Camshaft Sprocket Question

Not sure if this is the right section, but here goes. I am finishing up a project car I started last year and had a question about the Cam sprocket/head combo. The car is an 83' Omni with upgraded brakes and suspension and the motor is a 2.5 Tall Deck out of an 88' Aires. The car is going to remain carbed with a Weber so I don't need to worry about wiring or computers(Distributor got replaced with a unit Mallory made for our cars one upon a time). The motor is a bit of a conundrum since it came out of an 88', the head and seal covers are stamped 87' and it has round tooth sprockets as well as a 5 bolt small diameter crank/crank sprocket that supposedly was on 89-up blocks(No, it is not a commonblock crank, already checked). Although the sprocket itself does look slightly different than the commonblock sprockets I have. The bottom end has been completely rebuilt with 2.2 flat top pistons and I have a rebuilt 287 head that I am going to put on(I wasn't going to pay several hundred dollars to rebuild the 782 when I already had a good 287 ready to go). My question is: am I going to need use an offset cam key since it is a round tooth roller cam sprocket going on a slider head cam? If so, which key do I need to use? I can't seem to find this information anywhere and am hoping someone here has the answer.

Thank you,
Dan

Okay Dan,
You are correct the TD crank has a smaller snout than the CB. It is around .860" vs the CB .1.00" (approx.) snout. So you need to use the 88 TD crank sprocket. The TD crank sprocket (the pulley side) uses a larger than CB pulley locating ring, so you need to use a 88 only TD crank pulley. The neat thing about the 88 TD pulley is that the AC pulley is removeable if you are not running AC. It is a very heavy cast pulley. Very unlike the CB pulleys.
The 2.5 TD cam sprocket is as you know round tooth. That is also unique to the TD motor. It is stamped with #535 on it. It is advanced approximately 2° vs the 557 CB sprocket. The front crank seal is the same as the CB. Same with the oil pan gasket. The timing belt is longer and the tensioner is smaller in diameter than the typical 8V motors, but you probably already knew that (lol). When you resurface the deck of the block and the cylinder head you are retarding the camshaft slightly. FYI- The 89-93 2.5 NA also used a different cam sprocket. That one was a #690. It looks to be around 3° retarded vs the 557 sprocket. this would be around 5° retarded more than the 535 TD sprocket.
If I were you, I would either buy a set of offset keyways (these are expensive at around $50) or better yet buy a round tooth adjustable cam pulley. I recently found some new ones for as low as $87. I would also seriously consider running a roller cam as well. You can switch out the cam, springs, and followers and place in your 287 g-head. I say this because many have found running a g-head on a 2.5 motor can be hard to tune. Although with the slightly better rod ratio, this shouldn't be as big a problem as with the 2.5 CB. I would start out running the camshaft 3-4° advanced whatever way you go (keys or adjustable pulley). You might need to go as high as 6-7°. Absolute best thing would be to degree in the camshaft, though most people don't have the equipment or knowledge to do so.
Good luck, sounds like an interesting motor.
Todd

Thank you for the info, I greatly appreciate it. Any chance those $87 adjustable sprockets are still available? To make things more interesting, I have a 87' Aires wagon that has an 87 2.5 TD that has the larger diameter crank found on non-cb 2.2's and all square tooth sprockets. I've noticed over the years that Chrysler seemed to build these motors with whatever was lying around at that particular moment.

UPDATE: I was just out checking the engine and the intermediate shaft sprocket is a 535 and the camshat sprocket is the 557. The only thing that I can think of is that someone who had the car before me might have replaced if for whatever reason. Confusing, but the car always seemed to run fine until it rusted out. Holding the two pulleys together, they are exactly the same size, width, tooth count, etc. The only difference is the key-ways are off about a 1/16th of an inch off. What kind of adjustment am I looking at making with the slider cam and 557 sprocket? I was thinking about switching out the cam, followers and springs out of the 87' 2.5 Aires since it's not currently running but I would still need to adjust the cam to compensate for the 557 sprocket.

Dan looks like someone switched the aux. shaft sprocket with your cam sprocket at some point. The cam was just retarded a couple degrees from where it should have been. Having the #535 on the aux shaft didn't do anything as the crank timing is adjustable at the distributor gear. Since you need to advance the cam a couple degees for it being a TD and another couple degrees because you have milled the block and head, I would start with around 4 degrees advanced. I sent you a PM.

Quote:

---

Originally Posted by 4 l-bodies

Dan looks like someone switched the aux. shaft sprocket with your cam sprocket at some point. The cam was just retarded a couple degrees from where it should have been. Having the #535 on the aux shaft didn't do anything as the crank timing is adjustable at the distributor gear. Since you need to advance the cam a couple degees for it being a TD and another couple degrees because you have milled the block and head, I would start with around 4 degrees advanced. I sent you a PM.

---

Is it safe to assume that the 557 sprocket is supposed to be on the aux shaft? If I put the 535 back on the camshaft, what kind of offset am I looking at? Right now it seems like the easiest thing to do is make sure the correct sprocket is on the aux shaft and use an adjustable sprocket for the cam. Thanks again for the pm. Also, I only had the head surfaced and the block didn't need to be decked since it was still perfectly flat. Thank you for your help, this was all starting to make my head hurt.

Edit: Does anyone have any long-term experience with the Fidanza adjustable sprockets? How well do they hold up over the long run? Any known problems/issues I need to be aware of if I go that direction?

Okay, I may have just found really simple solution. I took one of the 974 square tooth sprockets off a spare 86' 287 head I had lying around. I wanted to see how far off the teeth would be with the 535 sprocket when I lined the two sprockets up in the correct direction. It was about half a tooth. Then I decided to see how far off the 557 sprocket would be. The damn thing lined up perfectly. With the teeth lined up center to center, both small locating holes were centered with each other and I could slide the cam key from sprocket to sprocket without changing position. The 974 seems to have exactly the same tooth count and they lined up as perfectly as a round tooth and square tooth sprocket can. It looks like I can just bolt on the 557 sprocket and be in the exact same place that the 974 sprocket would have been on the same head. I still have an 89' Omni I haven't scrapped yet that still had a sprocket on the aux shaft. I pulled it and it was a 557. That means that if the 2.5 tall decks are supposed to use a 557 on the aux shaft instead of a 535 I'll have enough 557 sprockets to get everything lined up. Please let me know if I am forgetting or overlooking anything.

I've read the fidanza pulleys are no longer as accurate as they once were

you would need to degree the cam with that pulley to know if or by how much it may be out

Dan,
Originally your 88 TD 2.5 had the 535 sprocket on the cam and a 557 on the aux. shaft. So someone at some point mixed the two up. You are correct that the square tooth and round tooth 974 and 557 used the same keyway location. The 88 TD from Chrysler used about a 2° advance built in the sprocket. So you will be very close running the 535 as intended. Why would you use al 557 sprocket on the camshaft knowing that you will be running the camshaft 2° or so retarded from what Chrysler intended? Almost all close to stock motors will benefit from some advance on the camshaft. The bottom end torque will pick up some.
Dr Johnny Dodge is correct, some Fidanza sprockets are off a bit. If you buy one, do the same thing you did with the 974 and 557 sprockets. Line the Fidanza and the 557 sprocket up and see if they are off any at the keyway. I've seen both retarded and advanced. Just line them up, adjust as necessary, and make a new mark where the real zero would be (if it is off).
Todd

Quote:

---

Originally Posted by 4 l-bodies

Dan,
Originally your 88 TD 2.5 had the 535 sprocket on the cam and a 557 on the aux. shaft. So someone at some point mixed the two up. You are correct that the square tooth and round tooth 974 and 557 used the same keyway location. The 88 TD from Chrysler used about a 2° advance built in the sprocket. So you will be very close running the 535 as intended. Why would you use a 557 sprocket on the camshaft knowing that you will be running the camshaft 2° or so retarded from what Chrysler intended? Almost all close to stock motors will benefit from some advance on the camshaft. The bottom end torque will pick up some.

---

I admit I forgot about that. I was thinking that since the teeth and the keyways lined up, I would be where I needed to be for the slider cam and G-head. Since the 557 lines up and is approx. 2* retarded you're saying that the 535 sprocket is actually closer to the stock 974 sprocket on the 287 head? Sorry to sound like such an idiot with so many questions, I just want to make sure this gets done right the first time, and once again that looks like an adjustable sprocket.

Dan, also note using the G-head over the swirl you are losing about half a point in compression ratio. That will cost you some torque and HP output. Assuming the FSM is correct a 88 NA 2.5 was 9.0:1. So now your looking at around 8.5:1. You will probably benefit from some additional initial advance assuming your calibration is based off swirl head.
As far as the retarding and advancing of the camshaft, Chrysler figured out that with a .470 taller deck, they needed to run cam a couple more degrees advanced (using the 535 sprocket) to get cam at intended centerline.
Todd

Quote:

---

Originally Posted by 4 l-bodies

Dan, also note using the G-head over the swirl you are losing about half a point in compression ratio. That will cost you some torque and HP output. Assuming the FSM is correct a 88 NA 2.5 was 9.0:1. So now your looking at around 8.5:1. You will probably benefit from some additional initial advance assuming your calibration is based off swirl head.
As far as the retarding and advancing of the camshaft, Chrysler figured out that with a .470 taller deck, they needed to run cam a couple more degrees advanced (using the 535 sprocket) to get cam at intended centerline.
Todd

---

I decided to go with flat top 2.2 pistons in place of the original dish pistons so I will still be good on compression. What I need to know is using the adjustable sprocket or 535 with offset keys, how many degrees of advance or retard do I need to get those sprockets where they should be on the 287 head?