea the windage tray makes it very difficult and there is enough residual oil to foul up The camera tip...... Now I know how the GI doctor feels after a bad colonoscopy .....

View attachment 1715468725

I experienced a situation situation similar to what you are dealing with here. Back in the early 80's my dad bought an early 70's van. It had a 360 in it and the tranny was bad. Dad put a tranny that was mated to a 318 in it. That motor always had a vibration in it like it had a dead cylinder but when you would pull the wires off one at a time they all would drop rpm about the same. This went on for over a year trying to find this " miss " in the engine. Next my grandfathers 318 in his pickup was getting tired and he had a low mile 360 out of a car to replace it. I went to this mopar guy in search of a pickup oil pan and pick up tube for the 360. He told me to make sure I change the torque converter because of the external balance of the 360. As soon as he said that I new what was wrong with dads van. We changed the converter in the van to a external balance and it ran smooth as silk.
Another example is on a one piece rear main small block chevys They are balanced externally at the flywheel. These can also be balanced internally with light weight pistons and rods etc. On a couple occasions because of miscommunication a motor has been started on the dyno with the wrong combination. When this happened it was pretty obvious as the dyno stand would shake pretty badly as soon as you raised the rpm off idle.
I'm not saying that you shouldn't try to get to the bottom of your balance situation but it might be obvious if it is the wrong balancer and flywheel when the motor is running.
I'm sure I'm not the only one to experience a mismatched flywheel and balancer. Hopefully someone else can relay their experience to help sort this out.

 

[340inabbody]

I get what you are doing and dang sure don't blame you.

If it was me (I'm not into doing more work than needed...the wife says I'm lazy) I'd rather pull the timing cover. You should be able to roll the crank around and see the parting line on it.

That's way less work than pulling the pan. Unless the engine is out. This is a long thread and I get confused.

Thanks YR I very much appreciate the help here from you!

 

[340inabbody]

I experienced a situation situation similar to what you are dealing with here. Back in the early 80's my dad bought an early 70's van. It had a 360 in it and the tranny was bad. Dad put a tranny that was mated to a 318 in it. That motor always had a vibration in it like it had a dead cylinder but when you would pull the wires off one at a time they all would drop rpm about the same. This went on for over a year trying to find this " miss " in the engine. Next my grandfathers 318 in his pickup was getting tired and he had a low mile 360 out of a car to replace it. I went to this mopar guy in search of a pickup oil pan and pick up tube for the 360. He told me to make sure I change the torque converter because of the external balance of the 360. As soon as he said that I new what was wrong with dads van. We changed the converter in the van to a external balance and it ran smooth as silk.
Another example is on a one piece rear main small block chevys They are balanced externally at the flywheel. These can also be balanced internally with light weight pistons and rods etc. On a couple occasions because of miscommunication a motor has been started on the dyno with the wrong combination. When this happened it was pretty obvious as the dyno stand would shake pretty badly as soon as you raised the rpm off idle.
I'm not saying that you shouldn't try to get to the bottom of your balance situation but it might be obvious if it is the wrong balancer and flywheel when the motor is running.
I'm sure I'm not the only one to experience a mismatched flywheel and balancer. Hopefully someone else can relay their experience to help sort this out.

Well mn9 you bring up a very good point. I had zero vibrations in park as I revved up the motor to 3500 to check advance. Maybe I am not needing to go any further if that is a good test. I assume in park that both the HB and TQ are spinning and at 3500 there is no noticeable vibration then the motor is in balance to a point I should not need to pursue this effort and get back to verification of timing.

Appreciate yours and anyone else's input on this.

 

[nm9stheham]

So the TC only had the drain plug ? I think the TC weight would be on the front of the TC but someone else may know better.
Forgot about any tray in there!

 

[340inabbody]

So the TC only had the drain plug ? I think the TC weight would be on the front of the TC but someone else may know better.
Forgot about any tray in there!

The ones I have seen have been located on each side of the drain plug! Thats why I took that shot clearly no weights around the plug area.

 

[nm9stheham]

Good deal!

 

[340inabbody]

Decided that I can’t detect any vibration I can move on to see what the cause of the poor drivability is. Seemed like there was no power but no vibe either.
I will put the new zero balance HB on (too tired tonight) and get the distributor verified as I was trying to do previously before I determined the HB marker was not in the right place. Then I will verify the timing and run it. I will buy some race gas and run it again and report back here with what I find out.
Thanks for following and the help!!

 

[nm9stheham]

IMHO.... Back way down on the timing to start. Your compression ratio is quite high.

 

[mrbill00]

I did this combo back in the 70's, then the gas got bad, Rattled like a kids toy. i had that same spark knock pitting, cut the tops off and lived happily ever after. I have those pistons today and i will get you some pics, can see the little pitting marks in the valve pockets. I also have another set Not Cut that i plan on using because now i can get the good gas......(post #18ish)
....BTW the TRW L2322F 030 piston and wrist pin weighs 824 grams (before cut).
Go get 2 gallons at whatever the cost and smile. Then you can take you time to decide which way to go. Your engine is fine

 

[340inabbody]

I did this combo back in the 70's, then the gas got bad, Rattled like a kids toy. i had that same spark knock pitting, cut the tops off and lived happily ever after. I have those pistons today and i will get you some pics, can see the little pitting marks in the valve pockets. I also have another set Not Cut that i plan on using because now i can get the good gas......(post #18ish)
....BTW the TRW L2322F 030 piston and wrist pin weighs 824 grams (before cut).
Go get 2 gallons at whatever the cost and smile. Then you can take you time to decide which way to go. Your engine is fine

Thanks yes I am almost ready to run. Will report back my findings. I did verify I am running J heads

 

[340inabbody]

One issue I had to deal with was the freaken HB one bolt was off just a bit. It was a blind assembly and I took a pick with my phone and say that. Its fine now as I filed the pulley hole to get that last bolt to fit.

 

[nm9stheham]

Is that HB (damper) center bolt unmarked? If so, that is an ungraded bolt... weak/soft. IIRC, that is a grade 8 bolt. It needs 135 ft-lbs of torque.... An ungraded bolt may strip the threads at that torque.... but I did not check the charts to verify that. And the washer under that bolt is very thick.

 

[nm9stheham]

....BTW the TRW L2322F 030 piston and wrist pin weighs 824 grams (before cut).

Is that weight with or without the pin? Tnx

 

[340inabbody]

Is that HB (damper) center bolt unmarked? If so, that is an ungraded bolt... weak/soft. IIRC, that is a grade 8 bolt. It needs 135 ft-lbs of torque.... An ungraded bolt may strip the threads at that torque.... but I did not check the charts to verify that. And the washer under that bolt is very thick.

135 ft lbs yes. Not sure that is the bolt that was on there.