: Optispark?! What the hell?!



I~LUV~Caddys8792
08-03-06, 12:03 AM
Why would GM install a distributor as complicated and inaccessable as the Optispark on the LT1 when they had the technology and the know how to install distributorless ignition on the LT1 like the system used on the 3800 and Northstar?

I ask because a customer brought in a '96 Caprice Classic into work today with the LT1, and when the tech had it on the hoist, he pointed it out to me, and to get it off, you have to get the fan out, and the waterpump off to get at it. PLUS, the spark plug wires are like 2-3 feet long then. And the distributor is atleast $350 to buy new. ATLEAST $350, plus labor.

90Brougham350
08-03-06, 04:05 PM
I'm sure one of the LT-1 guys will chime in, but my understanding is that the ignition components don't need replacing for like 100,000 miles and there's no carbon buildup on the contacts like in a gen. 1 smal lblock. Then again, I could be dead wrong, I have been before!

Stoneage_Caddy
08-04-06, 05:01 PM
i think LT1s eventually got distributor-less because ive seen a couple with the coil packs down low on the engine ......maybe it was just corvettes that got it ....

N0DIH
08-04-06, 07:21 PM
Nope, LT1's had Optis to the bitter end. 2 flavors out there, second generation is significantly better due to venting to reduce moisture.

They aren't perfect, but it is a new approach to timing, it is ANGLE based, as opposed to TIME based like conventional distributors. Being it uses a crank shaft and camshaft sensors, it can very accurately time the engine, unique as it treats the engine as 8 separate 1 cyl engines as opposed to having 1 8 cyl engine. So each cyl can have its own uniqie timing if the PCM determines that is needed.

I~LUV~Caddys8792
08-04-06, 08:10 PM
Did the usage of the Optispark have anything to do with the reverse cooling habits on the LT1?

Any other GM motors use Optispark?

N0DIH
08-05-06, 11:17 PM
Nope, no one else used the Opti other than the L99, aka the 4300 V8.

It has fantastic resolution, 720 pulses for each rotation. So there is unparalleled precision.

As for the reverse cooling, that was a feature designed into the LT1/L99, but never made it to other engines. If you look closely at the LS1, it looks like it was in the original plan, but the lawsuit that GM lost on the LT1 discontinued its use on other engines. Bummer....

The reverse cooling on the LT1 allows iron heads on a 10:1 compression with 87 octane and as high as 34 degrees timing in stock form with no pinging! I would say it works!

I~LUV~Caddys8792
08-06-06, 09:17 AM
The reverse cooling on the LT1 allows iron heads on a 10:1 compression with 87 octane and as high as 34 degrees timing in stock form with no pinging! I would say it works!

I always wondered how GM could squeeze that much power from that engine and not require premium fuel.

UGOTIT
08-07-06, 07:31 AM
The optispark on the LT1 is the worst,I always had prolems with mine.

I~LUV~Caddys8792
08-07-06, 04:37 PM
N0DIH, you mentioned the 4300 V8 earlier. I always wondered why they made that motor. It makes less power than the 4.3 V6 and just about as much power as the Series II 3800. Why would GM make such a lackluster V8? Was there a need for a smaller motor in the Caprices? It would have been kinda cool if they could take the RWD 3800 Series II and put it under the hood of the Caprices. You'd have a motor that could do a decent job of pulling that boat along, but it would get much better mileage and be VERY easy to work on!

N0DIH
08-07-06, 04:44 PM
It made 200 hp, which isn't bad from 4.3L, and 245 lb/ft torque. The same year 4.3L v6 made only 180 hp and 245 lb/ft torque, so the 4300 V8 would have done better, and the V8 makes it power at lower rpms.

Mainly to improve CAFE fuel economy I am sure. And people who buy big Caprices likely frowned upon the 4.3L V6 in them, they were lame. So having a 4.3L V8 would meet with more customer approval while helping CAFE some.

I always felt the 3800 would do better in a RWD, finally they heard me grumble and did it to the F Body. Couldn't do it in the 80's, it would likely beat the 305's!!!

UGOTIT
08-07-06, 04:51 PM
They used the 4.3 engines for the Busch series and stadium trucks years ago.

I~LUV~Caddys8792
08-07-06, 06:38 PM
It made 200 hp, which isn't bad from 4.3L, and 245 lb/ft torque. The same year 4.3L v6 made only 180 hp and 245 lb/ft torque, so the 4300 V8 would have done better, and the V8 makes it power at lower rpms.

Yeah I suppose it would have done better than the 4.3 V6, but it seems odd to make an entirely new motor when a proven, reliable motor of the same size makes just a bit less power. I could have sworn I read somewhere that GM had a H.O. 4.3 V6 that made 200hp and 260 lb/ft. Either way, the 4.3 V8 was a dog in those cars. 245lb/ft just isn't enough for a modern 4100 lb sedan. Would it have been possible to use the L98 4.9 V8 from the Cadillac in those? Or the S/C 3800? Either would have made more power than the L99 4300.

BCs71
08-08-06, 05:43 PM
The optispark has a really bad reputation which is unwarranted IMO.
What other distributor can you name that has the benefits that NODIH has mentioned as well as being SERVICE-FREE for at least 100K miles? Many folks have had 200 or even 300,000 trouble-free and service-free miles from their opti.
Also, it costs a tad over $200 from a GM service dealer in Ohio (Dal SLabaugh who sells at 10% over cost on all GM parts) - he is well known on the internet and ships all over the country, maybe all over the world.

So for 100K or even 200K+ miles and $200 worth of parts, I'd say it's a fair trade-off.
The only mistake GM made was locating it beneath the water pump on the front of the engine where it can be subjected to moisture. This also increases labor, as already mentioned in the initial post. But as NODIH pointed out, the issue of moisture was more a problem in the 1992-3 non-vented opti equipped F and Y body vehicles. The B and D bodies first got the LT1 in 1994 and the improved (and proven reliable) vented opti throughout its run.

As for the 4.3 V8 in ONLY base model Caprices (lasted only 1994-6), I scratch my head at that often times. What sense does it make to completely engineer a whole new engine for only ONE model vehicle when it already was designed for the LT1 engine, and all of its cousin cars (caprice wagon, roadmaster sedan & wagon, Fleetwood, Impala SS) have the LT1 as standard??? It must have cost a fortune for that limited run production engine!
I think NODIH hit the nail on the head, it must have had to satisfy some CAFE standard for fuel mileage or something. If GM just stuffed the LT1 into the Caprice as standard and never designed the 4.3 could they have made more money?
Was a smaller V8 engine REALLY a good selling point? I mean, both are still V8 engines and that's all the unknowing public cares about who would buy base model caprices anyway. "My car has a V8".
I still scratch my head that a 4.3 V6 from the Blazer/S10 was already avaliable and probably pulled in better fuel mileage (and was already in a truck mated to a 4L60E so it had planty of torque) but was not slapped into a Caprice.

I guess the retooling of a whole new engine was cheaper than the retooling of the PCM/engine compartment components to fit the 4.3 V6 into a base model car and then having different logistics for an upgrade engine LT1??
I dunno...

N0DIH
08-08-06, 05:50 PM
Tooling costs in the end probably cost them more than they ever could have saved. They must have thought the L99 program would have lived longer. I for one would have liked to see the L99 in a base Firebird/Camaro. And drop the V6. At least for the dud 3.4L they put in...I hate the sound of them!

Bet it still out ran a base 4.6L Crown Vic....

But custom rods, block casting, pistons, rings, all had to be pretty pricey to only run 3 production years. And the LT1 sharing Gen 1 parts like pistons and rings, that engine was likely cheaper too.

So it had to be to satisfy some warped requirement, because it doesn't pass common sense!


Yeah I suppose it would have done better than the 4.3 V6, but it seems odd to make an entirely new motor when a proven, reliable motor of the same size makes just a bit less power. I could have sworn I read somewhere that GM had a H.O. 4.3 V6 that made 200hp and 260 lb/ft. Either way, the 4.3 V8 was a dog in those cars. 245lb/ft just isn't enough for a modern 4100 lb sedan. Would it have been possible to use the L98 4.9 V8 from the Cadillac in those? Or the S/C 3800? Either would have made more power than the L99 4300.

Later 4.3's did better, but year to year, in 1994-1996 I don't think they ever did. The 3800 was still the hp leader at 205 hp.

SC's are $$, so a V8 with same hp/torque will always be cheaper than SC V6.

GM should have saved the $$ on the 4300 V8 project and lightened the B/D carline 300-400 lbs!!!

Stoneage_Caddy
08-08-06, 08:39 PM
There was a 4.3 V8 around in the mid 70s....Suppose it was really THAT engine with a few update ?

I didnt realize tho that the 4.3 in the 90s caprice was really a v8 , i thought it was a 4.3v6 ....so does that mean that the el caminos and mote carlos in the 80s that had 4.3 badgeing really had a 4.3 v8 and not the 4.3 v6 ?

I~LUV~Caddys8792
08-08-06, 11:30 PM
so does that mean that the el caminos and mote carlos in the 80s that had 4.3 badgeing really had a 4.3 v8 and not the 4.3 v6 ?

Nope, that's the 262cid 4.3V6, good for 140hp or so. Not the 265cid V8.

Stoneage_Caddy
08-08-06, 11:33 PM
interesting ....well after more reading the 265 has been around off and on since 55 ....

but why they ran that in the caprice when they had 305s is really odd ...but that gives me yet another possible crankshaft and bore combo to build my modern 302 with

N0DIH
08-09-06, 12:26 AM
No, in 1975-76 there was a 262 V8 (not V6!) that was seen only in the Monza. It was a 3.5" bore 3.5" stroke or so. Tiny little thing...

Ran ok, but wasn't a powerhouse. But in a Monza, was pretty fun!

This 4300v8 shares more with the originial 265 V8 than any other small block.

Yes, you can make a 302 LT1 if you want... It has been done actually on the Impala SS forums.

90Brougham350
08-09-06, 03:30 PM
A 302 LT1? Jesus I bet that thing revs to the moon! What kind of power do they get from them?

Stoneage_Caddy
08-11-06, 05:27 PM
back in the trans am days in the late 60s i think they (302 powerd z28s) were around 600-700hp and were reving above 8k ...back when the displacemnt limit was 302 inches ....chrysler even had a berif run with a 340 based 302 ...then of coarse the 302 stangs .....

im not sure if AMC was running in trans am dureing the 302 days ...i think when they arrived with penske backing the displacembnt limit was raised to around 350 inches ....

N0DIH
08-11-06, 05:50 PM
Gotta admit, would love to see a 95 Z28 with a 302 LT1 spinning to 7000 rpm (limit of LT1 PCM...)