8.1 496 double roller timing set
 

As to what the title says where is a place to source a double roller timing set for the 8.1. Also when buying a set what version is it going to be since there were 3 different versions and only the latest has cam sensors available still.

Not sure you can make that work with the cam sensors and how tight everything is. You can find the early black cam sensors if you search on eBay and such. I had two spares for my 2003 496s which I gave to the new owner. I also have an extra black cam sensor (same piece) for my 2003 Silverado 2500HD with the 8.1L as well.

What are people doing that are building these engines for timing sets. Where is the stuff being sourced do I have to go oem thru Volvo to get it.

OE replacement you can get thru GM.

Googled for aftermarket roller and found this, read the review as it may be helpful:
https://www.summitracing.com/parts/c...77-1/overview/

Also, not sure which cam sensor and ti,img chain cover type works with it. Again. I googled that. do your homework. :)
http://www.raylarengineering.com/vor...aft-gears.html

Yea I found that one and that is the only one I found, I guess you would just have to buy it and go from there on which timing cover and sensor too get.

Apparently Raylar are about the only people to see whenever you need stuff for this motor. In this case they don't even sell the stuff. But they provide the necessary information.

Tyler crokett is a 8.1 guru also from my understanding

I just felt it was good of raylar to put that info out there when they don't sell any of those sensors or gears.

Oh yea Raylar has a ton of information on his website that's for sure I have read thru it alot.

If you are keeping your current crank and cam sprockets and just want to upgrade the timing chain, then a standard aftermarket big block chevrolet 66 tooth type true double roller timing chain will work just fine. Cloyes, etc.

This is what my builder did on my rebuild.

The stock 8.1 sprockets can take a double roller chain?

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.

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.

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. .

So you have some of the early gen cam sensors available.

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.

Gotcha good info

Will add in this last sentence from Raylar not 100 percent correct with all 496 's marine side. Wrong info in the last wordings of their info. I will post the correct info when I get chance to. Also the crank sensor hall effect info is EFI 101 but there is more info to this on top of.

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.

Good to know

I just realized you have a VOLVO PENTA 8.1 in which is fine but a lot from Volvo 8.1 to Merc 8.1 is totally different just the long block is the same with some of the same sensors. The CAM sensor set up thru Volvo is done differently than Merc - the PCM is MEFI 4 and then in 2005 Volvo went to E Controls PCM in which is totally different set up completely and nothing like Mercs. Merc never used MEFI 4 unless replacing NLA MEFI 1 thru 3.

. Volvo more apps than not did not use an IAC especially after mid years. Also when Volvo had the IAC on their apps its not even the same as Merc set up nor the issues, even the IAC is totally different than Merc. As far as set up goes Volvo compared to Merc including all cooling parts are totally different and so is the set up. Just a heads up as most info up here you are going to get about the 8.1 is for Mercruiser so keep an eye on that because some of it or half it is not going to be what Volvo did for their marine build, Big difference in set ups once again. Many parts not even the same FYI.

Hi guys,

This an old thread and my first post, hoping that I could get some feedback on my situation. I have stock 2001 Crusader 8.1’s. They are stock but are the HO, 425 HP versions. I just had one rebuilt and doing the reassembly now. The shop who did the machine work said that they could only get a single roll chain. Is that an issue from a durability standpoint? He gave me back the old parts which included the sprockets so he didn’t just replace the chain itself.

Also, I installed the cam sensor (old style black one) and thought it didn’t seat totally flush to the block. I gave it a slight tap and stopped then installed the bolt. I’ll compare that to the other engine which I haven’t broken down yet. Does that have anything to do with a different chain/sprocket setup? Is there any reliability reason to upgrade to the newer/raised cover and sensor?

thanks
Bob

P.S. - sounds like I should have a spare cam sensor on board either way

you can not install single timing sprocket(s) when using the CURRENT cam sensor if that's what you want to do.. Using the current cam sensor has to use a double roller set up so the sensor reluctor wheel matches the cam sensor and vise versa. The timing cover and its depth has to match all this as well to get the correct gap for the cam sensor to the reluctor wheel so the ecm can receive that signal for a jist of info. There is a kit one can buy that updates all this and uses the current sensor. I do not have any of these kits in stock currently but can put my order in at anytime.

Also if helps ---- I do have the 2001 cam sensor and the 2002 / 2003 cam sensor in stock. Again these cam sensors has to match the timing cover and the cam reluctor wheel on the cam sprocket. This will work for the 2001 496s as I believe you are looking for ?

lightly lube the o ring for the install -- do hit the cam sensor with a hammer to install. If you use a hammer depending --- can cause an indent to the timing cover that will jack the sensor up against the reluctor wheel.

Can you use the 2004 timing cover ,sensor and single row timing gear and chain.Do Merc still sell the 2004 double row gears and chain

..

^^^^^^^ the timing cover is width ( spaced) to except the double roller chain sprockets. Keep in mind the double roller cam sprocket has the reluctor that the cam sensor needs to be gapped properly per cam reluctor so the signal is not lost to the ecm. A single row sprocket will not work period.

keep in mind the crank sprocket is for a double roller chain as well so all this is in perfect alignment. .

so to use the single row timing gear you would need to use a timing cover from a truck ?
Merc dont sell the double row sprocket any longer,so I have no other option but to use a single row

Mercruiserparts.com shows both sprockets and chain available. Your going to pay $$ for them though.

cam 892640001. $251
crank 881655 $129
chain 881626 $270

I called Merc yesterday and was told the cam sprocket was NLA

correction I called Merc again ,this time they tell me it is available for $250
I just heard from Crane they have both sprockets and chain double row $180,this is for 2004-2009 engine.Merc has the 2004 timing cover $142

Camshaft position sensor 2004-2009
Merc 892615002 $135
Ac delco 12591720 $28