1973 340 issues.

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trigger_andy

trigger_andy

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Hey all.

Well I finally got the 340 and 4 Speed transplant done in my Aussie Charger but the 340 is a tired worn unit that really needs a rebuild but the cost of the transplant and the other mechanical work that the Charger needs this winter does not allow for that.

So the '73 340 has been dropped in and semi-tuned by the local shop and runs fairly well but not as much a difference over the 318 that was pulled as I had hoped. Will still fry the rear tyre in first and a chirp in second though. Now has a stock Dizzy, New Cap, Leads and Plugs and a Weiand Action Plus Intake and a used 670 Street Avenger. Im also getting a lot of blue smoke on hard acceleration (seems to be only on hard acceleration) so I did a Compression test just now and the figures are not great at all. I ran the engine till hot then left ti to cool slightly for an hour before doing the Compression Test with a cheap kit I bought. The Lifters are also noisy.

Cylinder #1 = 120psi
Cylinder #2 = 30psi
Cylinder #3 = 115psi
Cylinder #4 = 110psi
Cylinder #5 = 110 psi
Cylinder #6 = 80psi
Cylinder #7 = 110psi
Cylinder #8 = 85psi

As there is no way I can afford to pull the 340 and rebuild it this year is there anything I can do to potentially get the Compression back? What are the issues with running the 340 as it is now? Any thoughts or comments greatly appreciated. :)
 
Not much you can do about the compression except new rings and a possible valve job.
 
should have checked that before you put it in.....2,6,and 8 are no good.....you can squirt oil in those 3 cylinders and recheck compression.....if it goes up then the rings are shot.....If it stays the same could be valves
 
bbrroowwnn said:
should have checked that before you put it in.....2,6,and 8 are no good.....you can squirt oil in those 3 cylinders and recheck compression.....if it goes up then the rings are shot.....If it stays the same could be valves
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It was a running engine I bought from someone in North Scotland in good faith. But it was out of the car it was pulled from so I could not really do much checking. As it ran I was happy just to get it installed when I was doing the 4 Speed swap. Still goes better than my 318 so I fairly happy and knew it was a risk. :)

How much oil can I squirt into the cylinders?
 
halifaxhops said:
Not much you can do about the compression except new rings and a possible valve job.
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Yes, I guessed as much. I wondered about Sea Foam and 'Restore' as a stop gap?

Would a few more miles on the engine help? Its been sitting for over a year and was quite neglected.
 
Rislone will help free up sticking rings and would help IF that is the problem. You just have to try. And more miles may help... again, you just have to try. But, the smoking under hard acceleration is a classic sign of bore and ring wear, so don't get your hopes up too high.

Use about 1/2 to 1 teaspoon of oil per cylinder... just enough to work around and coat the rings.

And just for historical grins... 30-50 years ago, JC Whitney sold pills that you would put into the cylinders and they would bring up the compression for about 100 miles.... maybe 200 miles in an older low CR engine LOL
 
even if motor is out of car, just hook up a battery to the starter and still check compression....Anyway, you are stuck with it now...as mentioned above, blue smoke is an indicator of bad rings and with those compression numbers I would think the engine should be missing....#2 cylinder is not working at all....and all 3 of those bad cylinders are on the same bank....they make products to help but it is just putting lipstick on a pig
 
bbrroowwnn said:
even if motor is out of car, just hook up a battery to the starter and still check compression....Anyway, you are stuck with it now...as mentioned above, blue smoke is an indicator of bad rings and with those compression numbers I would think the engine should be missing....#2 cylinder is not working at all....and all 3 of those bad cylinders are on the same bank....they make products to help but it is just putting lipstick on a pig
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Good point regarding the Starter. Ill keep that in mind for next time. :) Does not sound or feel like its missing but Im by no means an expert. I'll give the lipstick a go and see what results I get for curiosity's sake if nothing else. I'll get the other items on my list sorted out first then come back to the engine when funds allow. The car wont be moving much now till Spring as the weathers turning and its always wet out now.
 
Out of interest what PSI should I expect on a '73 340 anyway?
 
It depends on the mileage....but on a stock 340 110-140 is common....The thing with compression is they all can be low as long as they are pretty even.....like within 10 or so of each other and they will still be OK
 
I would expect 125-135 psi new at low altitudes ..... the actual static CR is down near 8:1 for those low-in-the-hole pistons.
 
bbrroowwnn said:
It depends on the mileage....but on a stock 340 110-140 is common....The thing with compression is they all can be low as long as they are pretty even.....like within 10 or so of each other and they will still be OK
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Thanks for the reply. :)
 
Well I never realized you are supposed to do the compression test with WOT.

So after running a can of car cleaner through the ebay soursed used Street Avenger and getting the engine nice and hot again I re-did the Comp Test and got the figures below. I guess its slightly better? Still real bad on #2. :(

Cylinder #1 = 100psi
Cylinder #2 = 30psi
Cylinder #3 = 110psi
Cylinder #4 = 105psi
Cylinder #5 = 105 psi
Cylinder #6 = 85psi
Cylinder #7 = 105psi
Cylinder #8 = 105psi

As Im waiting on the Sea Foam and Rislone coming in the mail I decided to fill the bores through the Spark Plug hole with 50/50 Acetone and ATF Fluid to see out of curiosity's sake if it would make a difference. Ill leave it over night and see what happens.
 
Weirdly the majority of the blue smoke comes from the 1,3,5,7 Bank and not the 2,4,6,8 bank. As there is no cross-over in the exhaust Im guessing bad Valve Stem Oil Seals? Might be changing them tomorrow too. :D
 
Acetone and ATF? That sounds pretty potent.

Were you able to put some oil in the cylinders or were the latest compression numbers with oil in the cylinders?

Yeah, not necessarily any correlation between smoke and compression depending on the conditions? Under what throttle conditions did you see the smoke from the odd side cylinders? (Passenger's side in the British Empire, driver's side over here in the US.)
 
nm9stheham said:
Acetone and ATF? That sounds pretty potent.

Were you able to put some oil in the cylinders or were the latest compression numbers with oil in the cylinders?

Yeah, not necessarily any correlation between smoke and compression depending on the conditions? Under what throttle conditions did you see the smoke from the odd side cylinders? (Passenger's side in the British Empire, driver's side over here in the US.)
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Did some research on homebrew mixes to free potentially stuck Piston Rings. Acetone and ATF fluid was one of the favorites. I'll leave it for 24 hours and see if it makes any noticeable difference. Then Ill siphon off the mix and fire her up. I have not put any oil in the bores yet for the Com testing. The new results are purely WOT.

I see smoke under WOT and hard acceleration only.
 
OK; smoking under those conditions is normally worn rings, pistons, or bores or some combination thereof. #2 could be bad down in the block like that, or could still be a weak head gasket or perhaps a bad valve seat; the oil will help tell the story there.

I'd run it again and get all that 'cleaner' out, and then do the oil and comp test.
 
Aint nuthin you can do for#2. It's toast.Tear it down and fix it right. If you think you're halfway happy with it now, you ain't seen nuthin yet.
 
nm9stheham said:
OK; smoking under those conditions is normally worn rings, pistons, or bores or some combination thereof. #2 could be bad down in the block like that, or could still be a weak head gasket or perhaps a bad valve seat; the oil will help tell the story there.

I'd run it again and get all that 'cleaner' out, and then do the oil and comp test.
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Actually now you mention it there is black smoke residue on the Headers by ports 2 and 4 that was not there when the 318 was in. I'll have to investigate that tomorrow when I get the 340 running again.

If its the Head Gasket will the Oil Trick tell me this?
 
Want real world confirmation instead of playing around with oil?

Remove the passenger's side valve cover. Remove the rocker shaft assembly so all the valves will be closed.

Remove the #2 spark plug. Put compressed air into #2 cylinder.

If air comes up through the carburetor, bad intake valve. If air comes out the exhaust pipe, bad exhaust valve. If air is rushing into the valve cover area, bad/broken rings or a hole in #2 piston.

The oil test is a total waste of time when you can diagnose it correctly with air that it is built to move.
 
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RustyRatRod said:
Aint nuthin you can do for#2. It's toast.Tear it down and fix it right. If you think you're halfway happy with it now, you ain't seen nuthin yet.
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Thanks for the reply. Its simply not an option just now. I just dont have the cash left. Yes, it looks like #2 is Toast but could maybe be the Head Gasket since Im seeing black smoke on the Headders? The Intake Gaskets are brand new and I have a set of Felpro Head Gaskets left over that I could use. Might be worth trying?
 
RustyRatRod said:
Want real world confirmation instead of playing around with oil?

Remove the passenger's side valve cover. Remove the rocker shaft assembly so all the valves will be closed.

Remove the #2 spark plug. Put compressed air into #2 cylinder.

If air comes up through the carburetor, bad intake valve. If air comes out the exhaust pipe, bad exhaust valve. If air is rushing into the valve cover area, bad/broken rings or a hole in #2 piston.

The oil test is a total waste of time when you can diagnose it correctly with air that is is built to move.
Click to expand...

Ok cool. Might be best doing this. I guess it will tell me if the Head Gasket it ok too?

By the way, what did you mean by this '' If you think you're halfway happy with it now, you ain't seen nuthin yet.''

Many thanks
 
trigger_andy said:
Actually now you mention it there is black smoke residue on the Headers by ports 2 and 4 that was not there when the 318 was in. I'll have to investigate that tomorrow when I get the 340 running again.

If its the Head Gasket will the Oil Trick tell me this?
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Not specifically that; it will just say that it is not likely rings. RRR's note is good if you have access to compressed air. If you are gonna do that, do it BEFORE you pull the heads.

The black residue could be an exhaust gasket leak too.
 
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