8.1 496 double roller timing set
07-18-2017, 07:04 AM
#11
Registered
07-18-2017, 10:51 AM
#13
Registered
Marine longblocks sourced from GM featured a dbl roller chain.
Posted by Raylar...............
The stock timing chains on 496 (8.1L) engines built in the GM plant in Tonawanda all had looser than most engine timing chains and it was more noticable in the double roller marine HD chains. This was I have been told due to the robotic installation of the front of the engine and its timing gears and chains and that GM designed the gear with a few thousandths extra smaller diameter to remove the tension on the chain during GM assembly. We have seen this on every 496 we have ever worked on and it has not ever been a problem as far as camshaft timing or noise. If if you install a new chain you will find nearly the same slop in the chain. For this reason I don't think your timing chain and gears are the issue unless they are damaged or improperly installed.
The camshaft sensor is just a simple on-off Hall effect sensor reading a 180 reluctor degree grove in the camshaft gear face. The location of the leading front edge and rear edge of that groove that tells the ECM when cylinders 1 and 6 are at their compression or exhaust TDC. This tells the ECM when the number 1 cylinder is at its compression point for firing and allows the ECM to locate #1 TDC quicker for quicker starts.
If the camshaft sensor circut is not operating properly the ECM will set a camshaft sensor fault code and the engine will either not start or start only after a lot of cranking and the engine will stay in a reduced power mode, not 100% power.
Posted by Raylar...............
The stock timing chains on 496 (8.1L) engines built in the GM plant in Tonawanda all had looser than most engine timing chains and it was more noticable in the double roller marine HD chains. This was I have been told due to the robotic installation of the front of the engine and its timing gears and chains and that GM designed the gear with a few thousandths extra smaller diameter to remove the tension on the chain during GM assembly. We have seen this on every 496 we have ever worked on and it has not ever been a problem as far as camshaft timing or noise. If if you install a new chain you will find nearly the same slop in the chain. For this reason I don't think your timing chain and gears are the issue unless they are damaged or improperly installed.
The camshaft sensor is just a simple on-off Hall effect sensor reading a 180 reluctor degree grove in the camshaft gear face. The location of the leading front edge and rear edge of that groove that tells the ECM when cylinders 1 and 6 are at their compression or exhaust TDC. This tells the ECM when the number 1 cylinder is at its compression point for firing and allows the ECM to locate #1 TDC quicker for quicker starts.
If the camshaft sensor circut is not operating properly the ECM will set a camshaft sensor fault code and the engine will either not start or start only after a lot of cranking and the engine will stay in a reduced power mode, not 100% power.
07-18-2017, 05:49 PM
#14
Registered
Thread Starter
Go info there, yes I have a double roller timing chain in my engine now. When input this long block in it came from the builder with a single roller set. So I took the one out of my own up engine and I stalled it on the new long block. There were no markings on the set that was double roller though. The single roller was a cloyes I think and as mentioned above loose fitting.
07-19-2017, 12:29 AM
#15
Banned
its all a match set - the timing cover is included in that in which can also determine cam sensor used. the first 2 gen of cam sensors is NLA. What you might see floating around for cam sensors the early gen is mostly non package stuff that was bought and passed around to these resellers whom bought all of them that did not pass the manu quality checks. GM stopped using the early gen cam sensors years ago. There was reason why the early gen cam sensors went away and of course most of it was because of emission related. I have the early gen cam sensors made here in the USA. that are OEM spec for a plug and play. These are determine what cam sensor is used by the Marine OEM engine serial number and or by the GM block code stamped on the side of the engine blocks.
As far as Raylar they were late to the table even knowing that the Marine 496 cam sensor was an issue and how the OEM's were going about it until later.. Also there was many other marine engine manu's that used the 496. Volvo , Marine power, Indmar and so on. They do not know any of their set ups. Also Raylor got their pics form the Auto world website forums of the different reluctors on the gears and the sensors to provide that info on their website. .
As far as Raylar they were late to the table even knowing that the Marine 496 cam sensor was an issue and how the OEM's were going about it until later.. Also there was many other marine engine manu's that used the 496. Volvo , Marine power, Indmar and so on. They do not know any of their set ups. Also Raylor got their pics form the Auto world website forums of the different reluctors on the gears and the sensors to provide that info on their website. .
Last edited by BUP; 07-19-2017 at 12:41 AM.
07-19-2017, 09:06 AM
#17
Registered
If memory serves, my builder could only source a chain and not the gears when he rebuilt my engine. With only 400 hours it was no big deal as the crank and cam sprockets were like new. I want to say he could only get a single chain set complete which of course would not work with my cover/sensor. Don't take this as the gospel as it has been about 18 months or so ago. I just know all he could do was a new chain and not the sprockets. My engine was manufactured 9/03 but has the newer sensor that is still available.
07-19-2017, 12:24 PM
#19
Banned
Marine longblocks sourced from GM featured a dbl roller chain.
Posted by Raylar...............
The stock timing chains on 496 (8.1L) engines built in the GM plant in Tonawanda all had looser than most engine timing chains and it was more noticable in the double roller marine HD chains. This was I have been told due to the robotic installation of the front of the engine and its timing gears and chains and that GM designed the gear with a few thousandths extra smaller diameter to remove the tension on the chain during GM assembly. We have seen this on every 496 we have ever worked on and it has not ever been a problem as far as camshaft timing or noise. If if you install a new chain you will find nearly the same slop in the chain. For this reason I don't think your timing chain and gears are the issue unless they are damaged or improperly installed.
The camshaft sensor is just a simple on-off Hall effect sensor reading a 180 reluctor degree grove in the camshaft gear face. The location of the leading front edge and rear edge of that groove that tells the ECM when cylinders 1 and 6 are at their compression or exhaust TDC. This tells the ECM when the number 1 cylinder is at its compression point for firing and allows the ECM to locate #1 TDC quicker for quicker starts.
If the camshaft sensor circut is not operating properly the ECM will set a camshaft sensor fault code and the engine will either not start or start only after a lot of cranking and the engine will stay in a reduced power mode, not 100% power.
Posted by Raylar...............
The stock timing chains on 496 (8.1L) engines built in the GM plant in Tonawanda all had looser than most engine timing chains and it was more noticable in the double roller marine HD chains. This was I have been told due to the robotic installation of the front of the engine and its timing gears and chains and that GM designed the gear with a few thousandths extra smaller diameter to remove the tension on the chain during GM assembly. We have seen this on every 496 we have ever worked on and it has not ever been a problem as far as camshaft timing or noise. If if you install a new chain you will find nearly the same slop in the chain. For this reason I don't think your timing chain and gears are the issue unless they are damaged or improperly installed.
The camshaft sensor is just a simple on-off Hall effect sensor reading a 180 reluctor degree grove in the camshaft gear face. The location of the leading front edge and rear edge of that groove that tells the ECM when cylinders 1 and 6 are at their compression or exhaust TDC. This tells the ECM when the number 1 cylinder is at its compression point for firing and allows the ECM to locate #1 TDC quicker for quicker starts.
If the camshaft sensor circut is not operating properly the ECM will set a camshaft sensor fault code and the engine will either not start or start only after a lot of cranking and the engine will stay in a reduced power mode, not 100% power.
07-19-2017, 12:37 PM
#20
Banned
YES I DO.
Boat owner story as he told me and then after the fact brought his boat to me last year, Its a early 2002 496 in a Baja - his cam sensor went bad as he had no engine start. They changed the crank sensor - still no start- his buddy had a 496 early 2003 version so they swapped the cam sensor out - the engine started, Easy fix he thought if he could find the correct cam sensor and did on ebay for I think 100 bucks or something like that. Brand new old stock unpackaged cam sensor. His boat was stored at a lake house above the water, They installed the brand new cam sensor from ebay - he dropped the boat down in the water to test start it. the engine started but ran very poorly and then back fired multiple times, so he shut down the engine. Well the engine sucked water upon that testing and hydro lock. Anyways short jist of it - sometimes you have to watch what you buy. I thought I would pass this info on.
Boat owner story as he told me and then after the fact brought his boat to me last year, Its a early 2002 496 in a Baja - his cam sensor went bad as he had no engine start. They changed the crank sensor - still no start- his buddy had a 496 early 2003 version so they swapped the cam sensor out - the engine started, Easy fix he thought if he could find the correct cam sensor and did on ebay for I think 100 bucks or something like that. Brand new old stock unpackaged cam sensor. His boat was stored at a lake house above the water, They installed the brand new cam sensor from ebay - he dropped the boat down in the water to test start it. the engine started but ran very poorly and then back fired multiple times, so he shut down the engine. Well the engine sucked water upon that testing and hydro lock. Anyways short jist of it - sometimes you have to watch what you buy. I thought I would pass this info on.
