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#2408689 - 11/25/17 12:34 PM Re: Stock 1970 340 T/A Block Compression Test [Re: f2502011]
f2502011 Offline
enthusiast

Registered: 04/19/12
Posts: 337
Loc: US
Here's what I got. Much more consistent, but not so great. Warmed engine up to full operating temperature then began removing things and by the time I got everything off it was not too hot to touch. I used two batteries in a series and a charger. Cranked each cylinder 7 times (wanted to be sure) did dry test and wet test on each cylinder as I went along. I can see tons of carbon on top of the pistons. As far as I know the engine is likely just a refresh and never completely rebuilt. I believe it got new bearings, seals, rings etc. Anyway here it is first number dry second number wet. I started at the back right when the engine was the hottest and it was 95/107. Went back after finishing and it was 90/95 dry/wet so I through the first one out.

Right 78/84 80/85 83/95 90/95


Front---------------------------->Rear


Left 83/83 80/93 82/98 85/94

_________________________
1970 EK2 T/A 727

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#2408696 - 11/25/17 12:41 PM Re: Stock 1970 340 T/A Block Compression Test [Re: f2502011]
amxautox Offline
Still Retired. Still Posting on Moparts. A Lot.

Registered: 05/13/03
Posts: 96645
Loc: On The Boat, On The Lake, Wa. ...
looks good. grin

Now make sure that your gauge is accurate, mine went bad the other year and was showing too light a pressure.

Also make sure the timing chain isn't stretched.

Also do the leak down test to check the rings and valves, etc.
_________________________
Tom

"Everyone should believe in something; I believe I'll go fishing."

-Henry David Thoreau

Men and fish are alike. They both get into trouble when they open their mouths

author unknown


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#2408716 - 11/25/17 01:35 PM Re: Stock 1970 340 T/A Block Compression Test [Re: f2502011]
fastmark Offline
master

Registered: 01/20/03
Posts: 4725
Loc: Abilene, Texas
Now that you have spent all this time on a cheap compression test, all it will tell you is you have a problem. Buy a leak down gauge and it will tell you what the problem is.

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#2408848 - 11/25/17 07:48 PM Re: Stock 1970 340 T/A Block Compression Test [Re: amxautox]
f2502011 Offline
enthusiast

Registered: 04/19/12
Posts: 337
Loc: US
Originally Posted By amxautox
looks good. grin

Now make sure that your gauge is accurate, mine went bad the other year and was showing too light a pressure.

Also make sure the timing chain isn't stretched.

Also do the leak down test to check the rings and valves, etc.


I have a brand new gauge and will double check the pressure.

Not sure how to check whether the timing chain is stretched or not??

Also purchased a leak down tester but am unsure how to perform the test as I have never done it.
_________________________
1970 EK2 T/A 727

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#2408852 - 11/25/17 07:53 PM Re: Stock 1970 340 T/A Block Compression Test [Re: f2502011]
amxautox Offline
Still Retired. Still Posting on Moparts. A Lot.

Registered: 05/13/03
Posts: 96645
Loc: On The Boat, On The Lake, Wa. ...
take the dist cap off

turn the crankshaft in one direction to top dead center mark

then turn the crankshaft in the other direction watching the rotor in the dist. when the rotor STARTS to turn, stop rotating the crankshaft

tell us how many degrees the crankshaft turns before the rotor starts to turn turns
_________________________
Tom

"Everyone should believe in something; I believe I'll go fishing."

-Henry David Thoreau

Men and fish are alike. They both get into trouble when they open their mouths

author unknown


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#2408853 - 11/25/17 07:53 PM Re: Stock 1970 340 T/A Block Compression Test [Re: f2502011]
Pacnorthcuda Offline
I Live Here

Registered: 11/19/07
Posts: 19364
Loc: Kirkland, Washington
Originally Posted By f2502011
Here's what I got. Much more consistent, but not so great. Warmed engine up to full operating temperature then began removing things and by the time I got everything off it was not too hot to touch. I used two batteries in a series and a charger. Cranked each cylinder 7 times (wanted to be sure) did dry test and wet test on each cylinder as I went along. I can see tons of carbon on top of the pistons. As far as I know the engine is likely just a refresh and never completely rebuilt. I believe it got new bearings, seals, rings etc. Anyway here it is first number dry second number wet. I started at the back right when the engine was the hottest and it was 95/107. Went back after finishing and it was 90/95 dry/wet so I through the first one out.

Right 78/84 80/85 83/95 90/95


Front---------------------------->Rear


Left 83/83 80/93 82/98 85/94



Um, just to clarify, cause it's pretty frikken important, I am sure you meant two batteries in parallel....not SERIES! GASP!

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#2408855 - 11/25/17 07:55 PM Re: Stock 1970 340 T/A Block Compression Test [Re: fastmark]
f2502011 Offline
enthusiast

Registered: 04/19/12
Posts: 337
Loc: US
Originally Posted By fastmark
Now that you have spent all this time on a cheap compression test, all it will tell you is you have a problem. Buy a leak down gauge and it will tell you what the problem is.


My thinking was that the point of doing a compression test was to see if you have an issue and needed to do further testing and diagnostics to narrow down the issue.
_________________________
1970 EK2 T/A 727

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#2408857 - 11/25/17 07:56 PM Re: Stock 1970 340 T/A Block Compression Test [Re: Pacnorthcuda]
f2502011 Offline
enthusiast

Registered: 04/19/12
Posts: 337
Loc: US
Yes, parallel
_________________________
1970 EK2 T/A 727

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#2408861 - 11/25/17 07:58 PM Re: Stock 1970 340 T/A Block Compression Test [Re: amxautox]
amxautox Offline
Still Retired. Still Posting on Moparts. A Lot.

Registered: 05/13/03
Posts: 96645
Loc: On The Boat, On The Lake, Wa. ...
leak down testing/tester;

put each piston at their tdc on the firing stroke and screw the fitting in the sprakplug hole with the piston at tdc

supply 5 psi or so, air pressure and listen at the carb, exhaust, radiator, oil fill or dipstick holes. listening for any air coming out and bubbles in the radiator. Also if the kit has a gauge then watch for pressure drop in a given time span, should be noted in the directions with the kit.
_________________________
Tom

"Everyone should believe in something; I believe I'll go fishing."

-Henry David Thoreau

Men and fish are alike. They both get into trouble when they open their mouths

author unknown


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#2408863 - 11/25/17 08:00 PM Re: Stock 1970 340 T/A Block Compression Test [Re: Pacnorthcuda]
amxautox Offline
Still Retired. Still Posting on Moparts. A Lot.

Registered: 05/13/03
Posts: 96645
Loc: On The Boat, On The Lake, Wa. ...
Originally Posted By Pacnorthcuda
Originally Posted By f2502011
Here's what I got. Much more consistent, but not so great. Warmed engine up to full operating temperature then began removing things and by the time I got everything off it was not too hot to touch. I used two batteries in a series and a charger. Cranked each cylinder 7 times (wanted to be sure) did dry test and wet test on each cylinder as I went along. I can see tons of carbon on top of the pistons. As far as I know the engine is likely just a refresh and never completely rebuilt. I believe it got new bearings, seals, rings etc. Anyway here it is first number dry second number wet. I started at the back right when the engine was the hottest and it was 95/107. Went back after finishing and it was 90/95 dry/wet so I through the first one out.

Right 78/84 80/85 83/95 90/95


Front---------------------------->Rear


Left 83/83 80/93 82/98 85/94



Um, just to clarify, cause it's pretty frikken important, I am sure you meant two batteries in parallel....not SERIES! GASP!
parallel is more amps = good

series is more volts = bad. will burn out the starter.
_________________________
Tom

"Everyone should believe in something; I believe I'll go fishing."

-Henry David Thoreau

Men and fish are alike. They both get into trouble when they open their mouths

author unknown


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#2408866 - 11/25/17 08:07 PM Re: Stock 1970 340 T/A Block Compression Test [Re: amxautox]
f2502011 Offline
enthusiast

Registered: 04/19/12
Posts: 337
Loc: US
Originally Posted By amxautox
leak down testing/tester;

put each piston at their tdc on the firing stroke and screw the fitting in the sprakplug hole with the piston at tdc

supply 5 psi or so, air pressure and listen at the carb, exhaust, radiator, oil fill or dipstick holes. listening for any air coming out and bubbles in the radiator. Also if the kit has a gauge then watch for pressure drop in a given time span, should be noted in the directions with the kit.


I'm sure it will be in the instructions but how do I know when each cylinder is at TDC?
_________________________
1970 EK2 T/A 727

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#2408869 - 11/25/17 08:10 PM Re: Stock 1970 340 T/A Block Compression Test [Re: f2502011]
amxautox Offline
Still Retired. Still Posting on Moparts. A Lot.

Registered: 05/13/03
Posts: 96645
Loc: On The Boat, On The Lake, Wa. ...
Start at #1, and use the firing order. Then stick a plastic rod, straw, or something that won't damage anything and won't break off in the cylinder, or use the pressure gauge, and turn the crank over by hand, it'll work out that way.
_________________________
Tom

"Everyone should believe in something; I believe I'll go fishing."

-Henry David Thoreau

Men and fish are alike. They both get into trouble when they open their mouths

author unknown


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#2408882 - 11/25/17 08:20 PM Re: Stock 1970 340 T/A Block Compression Test [Re: amxautox]
f2502011 Offline
enthusiast

Registered: 04/19/12
Posts: 337
Loc: US
Originally Posted By amxautox
Start at #1, and use the firing order.


Disclaimer: Please understand I have no experience of the process for a leak down test. To start the test I need to get #1 to TDC and do the leak down test. Next lets say I do #8. Question is do I just rotate the crank around to TDC again to get TDC on the next cylinder?
_________________________
1970 EK2 T/A 727

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#2408888 - 11/25/17 08:28 PM Re: Stock 1970 340 T/A Block Compression Test [Re: f2502011]
Cab_Burge Offline
I Win

Registered: 08/23/03
Posts: 31673
Loc: Bend,OR USA
Bring the motor up to TDC on # 1 cylinder on the firing stroke and test it, rotate the crankshaft 90 degrees clockwise to test #8,and another 90 degrees to test #4 and test, then rotate another ninety degrees to test # 3 and go through the firing order in sequence to test the rest, one at a time up scope(Imagine straight up as 0 degrees and 1/4 turn is 90 degrees work wrench
Most car motors in the car are hard to get 90 degrees rotation with one movement, if you stop more than 5 degrees before or after TDC the air pressure will probably blow the piston down to bottom dead center, make sure and remove the ratchet or breaker bar from the socket or crankshaft bolt before each test thumbs If you don't you may regret what it breaks or damages, like your arm or radiator shroud shruggy
The leak down meter will come with instruction, some are better than others, I own two, one old single gauge from Moroso that quit reading accurately years ago(it would stick runaway) and a newer one from Aircraft Spruce for testing my old airplane motor, it is a dual gauge tester and easier to use thumbs scope


Edited by Cab_Burge (11/25/17 08:35 PM)
_________________________
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

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#2408889 - 11/25/17 08:29 PM Re: Stock 1970 340 T/A Block Compression Test [Re: f2502011]
amxautox Offline
Still Retired. Still Posting on Moparts. A Lot.

Registered: 05/13/03
Posts: 96645
Loc: On The Boat, On The Lake, Wa. ...
Originally Posted By f2502011
Originally Posted By amxautox
Start at #1, and use the firing order.


Disclaimer: Please understand I have no experience of the process for a leak down test. To start the test I need to get #1 to TDC and do the leak down test. Next lets say I do #8. Question is do I just rotate the crank around to TDC again to get TDC on the next cylinder?
Yes, and you won't have to rotate the crankshaft very many degrees before the next piston gets to it's tdc.

_________________________
Tom

"Everyone should believe in something; I believe I'll go fishing."

-Henry David Thoreau

Men and fish are alike. They both get into trouble when they open their mouths

author unknown


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#2408962 - 11/25/17 10:44 PM Re: Stock 1970 340 T/A Block Compression Test [Re: f2502011]
Dcuda69 Offline
master

Registered: 10/17/05
Posts: 4022
Loc: WI
Those numbers look way more like running compression than cranking compression. Are you sure the gauge is accurate? Do you have another engine to try a couple holes on? I've seen plenty of cheap gauges read bad(think Craftsman) I've seen plenty of check valves(schrader valve in the end of the hose) cause inaccurate/inconsistent readings.I would be very surprised to see under 100psi on a decent running stockish engine...even cold with the throttle closed. Good luck!!

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#2408985 - 11/25/17 11:51 PM Re: Stock 1970 340 T/A Block Compression Test [Re: f2502011]
f2502011 Offline
enthusiast

Registered: 04/19/12
Posts: 337
Loc: US
Brand new gauges different results. Dry Test.

Right 120 135 125 130


Front-----------------------Rear


Left 128 129 136 130
_________________________
1970 EK2 T/A 727

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#2408990 - 11/26/17 12:02 AM Re: Stock 1970 340 T/A Block Compression Test [Re: f2502011]
amxautox Offline
Still Retired. Still Posting on Moparts. A Lot.

Registered: 05/13/03
Posts: 96645
Loc: On The Boat, On The Lake, Wa. ...
I'd be happy with that.
_________________________
Tom

"Everyone should believe in something; I believe I'll go fishing."

-Henry David Thoreau

Men and fish are alike. They both get into trouble when they open their mouths

author unknown


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#2408996 - 11/26/17 12:10 AM Re: Stock 1970 340 T/A Block Compression Test [Re: f2502011]
1E2C Offline
master

Registered: 01/20/03
Posts: 2623
Loc: Northern MN
Oh heck yeah.
_________________________
No E (70 'Cuda 340) (Gone)
2 C (65 Polara 500's; one hardtop, one rag.)

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#2409027 - 11/26/17 07:26 AM Re: Stock 1970 340 T/A Block Compression Test [Re: f2502011]
fastmark Offline
master

Registered: 01/20/03
Posts: 4725
Loc: Abilene, Texas
Those numbers look better. Do as Cab says on the leakdown test. I have a two gauge set. Set the in air to 100 lbs of presure and check the second guage. If it holds 90 lbs, you have 10% leakage. Listen in the oil filler for a ring leak, the carb for bad intake valves and the tail pipe for bad exhaust valves.

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