I had it dynoed the other day. 430 hp LS3 only dynoed 330 rwhp. I have learned more since my last post. The fuel pump fell off with high rpms. So that cost me some hp. I need to get a better in tank fuel pump. Also I don't have a cold air supply and I need one. That is costing me some hp. I was down about 23% from flywheel hp. I should only have been down about 18% with the automatic. So I need to change fuel pumps and get a plan worked out for a cold air supply to the engine. A lot of things affect hp, especially at high rpms.

I am running a 4L70E with aluminum (read light) drive and half shafts and a 373 diff. Again, I only weigh 3000 lbs. If he was 500 hp at about 3800 lbs; I should have taken him. I think the trany is slipping and not locking up a lot. I do think a 5 or 6 speed would be a good addition. I am getting tired of automatics. They do what THEY want to do. With a stick; you make it do what YOU want to do.

My diff is an aluminum. First year. I did replace the iron rear spring with a fiberglass one. I don't think my D 44 is the same that went on into all the C4s however. There are some parts that are beefier and weaker compared to the iron units I believe. I did put the 1350 u joints in the half shafts and a C4 carrier too. My bottom end will really go but it's the top end that seems kind of dead to me. And that's where I was, at 78 mph, when the Shelby pulled away from me. But I will get it retuned on a dyno and see what that gets me. Plus the trany tune too.

The more I think about it the more I think you are absolutely right!I really do have some potential with my set up. The car only weighs, empty with no driver or gas, 3020 lbs! I just weighed it yesterday. I have been ripping weight out of it for years and I am finally about where I want to be. I suspect the tune isn't right yet and there is something wrong with the trany. I don't think it is locking up all the time (because it revs and I don't go anywhere fast so to speak). It is a 4L70E. I put a 373 rear end in it all ready. I live out in the boonies in Montana and I need to find a good shop with a dyno to go over my engine tune and trany shift/lockup etc. This makes much more sense than pouring tons of money I basically don't have into it like the young man you helped out wanted to in the racing situation. I know the 5 speed stick fits right in but the 6 speed isn't an easy fit so they tell me. Would my Dana 44 rear end stand up to the shock of a stick with 430 hp? Anyway thanks for lining me out on this. I have a set of Wilwood brake calipers and a brake reservoir to install this winter and that will put me under 3000 lbs! I believe the stangs weigh in at about 3800 lbs. The math is in my favor but only if the engine and trany are performing as they should.

In upgrading the power of the LS3; What heads would you put on and does the "hot cam" add hp and tq along the whole rpm range? Someone told me that the cam lot tq at the lower rpms and what would all that do to gas mileage? Like a couple of miles to the gallon or?

I am thinking about it. Money, of course, is always the issue. I was passing a "shelby" on the freeway and he hit it and I hit it and he was pulling away. That's not acceptable! It said "shelby" below the door and he had a hood scoop but no racing strips. What would he have been running? It was a recent vintage and a stick I am sure. An auto, like I run, is less RWHP than a stick with the same engine so I am behind the 8 ball right off.

Where is the best place to buy a new or used LS7? Anyt
hing in particular to watch out for?

Has anyone had any experience with Wilwood's aluminum calipers in 6 pistons front and 4 pistons rear? They are about 23 lbs lighter and larger pistons and more pistons in the front. Like leaking or locking the wheel up or harder to install etc. They have a deal going now in buying all four. I am real happy with VBP's calipers and slotted rotters but always looking for better and lighter.

I have a '72 coupe with a not factory radio. I would like to replace it with a factory look a like radio but with modern features. Did the original radio have "corvette" on it? Was it black or chrome? What modern radio would look original but have lots of modern features to it?

We just found that a relay that got power from the battery and then supplied it to the fuel pump was getting 12 volts and putting only 9 volts out to the pump. When they hooked the pump directly to the battery it pumped way better. Maybe the problem has been not enough fuel going to the engine? I think it feels like more power now and is getting better gas mileage too by about 10%. Now dynos around here to re dyno and the guy I was using in Spokane went out of business. It sounds logical to me that less fuel is less power.

I think I know what happened and why I was down on HP. When I picked up the car they had programed in the wrong rear end ratio in the trany computer, I later found out. I think they also forgot to plug in advancing engine timing in the engine computer. Now I have the correct engine computer and trany computer and it runs great! I am still down a few hp on the dyno but I learned from all this that you can't really compare one dyno and a car to another dyno and another car. All comparisons need to be made on the same dyno run the same way. So it never was engine or trany issues but rather PROGRAMING ISSUES.

Did anyone see the article in HOT ROD magazine that just came out on DYNOS? It appears to me that to compare two cars you would need to use the SAME dyno with the same proceedures to compare your car to someone elses. In the article they took a Shelby Super Snake with 750 crank hp to five different dyno shops and got between 577 rwhp and 644 rwhp. That's a 67 rwhp difference. I see now that you can use a dyno to see what differences mods make to your car (assuming the proceedures were the same) but to compare numbers with another car on another dyno with possibly different proceedures; it may not be comparing apples to apples.

My set up doesn't have a CEL. Is that something that can still be put in? How do we get the "codes". Is that done by plugging into the ALDL port with the programing computer and it reads out the codes? And the "datalog". Is that too obtained by plugging into the ALDL port or is the datalog the print out I got when he was done tuning it on the dyno and it shows the HP and TQ in relation to RPM? Also someone said 385 hp at the crank with 322 rwhp. I don't believe that is right. If you are loosing 20% of your power due to trany and driveline losses then 322 rwhp is 80% of your crank hp. So you divide 322 by 80 and you get 402.5 crank hp? And coversly, if you know 402.5hp is your crank hp then your rwhp will be 20% less or 80% of your crank. 80% of 402.5 is 322. But I am still down at least 27.5 crank hp and I have 1 3/4 inch headers and 2 1/2 ich exhaust and no cats so you'd think I would be more than 430 crank hp?

Street & Performance in Mena Ar. put in the trany and called it a 4L70E. I too had never heard of that. I don't know the stall, maybe around 2200 or so. The guy that just tuned it said I should consider a higher stall like 2500 to 3000. The CPU is a "blank" from S & P as the one they set me up with was the 264 rwhp one. Then they sent me another one that didn't work at all and then I asked for a blank one. I did notice that my hp/TQ chart this latest programer gave me seemed to end at 5450 rpm. The LS3 is a 5900 rpm engine. Basically rpm x TQ is hp. I wonder what gives there?

No, I don't have any cats. 1 3/4 headers with 2 1/2" exhausts with a cross over. One of the magazines said that the 415 G8 hp was due to exhaust and tuning. I don't have the stock exhaust or stock tuning now. My torque curve really improved in this latest tuning however. It is 327 lbs of torque vs the old 317 but at 5400 rpm it is still 306 vs the old 227! That's like almost 80 lbs more torque at 5400 rpm! When I was drag racing last summer at spearfish it just seemed to fade as my rpms built up. I don't think it will now! But I'd still like to find my missing horsepower.

With a blank CPU the custom tuner, on a Dynojet, programed it and it made 322 rwhp. It is an automatic trany which is about 5% or so less efficient than a stick I understand but it still isn't where I think it should be. Maybe the Pontiac G8 LS3 really isn't the same as a corvette LS3? Maybe the trany is less efficient for some reason. We did change the rear end to a 373 and with "finding" over 60 hp it should wake it up quite a bit!But like most other corvette owners; I always want a little more! HAPPY NEW YEAR!

I finally got another dyno done on my car and it was a Mustang dyno. Now only 232rwhp! Sent the data to Street and performance and they sent me a new computer to install. Also they said they use "LS 1 Edit" programer which automatically locks the computer so you can't go back in and change anything. I guess that is way it is preprogramed from the maker of "LS 1 edit". The new computer says for a 411 rear end and mine is a 331 so I may have to send it back and get another one. Waiting to hear. I just wrote Hot Rod Magazine and asked them if there was any difference in a Pontiac GXP LS3, which I have, vs a corvette LS3. Waiting to hear. Vette magazine said the only difference was in exhuast and programing. I hope their right as I have custom headers and a different program (maybe I should have kept the GXP program!). Anyone know if there is a differnce in those two engines?

I put it in my '80 a couple of years ago and like it. The only negative I can see is that my turning radius got larger. And you still have to "drive" the car say on rutted pavement. I would have to drive a non steeroid car now to really see the difference again. But now and initially I liked it and my old system had just been made new but steeroids was an improvement over the old "new" system.

If you have an LS3 in your vette can you simply take it out and put a LS7 in it's place like in the old days of pulling out a chey 350 and putting in a new 350? Both LS engines are small blocks. Would the motor mounts be the same and front bracketry be the same and radiator inlet and exit all work. Otherwords would all the plumbing fit OK? This is assuming one coverted the LS7 from a dry sump to a wet sump of course. Just curios.

Thanks for all the information on what could be wrong with my DOWN 100 HP. I have been gone for a month and am now going to try and get it fixed and will let this site know what is/was wrong and what we had to do to get it right!

So does having a dyno to tune really, really help you tune the engine and auto trany or just a little better than playing with the laptop to adjust timing, fuel, shift points etc.? There are so few dynos around that probably most people tune the engine/trany without the use of a dyno and get it 90-95% right or something?

How do C4 and C6 seats stack up for comfort and ease of mounting in a C3?

Street and Performance I thought did an outstanding job of putting the engine in. It was far from easy. It looks like it came that way from the factory! They did put in a port to hook a computer to just under the dash. I don't know of anything else like the CEL you refered to. I pushed them to get the car done on my time schedule and I think it was probably hurried out the door. What I don't understand is that the guy in Spokane can't access the computer in the car. It's locked up so we can't get in I guess. I'd love to take it back to S & P but they are 2,000 miles away. I think you are right; take it back to Spokane which is only 125 miles and they have a dyno which seems to me to be the best way to tune any car.

Street and Performance in Mena Ar. put the engine in for me and tuned it there without the benefit of a dyno. The elevation there I think was around 1000 feet and I had it dynoed in Spokane Wa. where the elevation is about 2,000. I live in Montana at 2,400. So there is a datalog, if you can get into the computer, and it shows what is wrong(codes)and what is going on? And there should be o2 sensors in the rear exhaust pipes as well as just behind the air intake filter?

I didn't realize cats were "good" for the enviroment, really. I thought they were another BS government idea that in the real world hurt more than they helped.

Can the computer, that's running the show, shed light on what is wrong with it's data record? I didn't quite understand how the O2 sensors might have been tricked. I think that is where I will start looking for the lost power. Any more feedback on that and what the computer can and can't tell us?

I have an LS3 with a 4L70E trany, 1 5/8 headers, 2 1/2 exhaust, no cats, and aluminum drive lines. The car was set up without the aid of a dyno. I dynoed it the other day and only got 261 rwhp! It should be at least 360 rwhp. What could be wrong? Also the dyno said it was peaking HP at 5500 and the engine is supposed to peak at 5900. It seems to me the car in second is reving a lot but not going. Wouldn't it have to be either engine tune or the trany is slipping or a screwed up dyno? At Spearfish the other day, which is about 3500' high and it was about 80 or 90 degrees, it ran an 1/8th in 9.10. What gives?

To make more horsepower in my LS3 what would be the advantages and disadvantages of either installing a HOT CAM or SUPER CHARGER?

I have an '80 vette with a 4L70E 4 speed automatic trany. What percentage of flywheel or net horsepower will I loose when it is dynoed? I have heard 12%, 18%, 24% and 30%?

I entered my fist drag race the other day and is your time at the finish line computed from when the light turned green or computed from when you broke the beam when you launched? And if it is the latter then how is your reaction time factored in on the slip?