shotgun_000

As some of you know, I've had to install a new engine in the vette. During this time, I took advantage of the situation to add more hp. I spent countless hours researching, and posting on the forum.

In short, I've spent nearly 3K to rebuild another engine, add some nice high performance parts, and have all the work done by a corvette shop, only to have a marginal power increase :cry

The basis of my performance measurement is my G-Tech. It's not as good as a drag strip, but it's good enough to show a power increase. I use the 0-60 mph feature for two reasons. One, I'm too chicken to run a 1/4 mile on the street. Second, acceleration is what I am interested in, and seldom will I need to go faster than 60mph.

With the old engine(a 240hp engine from an 87' vette, stock, with Q-Jet) I made a ton of 0-60mph runs with the G-Tech. Best was 5.5 seconds, and the average is 5.9 seconds. This was during the spring and summer.

With the new engine, which has just over 800 miles and considered to be broken in by most people I talk to, the best time was 5.2 seconds, average is 5.8 seconds. This is recent, during the cold weather.

What am I doing wrong here? Check signature for mods The engine runs great, it just doesn't make the power I expected. It revs up nicely to 5500 with no problem. DD2000 shows my combination to produce 300hp. :bs This only shows how optimistic DD2000 is. Considering my 3.70 gears, and almost no wheelspin, 300hp should make me run 5 flat easy, perhaps lower.

Worst, if the old engine ran 0-60mph in 5.5 seconds in warmer weather, then my new engine really isn't that much better, considering the 5.2 seconds was with the help of the cooler outside air temperatures.

I figure at best, my new engine makes 20 more hp. Wow, that's only $150 per horsepower gain I got:rolleyes:

What could be the problem? I feel very confident in the heads, and the camshaft choice. What I don't feel confident in is my stock exhaust manifolds and performer intake. I think these two things are restictiing me, especially when you consider that the engine is basically a big air pump.

However, I honestly don't think that a set of headers and a performer rpm intake will put the power under the hood that I desire. I know that there will be some power increase, but probably marginal like everything else I do. So, why bother with them? At times, I honestly feel that even if I strapped some boosters from the space shuttle on my car, it still would run close to my current times. :(

Any suggestions? Currently, my plan is to drive the vette every chance I get, and rack up some miles. If I can hurry up and wear this engine out, this will help justify to my wife the need for a new engine; a 383 stroker, or maybe even a big block. :D Even then, I still think the car would have the same amount of power :jester

How many miles does it take for a new engine to make full power?


[Modified by shotgun_000, 8:43 PM 12/12/2002]

NassyVette

I may be wrong about this but 240hp to 300hp isn't really enough to feel an immense increase in power. You should feel a SOTP difference, but maybe your expectations were to high. Did you use a new carb, or modify your orignal to match your need heads/cam? And I would for sure put on a set of headers and true duals to let the motor breath.

PRNDL

First off, I really think you need to dyno the engine to find out what it is putting out (hp and torque) where (at what rpm, ie power curve). GTechs are fun (I have one) but I wouldnt use it as my primary testing tool to determine $$ spending!! You would be better off going to a dragstrip (better than GTech, maybe not as good as a dyno).

Secondly... what is the old engine from an 87 vette? Was that an L-98?
hmmm... I guess I am confused about your old engine... is that a typo? is it 77 or 87? with a qjet.... MJ :confused:


[Modified by MNJack, 9:03 PM 12/12/2002]

Marks69BB

IMO, those headers coupled with a free-flowing exhaust are going to make a big difference. I think that is what is holding your new engine back considering your other quality part choices. I'm no expert but headers have always made the biggest difference in performance when I've added them in the past. Also, is your DD2000 analysis taking into consideration that you aren't running headers or does it assume you are (I'm ignorant of this SW so bear with me here)? Re the G-Tech, I would get the headers on and then take it to your local strip and see what it will really do. I would also dyno the engine on a chassis dyno - again, to see exactly were you stand and then use it as a baseline as you add parts and dyno again. Let us know how it does when you get the headers on. :cheers:

shotgun_000

I can't really tell a SOTP difference. You hit the nail on the head, I guess I did expect too much.

I'm using the stock Q-Jet. It runs well, but I plan on a Holley Street Avenger later.

I'm not so sure the gain is worth the trouble and expense, considering my past experiences.

Oh well, gonna start saving for that stroker :yesnod: :cheers:

45ACP

Did you do all of these changes without re-tuning the Q-jet?

Are you still running the stock exhaust system with those stock manifolds?

"However, I honestly don't think that a set of headers and a performer rpm intake will put the power under the hood that I desire."

Well, perhaps not, but they will make a helluva difference.

What output is it that you desire?

shotgun_000

The only thing I do know was that it was an 87', with the aluminum heads and centerbolt valve covers. I'm a little ignorant of the factory engine codes for C4's. The factory Q-Jet and intake for my 1979, were installed in place of the factory fuel injection that was on the 87' engine.

Stingraycrazy

One word, Compression. If the block hasn’t been decked try a thinner head gasket. Detroit Gaskets has an embossed shim that’s 0.015" thick. A buddy of mine used a set on his 78 pace car and you could feel the difference. The cam you have listed will like the compression increase. Should bump you up to 10:1 or so.

I don’t have a rocket, but if that doesn't work I have this spare turbo in my garage... :lol:



I'll work on it for you and get back to ya later... :crazy:

shotgun_000

Yes, but I have talked with Lars about a rebuild after the first of the year.

I have dual exhaust, with some kind of turbo mufflers. I'm not exactly sure what they are, but they are a bit loud, so I doubt they are stock. Also, all emissions equipment has been scrapped.

For my car to be on par with a Trans-Am WS6. I tested one with my G-Tech, on the same roads I run, and it ran from 4.7 seconds to 5.2 seconds. I'm sure fuel injection helps a lot with bottom end acceleration over my Q-Jet.

shotgun_000

:eek: :eek: :eek: That might do it :yesnod: :lol: - If not, my only hope is to find a way to turn myself into pure energy and travel at the speed of light :jester

Chris O'

Wait 'till you get a decent dual exhaust! :yesnod: :yesnod: :yesnod:

shotgun_000

The 300hp is based on stock manifolds and mufflers. With headers and a good exhaust, it show nearly 350hp. Somehow, I don't believe it :D

45ACP

Well, there is a good part of the problem. Any time you alter the basic breathing capacity (heads, valves, manifold, etc) you MUST re-tune the carb. Until that is done, you ARE giving away a boatload of power. You cannot get the optimal amount of power out of a motor with incorrect jetting.

Lars has written at least one paper on the process. I believe you will find a copy of it at http://www.corvettefaq.com

shotgun_000

I pray that this is the problem :blueangel:

I do have a copy of the paper, but I'm going to spend a little extra money to let Lars do it. I don't trust myself too much. If there is a way to screw something up, I'll find it! :yesnod:

Metal Wulf

A WS6 puts 300hp to the wheels, so you'll need to bump up your engine a bit :cheers:

45ACP

"Screwing up" is part of the learning process. You just need to be patient and relentless in your quest.

As far as the carb tuning being the answer to the problem (not enough power), I can't promise that, but you will be able to make a fair evaluation of your combination's capability.

Shark Racer

One thing that might explain a bit of the lack of 0-60 gain is the way in which you shifted the powerband. The LT1 wasn't all that much quicker than the L98 0-60. Your engine right now runs comparably to one. I think the headers you're installing might be a bit large, but I'm not an expert, so don't count my opinion too highly. My 'vette makes ~200 hp, and 7.1 sec 0-60. There are lighter cars with the same horsepower that are a full second slower. Why? Torque. You probably did not increase torque much at all with the new motor. The headers will boost it quite a bit, throughout the RPM range. The carb tuning will help a lot, as others have said.

If you want a car that's superfast 0-60, the only answer is displacement or forced induction. Lots of grip, and no weight on the nose. ;) Also, take a look at some of the AWD cars that put out awesome 0-60 numbers. Compare to their 1/4 mile, and you'll see that all the low end launching gets them through the 0-60. Horsepower is what gets you through the quarter, and I would not be surprised at all if your new motor blows the old one out of the water in the quarter. How's highway acceleration compare?

-Steve

JoeC427

Change the camshaft

shotgun_000

I'm not really sure. Since I have installed the new engine, I tend to stay off of the highways. The deep 3.70 gear I have causes the engine to rev really high at 70-75mph. I love that gear too much to change it. I'll solve this problem later with a beefed up 200R4.

When the first of the year comes around, I plan to use my tax refund to rebuild the carb, add headers(Dynomax 1-5/8), Edelbrock RPM intake, and a ignition upgrade.

If this doesn't wake my engine up, then either I'll have to be happy with what I have, or I can resort to drastic measures. I'll buy some Type R and maybe a few V-Tech stickers, and put them on my car. That, along with a wing, fart can, tiny wheels, and a good stereo system, should add about 1200hp, and enough torque to put Amtrak to shame :lol:

'79ProwlerOrange

5.2 isnt fast? Z06s are 4.6 arent they? dang. i think im somewhere in the low 5s and im getting 347 hp at the crank. i couldnt feel much diffrence until i installed the 4.11s. now its like a diffrent car. it revs so damn fast now, it is a much faster power band. which i actually havent even gotten to redline. i started to get nervous arround 5000rpm :crazy: my redline is about 6500 :lol: one day ill go out and be mean to it, but ill wait till spring.