Dave Sigman

ok you can swap an LT1 cam and manifold onto the older smallblock without a hassle. so if I want to use my small cap hei when I do my swap it should work with the proper modifications made to the lt1 manifold. I'm asking becuase in this configuration it removes the very unreliable optispark from the equasion and just uses it to spin the water pump.

any info appreciated

thanks

pasky

I've seen someone use a traditional HEI distributor on the back of a LT1, but I think he went carb, kind of defeats the purpose unless you just want the reverse cooling.

LT1guy

iTrader: (1)

I have seen this done a few times, and not just on carbed LT1s. The Optispark supposedly doesn't deal with high RPM too well (over 7000RPM), and will come apart (the rotor is the culprit I think) after repeated use. If you were planning an LT1 swap using a FAST or DFI setup, eliminating the Opti for a regular distributor would be pretty easy. It would also be an easy way to swap an LT1 in place of a TPI, retaining the original TPI harness and computer; the TPI harness could be modified a little to accomodate some of the different sensors. Not sure how well this would work, but it could be done. I'd probably just do the coil pack conversion instead for most swaps, though, and remove the Opti's rotor to prevent any damage to the optical trigger.

Dave Sigman

thanks for the info sounds like I might be able to pull it off.

ShiftyCapone

iTrader: (7)

You may want to look at the opti direct. It is a true distributor-less ignition with multi coils. It eliminates the downfalls of the opti can supply a full spark past 4k where single coils typically can't rebound.

f-crazy

iTrader: (-1)

im running a carbed LT1 and yea yea defeats the purpose reverse cooled=more aggressive timing curve (mine is 36 degrees all in by 2,400)..but anyway, talk to john millican he converts LT1 intakes to run a rear mount dist....and also the opti has nothing to do with the water pump (other then a failed WP will fubar the opti)...the WP is drivin off the cam gear...

pasky

I am not one who advocates fuel injection is better although I will say if you have the fuel injection setup, why toss it away to throw a carb on it.

Dave Sigman

I want to keep the efi but I'd like to use the regular distributor so I can use the stock electronics and harnesses. its kind of a budget project and scince I can get an Lt1 for around the same price as a tuneport used if it'll convert reasonably I'l use it. your saying I can totaly remove the optispark and still retain the cam driven waterpump?

I've worked on lots of 3rd and 4th gens but I've never attempted to blend the motors together before.

FSTFBDY

iTrader: (33)

This is what Im gona run.

http://elitesparkplugs.com/Projectcars.html

f-crazy

iTrader: (-1)

On the end of an LT1 cam there is a dowel pin that is a half inch long..that is what drives the opti...on the back of the cam gear for the timing set there is another gear on the back of it that connects with a drive stub that turns the water pump...im running a carbed LT1 with a rear mount dist...the WP drive gear has nothing to do with it.....i would of went with EFI but i only had the shortblock and LT4 heads...and it was about a grand cheaper then the EFI setup...

Dave Sigman

ok I got it both drive off the cam but in different places

this sounds like its pretty easy to do then

thanks for all the replies

f-crazy

iTrader: (-1)

exactly...the hardest part would be drilling the LT1 intake...but you dont have to do that yourself...go to www.LT1intake.com

Dave Sigman

I was def planning on sending the manifols out to have that part done. its not real expensive and he does good work

LT1guy

iTrader: (1)

On a related note, if you want to go to an electric water pump conversion (both Meziere and CSI make one), you can replace the LT1's single row timing set with an 87-up double row set for a standard SBC (cheaper and stronger). Just unbolt the waterpump drive gear's retainer plate (held on by two torx screws, same as the cam retainer), and tap it out from the rear. I'm doing this on an LT1 I'm building for Redraif.

Traderartie

I'm currently running a small hei on my LT1... I did the machining myself. I dont have all the bugs out of it yet, but I'm really close. I'm using the LT1 PCM right now, but I plan to convert back to the TPI computer, because I cant get it to run right. It runs OK, But it doesnt idle smooth or start easily... I goes like hell though when I step on it. I plan on trying the TPI computer over the winter... I would do it now, but I'm in the middle of moving.

Z28ricer

iTrader: (2)

Yes we all know how badly the optispark is needed to be thrown out, especially on the thousands of 7k + rpm LT1 cars out there.....

Why does it seem like everyone makes a problem out of nothing, and then others come up with extra useless excuses to back the previous people ?

pasky

The optispark system itself is actually quite effecient and there is nothing wrong with it, the problem is its placement leaves a lot to be desired. For one, its directly under the waterpump, and if the waterpump weep hole begins to leak, you got coolant in your opti and in order to take it off you have to take off quite a few things on the front end which really doesn't take very long, but its a big pain in the neck to have to change your coolant everytime you wanna replace the cap and rotor, not to mention a cap and rotor runs for $140. I really want a delteq system which eliminates the cap and rotor from the optispark but leaves the optical sensor intact, but I just put a brand new opti on it over the summer, maybe next time it needs replacing i'll do that.

Dave Sigman

I'm just looking for cheaper and eaiser maintenece and I want to use my stock electronics.

if I had a 4th gen I'd leave it alone but I don't.

I also rather do a tune up for 40 dollars instead of 200 dollars


the main reason I'm swapping to an Lt1 at all is that they are just easier to find right now used with low miles.

I'm not trying to build a race car just nice reliable weekend driver to cruise around in.

Z28ricer

iTrader: (2)

Typically a tune up on an LT1 doesnt include the opti cap and rotor, though i suppose if you really wanted to replace it every few K you could so you want to use your stock electronics, eliminate two of the best parts of the LT1 swap, and be forced to get rid of the added mileage of egr. Oh you say you dont want to do the wiring changes ? ok but then add in the additonal costs of having the intake modified for a distributor, hours of chip burning time, and having to burn a new chip to get the most out of each little mod you add.

Sometimes i just dont get it....

Dave Sigman

ah I've left some things out.

I have access to a chip burner and reasonable dyno time.

I can sell the opti spark for more than what it costs to have the manifold machined

if I ever want it back to stock (restored) an uncut wiring harness would make it easier to put the 305 roller motor back in.

its a 90 GTA and my understanding is that they are kind of hard to find so I want to leave it as stock as possible but still use a better engine.

maybe the way I want to do it doesn't make sense to you but the closer to plug an play it is. Even if I have to make a new chip the easier it is for me to work on and enjoy.

LT1guy

iTrader: (1)

You obviously didn't read (or comprehend) my reply. It is well known that the Opti limits power in high RPM applications, and significant gains can be seen when replacing it. Increased reliability is just a bonus (yes, reliability is an issue with the Opti, and it has little to do with the cap or rotor). If you have a stock LT1, there may be no advantage other than increased reliability, but in Dave's situation it sounds like a good idea. And BTW, 7000 rpm capable LT1s are not that unusual, even on the street.

"Hey, lets make a moisture-sensitive POS distributor, and put it down low on the car and behind the water pump, so that it will be more prone to fail". GM service departments love the Opti, for the same reason I hate it. Its expensive, virtually unservicable (internally; you can get a cap and rotor, but thats about it), and likely the worst ignition part GM has put on a car in recent history. Why GM couldn't have equipped the LT1 with coil packs (available on other applications as far back as 1985 or so) from the beginning, I have no idea, other than increased income for their parts and service departments.

Z28ricer

iTrader: (2)

So please tell me, just for reference, and others information here, what RPM will the stock LT1 PCM support ?

This should be good, and i dont mean what can it spin to using set tables, actual capability controlling the motor using inputs....

The system can easily be modified for coil packs, several setups are already out, goodness, yes quick start drilling and hacking, not to mention going back to a computer that typically wont work as well for most around here.

LT1guy

iTrader: (1)

I think you are reading too much into my reply, and again, not reading what I actually said. Chill out. For one, the cars I was referring to are running something aftermarket for engine management, such as FAST or DFI, not the stock computer. You are ASSuming too much, and making an a** of yourself. Obviously your typical LT1 owner would replace the Opti with one of the readily available coil pack setups...that is what I would do, if running the stock computer. I'm not recommending hacking anything, only answering the guy's question. Is it possible to do what he asked? Yes. Is it the best way to go? Probably not. Thats a decision for the car owner, not me or you.

tamatt27

MSd is coming out with a cap and rotor for the LT1 within the next few months. We'll see if that does any better than stock.

Dave Sigman

I'm sure the coil pack setup works much better, but thats not what I want. when its finished it should run just like a regular old small block with the benifit of reverse flow cooling and the Lt1's more aggressive cam profile.

remember I'm looking for "fun to drive" not "dragstrip terror"

theres lots of good info in this thread I really appreciate all the replies

z92maroman

Dave, this is exactly what I'm doing. I also have a problem w/the reliability of the opti, and since I'm swapping an LT1 into my '92, Ive decided to go w/dfiVII on a modified intake. John @ lt1intake.com said he will do this portion of the mod and include EGR block off plates for $100! I have neither the tools nor the expertise to use the tpi computer, chip burning, etc., and feel I'll be well served by the Accel tunability, but there is nothing wrong w/your idea.(in MY humble(but always correct) opinion))

TexasLT1

7000 rpm

KiLLJ0Y

readingin GM High Performance mag a few months ago, they were comparing the new aftermarket coil system that some one here linked, to the opti-spark.

the opti- spark is actually only good to 4300 RPM, after that it is less and very inifective for timing. i'll try and find the exact month it is in, but it was a very good article.

Z28ricer

iTrader: (2)

So every distributor around must be as ineffective......

ljnowell

Stock, yes, kinda. I have had engines that spun easily to 7k, with stock HEI. Stock down to the coil and module. However, when upgraded, with a good coil, module, MSD box, etc., I saw fantastic gains. I would say that most stock systems, most, dont operate at 100% efficiency above 5000RPM. They still work above that point, just in diminishing percentages.