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Old 05-15-2008, 10:57 PM
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LT1 questions

I have a friend lookin to buy a LT1 outta z28 camaro. He's wantinto put it in a 280zx datsun. The LT doesnt have the computer or the harness with it. Should he try to find another harness and computer for it or what would be best to do? He wont listen to me when I give him ideas on what to do so I told him I'd ask some ppl who know what they're doin. Thanks.
-Justin

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Old 05-15-2008, 11:19 PM
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My first reaction to your post is to retain the EFI with whatever wiring/ECM he needs to obtain. EFI, in my opinion, is worlds better than changing the whole mess to carburetion.

My reasoning is this: I make it a policy to never build anything until I figure out how I'm going to be able to sell it. There will be many more interested buyers for an injected swap than there will be for a carbureted LT1.

And I don't want to hear...."I'll never sell it". I can guarantee that life changes that attitude and there will come a day when he will want to turn that old iron into cash.
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Old 05-16-2008, 12:44 AM
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I recommend keeping the EFI and stock computer. One of the design factors of the LT1 is a relatively high CR that is carefully controlled by fuel trim and (more importantly) a knock sensor that retards timing. It allows the LT1 to run 10.25:1 compression on iron heads or 10.75:1 on aluminum heads with a mild cam and lets it sip 87 octane all day. If you switch to a carb you're looking at no power benefits, but a definite switch to at least 93 octane will be required.
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Old 05-16-2008, 05:04 AM
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He's only givin $550 for the thing but it dont have the harness or computer. Dude's done sold those. He looked up a harness for it and its pricy! Almost 1200 bucks. Computer wont be a problem findin. We need help, ideas on what to do to get as much HP as we can get outta this thing. Cams, heads, intakes, chargers, whatever. I know its vague right now but I'll post numbers and specs bout it later today.
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Old 05-16-2008, 08:55 AM
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If you are looking for max Hp with the smallest investment than switch it over to carb, if you put a lumpy cam in there the computer will try to retard the timing so far that the thing won't even run.

With a big cam the computer will think the motor is Knocking and retard the timing to prevent detonation.

I would take that 550 bucks and put it towards something else. Like pistons and rods for a regular 350, you will end up changing everything else on that LT1 anyways so why start there?
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Old 05-16-2008, 01:02 PM
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Quote:
Originally Posted by Double_v23
If you are looking for max Hp with the smallest investment than switch it over to carb, if you put a lumpy cam in there the computer will try to retard the timing so far that the thing won't even run.

With a big cam the computer will think the motor is Knocking and retard the timing to prevent detonation.

I would take that 550 bucks and put it towards something else. Like pistons and rods for a regular 350, you will end up changing everything else on that LT1 anyways so why start there?
This approach is completely unnecessary. Many people are afraid of EFI and scrap it as soon as they can. He should keep it in the stock EFI configuration. I know people running solid roller cams with 250@.050 on the stock re-tuned PCM. With proper tuning this isn't an issue.
The LT1 in my 95 Camaro dd is not stock. It has a small (by most peoples standards) cam with 1.6 roller rockers. It runs very well, gets good mileage and the driveability is great.
Check F body forums to find the PCM and harness. They are plentiful and reasonably priced.
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Old 05-16-2008, 01:59 PM
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EFI is more trouble than they are worth to the average Joe doing a small block swap.

I agree that EFI is better on pretty much every level, and have used it myself.

But think about this.. there is no computer or wiring harness to start with from the original or the project vehicle. I am sure it is missing the intake ducting with the appropriate sensors, and they probably don't have the electrical engineering degree it would take to make the appropriate harness and program the computer.

A carb in this application would be cheaper, faster, and only slightly less powerful than a well tuned (not stock) EFI. Parts are easier to find and tuning will be easier and not requiere a lap top.
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Old 05-17-2008, 12:18 AM
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It has everything but the harness. All sensors are there. Can you put a distributor on the LT? He just pulled the intake off and there was a plate coverin a hole where one would go.
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Old 05-17-2008, 12:45 AM
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Quote:
Originally Posted by 350_88S10
It has everything but the harness. All sensors are there. Can you put a distributor on the LT? He just pulled the intake off and there was a plate coverin a hole where one would go.
Yes on the Distributor.
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Old 05-17-2008, 01:28 AM
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Ok thanks. That just made things a whole lot simpler. Whats a good intake to use? Carb? We plan on have somewhere round 4-500 HP. I forgot to get the numbers so I'll get them first thing tm. On the back of the block it says GM 5.7L SGI. I think SCI maybe. S somethin I. What does that mean?
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Old 05-17-2008, 02:26 AM
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Not sure about the SCI. I'm no LT1 expert. Check this post for some info. Also the site below should be able to answer the intake question.
Vortec heads on LT1

http://www.lt1intake.com/services.htm
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Old 05-17-2008, 02:53 AM
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Its SGI. We were just wonderin what that means.
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Old 05-17-2008, 05:30 AM
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Quote:
Originally Posted by Double_v23
If you are looking for max Hp with the smallest investment than switch it over to carb, if you put a lumpy cam in there the computer will try to retard the timing so far that the thing won't even run.

With a big cam the computer will think the motor is Knocking and retard the timing to prevent detonation.

I would take that 550 bucks and put it towards something else. Like pistons and rods for a regular 350, you will end up changing everything else on that LT1 anyways so why start there?
I disagree... with many EFIs that is the case, but the MAF system on LT1s is pretty intuitive. I know guys running 434 LT1s with crazy cams; in the 260+ intake duration (and that's @50, not advertised) turning in mid 9's on their timeslips on a factory LT1 computer. The flash-based tuning is a breeze to alter, and almost every single aspect of the tune can be changed.

I'll be running a 383 LT1 in my 96 Impala SS with a 222/230 cam with a tight 112 LSA, headers, fully ported heads, ported intake, a 58mm TB, 30 lb injectors, upgraded fuel pump, and 11:1 compression. Not only can I tune the computer in about 5 minutes, it will pass strict OBD2 emissions in Los Angeles which does three sniffer tests AND plug-in with computer diagnosis. I know this because I've known about a dozen guys who have done it with this exact combination.

I'll be putting nearly 400 hp to the ground with a little lump to the idle and it will pass smog with flying colors. It sounds like a big deal, but in truth its a remarkably mild build compared to what some guys have done with theirs. Cruise around some of the Impala SS forums and see how some of the folks are tuning their LT1s.

Hit a junkyard. Buy the computer for $50 and the wiring harness for $100 more. Get on the internet and find a wiring diagram. Plug, play, drive.

I'm no master tuner for EFI, but I would rather keep it than go carb in this case. An F-body LTI longblock is almost identical to an L98 TPI engine where it counts. The heads flow a wee bit better, but its pretty much just a one-piece rear main chevy small block with a different water passage location on the heads and deck. SO, what I mean is, with the EFI you can retain the stock 10.5+ CR and sip cheap fuel. If you go carb, you won't gain a single HP (and my lose some depending on your tuning ability) but you give up the detonation tolerance and would need 93 octane. The real benefit to carbs in this case is the ability to run insane cams without the trouble of foiling the MAP sensor.

Last edited by curtis73; 05-17-2008 at 05:36 AM.
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Old 05-19-2008, 03:14 PM
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He wont make up his mind. He wants to cam it, possibly stroke it, and who knows what else. I've told em, several others have told him to go with the carb. We've called every junk, salvage yard around here and they have nothin. I've got a carb that I'm basically givin him and hes gettin a steal on a distrbutor and everything. Alls he's gotta buy is the Intake. Whats the best for him to do? Keep it or dump it?
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Old 05-19-2008, 04:19 PM
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I have several friends that run LT1s, carburetors and distributors. They work
just fine, the LT1 is the best production 23 degree SBC made.
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