The Chevrolet LT1 thread

Hey all,

A fellow "Back 40" racer has told me I can have the LT1 engine (and presumably 700R4 transmission) out of a B-body (Caprice) that he brought out to play. It's got a blown head gasket (or so I assume from the water that pours out the exhaust pipe). It's not worth fixing for back 40 racing, but I see some serious potential there.

So, I figure I should jump on the opportunity and grab the engine. Just by the symptoms, it's going to need new bearings and gaskets and a teardown, clean, and reassemble.

I know the optispark and the water pump on these engines don't get along. This would be an iron head version since it's in a B-body. I hear the iron heads actually flow better than the aluminum ones...is this right?

I'll find something to put it in eventually, whether it be my Z28 (not likely), and '80s Malibu or Cutlass, '60s fullsize (Impala/Biscayne), or a truck.

Just wanted to get some conversation going about the strong and weak points of the engines as well as common upgrades and costs associated with the care and feeding of this engine. They seem to have had their 15 minutes of fame and are now overshadowed by the Gen III/IV engines (Was the LT1 the Gen II?). I gather they're still a very good engine though. I remember reading a lot about them several years back when I had my eyes on a Caprice/Impala for a daily driver.

Thanks all, Clem

I'm not sure the LT1 in the Caprice makes the same power as the Caprice in the Corvette/F-body. Someone please correct me if I'm wrong.

They jammed a caprice into an F-body?

Seriously pick up the new issue of Car Craft (gold barn-find 67 Z/28 on the cover. They go over the LT1 in depth. The LT1 was indeed GenII and yes the iron heads flow better. Optispark is still a problem and VERY expensive. The reverse-cooling works well until you over heat them. Expect to have to get a new crank, they go out of spec quickly. ECM tuning/MS is a must. The stock electronics have no idea what's going on when you do any mods.

Also, you'll need to check that it's actually a 5.7 LT1. Caprices could also come with some bizarre thing (4.8?) that looked identical on the outside and was a giant steaming pile of dog poo.

Yes, the LT1/4 are the Gen 2 SBCs. Internals are the same as first gen, just pick the correct crank. I'm not sure how good the iron heads are but I have seen Edelbrock and some other after market companies make heads. LT4 heads are also suposed to be a good upgrade.

But the biggest down side is that these engines only had a production run of, IIRC, 6 years('92-97?)

Also make 100% sure that it is an LT1 and not an L99, the 4.3 V8, wiki claims that they are 100% identicle on the out side. Just worth a heads up.

We have owned 2 caprice LT1's and amassed 500,000 + kms between the 2.

Optispark isn't an issue if you get a 96 vented unit. No need for an MSD unit. If it's from a Caprice, it won't be a 700R4, it will be a 4L60E and it's the weakest part of the package. In our first car the tranny was rebuilt with better servo's and a stronger gear carrier. The Carrier's can be swapped out for truck ones. Our second car is at 120,000 miles and I can tell the tranny is getting soft.

While caprices and Impala SS's are rated the same for power, the Impala has a electric fan , the caprice has a crank driven unit.

F-bodies got Aluminum heads...yes the iron ones flow better..but at the cost of weight. Vettes got 4 bolt main blocks. the rest are 2 bolt's.

Not much else to tell. With mild mods I was able to crack off high 14's in a 4600Lb wagon. Pretty drama free motors with lots of aftermarket. Things have really gotten cheap since the LS1 movement.

PS..the iron heads have to flow better for the weak cam they put in them. HUGE Hp gains come from changing the cam and an ECM flash.

I have seen a few people take the smaller 26? V8 and use the crank in the LT1 making a high winding 302 LT1... Hotrod had an article about it way back in the day

The one in question in my particular case is out of a 9C1 (cop) car complete with green silicone radiator hoses and such. I'm relatively sure I double checked the smog sticker to confirm the car was a true 5.7.

Thanks for all the info so far! I'm curious what's with the cranks on these engines...

Clem

According to Car Craft it's the thrust bearing and flange. The torque converter loads it pretty bad and that wipes it out.

I still have nightmares about my LT1 and the Optispark system, I thought I pushed those way back down deep into my memories, but they always come back!

maroon92 wrote: They jammed a caprice into an F-body?

A little lube, a shoehorn...

Damn. OK, you guys know I meant to say "the LT1 in the Corvette/F-body."

AutoXR wrote: I have seen a few people take the smaller 26? V8 and use the crank in the LT1 making a high winding 302 LT1... Hotrod had an article about it way back in the day

That motor coupled with ITB's and alot of anti-friction coatings is what I want for a Monster Miata motor. Something about the idea of 8 ITB's singing at 8k rpm with no top.......

Here's my take on them having owned several.

Opti's are not a problem. The "opti" part (optical trigger) is bulletproof, highly accurate, and wonderful. The "spark" part (cap and rotor) wear out like any cap and rotor would. All of mine are factory sealed GM opti's, the most of which has 130k on it. The cap and rotor are pretty iffy, but the optical part is still kicking. As someone mentioned, the 96-97 vented opti's are even more bulletproof. What kills them is the waterpump. The weep hole drips on it. As long as your pump isn't leaking (which is caused mostly by the cocktail of dexcool and clay tablets making a silicate jello and eating the packing) they'll last a long time.

If it had dexcool in it, flush, flush, and more flush. Then run green. GM has multiple lawsuits against the makers of Dexcool. Its satan's urine.

The LT1 is functionally almost identical to a 1-piece rear SBC roller block. Cranks, rods, pistons, rings, valve covers, starters, motor mounts, cams; many things interchange with little or no modification. Heads don't swap; they will physically bolt on, but the water passages don't line up. Intakes are different as well, although there are carb intakes sold for LT1s.

Your stock cam is 191/196 duration with .418/.430 lift and a 111 LSA. I used one in a Vortec boat engine and it gets that 3100 lb boat up out of the hole fast, but wimps out at 4800-5000. The stock iron heads do flow better. In fact, they flowed so well in 93 when they designed them, that they copied them exactly for use in the Vortec heads.

Functionally speaking, consider them to be just like a Vortec 350 as far as potential, but they have a great intake that can pretty easily support 450+ hp in as-cast form.

The LT4 is a nice upgrade, but its rare that the LT4 heads can be used with an LT1 intake due to higher ports on the LT4. The LT4's are also a bit on the large side for heavy street vehicles. With so many aftermarket options of LT1 heads, spending the money on LT4 stuff doesn't really make sense.

Go for it. I'm currently looking for one to build and can't find anything but wasted cores for $250-500, so if you can get one for free. Here are a couple things to get you started:

http://www.enginebuildermag.com/Article/2562/rebuilding_the_chevrolet_lt1_engine.aspx

Thanks for all the info Curtis. I'm reading throught that Engine Builder article now.

I'm curious. The 350s had a relatively hight compression ratio. However, they were supposedly able to get away with this due to the reverse cooling of the engine (heads first).

Can anyone confirm that these engines run fine on 87 octane swill?

Does anyone know a recipe for one of these engines to build a little more power than stock without a bunch of cash outlay? While I've got it apart, I might as well look at a few upgrades for durability and power.

Thanks, Clem

Here are a few links and info to consider:

Hate the Optispark? Here are a few options:

Remove the optispark, replace it with LS1 sensors, coil on plug

Delteq -- might be out of business??

Dynaspark -- billet Opti replacement

LTCC -- LT1 Coil Conversion

The above parts are related. Delteq and LTCC rely on the opti part of your optispark to provide a signal to external coil packs -- either LS1 style or Northstar style coilpacks. As some have said -- the Opti is good -- packaging the spark with it causes problems, made moreso by the possibility for leaking coolant.

I included the Dynaspark link for a really cool (cool and yet spendy at the same time) billet Opti trigger. You can use the Dynaspark to trigger the LTCC system.

I think I like the EFIConnection solution -- standard GM stuff that works on the LS motors, just adapted for the LT1!!!

Oh yeah -- if you want to go old school and run a dizzy on your LT motor, that can be done here

As far as the block goes -- standard tricks that are done to the Gen 1's work here (383 anyone??).

Cams -- there are a fair number of cams out there that will work. The LT4 Hot cam from GM is good.

Heads -- the LT4 heads are rare, more rare is the LT4 intake needed to match up to the heads, though Edelbrock is now making the intakes and have heads to match.

Check this guy out here. Very approachable, knowledgable, offers services to rework LT1 heads and provides cams to match.

I got a low miled (26k) LT1 motor and T56 trans for $2k. Motor and trans were verified working -- drove the car before they were pulled (owner was going big block/Lenco in his Camaro) -- been doing the research because the motor and trans are going in my TVR 2500M.

hth,

-jeff d

My 95 9c1 is fine with 87 oct. Why waste money on some thing it doesn't need? It is stock, however. I've always read that the GM HOT cam was a good, cheap way to bump up the ponies for cheap. Does GM still sell it?