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Old 11-25-2008, 09:23 PM
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Lt-1

Hey,thanks in advance to any advice. I am an older guy who just picked up a very clean 93 Transam with high mileage. I want to rebuild the engine to 400-500 horsepower. I have a deal worked out for labor but I am having a hard time putting components together. As part of my arrangement the block is going to be checked out. I need to put together a rotating assembly and cam, heads. Should I get after market heads or have mine reworked? Also I don't know if i should replace my intake manifold and how all these parts work together. Are there any kits out there for my situation?

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Old 11-25-2008, 09:37 PM
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What kind of budget did you have in mind. Anything is possible, somethings just cost more.
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Old 11-25-2008, 10:32 PM
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Hopefully someone will chime in here pretty quick that knows a thing or two about the Gen II LT-1 engine. I haven't built any but I have some ideas or a direction to head in..

There's a few concerns I have that may be yours as well...
- Do you have to pass an emission inspection? If so do they actually 'test' the exhaust gasses or simply look at the dash for a 'check engine light' (I live in NC and they just check for the light) Hopefully they check for the light.

-Are you willing not only to spend money on the engine but for a new clutch and rearend as well? (the stock rearend is very week and the stock clutch will not be able to handle higher rpm or significantly elevated levels of horsepower and torques- especially in the neighborhood you are talking)

Given that you have a plan for the two questions above...

I would find a stroker kit and go the 383 route (Eagle or Scat should have a relatively cheap kit- go with the cast steel crank and the 'cheaper' forged rods- they are both good 500hp-usually)

Machine work- have it all done by your prefered machinist.

Pistons- Usually come with the kit but have options for dome or a dish design piston. I would try to find a design that puts you in the neighborhood of 10.5:1- probably the absolute limit you want to go- BUT with FI and a good tune and large cam you could maybe get away with 11:1 Forged Pistons would be prefered but not mandatory- Hypereutectic would be more than reasonable. Moly rings are usually included in the assemblys as well.

Invest in some good heads- AFR 195 and Dart Pro-1 Platinum 200cc come to mind (you could probably get away with 450 hp on the LT-1 heads with some minor port work to help the cfm's out but the 1.94 valve is going to hurt peak power and cost some numbers across the rpm range) The heads are the most important part of the equation when it comes to making big(ger) power, this is where you need to spend the money.

I know Edelbrock recently released a LT-1 intake, I think it's good to 6,500, not sure but that woudl be a piece to invest in. (The stock intake is done at 5,500rpm and you are gonna need to turn more rpms to get near the 500hp mark)

Computer- not sure here but I have no doubt there are some tuners out there that can help you out (I would find someone you are comfortable with and then talk to them about your goal FIRST- they'll help you 'design' a combo that will work best for you or if you've got your heart set on something already then they can work around it as well, it just might cost more)

Cam- pretty important here, you need some vacum to run the power accesories but you also have high aspirations for power... call a cam company talk with them. (if you are running a vaccum canister, that could help with a larger cam and power brakes) If it were a carb sitting on top, I would imagine something in the mid 240 @ .050 and .550-.560 range for a hydralic roller.

Gear- don't forget this, the stock 3.42 or whatever came in it will need to go... if it's a 5 speed all the better but you didn't mention it so I'm thinking it's an auto. 3.73 minimal, 4.10 prefered. Don't forget about a larger stall speed for the converter, something like 2500 rpm.

Exhaust- some tubular headers would would help a lot and necessary for getting the most out of this combo. You could keep a y-pipe into a single 3" exhaust but a dual with an X-pipe would be prefered.
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Old 11-26-2008, 09:32 AM
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The AFR heads for LT1 are just junk. They're not worth the scrap value of the aluminum. Seriously. Ask about them over at any LT1 forum and they'll tell you to run away. Keep in mind that AFR gets their big numbers because they CAST the head at 195 and THEN port it. Finished port volume is more like 205-210cc. Then the use clay to radius the intake and pipes to fluff the exhuast numbers.

Top notch head porters exist for LT1 heads. Send your stock aluminums to Advanced Induction. They will CNC the ports, flatten the deck, CNC the chambers to whatever size you want, do an F1-spec valve job, beehive springs, Manley race valves, resurface all mating surfaces, and even include a cam for about $1700. Its a steal. NICE work. AI's 190cc head outflows AFR's 195 (actually 205cc) head by a fair margin with less port volume. They flow 275/196 cfm without clay or pipes, which is enough to support 400+ at the rear wheels if you have enough cam.

I'm building a 383 LT1 right now with AI's heads, a GM 846 cam (222/230), headers, gasket matching the 58mm TB, computer work (obviously) and 11:1 and I'm looking squarely at 420 hp at the crank while barely squeaking past emissions testing.

GenY is right... the stock axle will grenade the first time you hit the pedal. The only real options are a custom-fabbed 12-bolt or 9". Big bucks. I disagree though with the Intake assessment. The stock LT1 intake is quite ready for 500 hp. The Edelbrock intake doesn't actually flow much more; its mostly a stock replacement. Its just cast better and thicker for more porting and better sealing.
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Old 11-26-2008, 09:37 AM
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Those Lt1 intakes and heads have a lot of potential IF YOU GET THEM PORTED RIGHT. YOu really need to send them out and get them cleaned up by LT1 specialists. That and a 383 kit can easily get you over 400 at the wheels, if you have cam and compression to match.
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Old 11-26-2008, 11:04 AM
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Quote:
Originally Posted by cjajz
Hey,thanks in advance to any advice. I am an older guy who just picked up a very clean 93 Transam with high mileage. I want to rebuild the engine to 400-500 horsepower. I have a deal worked out for labor but I am having a hard time putting components together. As part of my arrangement the block is going to be checked out. I need to put together a rotating assembly and cam, heads. Should I get after market heads or have mine reworked? Also I don't know if i should replace my intake manifold and how all these parts work together. Are there any kits out there for my situation?

The LT-1 is a good engine as it comes. The heads are very good.

The decision point for you to a large extent will depend first on emissions requirements and budget.

If you must meet emissions then staying with the OEM fuel injection and it's supporting systems is your best option, they will accept mods that will take this motor to the power levels you're considering. If you don't need to meet emissions, then reconfiguring the engine to a carb is an option. However, this can become rather involved in both expense and effort, I'm not just going to throw the parts of this out there unless you really respond with wanting to go this path as it's a lot of writting.

If the Transam is running an automatic, you'll have to put aside money to rebuild or replace it. The 4L60E does not have a super reputaion for a long life behind engines of high output that gets used with much frequency. A 400-500 horse fresh engine strapped to the front of a 4L60E (or any other aged, OEM automatic) will take the rest of its life span out pretty quickly. There are many reputable shops around the country that rebuild these for performance with reliability.

Bogie
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Old 11-26-2008, 08:45 PM
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That's interesting about the AFR's... I've always read their cross sectional areas were always excellent and where were they really got their impressive flow numbers from...it's funny how you want to believe so many good things you hear about them- but clay and pipes? There's always that hand full of people that work at every place, shaking there heads when they see what really goes on... and I'm happy those people talk! Now that you mention it Curtis, I don't doubt it, I mean, if you compare the eliminator series of heads to anything else... they absolutely CREAM the competition... I always look at the bore size used when flowing a set as a way to identify fluffed numbers but you have released some very interesting info. The RHS Torker 2.02 head was tested on a 4.2" bore according to theirwebsite

Bogie- correct me if I'm wrong but when I looked at a bone stock set of LT-1's on a superflow they were like 199cfm @ .4 and 212 @ .5 lift (or very near those figures). If those were correct, I wasn't impressed at all since the vortec head (which I thought was the same design but cast iron) seemed to flow better? But in the end, the head is a great production unit and I'm sure way more flow can be extracted from those heads. In no way did I mean they wouldn't support the hp #'s he's shooting at... I was just thinking some do it yourself porting (done right) would get him to the 450 range if he didn't want to plunk down big bucks for an aftermarket set. Do you know if a 2.02 valve helps/hurts a stock head or one with some minor bowl work and short side cleanup?
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Old 11-27-2008, 02:07 AM
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Here's the straight dope on LT1 heads.

Aluminum LT1 heads come in two aluminum castings (374 and 649). Early castings were 2.5 lbs heavier due to extra meat above the intake ports but it doesn't really affect reliability or power. There are two iron castings, 290 and 890, the latter of which is found with small chambers on the 265 L99 4.3 "baby" LT1.

The aluminum heads were revised L98 TPI heads. They flowed about 15-20% more than the TPI heads. In 94 they revised it again and cast it in iron, and they saw an additional 20% flow. The 94-97 iron heads actually flowed so well from 170cc that they made direct copies of the ports when they designed the vortec heads. Vortec heads that came out in 96 were thought to be so wonderful, but few people realize that the iron-head LT1 was the same basic engine two years before.

Iron heads are the easy performance winner in stock form, but the aluminums are easier to port, and make very respectable power in the hands of the right porter. Ported iron heads probably have a touch more potential, but getting the hard iron ported out to the same spec as the aluminum is a pain in the butt, and since so many porters have very impressive CNC plots to make the aluminums top of the heap, there is no compelling reason to spend money on the irons. The only reason I would switch to iron heads is if I wanted a mild performance increase without porting. Switching from aluminum LT1s to iron LT1s is very much like swapping from SBC smog heads to vortecs.

Concerning the AFRs, I spent a lot of time up there at their facility resolving major issues. I had one head that the CNC machine totally missed the one side of the port, and cut THROUGH the other side of it. I visited them for satisfaction, and (although I won't go into it here since there are many AFR lovers on this forum) lets suffice it to say that its a lawsuit waiting to happen. You know those 20/20 news stories where there is some italian guy in NYC who was caught on camera ripping off customers? Yeah... that's the feeling I got. Slimy, shady, lying, and they didn't even try to cover for their lies. They told me all about their 5-axis CNC, and I'm standing in front of it reading the label on the screen that says its a 3-axis machine. I asked Mike about it and he just said that the only difference is the software. Lied to my face even after I called them on a lie. The one truth they did spill was that they cast their heads at the advertised CC and then cut them, so the finished port size is much larger than advertised.

People see big flow numbers, but actual flow numbers mean ZERO. I have beaten SO many AFR headed cars with home-ported stocker heads that I have given up counting. My buddy had an otherwise stock 1995 LT1 in a Camaro with AFR 195s, a 4L60E, a stock 205 duration cam, and 3.42 rear. I had some lightly massaged stock LT1 aluminums in an Impala SS with a stock 191 duration cam, the same tranny, and a 3.08 rear. I could beat him every single time without fail. I had maybe 180cc heads and less cam, he had 205-210 cc heads, much less weight, and more rear gear, but he couldn't keep up. Part of the problem was he thought he was buying 195cc heads, but he was actually buying huge-port heads. AFR's flow numbers look like a little better than normal for their port size, but when you consider that they are basically lying about port size and then further padding their numbers with clay and pipes, they only stack up to be about average heads.

I won't buy heads unless I see published dyno curves and timeslips, and the fact is (cfm for cfm) many ported stocker LT1 heads will beat anything that AFR has to offer by a large margin. I've seen 190cc ported stockers beat AFR 195s (that actually measure 205cc) by almost a half a second. That's big. As with any thing, bench numbers mean next to nothing. You can have two different porters prepare two heads with equal flow and port size, but one will beat the other every time. Its not quantity of flow, its quality. We race the clock and our seats, not dynos. Flow numbers are even more removed from that equation. Flow numbers suggest dyno numbers which suggest ET, but to assume that flow is the only factor in head choice is not a wise thing. Look at proven timeslips.

From what I understand, AFRs other offerings are top notch, but knowing what I know, I won't waste $2500 on AFR's lies when I can have my cake and eat it too with ported stockers for $1700 including a custom billet cam.

Source: http://www.enginebuildermag.com/Arti...lt1_enige.aspx

Last edited by curtis73; 11-27-2008 at 02:14 AM.
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Old 11-27-2008, 08:13 AM
How fast is fast enough?
 
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To say taht dyno tests cannot justify head purchases as well as ET's is crazy. There is a more direct relationship from head quality to power than there is from head quality to et's. when you factor in ET's then every other aspect of the car, track, weather, etc. comes into play.


I agree that flow quality is a HUGE often over looked factor, but that factor will also show up in a dyno test.
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Old 11-27-2008, 01:00 PM
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We don't race dynos, and published head flow numbers don't mean squat on a dyno. Especially when you have one pair of heads that are advertised at 195cc but actually measure 205cc, then use clay and pipes on the flowbench - versus heads that are 190cc actual and don't use clay or pipes on the flowbench. I agree that you should choose the heads that make more of the power you want on the dyno, but to assume that head flow = ET is two huges steps that you can't make without knowing a thousand other factors.

The published numbers for those two heads above are nearly identical, but the power they make (as well as the low RPM torque figures) would be MASSIVELY different. Guessing on HP from published flow numbers is like guessing from compression ratio.

Flow numbers don't mean ****, dynos only tell you WOT power. Races tell you who has more average torque and hp, and all the power in the world won't make you fast if the hundreds of other chassis factors don't match the powerband of the car. The engine is just one tiny part of winning the race.
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Old 11-27-2008, 02:36 PM
How fast is fast enough?
 
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actually dynos tell you what power and torque the engine is making everywhere under the curve. The thing I pay most attention to isn't peak power but the torque curve, how big it is, how flat it is, and where it peaks.
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Old 11-27-2008, 05:18 PM
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JMO
valid flow numbers are only given with radiused intakes and piped exhaust. It IS the standard of the industry, just like using 28" suction.

Unless you happen to run intake manifolds that are 1/2 inch bigger than the head ports and blow your exhaust right out the bare head.

I think that maybe the problem with the technical discussion is that most people do not realize that when running, engines do not suck at 28" through the heads.
During overlap suction can be 100 and with the intake valve closing and the piston slowing down, it might only be 12.
Flow bench numbers are only that...... comparisons at one point of suction. period.
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Old 11-27-2008, 06:28 PM
How fast is fast enough?
 
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that is a very good point! It only puls at 28" twice during a full engine cycle, and only for a very brief moment.

I think that dyno tests are probably the most valid way to measure power potential. Though they do not equate to better ET's everytime because the rest of the car has to match.
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Old 11-27-2008, 10:41 PM
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Agreed. We're all on the same page, just different words.

Scot, I also agree on the industry standard, but I was just pointing out that you can't use the raw numbers since they might not be following the standard testing procedures.
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