muddyjimmy

iTrader: (2)

A buddy of mine just bought a 91 RS with the 305 TBI and auto trans. The car has a rod knock and needs a new engine. He is not looking for all out performance but just a nice street car that will pull in the 13s at the track. At first he was throwing around the idea of the vortec head, LT1 cam 355 with all the supporting mods. We also have a 1996 Complete LT1 without the harness or ecm. I have found carb intakes for the LT1 and figured running a 670 TBI with adapter plate. I thought that going this route would be the best option because he already has the LT1 and does not have the vortec heads or roller cam block. Has anyone done something like this? What would be the options for removing the Opti-spark and replacing the timing cover? Anything else I am not thinking about? I have all the chip burning tools and software and I know that it will have to be done to run right. Let me know what you think.

KrisW

iTrader: (5)

I think if you strip your block and use your 305 stuff, you will be okay. Your LT1 had reverse cooling as well, right? If you're switching to a carb intake then you can sell your LT1 intake here to re-coup some cash. You still have to modify the heads to flow in a normal cooling system though (I think...) so you may want to look for those vortecs or some good LG4 heads or whatever.

Anything is possible but I think I would treat it as a 350 short block and sell all of the LT1 stuff off of it as a package. Then, continue on...

FreeLoader

this...is an extremely involved undertaking. you're talking about two VERY different blocks there.

there's an LTx swap board on the main forums, they can probably give you better answers if you can't find them here.

I just...there's a 30 hp difference between most tpi 350's and most lt1 350's, wheras the price difference for parts, the difference in work..it's just insanity. I wouldn't do it, personally.

muddyjimmy

iTrader: (2)

I know that there is a difference in the blocks, heads, and intake. I know all the detailed differences between the lsx, ltx, and Generation 1 small blocks. I am well trained in most things automotive as I am full time mechanic. I can usually wire up almost anything as I have a 75 K5 with TPI and have installed a 1996 OBD2 LT1 in a 79 Monte Calo. I am not talking about bolting LT1 heads to a older gen 1 small block or vice versa. I have read the sticky in at the top of the TBI section and was thinking since I already have a LT1 block with cast iron heads (which is what the 96 and up Vortec heads were designed after) why not just buy a carb intake and run a TBI adapter and 670 TBI. I know that the engine bolts in the car just fine (except for the F body and B body A/C compressor) with little modifications here and there. I thought this question was more related to TBI rather than engine swap because I am more intersted in trying to see if anyone has done this before. The issue here is my buddy does not have a 350 block or Vortec heads so he is starting from scratch. Where as the LT1 block (which has the LT1 roller cam everyone is running) and heads are already there the just need a rebuild. Would I be leaving anything on the table going this route? Would the gen1 approch leave me with better options down the road? I would always be able to switch it back over to MPI later if he wants to. What does everyone think?

Fast355

iTrader: (2)

I say DO IT. Ebay houses alot of 454 TBI units with the Factory 454 TBI-Carb intake adapters. GMPP makes an intake that bolts a regular old spreadbore carb and rear mount distributer to a LT1. Drop the 454 TBI unit and adapter on the carb intake and mount the TBI distributer. Install the CTS in the water pump and go. I even happen to have a .BIN that might get you up and running. (LT1 cammed Vortec 350)

muddyjimmy

iTrader: (2)

Thanks Fast I was hoping you would chime in and say Go for it or I was off my rocker. I might be getting a hold of you for that .BIN when I get closer.

FreeLoader

would the cam even line up with a dropped in distributor?

I was under the impression that the cam was reversed as the distributor was in front of the engine as opposed to the back, are we talking a simple remove/grind/reverse to the cam, would that even work? am I missing some important piece of information?

what about the reverse flow cooling? would you find some way to hook up a mechanical(and traditional) flow pump to it? would you get some flexable hose to hook up the stock radiator to it? would you take an lt1 radiator and stick it in the car?

the power steering setup is different, and the reservoir is seperate, so you'd have to bolt it somewhere.

the a/c is an issue...though you already know that.

also, you have to notch the k-member if I remember correctly in order to drop it in...don't you?

not to mention a fairly involved amount of rewiring...this, more than anything, is what would keep me away from the swap, personally.

hey, do it. I hope it works...in fact I'm sure it could. it just sounds really involved. in fact, if you don't mind, keep us updated. I'd like to know in detail how exactly you'd do this swap.

Fast355

iTrader: (2)

The distributer is driven off of the camshaft through a long dowl pin that runs into the front of the cam, through the timing gear. The water pump is gear driven of the camshaft timing sprocket. The gear on the cam is still there on the LT1 engine as it still has to drive the oil pump through the short little stub shaft.

No need to switch out the water pump, just use the hoses for a LT1 F-car and the stock 3rd gen radiator will hook up fine.

Use the pump from the the LT1 car with your existing hoses, just route the return hose with some power steering return hose from a parts house.

You only have to notch the K-member if you want to use the low mount style B/F car A/C compressor on the 3rd gen. If you ditch the low mount compressor, you can remove its mounting bracket. The mounting bracket is bolted to the traditional small block mount. Remove the A/C and the bracket and your stock TBI motor mount pads will bolt right up to the LT1 in the correct location.


ABSOLUTELY NO RE-wiring will be needed outside of relocating the Coolant Temperature Sensor connection from the front of the TBI intake manifold to the LT1s water pump.

I built a LT1 TBI engine for a 1995 C1500 about 2 years ago. It was a cast-iron head engine with a F-Car LT1camshaft in it. We used the GMPP intake manifold and a 2" bore 454 TBI unit with the factory GM Q-Jet-TBI adapter. We retained the stock C1500s TBI distributer. The truck kept its stock exhaust manifolds and stock air cleaner assembly. I reprogrammed the PCM to re-calibrate the fuel delivery and the timing to match the engine, cam, and 90# 454 injectors. The truck felt like it had about 2x the power of a stock TBI truck above 4,000 rpm. I used the Corvette high mount accessories and the LT1 bolted right in. You have to switch the harmonic balancer/crank pulley to the LT1/LT4 corvette unit though.

FreeLoader

the sd tbi setup will plug into the lt1 maf pcm?

and what about the transmission? if you wanted to do this to an auto(700r4), would the plugin for the OD connect to the pcm, or would you have to set it up to run off of vaccum?

also, if I remember correctly, the corvette high mount accessories is like 300+ bucks alone, wouldn't it be cheaper/easier to just notch the k-member?

Fast355

iTrader: (2)

I think you are confused here. If, "I" were doing the swap, the LT1s factory intake would hit the scrap pile. I would use the GMPP carb LT1 intake manifold. I would then install the TBI setup from the existing engine.

The transmission will bolt right up to the LT1 and function just like your TBI engine that was previously in there.

You could notch the frame, but IMO it is a pain in the ***.

kdrolt

No it wouldn't. You'd sell it to a TPI owner. <g>

muddyjimmy

iTrader: (2)

I will still be using the original transimssion, computer, harness, and sensors. So that will not be a problem at all. I have done two complete LT1 swaps and they are pretty simple. One in a third gen with a T56 and the other in a 79 Monte Carlo with the 4l60e. I am planning on running the GMPP LT1 carb intake and most likley the belt setup off the B-body car and just talk the guy out of running a/c. The power steering is no big deal at all just mount the remote resivoir and get a new pressure line made up with the correct fittings. Local guy does it here for like $25.00. Thuy guy I will be building it for just wants a 13 sec street car that he can cruise around in and take to the track once a month. Thanks for the help and I will let evryone know how it runs when I am done with the car.

FreeLoader

actually, that's the part I was confused about.

I assumed he was going to keep the pcm(which I forgot, he doesn't have), and trash the ecm. but he's keeping the ecm, and now everything makes more sense.

the only part I was really confused about was whether or not the rest of the engines sensors would hook up to the older tbi ecm and wiring harness...I guess they do.

sorry for hijacking your thread, muddyjimmy.

oh, and just to make sure it's mentioned, two other things worth mentioning:

1. fuel. the holley 670 comes with 65 lb injectors I believe, and even with stock 275hp(and that's a low end lt1), you'd still need something like 18-20 psi to run the motor properly. the stock pump may or may not be able to handle that. I could be wrong but I believe I got the formula right.

2. exhaust. if I remember correctly(I might be wrong), the stock lt1 manifolds have a 3 bolt setup where the thirdgen y-pipes have a 2 bolt setup. I'm not sure what you're going to do with the exhaust, there's a hundred ways around it, it's no big deal, I just thought I'd mention it.

muddyjimmy

iTrader: (2)

I will be using the all the TBI harness, sensors, and ecm. Its just like doing a regular 350 swap with a few added mods because it is the LT1 block, heads, and accesories. The fuel pum will be replaced with a higher flow unit to keep up with the demands of the engine. The car will have headers with a custom y-pipe to make it all line up with a 3" cat back system. Right now I have him looking around for all the right parts to get the car together so as soon as he does its go time.

Dont worry about hijacking its all about learing new things. So ask away.
I was more worried about if I was going to be putting together an engine this way would leave my buddy wishing we would have done it differently. Just tryin to get it done on a his buget and get the most for his money.

graebz28

iTrader: (5)

Is there a way to reuse the stock accessories from a LO3? Not sure if the bolts exist on the LT1 heads to reuse the serpentine or if you could drill and tap it yourself. I know you could not use the water pump, but you could use the LT1 pump or get Summit's electric pump for 160.

muddyjimmy

iTrader: (2)

I dont think that you would be able to use the tbi accesssories because of fitment issues. I havent tried to see where everything would line up but I would bet LT1 acc would be better if you could get ahold of them cheap enough.

gmk257

I'm sorry to come back to such an old thread, but I'm working on the same type of swap in an '89 C1500 pickup. I need to stay emissions-legal, though. The GMPP intake is quite tempting but I don't see how to get EGR or throttle-throttle-plate warming to it. Any ideas?