sonomacrew01

There's so much info out there on these two items that its tough to find the correct answer. I have a 93 LT1 that I am looking for a solid timing set to replace the worn original one (has some play). Also, I will be adding the meziere HD electric waterpump later on. I've looked at cloyes timing gear sets but which one am I going to need when I will no longer have the sprocket and shaft for the mechanical waterpump. And I also believe that the sprocket for the cam is slotted with teeth for the cog that goes to the opti. I don't see that on the cloyes 9-3175 or the cloyes 9-3145.

I plan on welding the opening on the timing cover for the cog that impells the mechanical waterpump to install the meziere. Is this a simple electronic plug in? I also read somewhere that I have to bypass the heater core... Can someone explain?

Any other infowould be helpful

Zix

Well, for timing sets you have two main options;

-LT4 Extreme Duty single roller
-Cloyes 9-3145 double roller

I have the 9-3145 double roller in my LT4, it works with the opti just fine. Just be sure NOT to get the 9-3145A, as it does not work.

The waterpump is an easy plug in deal, but you will have to splice it into a power source. I used the fan relay. There is no need to bypass the heater core...not sure where you got that from.

Corvette Kid

No need to bypass the heater core. The Meziere does nothing to affect the plumbing, routing of the LT1's cooling system. It installs in the factory pump housing. I may be wrong but I'm not sure if it's possible to use a Cloyes True DR w/o changing to the later, pin drive opti. If this is indeed the case, you'll need a '95 cover and of course the later opti. I and many have used the 9-3145 Cloyes set, I'm not sure how the 9-3175 set that you mentioned differs.

sonomacrew01

then I would have to convert the front to a 95+ design (new opti and timing cover).Not sure I want to do that.

Bruce

check it out. I just did this last week.
http://forums.corvetteforum.com/show...81&forum_id=48

93 ragtop

When I did mine, I purchased the opti in a kit from http://www.samtaylor.com/en_US/. They have a kit that includes the opti, timing cover, harness, and the vacuum nipple needed at the manifold. The advantages to the conversion are, better opti, cheaper opti, (95 opti is cheaper then 92-94) can use a standard double roller chain such as the coyles 9-3145 along with a electric waterpump.
Give them a call and get a price, (tell them you want corvette forum pricing)
I believe you will find that if you are planing to do the electric pump, a new opti, and a new standard timing chain set, It is just as cheap or cheaper to go ahead and do the conversion because of the savings on the 95 style opti, and the savings on the standard double roller chain set compared to the LT1 set.

sonomacrew01

is the timing cover gasket for the 93 the same as the 95+?

93 ragtop

The gasket should be the same.

Corvette Kid

But get the front cover gasket and seal set for a '95 (if you do the opti upgrade) so you'll get the correct opti seal.

93 ragtop

Ask to be sure, but I believe the seal came installed already.

Hotred94

It is possible to use a Cloyes 3145 with the old style opti and a Hot Cam. I did that on my 94 because I put a new cam in but I didn't want to buy all the stuff to adapt the newer style opti when I had a perfectly fine old style opti. You have to do two things to adapt new cam/Cloyes chain to the old style opti. (1) Shorten the pin on the Hot Cam because it comes adjusted to fit the new style opti. (2) Align the cam shaft/opti shaft with the new cam gear by using the old gear as an index.

The opti drives off the end of the cam through a splined shaft that fits in matching splines cut into the stock cam gear. The Cloyes 9-3145 is not splined for the opti shaft, but it has a hole in the center larger than the shaft. I machined a washer-like spacer to fit snugly in the hole of the Cloyes gear. It looks like a thick washer and is as thick as the cloyes gear with an outside diameter the size of the cloyes center hole, with a center hole the diameter of the opti shaft. Press the opti shaft into the hole and weld it to the spacer, ensuring that it is straight up and down to the spacer. Only weld on the front side as the back side must fit flush on the nose of the cam. I used three spot welds to reduce heat and distortion. Remember, the only load this shaft carries is the rotating part of the opti, so it doesn't require a lot of strength.

Now comes the tricky part--indexing the new Cloyes gear and opti shaft to match the position the shaft was in on the old stock gear (remember the opti shaft is keyed to only fit one way so the opti timing and the cam position will be exactly timed as they were originally). I hope this makes sense. Now we have the opti shaft welded into the machined spacer, but not welded into the Cloyes cam gear. The spacer needs to fit loose enough into the Cloyes gear hole to be able to rotate, but tight enough to hold the spacer in whatever place you twist it. The idea is to weld the shaft into the Cloyes gear in the same position that it would be in the splines of the stock gear. To index the shaft, put the Cloyes gear face up on a welding table, put the splined opti shaft into the hole so it sticks straight up, put the stock cam gear over the shaft (so you have one gear sitting on the other gear, the stock gear engaging the keyed splines on the shaft but the other end of the shaft with the spacer on it fitting into the hole of the Cloyes gear). Now twist the two gears to align the timing marks on each gear to the other. This step uses the stock gear as a templet to place the opti shaft in the Cloyes gear exactly in the same position it is on the stock gear. Align the tooth with the timing mark on one gear with the tooth having the timing mark on the other gear. When the points of the gear teeth are exactly aligned with each other and the shaft is straight up and down, then weld it in place. Clean up the welds so they don't interfere with anything and you're ready to put it in.

Some people have questioned if the timing can be matched close enough to not cause any problems. The answer is absolutely. The computer has to adjust for timing variances due to wear and chain stretch anyway. I estimate a brand new stock setup can have up to 1.5 degrees variance just in the accumulated tolerances of the mechanical fittings of the chain and opti shaft. I got mine indexed to one half of one degree. This new setup increases the stability of the timing to match that of the later style opti by eliminating one of the slip fits on the shaft.

Just be careful about what you are doing, you know...gear right side up, everything is straight, nothing looks goofy, and all that stuff. Understand the logic of each step before you do it. After I finished all my engine work, the engine started instantly, and I've been running with this mod all summer with not even a hint of a problem.

Corvette Kid

Now we know it's do-able. Very well thought out, Hotred!

ScaryFast

If you want to keep the same opti then there is no Cloyes timing set available. You have to get a stock replacement (which will have the gear for the WP drive). I just did this change on my '93. Based on research done on the forum I thought I could update to one of the better timing sets, however once I purchased it I found that you still need the splined hole in the cam socket to run the opti.

You can do something like Hotred did, I didn't mess with it as I've had so many issues with misaligned opti pins that to me it wasn't an option.

So you have three options:

1. Stick with current timing set (stock replacement), opti, and pin

2. Modify set up as mentioned above

3. Upgrade your opti to the 95+ version which opens a whole new world of timing chain options. This is what I would have done had I known that there were no stronger timing sets available, but I ran out of time...

To do #3 you need a new timing gear set, new timing cover, newer style opti, and a new opti drive pin.

Corvette Kid

Just to clarify so no one gets confused, the later vented opti's drive pin is actually a longer cam pin that protrudes through the cam gear to drive the opti. It needs to extend .620" from the cam. The earlier opti is driven by a splined shaft from the center and not by the cam pin.

sonomacrew01

I purchased the 95+ style timing cover and a 95+ style Hotcam. Dynatech is on backorder for the 95+ opti but that is next on my list. Jason from the parts department at Sam Taylor buick said that this style opti along with the timing cover and camshaft will bolt right up and work....Along with the opti harness and the vacuum nipple needed at the manifold. Am I still going to need the newer style pin or does it come included with the cam?

Corvette Kid

The cam will come with the long pin installed.

Hotred94

[QUOTE=ScaryFast]If you want to keep the same opti then there is no Cloyes timing set available. You have to get a stock replacement (which will have the gear for the WP drive). I just did this change on my '93. Based on research done on the forum I thought I could update to one of the better timing sets, however once I purchased it I found that you still need the splined hole in the cam socket to run the opti.

If you want to go to an aftermarket timing chain, it is implied that you must use an electric water pump. Last time I checked, the 93 is just like the 94 and I am using a Cloyes chain with the old, original opti. See my response above to learn how to mod the Cloyes cam socket to handle the missing splined hole.

ScaryFast

I'm not sure if you're agreeing or disagreeing with me.

Regardless, that's exactly what I said. There is no stock replacement Cloyes timing set that will work with the older style Optispark, I spoke directly with Cloyes when I realized that the set I ordered didn't have the provisions for the old pin. You can modify one as you suggest, but in my opinion that is not the same as a direct replacement.

And yes, you'll have to use an electric pump as the new timing set will not have the gear drive on it to spin the WP cam sprocket. Although to be fair, I didn't check, so there may be an updated Cloyes set that has this gear. Someone else will have to answer that.

ScaryFast

So CKNC, clarify something for me as I will do this update also if I have to go back into my timing set.

The old style opti will not work with the new style opti pin, right?

To update, one would need a different cam (anything other than the 92-93 stock part), 95+ opti with new style drive pin hole, new (longer) pin, timing set with the larger hole, and new timing cover.

Corvette Kid

Right, the early optis are driven by a splined shaft which spins directly with the center line of the cam. The '95 and later optis are driven with the cam pin which is offset from the cam's centerline. Interestingly, the big LT1 cars (Caddys, Buicks and Chevys) got the updated opti in '94 but the F bodies and Corvettes didn't get it until '95. One should check with whatever cam manufacturer they're using but most if not all cams made specifically for these engines should have the longer pin which can be cut off if not needed. I've read of people on here saying that they've been unable to remove a short pin to install a longer one. I've never had a reason to remove one from these engines but I have removed other engine's cam pins before. That's not to say though that they necessarily used the same fit tolerance as the Chevy, though.