can't edit the title... it's a 93 crankshaft


So I took a 95 LT1 out of a Firebird formula and I put it in my 86 Z28 long story short I spun a couple rod bearings.

So I took the 95 LT1 out flipped it over pulled the crankshaft (not an easy job without taking anything else out) but I successfully installed the crankshaft from a 1993 Z28 in it.

I did notice as I was doing this that the Opti from the 93 was totally different then the one in the 95 LT1.I have six LT1's, I've had two or three of them apart and they've all had the old style splined Opti, where my original engine that is in my z28 Opti that has the pin that will only fit in the one slot, with relief's for the cam bolts. so using the 1993 crank I put a new timing gear on and chain (there's only one key slot in the crank) and put the engine back together rotating it with a breaker bar as I assembled and torqued, everything looks perfect, double checked the crankshaft to camshaft timing marks too.However it will not start. if it sits for a few minutes, the first revolution, if goes fffffssstt once, almost a back fire but not... acting like something is out of time.

My theory is possibly the 93 crankshaft key slot is at a different position to work with the old style spline Opti.

Thanks in advance,


Robert

 

Something wrong - a 1992 Z28 had the L98 engine, would not have an Opti. 93/94 F-Body, 92-94 Y-Body are splined shaft driven Opti, 95-97 F-Body, 95/96 Y-Body are cam dowel pin driven. Not aware of any differences in the crankshaft keyway.

An L98 crank also has different counterweights than an LT1 crank. See “Cranks” in this article:

LT1 Engine - Chevrolet Rebuilding

 

Well, it's been a while... It wasn't my car that I pulled the engine from, it was a 4th gen Z28... it was an LT1. it wasn't a MAF system.

It had a cracked block. I swapped engines as I had a good LT1, I got 1985 corvette and I got to keep the engine with the cracked block for the swap. the cracked block engine has the splined end opti My 95 LT1 doesn't so I used the front cover and opti from my 95 engine.

It almost starts.. I have 50 psi fuel pressure at the rail while cranking, stop sranking and it stays at 40 for a long time so injectors are good. I have spark, I have 12v power at the injectors, I've double checked the plug wires into the opti fit and at the spark plug end. The opti will only go in one way... the crank to cam only lines up one way, new timing chain and gears.. rotated assembly several times to double check that the timing marks were correct.

kinda at a loss here...

 

I am significantly out of my depth with the '85 Corvette, but I will take a stab.

What do you mean when you say it almost starts? Does it run for a few seconds then die? Where did you check for spark? What other things have you done as part of this swap? If you are saying you have the opti, did you also swap the PCM from the LT1?

 

removed.. see the next reply from me.

 

Things are still a bit all over the place. I see you edited the initial thread, which makes me think that information is now correct, but things are still not lining up. So the Corvette is out, and in is the ' 86 Z28.

From what Fred mentioned in post #2, the 92 is an L98, and the crank shaft is different, and also wouldn't have an opti, so is this really a '93 crankshaft, and the opening thread is still wrong?

Also, since we are talking about about the engine being in an '86 Z28, which used a different everything, what else has been swapped into the '86 to make it work?

 

I have a 1986 Camaro that I have a LT1 in, the LT1 came from a 1995 Pontiac Firebird Formula I had to change the crankshaft because I spun two rod bearings. I took the crankshaft out of a probably 1993 Z28 with a LT1 and now it won't start and I thought maybe there was a difference in the crankshaft because the Opti changed from the spline type to the one that runs off of pin.

My original LT1 that is back in this car is a newer LT1 (1995) that has the pin type Opti I have spark I have fuel, it won't start

 

Start here: 4th Gen LT1 F-body Tech Articles

Also, I know you have verified your fuel pressure, but have you verified that the injectors are being pulsed?

 

If the opti tests out, have a parts store test your ICM.

 

with the key in the run position, I have voltage at the injectors... if test if they are pulsing is different... say make a more permanent connection, crank the engine and see if the light flashes I will try that. I have extra computers... never thought of that one... I can swap it out.

 

Using a lighted probe... I did this on both the Positive and negative side of two different injectors, while cranking .... solid light... if there was a pulse it was quicker than the eye can see.

 

The ICM, not the PCM =D. I am not sure about the differences in the ODB1 computers, so I couldn't steer you one way or the other in that regard.

 

sorry... had a blonde moment... I have several of those as well...and have swapped them. one from a running LT1.


pulsing fuel injectors... did I do that correctly.?

 

I think it would be too fast to see. I would pull the rail up and bump it once or twice to verify that fuel is spraying. If you are solo, put heavy paper towels under the injectors, turn it over, then inspect the towels for fuel.

 

While in theory the cam dowel pin only fits in one slot, it is fairly common for the pin to be forced into the wrong slot, or even not in a slot at all.

http://shbox.com/1/opti_back.jpg

Timing set alignment:

http://shbox.com/1/keyway2.jpg

http://shbox.com/ci/sprockets.jpg


What kind of "light" are you using to check for the injector pulse? You need a 'noid light, capable of responding to a pulse that is in the range of milliseconds. The pink wire on each injector should be 12V with the key on. That proves the wiring is good, not the injector. The PCM provides a brief ground to pulse the injector. That is what the 'noid light responds to.


Your fuel pressure may be on the high side. Spec is 43.5 PSI with no vacuum line connected (or engine not running). GM accepts anything in the range of 41-47 PSI. Shouldn't prevent the engine from starting. Something to check after you get it running.