rottenbind

I just rebuilt a 1996 LT1 383 engine and it won't start. The car cranks and putts and backfires a bit, but won't go any farther. I've got the EASE computer-based scan tool and no codes are showing.

When I pulled the plugs, I'm seeing that they are blackened pretty bad. They are brand new plugs - Bosch Platinum +4's that don't require gapping.

I have verified that all plugs are firing by pulling them one by one, replacing with a new, unblackened plug, and seeing spark during the cranking.

I did a compression test and found good compression in all cylinders (around 200 psi).

I checked the fuel pressure and its around 45 psi. The injectors are new and a noid light shows that they are all activating.
　
A friend of mine told me that I may have set up my timing 180 degrees off, with the spark firing on cylinder 1 when it should be firing on cylinder 6 for example. How can I even verify that the timing is off by 180 degrees? I thought about doing a quick check with a timing light, but in thinking about it, since the cylinders travel up and down twice per cam revolution, the timing light would still show the correct timing, but on the wrong stroke if things were off 180 degrees. I could turn the engine by hand with spark plug #1 out and I could probably determine if I'm on a compression stroke. Then what?

Is it even possible to get the timing out 180 degrees? In thinking through this, it seems like all of the timing components are keyed and can only be assembled in one way. If, for example, I set up cylinder 1 at TDC on the wrong stroke, and assembled the timing sprockets, then this would put the cam's pin for the OptiSpark positioned for the #6 setup. So the OptiSpark wouldn't fit on unless the rotor was rotated for the #6 position rather than the #1, and all should be fine. I think...

I'm beginning to think that the problem may lie elsewhere? Any ideas?

Ron

Project 3.4 Camaro

I can almost promise you the timing is off, just start working your way around in a circle by rotating the wire plugs on the cap, and or turning the cap itself. That will get you in the neighborhood and running at least, at which point you can use a timing light to get it spot on, or you CAN just go by ear, though obviously not as accurate.

rottenbind

I wish I could do that, but the distributor is an OptiSpark where the spark advance is controlled by the computer, so I can't turn the cap to do adjustments like you can with older stlye distributors. Sure, I could pull the wires and switch them around, but that will be a coarse adjustment at best... plus my plug wires aren't long enough to reach unintended destinations.

As I understand it, the timing on the LT1 is pretty straight forward. There's no adjusting to be done really, apart from PCM reprogramming. Just line up the dots on the sprockets and you're done. If you're off, you're off by one sprocket tooth, which would be quite a lot. Hopefully I'm missing something and someone can set me straight.

Project 3.4 Camaro

Can't say I'm familiar with that setup, but I do still think the timing is off from the problem you describe and the things you checked that showed good.

torque_is_good

who did the rebuild for you or from where did you get it?

if you had black plugs it's obvious that you did not do it because nobody would slap in an engine with old plugs

your opti is on wrong. Despite what some people say, it can be forced on incorrectly if you gorilla the bolts . Here's the bad part about opti's. You need to drain the coolant, remove the waterpump in order to get to the opti. Tell who ever did the rebuild to get over there and do it and bring 2 gallons of coolant with them and new water pump gaskets. Be sure that the guy doesn't soak the opti when he's removing the waterpump because they cost $250 and more.

You can fire up the LT1 for about 5-10 seconds with no waterpump or coolant just to be sure the opit is on correctly once he re-installs it. Have him do that but do not rev the engine or run it any longer than to verify that it fires.

rottenbind

Actually, I did do the rebuild myself. And no, I don't know what I'm doing, so I need help. The plugs were new and got blackend after only about a half-hour of unsuccessful cranking.

It's very possible that I didn't get the OptiSpark on correctly. You have to get the front shaft in first, then slide it down so that the pin engages the slot in the rotor. It is very possible that the pin is not in the slot.

Is there a way to know definitively that the timing is out before I do the teardown? I'd hate to go through all of this only to find out that it's a stuck EGR valve or some other random thing.

torque_is_good

it's not the egr valve

your opti was installed incorrectly

let's back up a little

did the engine run prior to being rebuilt?

if yes, was the same opti used?

If the opti was replaced, did you get a vented one which is for the 95-97 LT1's

rottenbind

The engine was rebuilt because it had a spun rod bearing, a stuck lifter, a push rod that was dangling loose, and valves that were pretty well crudded up. Before all of that happened, yep, it ran pretty good with the same vented optispark.

I'll pull the optispark and let you know how I make out.

Thanks,

Ron

torque_is_good

you may have soaked aka ruined the old optispark when you tore it down and removed the waterpump.

If that's the case, it's what my dear departed daddy used to call a "bull in the china shop" and you learned an expensive lesson about how the tear down is just as important as the build.

Optisparks do not like coolant and once soaked and affected, a cap and rotor is not the fix. The optics got corroded. If you need one, try one of the optis from Summit for $250 or even give Chandler's Chinese unit a go at $100.

rottenbind

I plan to check the condition of the Optispark when I get it out. You may well be right - it may be corroded really bad, making it do crazy things.

rottenbind

I just wanted to follow up and let you guys know how I've made out. I've been doing this project in my very limited spare time so it took me a while to get through things.

I've disassembled the front of the engine to get to the OptiSpark and found no issue. I'm not sure as to whether the pin of the cam shaft was seated correctly or not, but I'm sure that I got it right this time around. I also went further and removed the timing gear cover and verified that the timing is in good shape.

Finding nothing that looked unusual or wrong, I put things back together and guess what? The engine started up immediately without any hesitation whatsoever! WoooHooo!!!!! I don't know what the problem was but I apparently fixed something in the rebuild. Probably the camshaft pin engagement in the Opti was the issue, but who knows.

Thanks for the help guys!

torque_is_good

that's great news

despite what others may tell you, an opti can be installed incorrectly with enough force. You knew from the get-go that it was a timing issue but probably heard the same people telling you that even the newer vented optis can't be put on incorrectly; they are wrong. They can be put on wrong.