Guest LT4Justin Posted September 4, 2002 Share Posted September 4, 2002 here's the basic situation, I have a carbed LT4 crate motor w/ hotcam that's going (back) in my 71... but with EFI instead. I'm not sure if I should just buy a complete motor, swap everything over, sell the leftover long block and go from there, or go with an aftermarket standalone ECM, painless wiring harness, and scrounge around the junkyards for the other stuff I'll need and buy them piecemeal... I more or less need: PCM wiring harness intake fuel rails injectors fuel pump fuel regulator Throttle Body Opti timing cover Coil ignition module sensors: Knock Coolant Fan IAC IAT TPS Oil Pressure MAF MAP Oxygen Crank Postion ...and all associated hosemongery as well as whatever you guys happen to think of that I'm missing. I know that in the end it'd be cheaper to buy a complete motor and sell off the leftovers, and that in the JTR manual it tells you for any EFI swaps to buy the motor complete approximately 100 times... but here's the thing... a LOT of those parts I'm not going to use if they come with the motor... here's the above list with any part that I would be replacing with new or aftermarket bits not in bold print PCM wiring harness....painless to avoid hundreds of dead end wires in engine bay intake............LT4 fuel rails injectors.........need more than the 24lb LT1 stockers fuel pressure regulator....will go with adjustable aftermarket one Throttle Body.....will go with bigger than stock 48mm Opti..............will get new one timing cover Coil..............new ignition module Also, in the somewhat-distant future the motor will more than likely be built enough that retaining the stock PCM and tuning with it will be a PITA. Basically JTR says one thing, my brain says another, and my gut tells me I need a beer. Send any kernels of knowledge this way that you guys can give me to sway me one way or the other. Quote Link to comment Share on other sites More sharing options...
biohzrd Posted September 4, 2002 Share Posted September 4, 2002 sounds like to me the easiest "maybe not the cheapest" would be to find a donor car. i'm not sure if you know it or not but the only differance between the lt1 and the lt4 is the port height on the intake side. you could very easily port out a lt1 to flow as good as the lt4. if you go this route you could always find complete lt1 engines with sensors and wiring harness for under a grand. a buddy of mine can get complete lt1's with a t56 for $1400. the lt4s only came in vettes and are few and far between. as far as a computer goes you can get one for a 93/94 model camaro for around a hundred bucks. they can be reprogrammed pretty easy wihtout much money. for injectors look in jegs and order the ford svo 30lbers for aroun $200. they will work on ford and chevy and are alot cheaper then accel or another aftermarket brand. i've seen them handle up close to 500hp with no problems. just get an adjustable fuel regulator and turn it up to about 50 to 55 lbs. Quote Link to comment Share on other sites More sharing options...
Guest LT4Justin Posted September 4, 2002 Share Posted September 4, 2002 It's always been my understanding that in addition to having larger intake ports, the LT4 ports were farther up in the head then the LT1's... meaning that although a ported LT1 intake would flow just as well, air flowing through the bottom of the runner would hit an aluminum wall. In any case, LT4 intakes are easily picked up for like $150 so that's not a huge deal. And yeah... FMS 30lbers and either an accel or hypertech adjustable fuel pressure regulator are the plan.. LT4's originally came with 28lb injectors I believe, so 30's should be just fine... and lots cheaper than OEM's. As far as reprogramming goes, well... my buddy spent the last few months trying to iron out the programming bugs on the D1 ATI procharged 383 in his 94 Z28 (and still had more to go before he broke the snout off his crank saturday)... if and when I redo my motor, I may destroke it to a 302 and make it an 8 grand screamer... the problem with the stock PCM being it doesn't have fuel maps past 7000. But maybe I'm just thinking too far ahead Other things I just remembered: I'll be going with a granatelli MAF (meaning another stock part I won't be using), and if I want to keep the fuel lines on the passenger side of the motor I'll need a corvette fuel rail as the F-body inlet is on the driver side. Quote Link to comment Share on other sites More sharing options...
zgeezer Posted September 6, 2002 Share Posted September 6, 2002 If you have GMPP carbed LT4, then you have a distributor in the back and your "Opti" unit is blocked off with a plate. If you keep that distributer you can run any number of after market stand alone systems (SDS, comes to mind as do Holley and Accell). Your problems would be the FI intake, which has no provision for the rear mounted distributer. Take a gander at this web site: "LT1INTAKE.COM". He will modify your LT1/4 fi intake manifold to accept the rear mounted distributer. As far as wiring a stock lt1 control unit, consider Ron Francis's Wire Works. A bit pricy (aren't they all), but its a well done unit and it works. GW Quote Link to comment Share on other sites More sharing options...
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