3500 CPS Adapter

[geoffinbc]

Everything looks good. Size of the timing wheel does not matter at all. Wether it is larger or smaller the same amount of slots will pass by the sensor on every RPM. So no need to worry about that. Just be sure they are the same spread as the stock reluctor.

My only concern is that you are going to be machining the outer dampner ring for your trigger. The only concern would be if the ring shifts on the center hub because of the rubber isolator. Now on the FWD cars the dampner is designed to turn a belt so I think that it is locked in place and you shouldn't have a problem. But what you may want to consider is a reluctor that bolts to the center hubs 3 bolt holes

The way I made my trigger ring was to weld a ring to the back side or a RWD pully. This was also good because you could do a belt change and still leave the ring and sensor in tact.

Just for anyones refrence the stock PCM will allow about 10* difference before it sets a code. When it does you will be running on default fuel and timing tables and will burn ALOT of gas.

[tejohnson]

I'll get a shot of the n-body belt routing on the stand this evening. Gotta put the new P/S pump on anyways...

[tejohnson]

Yep, I feel like an ass.... Nevermind my concern... The tensioner is higher than I thought. Should work fine in the N-body too. See:

http://groomlakelabs.com/?q=gallery&g2_view=core.ShowItem&g2_itemId=2301

-and-

http://groomlakelabs.com/?q=gallery&g2_view=core.ShowItem&g2_itemId=2304

[bszopi]

I'm gonna agree with Geoff (bty) on this one. Don't machine the damper, just move the sensor out 1/4-1/2" and make a trigger ring that will bolt to the front of the damper. There are the 3 bolt holes used for pulling the damper off that work great for mounting a trigger wheel to. That is how I did it for my standalone (that I never got working). The trigger wheel worked out great bolted to the front of it. And, it would be easier if you wanted to "mass-produce" this. Much easier to supply a simple bolt-on trigger wheel than to supply a machined damper.

[gpse3400]

My reasoning for not using the damper is because it will flex.Quite possibly scatter the signal. Some dampers get wobbly as they age as well. Mounting a tone ring to the front of the damper on the puller bosses I think is a good idea. Question is are there the same provisons on the newer 35/3900 damper? Can we even fit the old damper on the 35/3900 crank? One last thing, is the sensor mounted to the block? If so those bosses the sensor bracket is mounted on is for the old motor mount bracket on the 2.8/3.1 and on later 3.1's the power steering lines were secured there as well.Which I gues doesn't really apply to most of us but on my setup, I use those bosses for my p/s lines and now I use it to tie in an extra motor mount....I might need somthing alittle different, I could get rid of the p/s line mount, and that would only kick the sensor out a 1/8" for me.. Eitherway I'm happy to see that there are people willing to take on this task of getting these engines to fire up.

[IsaacHayes]

Then you can use a FFP UDP at the same time too!!

[RacerX11]

Then you can use a FFP UDP at the same time too!!

Only problem with that is the FFP UDP and stock damper/pulley have different bolt patterns for the three holes.

[CNCguy]

There were some reasons that I didn't use a bolt-on plate.
1) It has to be steel and would add rotating weight.
2) The faces of the spokes are not machined (the ones I have here are not machined) and the plate would not run true.
3) Unsure if the locations of the holes are consistent in relationship to TDC.
4) It is cheaper to machine an existing part than to make a new one (just trying to keep the cost down). I plan to skim the outside and face to a common dimension before slotting the dampeners. My plan was to pick up around 10 dampeners, machine them and replace them with cores.

As an option, (if there is a demand) I was considering making an underdrive pulley with the 7x ring mounted to it and maybe even a setup for the 24x.

The 3500 dampener is a stamped steel unit that doesn't have the 24x ring on it (I assume it was replaced by the dual reluctor ring set-up). So anyone wanting to use OBD-II will need to switch to a 3400 front cover and dampener.

I was told by a reliable source that the dampeners and covers are interchangable but I did not actually measure them myself. I will measure the cranks and slip a 3400 cover on tomorrow. The front bosses and holes are the same where the CPS adapter mounts.

For those who have some other bracket mouted on the bosses, the base of the CPS bracket can be cut/ground off a little to maintain the proper sensor relationship.

I am also considering picking up a 3900 to experiment with since I have some ideas that I want to work on regarding VVT. I have too many ideas and not enough time or money.

[tejohnson]

3900 swaps may be more of a reality due to some new hardware and PCM tuning options that are on the way Can't wait to see the CAN interface with DHP's sticker on it....

[Superdave]

Just for referance, i have about 1" between the tensioner and the fenderwell in my Jbody. I can't even fit a ratchet in there...

[tejohnson]

Just for referance, i have about 1" between the tensioner and the fenderwell in my Jbody. I can't even fit a ratchet in there...

Good point.... Same with the N-Body cars...

[CNCguy]

Just for referance, i have about 1" between the tensioner and the fenderwell in my Jbody. I can't even fit a ratchet in there...

How much clearance is the near the dampener? Can you change the dampener when the engine is in the car? More important, is there room on the left of the dampener for the CPS bracket?

[IsaacHayes]

Same thing with L body. You have to use a flast tensioner tool to get at it from the top side. But on a W body you have room to actually just put a 3/8" ratchet in the tensioner. Here is a link to a picture from FFP's UDP installation page. That's what you got to work with on an L-body. Notice how the engine mount bolts around to the left side of the dampner.

[bszopi]

I've always used a 3/8" breaker bar on my Beretta for the tensioner. Sure, it wasn't the easiest to get down there, but it worked.

But down around the damper, there is plenty of room...

[Joseph Upson]

I initially considered an external sensor setup until I received what I felt was an astronomical price for such a simple part and opted to do the internal instead. My concern about notching the balancer is the fact that although the outer rim can turn the accessories it is still a balancer designed to dampen vibrations, given how much the outer rim on the 3500 dampner moved from center when pried on a little in an effort to remove it from the crank, I suspect that in addition to the threat but unlikelyhood that it will slip, is the ability to cause inconsistencies with rotational tracking as high rpm or sudden acceleration loads are applied, in other words the gap between the sensor and ring will very likely vary more so than the slight deviation of outer rim degree relative to inner hub degree on load changes.

The gap tolerance according to my GM manual is .020 to .070 with the gap setting at .050 in the middle and a deviation from it resulting in a higher or lower voltage induced depending on which direction the gap changes. The harmonics will not affect accessories at all but it could have a drastic effect on the timing. Another issue is that the 3500 balancer is about a half inch taller than that found on the 3400 at least that's about the difference between my comparison of the two and I considered installing the smaller balancer to serve as somewhat of a stock underdrive until It dawned on me that GM likely made that change for better power output from the alternator during idle as well as better water pressure in the cylinder heads at idle and above so I opted out on that change as well.

Your progress so far looks very promising in my opinion but I would do the bolt on hub instead of notching the balancer, and you can also do what I considered to defeat the need to bolt it to the balancer; cut the keyed snout off of a used crank, drill it through so that the balancer retaining bolt slides through it, shorten it so that about a quarter of an inch of it sticks out beyond the balancer once the balancer is installed on the crank and this little piece is inserted into the open end of the balancer, have the external reluctor wheel center hole sized and keyed to fit on the end of the makeshift adapter piece sticking out of the front of the balancer and install the balancer retaining bolt and it should all be centered and keyed so that it will not slip and you're done. After you torque it down that is.

I thought I was special when I approached a solution to the reluctor ring issue on the newer engines but today I found that there are at least two others working on this problem so I guess I'll have to turn to the 3400 rods and offset crank grinding to commence the stroking craze, so far I have received a quote of $180-200 dollars for the offset grind, not bad. Can you imagine turning a 3900 into a 60 degree 4.3L with a .2 inch stroke and cylinder bore.