No compression on a rebuilt 440
#2272497
03/19/17 07:10 PM
03/19/17 07:10 PM
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Joined: Jan 2003
Posts: 1,279 Buzzardbreath Wyoming
BigBird
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I recently rebuilt a 440 out of a 76 New Yorker for a project I'm working on. This weekend was time for a first start. When cranking it showed no compression in any cylinder. Pulled the rocker assembly and it has compression (about 75psi but no air in I didn't expect it to be real high). Put the rocker back on lose and no compression. All new parts, pistons, cam, bearings, heads rebuilt (surfaced but not more than a few thousandths removed). Parts came from the engine guy that did the machine work. Cam should be like a 70 magnum grind, pistons were 30 overbore with a bump to 9.5 to 1. I did the assembly on the block, no problems during bolt together. Any ideas what might be the problem? Possible wrong cam? Pulled another 440 valve train and checked the lifters for difference (Where the push rod sits it is same height but overall length 1/6" taller) , push rod length, all the same. Checked it for another type new lifter but they were the same.
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Re: No compression on a rebuilt 440
[Re: buildanother]
#2272595
03/19/17 10:17 PM
03/19/17 10:17 PM
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Joined: Jan 2003
Posts: 1,279 Buzzardbreath Wyoming
BigBird
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Timing chain was installed by myself (done 20 or so) so I'm comfortable that it is correct. Not my first engine rebuild so I am comfortable that all was assembled correctly. Rings were set as per the factory service manual, checked ring gap with a feeler gauge and filed for fit. Engine shop fitted the pistons and installed them on the rods for me. Went to start the engine and it was blowing the gas back out the intake as well as pulling it in. I know hydraulics lifter should feel solid when working correctly but they don't bleed down when it sits overnight either. The engine never even back fired. Has spark and fuel (another story with FITech). As I have stated it has no compression with the rockers on.
Last edited by BigBird; 03/19/17 10:21 PM.
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Re: No compression on a rebuilt 440
[Re: BigBird]
#2272607
03/19/17 10:27 PM
03/19/17 10:27 PM
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Joined: Aug 2005
Posts: 11,543 chicagoland,usa
buildanother
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The only odd thing you said yet was that at tdc(cyl # 1 I assume), the cam lobes are away from lifters, and you said that if you then turn crank 1 revolution, that the exhaust valve is open. Well the exhaust AND intake should be open then BUT only a minimal amount. I'm thinking that if you cannot turn any pushrods easily after it sits a spell, that some components are mismatched. (pushrods, lifters, rockers etc.)
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Re: No compression on a rebuilt 440
[Re: buildanother]
#2272617
03/19/17 10:44 PM
03/19/17 10:44 PM
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Joined: Jan 2003
Posts: 1,279 Buzzardbreath Wyoming
BigBird
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It was #1 cylinder. The exhaust was defiantly open and the intake might have been just barely open due to overlap. Rockers and push rods were in the running engine when I tore it down. The cam and lifters were new and bought as a set. Lifter part numbers cross reference to a Mopar #3004647. Off by a tooth it should at least fire. I've had a gear go bad and jump a tooth but I could still make it run. Wouldn't hardly pull it's self but would run and still had compression.
Last edited by BigBird; 03/19/17 10:48 PM.
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Re: No compression on a rebuilt 440
[Re: BigBird]
#2272620
03/19/17 10:46 PM
03/19/17 10:46 PM
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Joined: Jun 2012
Posts: 1,899 MYRTLE BEACH SOUTH CAROLINA
ek3
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Timing chain was installed by myself (done 20 or so) so I'm comfortable that it is correct. Not my first engine rebuild so I am comfortable that all was assembled correctly. Rings were set as per the factory service manual, checked ring gap with a feeler gauge and filed for fit. Engine shop fitted the pistons and installed them on the rods for me. Went to start the engine and it was --- "blowing the gas back out the intake as well as pulling it in. -- " I know hydraulics lifter should feel solid when working correctly but they don't bleed down when it sits overnight either. The engine never even back fired. Has spark and fuel (another story with FITech). As I have stated it has no compression with the rockers on. THIS.......WHEN AIR COMES OUT THE INTAKE ... THE VALVE IS OPEN AT THE WRONG TIME.
Last edited by ek3; 03/19/17 10:48 PM.
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Re: No compression on a rebuilt 440
[Re: ek3]
#2272623
03/19/17 10:51 PM
03/19/17 10:51 PM
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Joined: Jan 2003
Posts: 1,279 Buzzardbreath Wyoming
BigBird
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Timing chain was installed by myself (done 20 or so) so I'm comfortable that it is correct. Not my first engine rebuild so I am comfortable that all was assembled correctly. Rings were set as per the factory service manual, checked ring gap with a feeler gauge and filed for fit. Engine shop fitted the pistons and installed them on the rods for me. Went to start the engine and it was --- "blowing the gas back out the intake as well as pulling it in. -- " I know hydraulics lifter should feel solid when working correctly but they don't bleed down when it sits overnight either. The engine never even back fired. Has spark and fuel (another story with FITech). As I have stated it has no compression with the rockers on. THIS.......WHEN AIR COMES OUT THE INTAKE ... THE VALVE IS OPEN AT THE WRONG TIME. As stated lifters are holding the valves open and no compression so the pistons pull and push air in and out of the intake valves/intake.
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Re: No compression on a rebuilt 440
[Re: BigBird]
#2272627
03/19/17 10:54 PM
03/19/17 10:54 PM
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Joined: Jun 2012
Posts: 1,899 MYRTLE BEACH SOUTH CAROLINA
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what changed ? the heads shaved ? your push rods are orig and rockers ? did you deck it ? try shimming the rocker shafts with some tin foil [just to check] to see if that corrects it .or maybe you have some rocker shims.. ?
Last edited by ek3; 03/19/17 11:00 PM.
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Re: No compression on a rebuilt 440
[Re: ek3]
#2272636
03/19/17 11:03 PM
03/19/17 11:03 PM
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Joined: Jan 2003
Posts: 1,279 Buzzardbreath Wyoming
BigBird
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what changed ? the heads shaved ? your push rods are orig and rockers ? did you deck it ? Heads and block were milled less than 10 thousandths total combined. The only thing new were the cam and lifters in the valve train. I've milled a pair of 440 heads 60 thousandths with out issues on the valve train in the past.
Last edited by BigBird; 03/19/17 11:04 PM.
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Re: No compression on a rebuilt 440
[Re: BigBird]
#2272650
03/19/17 11:31 PM
03/19/17 11:31 PM
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Joined: Jun 2012
Posts: 1,899 MYRTLE BEACH SOUTH CAROLINA
ek3
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SO WHY WOULD THE VALVES BE HELD OPEN ? nothing changed . maybe the .010" lower added to the push rod length and you need to shim the shafts to get the preload back ?? maybe a lifter variance ? that's about it . .something had to get longer to hold them open .
Last edited by ek3; 03/19/17 11:37 PM.
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Re: No compression on a rebuilt 440
[Re: ek3]
#2272669
03/19/17 11:55 PM
03/19/17 11:55 PM
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Joined: Jan 2003
Posts: 1,279 Buzzardbreath Wyoming
BigBird
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SO WHY WOULD THE VALVES BE HELD OPEN ? nothing changed . maybe the .010" lower added to the push rod length and you need to shim the shafts to get the preload back ?? maybe a lifter variance ? that's about it . .something had to get longer to hold them open . That's why I posted here. I've worked on my own Mopars for close to 40 years and not seen this before and was hoping some here had. I've rebuilt at least 6 440's as well as several small blocks and several different Chevy and Ford engines. I always have made sure the timing marks are correct as it is so hard to go back and check once it is installed.
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