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Old 06-19-2013, 01:13 AM
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TBI to LT1 swap help

I have a 91 caprice 305 tbi and I want to swap it for a 350 lt1. I need some info on the swap but here is what info I think I have right as of now.

If I get a lt1 out of a caprice with the harness, fuel pump, and pcm I should be able to bolt it in plug it up and run?

Is their anything else I will need will it be a bolt and go or am I missing something?

I would also like to add a small camshaft for more sound but not losing a lot of MPG. Is their a good cam that will work with the pcm and I will also be putting the headers off my 305 on the lt1 if they work.

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Old 06-19-2013, 01:30 AM
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gauge cluster, trans(if different 4l60 or 4l65), trans buffer if equipt.
if you plan on use'n the factory ecu.
different cooling system (reversed cooled)
change fuel tank and pump and filter as the lt1 runs at 60psi the tbi 15-18
basicly have the whole donor aval.
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Old 06-19-2013, 08:09 AM
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It's easy enough to do, but fairly expensive. A decent running, driving donor car is 'gonna cost about 2,500 to 3,000 dollars and then you've got 2 full days of switching everything out. You've got to really like your car to make it all worthwhile dollarwise. I have a couple of '95 Impalas that I've got a ton of money in that I'll never get back....but I enjoy them.
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Old 06-19-2013, 09:21 AM
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Quote:
Originally Posted by mafiacustomz View Post
I have a 91 caprice 305 tbi and I want to swap it for a 350 lt1. I need some info on the swap but here is what info I think I have right as of now.

If I get a lt1 out of a caprice with the harness, fuel pump, and pcm I should be able to bolt it in plug it up and run?

Is their anything else I will need will it be a bolt and go or am I missing something?

I would also like to add a small camshaft for more sound but not losing a lot of MPG. Is their a good cam that will work with the pcm and I will also be putting the headers off my 305 on the lt1 if they work.
An alternative would be to convert the LT1 to the TBI. Although a little complex this is a lot simpler than converting the chassis to run the LT1 engine.

To do this you will need the GMPP carb intake for the LT1 p/n 24502592. You will need a TBI to spreadbore 4 bbl adapter plate or fab one yourself. You will use the TBI distributor you have that just drops in. The GM intake comes as a kit which includes the plug for removal of the LT1 Opti-Spark. EGR is the bigger headache as the GMPP intake has no EGR provision. Edlebrock sells an adapter intended to move the SBC EGR valve p/n 1476. While not directly solving the problem, with a flat aluminum plate to offer a gas tight mount and some tubing from a header tube and some more to a hole you make in the carb to TBI adapter plate a suitable EGR system can be fabricated for less than a hundred bucks. The LT1 cam is actually pretty similar to the 305 TBI passenger car cam though having more resembalance to the 300 horse 327 cam it has a wide LSA which holds the idle vaccum up which is highly likely to let you get away without having to replace the chip in the TBI computer.

Without changing the TBI to a 454 Rochester (1-7/8ths throttle bore) or a 670 CFM Holley (2 inch thorttle bore) either with 80 pound injectors will let the engine devleop its rated power. Using your original TBI (1-5/8ths throttle bore) will limit engine power to about 240 hp with the stock 60 pound injectors. This is a fueling and air flow limit of the 305 and 350 production TBI. The larger 454 engine's TBI or the Holley 670 cfm with 80 pound injectors will let you push to 320 hp which is about the LT1's rated output.

Bogie
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Old 06-19-2013, 09:24 AM
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You COULD feed that iron headed LT1 with the stock ECM with a recalibrated chip in it. Grab a GMPP carb/LT1 p/n 24502592. This intake can boost torque over the short runner LT1 intake with its longer runners.
http://www.summitracing.com/parts/NAL-24502592/

Then just run your stock distributer, as IIRC your stock 305 should have a roller am in it already.

Then you'd have to worry about cooling and front accessories.

The iron headed LT1 5.7 AND the 4.3 Vee-Eight-L99 both run the Vortec 305/350 191║/196║ duration, 0.412"/0.428" on a 111║LSA.

The 203║/210║ 0.476"/0.480" on a 115║LSA.(with a 1.6:1 ratio) cam from the LT4 would work nicely. I know of a Vortec 350 with the LT4 cam that is TBI injected that works very well, and is nice on fuel.

In all honesty, you would have the same outcome if you got a good Vortec 350, and either use the Vortec/TBI intake, or run a Performer RPM Vortec intake with your TBI on top. That would be the easiest swap.
12496821

The iron LT1 heads and the iron Vortec L31 heads share port design and have a small advantage over the LT1 alum heads.

peace
Hog
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Old 06-19-2013, 04:58 PM
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I would like to get a whole car froma junk yard and strip all the parts I need. I don't know what a junk yard car will cost and I don't want to go carb.

I can get a 350 with dart goodies 650 double pumper but I would never be able to drive it.

I know I need a lot of parts im not going to buy a running driving lt1 caprice don't want to destroy a good car.
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Old 06-19-2013, 07:21 PM
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Why couldn't you drive a 350 with dart heads and a carb? An LT1 is a good engine but it's not miraculous. If you're going to swap everything just go LS.
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Old 06-19-2013, 07:57 PM
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Hell ya send me the money for a ls motor pcm wiring harness to fit a caprice classic 5-8k should do LOL.

I would love to go to a ls base motor but their very high at this point 1200+ for a 5.3l ls base motor with out harness pcm and a wiring harness to make it work in a caprice.

I want a LT1 because their not to high prices and can get them with the harness and pcm for about $4-$500 and another $200 for everything else junk yard price.

I cant run the 350 with dart heads and carb because its a show car not a race car. I have to drive it from car show 2 car show. The dart 350 would be like 8-9 mpg. I was told it was build for racing huge camshaft, dart heads, and 650 double pumper.

I was thinking of running some of the numbers off the motor see what heads and see if I can sell it for more thin 450.
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Old 06-19-2013, 09:41 PM
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If someone knows the math 350 650 double pump with duals, 700r4 with monster rebuild vette servo, and the stock 2.56 gear ratio.

What about would my mpg be I know their isn't realy a lot of motor info but that's all I know.
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Old 06-19-2013, 10:01 PM
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Quote:
Originally Posted by mafiacustomz View Post
Hell ya send me the money for a ls motor pcm wiring harness to fit a caprice classic 5-8k should do LOL.

I would love to go to a ls base motor but their very high at this point 1200+ for a 5.3l ls base motor with out harness pcm and a wiring harness to make it work in a caprice.

I want a LT1 because their not to high prices and can get them with the harness and pcm for about $4-$500 and another $200 for everything else junk yard price.

I cant run the 350 with dart heads and carb because its a show car not a race car. I have to drive it from car show 2 car show. The dart 350 would be like 8-9 mpg. I was told it was build for racing huge camshaft, dart heads, and 650 double pumper.

I was thinking of running some of the numbers off the motor see what heads and see if I can sell it for more thin 450.
5.3 ls 50k 500-800 bucks, holley hp ecu to run it 1000-1200 or msII or III 400-800 harness comes with engine. still need fuel pump change, but a stand alone efi unit would be cheaper in the end. same with the lt1, only the lt1 is a not supported engine, mostly. I'd go ls if I was swap'n up engine family generations. more power, longer life, better mpg
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Old 06-20-2013, 06:55 AM
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Quote:
Originally Posted by gearheadslife View Post
5.3 ls 50k 500-800 bucks, holley hp ecu to run it 1000-1200 or msII or III 400-800 harness comes with engine. still need fuel pump change, but a stand alone efi unit would be cheaper in the end. same with the lt1, only the lt1 is a not supported engine, mostly. I'd go ls if I was swap'n up engine family generations. more power, longer life, better mpg
Thanks do saving me the effort of writing that. Would like to add that if you go lt1 I would still go with megasquirt and do an edis conversion.
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