Joe_G

Decided yesterday to overlay all my mods since I've self tuned and dyno'ed each time I did major mods.

I found it interesting and thought I'd share.

See below. Each line represents progressive mods:
1. stock;
2. headers & tune (3.90 gears at same time);
3. G5x3 cam & .040 gaskets (11.4 compression);
4. FAST, and
5. used AFR 205 heads.

What strikes me is how dramatic the gains from headers and a tune were. Combined with the gears, it felt like a different car, and I got a full second + 10 mph in the 1/4 from those mods, from 12.9@108 to 11.8@118. The car was dead nuts reliable at this level.

The second take away is how all the remaining mods really only mattered from 4500 on. Thus I very seldom notice them on the street, only on the track. Not counting the cool sound of the cam.

Mods 3-5 did take off another second and added 10 mph - to 10.8@128. But it cost a lot more and I broke a diff and two transmissions on my way.

This graph shows what I've been saying for while; headers, tune and gears give you by far the best bang for the buck from idle to redline, the remaining mods only matter from 4500 on. Most street driving is below 3000 rpm...you do feel gears and headers even at that level.



Hope someone finds this useful as they decide upon mods.

I need to add...without question...the best mod for return on $$ is...

SEAT TIME.

And personally, I find that mod the most rewarding.

Another item Tommy kindly reminded me of, is weight reduction.

If you are drag racing, you can expect .1 to .15 from putting skinny tires up front (saving 50 lbs+ of rotating weight) and taking out your passenger seat (53 lbs).

By the way, If you don't race on the track but want your car to feel 10 times quicker for a very low price, look into the cow booster. Here is my review of that mod. After two years I'm still not used to the snappy throttle response my car has with it. It feels so quick just cruising around town, it's a great mod.

https://www.corvetteforum.com/forums...-buck-mod.html

acscogginjr

This is helpful to "us" daily drivers who do want to get more pop on the street, like myself! Just out of curiosity, was was the affect on gas mileage of the gears?

Thanks, Austin

Joe_G

I'm glad, I was hoping it would be. Good question.

i've got a record of all gas put in the car since new.

1.0 less from the headers and gears. But keep in mind this is my daily driver and in those days I drove mostly city about 40 miles each day, average mileage went from 19.94 to 18.94. I think I lost more on the highway but didn't drive much highway.

I lost 2.0 from the cam in mostly city driving to about 17 mpg city.

Now that I drive mostly highway about 60 each day, but in a fair amount of stop and go, average tank mileage has improved to about 21.

Anthony at LG posted up the following information which I think is a terrific summary of the pros and cons of different types of blowers and cams. Since I quote my thread quite a bit, and I think this is on point with the spirit of the thread of helping those seeking additional information on mods, I'm going to add it here giving Anthony full credit of course.

Tommy D

Joe


Great chart but you forgot a couple of very important "free" mods

1.) The best mod of all the driver mod. You take it for granted but you just happen to be a gifted shifter. Seat time is important, like any other sport you get better with practice. While we all think that we are pretty good drivers you can always learn from others, driving is an acquired skill.

2.) The weight mod Take everything out of the car and only travel with what you need. For those of us a bit over weight a diet makes the car faster.

3.) Know you car. There are optimum temperatures for coolant, oil and trans fluid. The correct tire pressure can be the difference between spinning and hooking.

Some of you may have seen the above short list before. I can not stress the importance of taking care of the little details as well as careful planning of modifications.

JUIC3D

Great chart Joe! Thanks for sharing

TNTC4VETTE

That is awesome.

Neumonic2002

Nicely done Joe!!

I thought my Fast gave me the most bang for the buck as it achieved an additional 18 rwhp and 21 rwtq over my ported LS2 unit for $799 but I already had the headers and Vararam in place which certainly helped the Fast achieve those results.

I wish a gear swap wasn't such a chore/expense.



John

Keith Tedford

It would have been interesting to see how the gears alone would affect the numbers. Having driven 4.10 geared Chevelles for the last 40+ years, the first thing I noticed with our 2005 was that it sure wasn't geared for drag racing. Still, it's an excellent performer and it would be interesting to see what a switch to 3.90 or lower gears would do. Old habits die hard.

FloydSummerOf68

I'm not sure the specs on the LG cam you're running, but I'm thinking it's likely set up to take max advantage out of the stock-like intake. Your gains going to the fast POST cam are lower than what most (including myself) typically see PRE cam.

For instance, I picked up ~20rwhp and 25rwtq peak compared to your 15/12

Interesting graph though thanks for posting it up.

It still convinces me further that heads really aren't worth doing unless you just REALLY want a max effort N/A setup. The gains for the $ just aren't there to be attractive to me. I'd rather just bump compression a bit and rock the biggest cam you can live with. After that add a little shot of gas.

That's just me though.

Joe_G

236/242 but old lobe design. I was disappointed in the FAST dyno results but the track results were very solid, .2 and 2 mph every run with similar 60 foots.

I agree that heads are not a good bang for the buck mod and I've been telling everyone so. They are the last mod to do IMHO. I will say the car feels faster and is 2 mph faster with them despite what the dyno says.

Joe_G

I tell everyone that will listen that gears on a manual vette is the best mod after a CAI. Worth every penny as they work from 5 mph on up..the car just feels 500 lbs lighter. John you can do it yourself, it's not a bad job at all.

Difference between our cars and a A body GM with 4.10's is we have 6 gears...I had an A Body with 3.90's and it sucked gas like it was leaking. I only lost 1 mpg in city driving, probably 2-3 on highway as my best highway mileage is 22 with gears on straight highway trips at 80+ mph (gotta keep up with traffic on the FL turnpike).

Here is a dyno graph to prove it. This is my car compared to a guy with same cam, he had a FAST vs. my ported ls2 at the time. He had stock gears, I had 3.90's. It's not the same car, trust me.



How here is the same two dyno runs, with speed as the x axis vs. RPM. Note how much more horsepower I have at any given road speed due to the fact that the engine is spinning faster. Of course you could downshift and get this same effect, but trust me, it's not the same. Anyway, this is graphic proof of how gears make the car feel faster. You've given the engine a longer lever to work with....literally.

JUIC3D

Wow Joe, I've never seen the information presented like that.

That post should be a sticky

If I'm understanding it, the only change in those 2 graphs is the X axis being MPH instead of RPM?

Joe_G

Thanks, and yes it's the same dyno runs, only difference is x axis choice.

debo

Definitely a great breakdown so everyone can see how to plan there next mods. Thanks Joe.

Sativa

Great info! I already have intake, headers, and tune.
Was planning on a cam next, but now you have me thinking about gears...

Joe_G

If you can, drive a car with gears and see how much more lively it feels.

Neumonic2002

Joe,

That really sheds a ton of light on the impact of the gears! Thanks for posting...I am pretty much finished modding my car so gears are something I will definitely consider.
Now when you say I can do it myself...are you talking about setting up the different gears in my existing case or switching out my stock unit for a case setup with let's say 3.90's from RPM?

Thanks,
John

Bill Curlee

Unless you have the Kent Moore C5-6 Set up tool,, Your are NOT going to be successful installing gears in a C5-C6 differential!

There are several Mods that you can do to a C5 / C6 rear but gears without a set up tool,,,, ISNT one of them.

Trust me!
Bill

nmalik3000

Excellent thread OP

Joe_G

Bill Curlee is right (as usual) - the suit cases of tools needed is a pricey proposition (like $4k) and the know how to use them doesn't come with them. There are many places, including forum vendors, who can do the job.

You can exchange the rear end in your driveway - you buy one and return your core. It's a day job even the first time, not so hard on jackstands, and if you have a manual car, no need for a tune or anything. Just bolt in, break in, and go.

By the way. And I don't want to turn this into a debate, please...but I've had both 3.90's and 4.10's. My strong recommendation is to go with 4.10's. It's just more of what you are buying gears for. The 3.90's are only needed if you plan to use nitrous or go FI and thus need the higher 140 or so trap speeds they allow in the 1/4 before shifting to 5th.

And frankly...even that argument isn't that valid as you can buy taller slicks if you need them, negating the need for 3.90's, and the shift to 5th if you need to make one doesn't really matter that much as it's at the end of the track. Drag racers will tell you ET is decided in the first 330 or so...you want that acceleration curve to be as steep as possible, as the last 660 is just going for a ride. 4.10's are surprisingly more effective in the 60 foot, I didn't believe it until I tried it myself.