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LT1-LT4 Modifications
1993-97 Gen II Small Block V8

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Old 08-30-2011, 09:33 PM   #1
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Unhappy Got an L99 unstead of an LT1, have some questions.

So, what I thought was an LT1 turned out to be an L99. I'm not terribly butthurt since I traded a tired 350/350 combo for it. But from what I have read so far, the engine is identical externally to the LT1, so I guess my main question is how much of an LT1 do I need to get elsewhere? I.E., can I use an LT1 block/rotating assy combined with the rest of the stuff off the L99? Or would I need block+heads? Or block+heads+intake? (See where I'm going here?)

Also, are there any other good uses for anything on this motor? Is there another block the intake could be bolted on to for a performance gain (I doubt it due to the Optispark, but never know till you ask). Any other performance-oriented suggestions to get at least some use out of this thing?

BTW this engine/trans is going in a '75 GMC SWB project, so I figure I can at least get it installed and get all the bugs worked out, then drop an actual LT1 in later.

Any (constructive) info/suggestions will be appreciated! Thanks in advance.
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Old 08-30-2011, 09:42 PM   #2
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Ditch the entire motor and find an LT1. There's not a whole lot of use for L99s.
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Old 08-30-2011, 09:44 PM   #3
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The block is a smaller bore, the crank is a shorter stroke. The rods are longer at 5.94 from memory which means you would have to get really creative to find something to work with them on a performance build.

The intake is the same as an LT1, the timing cover/set, valve covers and oilpan are all useful, the cam is the same as the b-body LT1s got. Save things like the oilpump drive as a spare. The TB is the same other than the IAC bleed hole size which usually needs to be drilled out with larger cams anyway. Fuel rail is the same but injectors are only 19lbs which is about barely enough for a stock LT1.

Should be the big points, if you have any other specific questions ask I will try and help. Just be careful, lots of missunderstanding and missinformation about the L99s and b-body LT1s.
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Old 08-30-2011, 09:47 PM   #4
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I couldn't agree more... If I had it to do all over again , I prob would have held out for another lsx f-body platform .. I say don't screw with the l99 if you want a lt1..
Sorry for your misfortune ..
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Old 08-30-2011, 09:54 PM   #5
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you can destroke an LT1 with an L99 crank so instread of saying you got a tree fiddy like the rest of the world you can have a tree oh five.
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Old 08-30-2011, 09:57 PM   #6
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Well, I may have found a solution. There is a '95 Caprice Wagon for sale locally for $450. If I read correctly in another thread, the wagon should have an LT1, correct? I will be sure to check the back of the block this time, but thought I would ask before I make a trip out to see it. I know the Camaro/Firebird LT1's are more desirable, but this one should be OK for the price.
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Old 08-30-2011, 10:00 PM   #7
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you can destroke an LT1 with an L99 crank so instread of saying you got a tree fiddy like the rest of the world you can have a tree oh five.
LOL, but I like 'tree-fiddys'

If I can get an LT1, I don't see the point of destroking it, since it would be restricted by the stock PCM's rev limiter, correct?
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Old 08-30-2011, 10:06 PM   #8
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There are rumors of one L99 optioned wagon but last I heard they were unconfirmed.
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Old 08-30-2011, 10:24 PM   #9
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I drive a 96' Caprice with the L99 as my DD. Great engine, gets terrific gas mileage, smooth and has a good amount of power for how small it is. It has never had a problem moving around the Caprice and that is one HEAVY car... Not a race car no but it will hang with 16 sec cars. haha Used to run side by side with my buddies 95' Ram 5 spd 5.2L Reg cab/ shortbox. And that truck would run dead nuts side by side with my Camaro when it had the original 5.0 TBI. For how big a Caprice is and how small the engine is its quick incredible... I've always wanted to make the L99 run 13's and basically be a sleeper that gets good gas mileage and is quick but reliable. How many ppl can say their L99 Caprice runs 13's. haha For a performance build go with the LT1 though...

On another note it has 5.94" rods like 96capricemgr said and from what I've seen ppl are buying them. You could probably sell them to make a little money back...
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Old 08-31-2011, 12:25 AM   #10
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Yeah, come to think of it, my '07 GMC Sierra had a 4.3l V6 rated at 200hp, and that truck drove just fine, pulled boats, cars, etc. without any problems.

So, I think I will just put the L99 in for now, work out all the bugs, and work on getting an LT1 for it. Once I have the L99 working properly swapping in an LT1 will be a snap.

Also, the truck it's going in currently has 4.11's in the rearend, so I shouldn't have any acceleration problems, even with 'only' 200hp, lol
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Old 08-31-2011, 06:55 AM   #11
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Quote:
Originally Posted by stevo9389 View Post
you can destroke an LT1 with an L99 crank so instread of saying you got a tree fiddy like the rest of the world you can have a tree oh five.
a 4" bore and 3" crank translates into 302ci actually

hey Dwayne are L99 rods PM or forged? or did they switch from forged to PM in 95(?) like the LT1?
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Obviously, somethings not right there. Is the supercharger set to suck instead of blow?

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Old 08-31-2011, 09:01 AM   #12
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So, I think I will just put the L99 in for now, work out all the bugs, and work on getting an LT1 for it. Once I have the L99 working properly swapping in an LT1 will be a snap.
The L99 is a great little motor. They have a really small cam from the factory. I think that it is .419/.430 lift. Change that and they really come alive. As with all the cast iron LTX heads, you might want to cut the guides down and change to screw in studs.

I built a cam only L99 years ago that made good HP and ran mid sevens in the 1/8th at 3300 lbs. There are quite a few of these motors running Super Stock GT that are well into the tens in the quarter. So, don't write them off as a performance motor. Mod for mod they seem to make a little more HP per cubic inch than the LT1 (Stock/Super Stock).
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Old 08-31-2011, 09:02 AM   #13
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.....are L99 rods PM or forged? or did they switch from forged to PM in 95(?) like the LT1?
They are PM.
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Old 08-31-2011, 09:37 AM   #14
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Not an LT or LS? Kill it with FIRE!!!!!
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Old 08-31-2011, 09:37 AM   #15
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Sarcasm ^
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Old 08-31-2011, 10:25 AM   #16
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^lol

thanks for the 411 Darren
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Obviously, somethings not right there. Is the supercharger set to suck instead of blow?
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Old 08-31-2011, 04:17 PM   #17
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Yeah, I figure dropping the L99 in now will the truck back on the road, then when I do get my hands on an LT1 I can take my time and build it the way I want it.

And maybe once I get that done I'll rebuild the L99 and stuff it into my Astro to replace the worn out 4.3 V6 that's in there now, lol
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Old 08-31-2011, 05:46 PM   #18
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you can destroke an LT1 with an L99 crank so instread of saying you got a tree fiddy like the rest of the world you can have a tree oh five.
what's the point of that?

so you can say

"Rollin' in my 5 point oh, ragtop down so my hair can blow"

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Old 08-31-2011, 05:53 PM   #19
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I couldn't agree more... If I had it to do all over again , I prob would have held out for another lsx f-body platform .. I say don't screw with the l99 if you want a lt1..
Sorry for your misfortune ..
I agree. Don't mess with the l99.
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Old 08-31-2011, 06:10 PM   #20
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I agree. Don't mess with the l99.
Well I wouldn't call it 'messin' with it, essentially just gonna use it to get the truck setup for an LT1 since I'm dropping a 90's motor in a '70's truck. And I can lie to the tards and tell them it's an LT1, lol

The Astro comment was mostly a joke, because I saw another Astro on craigslist with an 'LT1' in it, so I know they can be made to fit. The L99 wouldn't be a displacement increase, but it would certainly be a power/milage increase over the TBI 4.3 that's in it now.
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Old 08-31-2011, 06:10 PM
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