johnt365

I am posting this data for others who are considering this cam and how it will result in rear wheel horse power and torque. Below is some data and a question at the end.

TH400 trans, 3.08 gears, base 160hp 350 bored .060, Performer intake, stock 76cc heads, Headman headers, 2.25 inch pipes with generic turbo mufflers, Stock HEI.

Baseline results: 178 hp

Added Edelbrock Performer centerbolt heads, Harland Sharp roller rockers.

Results. 203 hp

The a/f ratio was very lean at this point with the stock Quadrajet. I recalibrated the jets and rods per Cliff Ruggles advice,

Added Comp Cams XE268H and Crower CamSaver lifters.

Results are below 262 hp. That is an 85 hp gain from where I began. Thats about 60 rear wheel hp from the cam. I feel like I have corrected the lack of power this car originally had and think it can be officially a Corvette. It runs awesome from 3k rpm to 4.5k rpm. However, as fun as it is to drive now, it is still a dog off the line.

I feel like a Corvette should be able to do a burn out. The dyno guys told me I should have used Rhodes lifters for more torque. Too late for that. Do you guys think a 2800 rpm torque converter from Performance Torque Coverters would light things up?

thebruce

When I upgraded my top end, the first cam I used was the one you've got. Same results as you-- great mid to top end, nothing special on the bottom end. When I wiped a lobe (and I am not blaming Comp Cams like everyone else-- I just wasn't careful with preload because I didn't know what I was doing) I switched to a 262 series cam (I went with a Lunati cam that was recommended because I was going to swap to TPI at some point) and got a noticeable boost at lower RPMs-- a lot more low-end torque.

I can't answer the higher stall converter question because I've got a 4-speed, but it makes sense that you'd notice some difference, looking at the dyno numbers.

427Hotrod

Converter would surely help..but I'd take a look at distributor curve first. Is it stock or have you tweaked it any? Increasing initial timing and then limiting advance can really help off the line driveability.

JIM

johnt365

I did tweak the timing. The total timing (less vacuum adv) comes in between 2200 and 2300. I have tried 32,34 and 36 degrees and the results were about the same on the steet as well as the dyno.

The Money Pit

Converter will help,but the rear gears,......If I were to spend your money,...I'd go with 3.70's out back, and leave the converter in till you need a new one,...then maybe go to 2500 stall. The gear advantage is spread acrossed all three trans gears, so you get a "boost" in every gear. The converter really only helps off the line with really healthy cams.

hugie82

2400 converter should do the trick without any drivablity issues and don't forget the trans cooler!!!

7t9l82

I'm a big fan of converters, but you don't have alot of low end. so I'd say a gear change a 3:55-1 ratio has always been a good street gear a 73 is a little much without an overdrive. the best thing is both! my l-82 has 355 gears and from an idle not power braking smokes the tires for about 30 feet . with heads,cam,etc you should be there

Korevette

As mentioned gears or a shorter profile of tire, that was all we could afford as kids with a old 1974 Chevy 1/2 ton.

Dano,

Ironcross

Your not going anywhere unless you change the gear to a 4.11 and a good converter is a must for good idle manners...otherwise its a constant foot switching from the brakes to the gas pedal, back and forth at a dead stop when in gear.....

Vetterodder

A 2200-2500 converter will allow it to go immediately to where it's making some power, making a big improvement. Combined with lower gears, you should see a huge improvement.

johnt365

ok let me ask this. Is there a tire smoking cam for 3.08 gears? Are the gears my problem or the cam?

A rear gear change is a major expense for me right now.

7t9l82

when you choose a gear take into account where you drive most if you never go over 40 MPH you could run a big gear but like here in Florida you will get run over doing 80 on the interstate soon too big a gear will not be good. if this is a drag car or street racer yes big gear if your going to cruise the highway a moderate gear is better. no material what dump the gear you have

Les

Your cam is kind of a medium street performance cam and really isn't the problem. Gears would make a nice difference- as mentioned by 7t9l82 I'd go with 3.55s unless you plan to drag race or get an overdrive auto trans. If you can't afford rear gears right now a looser torque converter (w/ trans cooler) in the range mentioned by Vetterodder would really pick up your pull off the line. Anything higher numerically could create excessive heat in your trans on the highway with your current rear gears. Good luck.

7t9l82

solid advice!

63mako

The 268 cam don't really need a higher stall converter 3:55 gears will be the answer. Or leave the rear and do a TKO 500 swap. That would make it a different car.

7t9l82

he is concerned about cost, gear or converter will help both is better. for gears check around someone may trade rears with you or maybe someone on here has a seat up rear for sale gears aren't expensive a couple hundred bucks maybe someone on here will set them up for a good price or help you do it maybe a local mechanic would do it on the side you may get there pretty reasonable. someone near him to help a Guy out? he is probably about heart broken, he spends alot of money on his car and now he is affraid it wont ever be what he wants.maybe someone can help out? i don't think a t56 swap is practical, nice but not realistic

JohnRR

Keep checking the parts section of this forum, Craig's list, or eBay for someone parting out their Corvette. You might be able to find a whole rear end with a very popular 3.36 gear ratio. This would give you an immediate 9% increase in torque to the rear wheels and you would still have your original rear in case you ever want to go back. Changing out the rear pumpkin is pretty straight forward. If you can change a cam, then I'm sure you can bolt in a rear.

John

PowdercoatBill

If it were me, I would pull the rear pig out and take it to a rear end shop and have a 3.55 or a 3.73 put in it. A ring and pinion and a bench job shouldn't be much more then a good converter. By you pulling the rear end out will cut the labor rate down a ton!

63mako

Going down on the cam moves your power back toward where your build came from. This is a very common issue. Matching components throughout produce best results. Your engine has them and you see the results. Your gearing does not match the engine build. I had the same issue when I got my 63. It had a built 302 with 3.08 gears. No bottom end and it was a pig out of the hole. Dropped a 3:55 in it and it transformed the car. I was in the cam earlier and it pulled much harder through the gears. It was also in the operating range of the cam at cruise and would still go down the interstate at 75 MPH with no problem.

SanDiegoPaul

The torque multiplication of good converter will overcome those gears.

I use a crane to 272H Cam with 2500-2800 stall converter. 3.08 oem gears too. Burnout is absolutely no problem if I choose to do that. When I first built and installed the motor, I had the original q-jet on the new motor. I had done the transmission too, but it was still a Dog off the line. I pulled a new Transmission back out and put in the new converter...life is been great ever since.