I just got a 95 LT1 that I am going to put into my 73 firebird. I will not have any smog restrictions and would like to have at least 400rwhp preferable more. What is necessary for mods to achieve this. Stroker kit, heads and cam were some components I had in mind to get there. Which exact ones I don't have any idea yet. Any help to reach this goal would be appreciated.

 

since its a 2 bolt i would recommend splaying the main caps and stroke it to at least 383, then add some nitrous.

 

I would like to do this without nitrous......possible?

 

whats your goal with the car? is it just going to be a cruiser? or all out race car?

 

My goal is to have an 11 second street car. No smog requirments and it will not be a daily driver so I am not too worried about drivability.

 

you can do it without nitrous and without stroking it if money is a concern.....

and without splaying the main caps... although I do recommend the 4 bolt mains and stroking it for durability's sake it's not required....

I made 422 to the wheels with a T56 (roughly 500hp at the motor) with a stock crank, 6" rod 355 LT1..... and it wasn't with exotic parts, just a good combo that worked well together.....

here's what I had:
LT1 block bored .030 over with torque plates
SRP forged flattops (came out to 11.75:1 compression with my heads)
6" Eagle H-beam rods
stock LT1 crank (polished journals and magnafluxed prior to buildup)
heads were LT1 castings ported by racenet (flowed 258 intake and 203 exh at .600) valves were 2.0/1.56 manley's
cam was a 236/242 .556/.576 112lsa comp cams xtreme energy hydraulic roller
comp cams "R" series lifters
trick flow hardened pushrods
ported and modded for 58mm throttle body LT1 intake
30 lb injectors
58 mm throttle body by BBK
Hooker long tube headers
Mufflex 4" catback with flowmaster 2 chamber
comp cams pro magnum roller rockers 1.6 ratio int/exh

got the engine running and in the car and Joe Overton did like a quick tune on the DFI (I had a gen VI piggyback system) and she was running like a ****.... took it to the track and went 12.1 on the motor first pass @119mph.... over a few months I got that down to a best of 11.7 with the T56 and 11.62 when i swapped to a TH400..... same motor went 10.40@131 with a 150 shot TNT system and the TH400.....
A motor like this will require a bit of tuning on a stock PCM to idle and cruise fine but nothing too difficult.... the cam has plenty of mid range to high end pull.... Pulled all the way to 6500 strong then power started to peak.... i would shift it at 6400-6500 at the track... good luck with your project and what you decide to do..... 400hp is pretty easily attainable....

 

Thanks for the info OutlawZ, that was great. The times that you put down is exactly what I am looking for. How much modification to the block is necessary to stroke the motor. I assume it's not just dropping in the new crank, rods and pistons? Also I have the B-body iron heads and want to run an aluminum set. Worth getting an aftermarket set or is a stock reworked set fine? Thanks for all the help, I'm still searching the forums to soak up as much as I can. I'm still in the old traditional pontiac motor mode . This is my first new age motor.

 

I saw your post about getting the motor from a Caprice. It's an iron headed LT1 (assuming it's the 350 - there's also the 4.3L L99 that looks identical ).

MY opinion, is if you're going to build a 383, would be to do your retrofit with the Caprice motor, and simply purchase an LT1 block to start the build up on. You'll want LT1 aluminum heads (MUCH lighter than the iron Caprice heads). Get the bugs worked out of the retrofit with the stock Caprice motor, and once it's in and everything's running, build the 383 at your leisure, and then swap it out and sell the Caprice motor. Less down time, easier on the wallet.

 

I have confirmed that it is the 350 5.7.

I would rather build this motor and go, not to worried about down time seeing how it's already been three years since I've driven my bird. I'm going to build this one and roll with it.

After reading some more posts, looks like some pretty good power can be made with a 355 and some ported lt1 castings. Can you guys support this with some more references or info.

I hope this isn't a stupid question but is moving up 28ci really worth any significant power gains...just looking for 400+hp at the wheels and 11's low 12's.

 

Well the answer to both your questions is this.... To run the 3.75" stroke crank for the 383 you'll need to clearance the bottom of the cylinders in the area where the rod bolts pass. your engine builder would figure it out when mocking up the block (he probably already knows however cause the 383 is a popular motor and LT1's require this clearancing in the same spots) here's a pic of what the clearancing looks like on my block.



The deal with your set is twofold. One I would use the aluminum LT1 castings. A step up to AFR isn't really required in the power levels you are trying to attain HOWEVER most companies are going to want a core exchange (your aluminum heads for their ported/polished versions) to avoid the core charge (generally like 500 bucks).... SO if you don't have a set to trade in a purchase of some AFR 195cc LT4 heads might be worth it since they're like roughly about 500 more than a set of LT1 castings after you get your core charge back (don't know if that makes sense)....

Okay onto your second question.... The 355 deal is this. It's cheaper to build cause you can keep the stock crank if you don't intend to slam it with massive amounts of boost or nitrous (although it will be plenty strong enough for a small shot of 100-200 hp kit) You can put a good 6" h-beam rod in it and get a great piston to rod ratio and piston options are just as plentiful as with the 383 (it's still a 4.030" piston).... I went with SRP's to save a little cash but a step up to a full JE is a good option for 200ish more.... The usual reason people do the 383's (I'm building one now) is because the cost of the 3.75" crank is the same as the 3.50... so it makes sense that if you are going to build it with an expensive crank (ie not stock cast steel) you should just step up to the 3.75 crank and spend the few extra dollars in getting the block clearanced.... you pick up 28 cubes for the cost of block clearancing.... And the 383 will out-torque the 355 9 times out of 10..... but the 355 can make an assload of power and it's an efficient motor..... So realistically it depends on you and how much cash you want to spend. If you have money for the forged crank upgrade then go 383, if not you can easily make 400 at the wheels and run low 12's high 11's all motor by sticking with the 355 and saving yourself about a grand not buying a crank....

 

thats why i chose 383

 

Yup that's why most do..... when my 355 called it quits (not the engine's fault but the converter destroyed the thrust bearing) I had all intentions of just buying a 3.50 stroke forged crank, losing some weight out of the car, and putting the engine back together identical to what it was with just a forged crank but still a 355.... my engine builder talked me out of it and into doing a 383 using my heads/intake/cam and all the rest (would have needed to downsize the rod length and quite possibly purchase new pistons since they were setup for 6" rods and 3.50 stroke)... Either way that was the plan.....

2 years later I have NOTHING left over from that 355 (sold all of it) and I'm about 15K into the ultimate LT1...... I think my engine builder planned all of this ****..

 

Once again great info, thanks. I like the way your looking at it. I will go 383. The cost for a set of 6" h beam rods and 30 over pistons outweights the cost of this forged 383 kit from

http://www.dyno-flo.com/../index.php?pr=rotassemblies

LT1 383 Kit. This with the AFR LT4 195cc's would be around $2500 parts only. Block needs to be clearanced for the rods but what else should be done to the blcok. I'm going to try and get an idea of the machine costs I will be looking at. Still need a cam and lifters... From what I've seen the hydraulic roller lifters are pretty expensive as far as lifters go. I'm sure a 58mm thorttle body is in line, requiring porting the intake. Does the rest of the intake need any attention with these heads and what ever cam goes in. Thanks again for your help, I'm getting a better idea of where I want to go with this thing now.

 

383, can't go wrong with redoing the whole block

I made 407 RWHP with a real bad vibration (due to weight on fly wheel) and 75 miles on new motor. After breaking and no vibration I'm probably at 415-420 with a small cam.

 

It is very easy with the LT1 and 383 cubes to create more than 1 HP per cube without throwing gobs of money out the door. I spent 4 months doing research before I bought anything and the end result was jaw dropping HP even I was impressed and the look on anybody's face when you step on the gas in 2nd gear and start running over 5000 RPM and then just run threw a gear or to is priceless.

 

machine work you are going to want done to the block besides the clearancing for the crank is a .030 overbore with torque plates, align hone the mains for the new crank, resurface the deck, install new cam bearings and freeze plugs, balance the rotating assy (if not already done)...

If you do hyd roller get the Comp R Series lifters... they're really good and did well on my motor... go with good pushrods (I like comp or trick flow) that are hardened for use with guideplates... The 195cc AFR's are nice heads.... you'll like em... Defintely have the intake ported and modded for a 58mm throttle body.... and put a nice cam in it...... as long as you don't have smog in your state....

 

Worked for me, have that stuff on my setup

 

Another vote for the 383...Mine consists of the following, again simple, durable and gets 20 mpg on the hwy...Times in my sig were on 16x8s, shorties, and stock wp...New times with the Kooks, ewp, and Bogarts should be better..went 10.98 on a Mustang dyno 1/4 mile blast...

Corvette 4 bolt block
Callies crank
Oliver 5.85" rods
JE pistons

LT1 heads CNCd/hand ported by LPE in 1995 2.00/1.56 valves
Freshened/re-ported in 2005 by E.B Porting
Joe Overton 226/234 .568" cam

58 mm Accel/LPE TB and Ported intake
30lb injectors, stock fuel pump

Built 4L60E with Vig 3600/Strange 12 bolt 3.73s

Assortment of Hotchkis/Spohn stuff with stock springs and Decarbon shocks

Bottom end has been together and untouched since 1995 (11 years!)

PCMforless tuned and shifts at 6300rpm...no need to spin it to the moon....take care..

--Alan