I just got done building a 383 Stroker LT1 for my 1994 Trans Am. I had a local mechine shop do all of the machine work and assembly. I have listed all of the parts below. When the engine was started in the car and had a few miles on it, it was really slow, slower I think than stock. Because I replaced everything on the engine whether it needed it or not, for reliability reasons, I had $10,000 into it at this point. I went back to the machine shop and asked them what the deal was and they told me that since I was still using the stock fuel injectors, throttle body, fuel pressure regulator, and MAF, that it would do that. So I went out and bought all of those parts at a cost of $1200. All that and the car is still slow. So much so that my cousin's R/T Dakota beat me. I went back again Monday and I told the shop that I put on all of those parts and still nothing and they said now I need a reprogramed computer. I am starting to think that this shop doesn't know the computer cars and I don't want to sink any more money into this thing and have to still be slow. Do you have any suggestions? Again the list of parts is below so you can get an idea about where I am at. Thank you for your time.

Engine;
Scat Forged 383 Stroker crank
Scat Forged rods
Keith Black hyperuetetic (sp) pistons
High flow oil pump
ARP head bolts and screw-in studs
GM LT4 hot cam
Valve springs
Roller rockers
Comp Cams chrome moly push rods
Summit oil pan
Water pump
Opti spark distributor
Plugs
8mm Accel wires
Starter
Hooker Super Comp headers
O2 sensors
Accel 36# fuel injectors
Jet adjustable fuel pressure regulator
BBK 58mm twin throttle body
Ganatelli MAF
Ported and polished heads with 1.94 and 1.60 valves
Larger exhaust valves
Rebuild on the heads and block
Balanced and blueprinted
MSD hot coil
High Flow Cat
New spark advance unit

 

The only thing about your combo i can find any fault with is the Accel wires (i wouldve went with MSD 8.5mm) and the KB pistons.

Hell even without a program you should be doing better than stock. Youre prolly running really rich or lean somewhere and the stock program is adjusting timing too much. Also, i would think #36 might be on the 'big' side for a 383?

Youll need a program to get optimum power for sure, but i have the suspicion that something is up with something else.

 

Even w/o a reprogrammed chip your car should be tearing the tire. Also maybe the throttle body and injectors are too big, what shop did you take your car to so I can keep a red flag on 'em.


[Modified by 87Beast, 1:58 AM 8/12/2002]

 

They are actually very good, I just don't know what is going on here. I took it to Tom's Performance Machine.

 

There are about 300 things that could possibly be wrong. The first thing you need to do is get a scanner on it while you drive it. See what the A/F trims look like and just see how it is running as far as rich/lean. If all of that checks out then you'll need to start digging a little deeper. Run a compression test and a leakdown test.

If all of that checks out you may have the problem I had. I got my cam a few degrees out of time and my 12 second car could only mange mid 14's.

 

Ported and polished heads with 1.94 and 1.60 valves

Did you open up the intake at all??? I would have went with bigger valves and intake hollowed out some. The 1.94 is stock, 2.02 would be better. ALso what about the intake runners those need to be more than stock too. What about exhaust, headers, and ect? I just think that your choking the motor. Computer work must be done too, I'd send it to Ed Wright. What size is the motor now? Did you bore it out at all? As I read the mods below all you said was 383 stroker crank. Long story, made short and my .02 is that the motor is being choked.

 

Not always. Certain engines, the LT1 being on of them don't really like 2.02 valves. They kill intake velocity and thus give up alot of low end torque with little to no gain on the upper end.

One of my best friends works at Total Engine Airflow, he gets the best flow across the board with 2.00 /1.56 valves. Bigger is only better to an extent.

However, that being said, I do agree with you somewhat. I'm not sure why you would put huge exhaust valves on there and retain stock intake valves. Choking the motor however can't be the entire problem. Regardless it should make more power than the stock 350 if everything is functioning correctly.

I'm going to guess that it's either a few degrees out of time, or those injectors are WAY too big for the current program, or both. I put 36# injectors in mine just to see what would happen, it would barely run being programmed for 24's.

You will have to do some computer work, there is no way around that, but you need to make sure everything else is cool before you waste the time.

 

The shop recommended going with larger exhaust and not intake. Reason being to try and make the percentage of difference between the two less. I did have it bored so it is now a 383. The car didn't run any different with the stock fuel injectors, MAF, and adjustable fuel regulator. I am running Hooker Super comp headers. Everything else is brand new. How can the timing be off if the computer sets the timing? I am new to all of this computer car stuff.

 

If they timed the cam wrong the computer will adjust it, but its the stock programming thats doing it. That will mess everything up.

 

Sorry but it sounds like your shop doesn't have a clue. No car has as large an exhaust valve as they do intake, it's not needed.

As for timing, yes it is computer controlled, but if your cam is physically out of time with the crank like mine was it will give you trouble. If the cam is out of time the spark will be out of time and the car will run like crap. If it's too far out of time you can do some serious damage as a piston slaps a valve.

 

Sorry, but that is not correct.

 

So the computer is not adjusting the timing at all? Its only the cam that is timed wrong?

 

Actually the car runs really well it just has no power. Just like stock. The hot cam can barely be heard and the car just runs stock, good but slow.

 

So did mine. It ran far to well to have a problem, or so I thought. I wasn't really aware of it being as bad as it was until I got it out to the track.

Vader, the way the LT1 works is strange. The opti is driven directly off the cam and will only really go on one way. This means that the opti always travels in relation to the cam. Now the computer can advance or retard the spark within it's range, but the opti's path of travel never changes. So, if the cam is out of time with the crank, so then will be the spark. Even though the spark can be in perfect time with the cam, it's still off from the crank.

Clear as mud? :cheers:

 

How do you check to see if the cam is off without pulling the timing cover? Why was yours off? Installer error or was the marks wrong? I see you are running the same cam I am. Do you hear yours much? Thanks for all of your advice.

 

You don't really. If you can prove that cylinder 1 is at top dead center you can look at the rockers and see if they are close to the right position, but the best way is to pull the timing cover.

Yes, installer error, mine.

I have some sound clips in my signature below. However I've got long tube headers and flowmaster mufflers, that will tend to make it a little louder than if going through stock mufflers. Also any given cam will sound a little more mild as the displacement goes up. However you should still be able to hear it lope a little bit, especially if it is still trying to idle at the stock RPM.

 

Wow, bro. (Nathan)

I am going to start building my 93's lt1 (beginning) next monday.

I was going to use the LT4 hotcam package, but I am not completely sure yet. I was going to bore/stroke, but have decided against it. I have a few things that I would like to ask you if you could email me. I am taking the motor to a shop where they have all of the tools I will need and I am going to build from the bottom up. I will have a resident expert in the motor with me. Please advise me not to put together a stock motor to put in my vette!

brobert10@hotmail.com
:chevy

 

SO, let me understand correctly, you are running a 383 bottom end motor with some mild heads and 36# injectors on stock tuning?

With that combo, you could run so rich you will wash the rings out and have to rebuild it all over again. Also, you will want to drop timing considerably from stock for the more cubes. I would put the stock injectors back in until you can get a program. It wil run a LOT better. Plus, you probably don't need anywhere near that much injector.

 

Oh, and most people do 2.0/1.56 in LT1 heads because that is the largest you can go without having to replace seats and added machine work. Should still run OK with 1.94/1.60, but not as well as a 2.0/1.56 combo. Sounds like you are getting recommendations from people that don't know LT1 motors.

 

I would never go back to that machine shop if I were you for these reasons:

1. They should not have advised you to change the throttle body, injectors, MAF and fuel pressure regulators unless those parts were defective. The car should run okay with them. The injectors should be changed to 30# units.

2. They should not have put in larger injectors without a reprogram.

3. They should not have done the work since its obvious that they know nothing about fuel injection engines.

When I first installed my 383, it had a slightly larger Crane cam than the stock one, bigger heads, stock throttle body, stock fuel pressure regulator, stock injectors and stock MAF and was much more powerful than the 60k mile 350 it replaced.

Your setup has all the right parts and is probably assembled correctly. The engine will run very poorly if at all if the timing chain was off by one tooth so I doubt the timing chain is off.

Your car might be slower for the following reasons:

1. Engine is not 383 cubic inches
2. Heads were not ported correctly. If the porting was done by people who don't know LT1 heads, this is a likely possibility.
3. Your car is not setup for the LT4 cam because its an automatic with the stock converter and stock rear gear ratio.

I suggest you do the following things.

1. Check the ecm for codes. Get the ecm reprogrammed for the new engine and injectors (I can do this for you for what 350. I have the original Fast Chips programming and modifications I made since then. My original setup (after I added the hot cam) was similar to yours and I live near you).
2. Make sure the conveter has not been damaged by the rich condition caused by the larger injectors.
3. Figure out what rear gear you have and get a higher stall converter if you have an auto. Change the rear gear if its below 3.45.
4. Have the setup dynoed to see what the power is AFTER the motor has been broken in.
5. Replace the high volume oil pump with a standard pump. The high volume one will ruin the oil pump drive shaft gear if you don't. There is no reason to use anything other than a stock pressure pump and high volume ones have been known to drain the pan at higher rpm.
6. Find out what the spark advance unit is. The older engines had a a separate electronic spark control unit but the later ones including your LT1 do not have them.

Your setup looks good. 36# injectors are large for engines that make less than 500 hp but they work fine on a 383. I had them on my car for a while. I hope the shop did not get you Accel injectors. Some of us have had them on the forum and had bad luck with them.