Has anyone ever changed the 2.5 from gear driven cam to chain driven ? I found a lot of reverse rotation cams for boats. This is for my sd4. Was thinking if it was ran off a chain, it should work in a car. So any ideas ?

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85 GT 3.4
14.9 @ 90 1.9 60' Old TH125/3.06
Unknown New 4T60/3.42

The 2.5 Mercruiser used in boats is a Chevy 2.5, which isn't the same as a 2.5 Pontiac.

Why would you want to switch the gear to chain drive? You would have to change the size of the gears to get a chain to even fit on a Pontiac 2.5, if it is even possible.

While later years have chains , not much point trying to add that even on SD. (don't know if is VIN R or U. look up 91-92 Duke chain set.)
Most dukes to at lest to 88 are made w/o a harmonic balacer and lacking oil to gear set cause many problem.

87 & up gets a balancer.
All gets a 1mm hole in the oil gallery plug behind the big gear.
But few bother to read a TSB or my Cave, Cam Gears, let alone drill the hole.
Every shop w/ ALLdata has access to GM TSB but very few read them. This TSB was publish in 2/1990...
Titled: Gear Kit Should Be Installed When Servicing Timing Gears
Subject: Servicing Camshaft/Crankshaft Gears (Install Torsional Damper)

Then add Any problem w/ oil pump or 86 and older the distributor and puts a big load on any gear/chain. Most never bother to check either and blame the gears and new gears break too and still blame only the gears.

Many "performance" engine builders want to eliminate chains as a weak point to break etc. Silent chains (another name for standard chains) more so because of wear to the chain, gears/sprockets and often the guides for the chains. (Dukes w/ Chains have chain guides.) These chain sets often won't handle loads in engine that reach above around 5000-6000RPM for very long.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

quote Originally posted by theogre: Many "performance" engine builders want to eliminate chains as a weak point to break etc.

Exactly. That's the reason why there are aftermarket gear drives for V8 engines. Because the gear drive is more reliable than a chain.

Edit to add: For the OP, I would suggest getting the metal camshaft gear, and make sure the block has the oiling hole, as Ogre described.

[This message has been edited by Blacktree (edited 03-09-2018).]

I knew I had seen somewhere that a chain was used instead of a gear. The thing is finding a blank cam for my sd4. Alot of reverse rotation cams no standard rotation. That's why I was thinking of using a chain. A double roller should work nicely. Still waiting on replies from several cam companies.

they still have aluminum version. Can make more noise and can last longer but is not a guaranty of doing so because of above. RA look in Timing Cam Gear
Can get Straight Cut Iron set but likely need other parts to use them. RA look in Timing Set

Why...
OE "beveled teeth" setup locked the cam axial loads to the cam retainer. IOW retailer and gear face hitting it are controlling cam runout.
Straight cut teeth can't do that and can needs a cover to have a way to set cam runout or cam can wear the retainer's back side even breaking the retainer because the part has no support by the engine block loaded on the back.
More so depended just how driving teeth for Oil pump and distributor are cut. The loads could try to push the cam out of the block w/ straight cut gears.