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Strange Sucking Sound

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PHAT69AMX View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Sep/30/2018 at 10:12pm
Intake leak between #5 & #7 ?...  #5 & #7 fire in sequence... 1-8-4-3-6-5-7-2
so... #5 going down on Intake Stroke & #7 going up on Exhaust Stroke...
Intake "suction" manifesting in exhaust pipe during adjoining exhaust stroke...
Uncommon but possible, Intake Mounting Bolts bottom in Head tapped holes
BEFORE actually clamping Intake to Heads & sealing intake gasket, maybe...
All questions more than a statement...
Have seen Intake Bolts bottom out before actually "clamping" intake down to heads...

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Post Options Post Options   Thanks (0) Thanks(0)   Quote RTTComanche17 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/01/2018 at 12:13pm
Even though by the book it says it's all leaking past the rings, I'd still do a leakdown test. I concur with 304-dude that there might be some burnt/bent exhaust valves. It really sounds like you engine is being a "pump" and that one of the valves is letting air by when it is "closed".

If you do a leakdown, you should be able to hear the air through the exhaust if it is an exhaust valve leaking.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 232jav3sp Quote  Post ReplyReply Direct Link To This Post Posted: Oct/01/2018 at 1:16pm
Leak down is the way to go.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ghcoe Quote  Post ReplyReply Direct Link To This Post Posted: Oct/12/2018 at 5:53pm
Just tried to rent a leak down tester. Looks like I will have to purchase a unit since no one rents them. Going to be a few weeks before that happens.

On another note I just got done with a 800 mile trip with the Jeep. Just before I left I went and added 1/2 quart of ATF to see if it would loosen something up. Just did a compression test again. The cylinder that had 70lbs came up to 115lbs. The cylinder that had 80lbs. came up to 105lbs. Not sure if the ATF had anything to do with that or not, but maybe something is unsticking....

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Oct/12/2018 at 9:16pm
Originally posted by ghcoe ghcoe wrote:

Just tried to rent a leak down tester. Looks like I will have to purchase a unit since no one rents them. Going to be a few weeks before that happens.

On another note I just got done with a 800 mile trip with the Jeep. Just before I left I went and added 1/2 quart of ATF to see if it would loosen something up. Just did a compression test again. The cylinder that had 70lbs came up to 115lbs. The cylinder that had 80lbs. came up to 105lbs. Not sure if the ATF had anything to do with that or not, but maybe something is unsticking....



You put a 1/2 quart of ATF in the engine oil?
(just asking because pouring it slooooooowwwwwllly into the carb is also done from time to time)
^sends some pretty good smoke signals too LOL

Sticking rings could def cause low compression, and could be freed up by driving with some a ATF in the pan.

I don't know how they could cause the sucking sound tho.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Oct/12/2018 at 9:25pm
Originally posted by jpnjim jpnjim wrote:


Originally posted by ghcoe ghcoe wrote:

Just tried to rent a leak down tester. Looks like I will have to purchase a unit since no one rents them. Going to be a few weeks before that happens.

On another note I just got done with a 800 mile trip with the Jeep. Just before I left I went and added 1/2 quart of ATF to see if it would loosen something up. Just did a compression test again. The cylinder that had 70lbs came up to 115lbs. The cylinder that had 80lbs. came up to 105lbs. Not sure if the ATF had anything to do with that or not, but maybe something is unsticking....



You put a 1/2 quart of ATF in the engine oil?
(just asking because pouring it slooooooowwwwwllly into the carb is also done from time to time)
^sends some pretty good smoke signals too LOL

Sticking rings could def cause low compression, and could be freed up by driving with some a ATF in the pan.

I don't know how they could cause the sucking sound tho.


Remembering the time I ran 12 miles on a dropped valve with a stock 304. There is a lot of clearance in the compression stroke with dished 304 pistons. He may have gummed up valves, from bad seals and carbon build up. Which would cause some valves not to close fully, until enough work and use of ATF loosens it up. Who knows after a few miles the sucking sound will go away.

From what i hear 1 quart ATF to a full pan, will clean an engine after a few miles of light driving.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote ghcoe Quote  Post ReplyReply Direct Link To This Post Posted: Oct/12/2018 at 9:46pm
I might try some ATF down the intake. Not sure why I have not done it yet. Just did this with my daughters Opel earlier this year when she started to shatter rockers...

I really am thinking this is a valve/lifter issue since the sound comes and goes. Over pumped lifters? I will update when I get this figured out. I really was hoping to do a leak down test today. I think you guys are right on with that.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Oct/13/2018 at 6:24pm
Never heard of ATF down the intake, but WATER poured down will cut carbon. You have to slowly pour it in and work the throttle to keep the engine running. Could be gummed up rings or carbin buildup on the valves. Water down carb might do the trick...

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Oct/13/2018 at 8:08pm
Originally posted by farna farna wrote:

Never heard of ATF down the intake, but WATER poured down will cut carbon. You have to slowly pour it in and work the throttle to keep the engine running. Could be gummed up rings or carbin buildup on the valves. Water down carb might do the trick...


We've done both water and atf

like you said, slowly is the key.

I don't advise anyone to do it,
I feel it has helped me in some instances, but I wouldn't want to be the reason someone hurt their engine 


edit
the best one was when my cousin came running out of his house with a fire extinguisher because I was at his neighbors house doing it and the street was filling up with smoke LOL


Edited by jpnjim - Oct/13/2018 at 8:14pm
71 Javelin AMX P-code Go pac 360/4spd/3.91's
was Green/green now T/A red w/blk leather

88,89&98 Jeeps
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