Ok, I installed my new motor in a 68 Vette I bought earlier this year. The motor dynoed at 452hp but I believe after some tuning I squeezed a little more out of it.. My question is in regards to the reaction of a launch (on the street).. For an unmodified suspension this thing has incredible weight transfer and launches real hard from an idle with my 3000 stall but I cant even break the tires lose if I try and I'm running 10-1/2" BFG T/A radials.. Now, just so you know, I am still running the stock 3.08 gear but I have talked to guys running the same gear that are able to bust tires lose not only from a stand still but also hitting second gear with less power than I have.. I'm running a BG Mighty Demon 750DP that's has great off idle response.. I also tried increasing my squirters sizes but I'm not noticing a difference at all.. I know busting tires lose doesn't win races but it seems pretty sad when my car sounds like it has 600+hp under the hood and I cant even do a burnout.. I cant even break-torque a burnout. Can my weight transfer really be that good that it wont bust the tires lose on the street or does it sound like there is something else going on here? Like I said, the off-idle response seems great and it launches hard with absolutely no hesitation or bog and it smoothly goes into a hard pull through the gears. On the street this thing hooks up as good as my 73 Camaro that ran 10.80's at the track did with slicks but just seems strange that I can even do a burnout.. I even have my timing locked out at 36 degrees, which should improve things even further. I have taken a few guys for drives and launched it from a stand still and even they cant beleive how well it hooks but cant break the tires lose. One guy said we left his stomach back there and need to go back and get it Any ideas or explanations?

 

Well jmo, but you don't mention Big Block or Smallblock or the cubic inches w/your 452 HP.
Or if your bullit is built for Steroids or not.(NOS)
Or where your cam kicks in. 3500 RPM+? Etc. Etc.

Great to have the Horsepower, but if your motor makes torque up high, your not getting to the range with 3.08's off the idle, or even to 2000+RPM.

But sure 3.08's will fry tires on a big cube, low RPM Torque Monster as they do in my '71 Buick GS455.

Besides, the transfer of the weight on that IRS in your C3 is stupendous,..... till you put in a *4.30 gear or so, and feel the breakage. (*3.73 if you're sprayin' it with Steroids). Best Regards & Enjoy!

 

Motor is a small block and dyno sheets show just over 400ft of tq coming in at 2800rpm which is just under my 3000 stall. Torque remains over 400 all the way up to 5400rpm with a peak of 436 @ 5100..

 

Well you don't mention cubes.
No Steroids? Ok, rule of thumb. Smaller the Cubes, Steeper the Gear.
Like 3.73's with 383+ cubes. 4.10, 4.30 w/355+, 4.56 -5.13 w/327.

5.38's, 5.57's, 5.86, 6.14's if 265 -302 etc. Of course on the street 4.56 would be the max and even then it's a chore. I'm guessing you're around 383 or so on that bullitt.

If you may only go to the track once in awhile. Enjoy a 3.73-4.10 max..... oh, and btw, check that rear!(U-Joints, HalfShafts, etc. Check out IRS components from TOM'S, when & if the time comes....

 

Its a 355 with no juice.
I know and already plan on getting steeper gears but I dont understand why I cant even spin my tires on the road with street tires when I'm running over 400 ft lbs of tq where my stall comes in.. I see much milder vettes with standard converters doing it and I also see stout vettes like mine doing it with no problems at all... Ok, lets say the weight transfer is really that good but that doesnt explain why I cant break/torque a burnout when there is no weight transer even going on? If my 1/2 ton 4.7 liter motor can override the rear breaks, surley this motor should be able too.. Not much fun when your in a cruise and you hit a spot where everyone is doing burnout and I cant, especialy when I have one of the most radical motors in the cruise..

 

1) Ask those other rides you mention what gear they're runnin', as I'm thinking steeper than 3.08.
Again, when your smackin it, you don't have the torque' curve building yet. Punch in 39* - 39.5* timing for the street.(around max).
Be happy that you probably have a good bracket racecar there.

2) Smallblock & an IRS = Great Launches!

3)Put on a 235/65x15 street radial, and smoke em' up sideways!

 

Screw bracket racing, this would make one heck of a street racer
Not to many street machines could launch from a light like I can

 

*Been There, Done That, Am all over the idea!
(*454/450 "LS6" rides back in the mid seventies up in NYC... No Spray, No P/A, No Open Hoods!...oh, and "396" under the SS emblems on the '70 Velle fenders, and the correct "302" hood emblems on the '69 Z cowl hood...lol)

 

I have absolutly no experience with an auto, but my 4:11 geared, 4-speed has no problems spinning the wheels. You have a lot more tire then me, as I drive aroung on 8 inch Mickey Thompson drag radials. I would guess I have between 350 and 375 rear wheel horsepower.

Are you saying that with your foot on the brake and steping on the gas you can't get the rear wheels to break loose?? Maybe you need to drive thru a puddle first!

 

Just my 02 worth ,with experince "DUMP THE BARY GRANT CRAP".
I would try a holley and one of your buddies should have one you can try.

 

You are running the BFG T/A radials. IIRC, those are street legal drag radials and they will be difficult to spin on launch. You are not running a torque monster engine so it will take work to break them loose.

 

These arent the BFG drag radials, they are just the standard BFG T/A's in 275/60-15.. I would think over 400 ft lbs at my rated convertor stall should be enough to bust them lose on demand, especially on the street. I see guys running less power than me bsuting them lose in second gear with an auto trans.. I just didnt think a stock suspension could hook good enough to keep this kind of power to the road like it does but then again I never owned a corvette before either

 

Now that you brought this up
The faster I mash the pedal, the better the reaction I get. Matter of fact, to achieve the best reaction, I have to really mash the pedal to the floor as fast as I possible can.. With that being said, the BG Mighty Demon (mech sec.) comes with a progessive linkage for the secondaries that causes the secondaires to open at about 3/4 pedal. Is it the same way with a holley? It just seems like a better set-up would be more of a 1:1 ratio so the secondaries open up when the primaries open or only slightly there-after and not 3/4 of the way down.. If I slow the pedal response down, I can feel the pump shot from the secondaries coming in so I now understand why it responds better, the faster I mash the pedal but that just doesnt seem right to me. Dont most drag cars have it set-up so the pump shot on the pri and sec come in at about the same time?

 

While I have heard it said that the C3 is a good setup with battery in the back and the driver sitting right infront of the rear wheel. My personal experience has been difficult to keep car from spinning, again its a different thing all together with the 4-speed.

I don't see what difference the carb, seconadary and jets have to do with putting your foot on the brake and then stepping on the gas. If it can't break the rear wheels loose while doing that exercise there must be something wrong.

 

If I try to do a brake/torque burnout, the power will over-ride the brakes and it will actually start pushing the car instead of breaking the tires loose.. I'm sure a line/lock will solve that problem

I might purchase one of those Performance Meters because I would be curious to know what my 60' times are on the street.

 

Oh!!! I did'nt understand. Those must be some good tires!