Spinning rear tires

[LannyL81]

Is it even possible to spin the rear tires with the 2.87 rear end? I can barely get a chirp out of mine even with the engine changes. Just thought I would be able to....not that this is something I will do very often....but it would be nice to know. May be its just me and not wanting to abuse the power train.....

edit: stock manual trans

 

[Rawj]

I can spin my tires (nothing drastic) from a dead stop. And that's with the original rear end & engine.

Maybe this car is on steroids.

 

[LanceB]

Mine is stock and can chirp them pretty decently from a dead stop....and my engine has 90K on her and she's kind of tired. My brothers 77 is probably putting out 60-70 more hp than mine, has lower gears and he can't get his to spin for anything. It sure will chirp them when it changes gears though. Doesn't make much sense....

 

[spikebot 81]

Long tube headers, duel exhaust, magnaflow mufflers, and a little power braking. Stock rear end. My tires will burn a good 40 to 50ft once the rpm comes up. Also you can look for a puddle of water. Yeeeee Haaaaa

 

[LannyL81]

The engine has a 268H cam, higher compression, larger valves, Hooker Sidepipe/headers, but stock intake and carb. And it goes does the road pretty good....just does not have that "press you into the seat" power that both my 95 LT1 and 96 LT4 have.

I am wondering if I still need to do some more tuning to this engine....or if it really is the high rear ratio. Cause around town....running in 3rd gear is fine...no real need to put into 4th as RPMs drop to around 1000. The cam does not wake up until 2500 or so.

 

[Peer81]

The engine has a 270H cam, higher compression, larger valves, Hooker Sidepipe/headers, but stock intake and carb. And it goes does the road pretty good....just does not have that "press you into the seat" power that both my 95 LT1 and 96 LT4 have.

I am wondering if I still need to do some more tuning to this engine....or if it really is the high rear ratio. Cause around town....running in 3rd gear is fine...no real need to put into 4th as RPMs drop to around 1000. The cam does not wake up until 2500 or so.

What did you change to get the higher compression? Maybe you have a higher static compression but with a middle to larger cam (270H?) your dynamic compression will go don't because the intake valve closes later. Also don't know if you have stock intake sized runners or later, to large will have a drop in intake flow so your low and middle power will go down. Just a few tips, not that I know anything but just started reading books!

Groeten Peter

 

[73shark]

Have you optomized your initial timing and mechanical advance?

 

[LannyL81]

Higher static compression was acheived by: zero decking the block, flat top (2 valve relief) pistons, shaving 882 heads down from 76cc to 74cc. Also have 2.02/1.60 valves, 1.6 roller tip rockers (yes had to measure and change push rods by 0.100 inch), stock intake manifold, stock E4ME carb.

Timing was set to be at 32-34 at about 2500 rpms. No mechanical advance, all electronic (7 pin ignition module).

I do not have the specs on the Comp Cams 268H cam in front of me, just know that its the largest they offered for use with the CCC. I have a fully functional CCC; installed a heated O2 sensor in the header collector.

I am sure that there is more to be optimized...I am just not sure at this time what to try next. Need to do more reading.

 

[Curtis]

I dont think you are getting much benefit from your cam because of the computer controls. That 270H seems pretty radical to me for a stock computer. And even if you got a good chip for the computer, the anemic air flow with the stock intake and low volume runners in your heads are drastically limiting the power. I doubt if you are making 350 HP. As far a smokin the tires, even 180 HP will do that if you rev it up and dump the clutch.

 

[BADRACR]

SPIN 'EM

I have an 84 crossfire 4+3. I can smoke mine, no problem. I came in to work early last week one morning just to put a nice black "D" on the pavement. Not a doughnut, a "D". First letter of mt last name! Looks really great!

 

[Curtis]

I have an 84 crossfire 4+3. I can smoke mine, no problem. I came in to work early last week one morning just to put a nice black "D" on the pavement. Not a doughnut, a "D". First letter of mt last name! Looks really great!

Ha Ha ha... YOu should see the donuts I put in the two lanes between the guardrails underneath the overpass !!!!otfl Way too much fun

 

[BADRACR]

SPIN 'EM

Ha Ha ha... YOu should see the donuts I put in the two lanes between the guardrails underneath the overpass !!!!otfl Way too much fun

The morning after they put down the new pavement I got the first doughnut on the lot.
We were talking the other day about Earnhardt doing the "3" in the infield at Daytona in '98 after his win and I got to thinking, "You know, I bet I could do a "D" ". I figured the first chance I got I would see. It looks really cool. Because I had both tires spinning I got a double "D". That is my son's initials. He liked it more than I did! My first initial is "B" so I didn't go for that. But the "D" was easy. Rev it up, pop the clutch. turn hard right after a few secs, turned out great!

 

[spikebot 81]

Lanny, I'm thinking you got somthing not quite right. I to have 882 smog heads with the smaller valves and as stated earlyer this old car can lite em up. I do have long tube header and duals. The computer is all gone now. Maybe recheck your timing curve or possably valve lash. Just a thought.

 

[Peer81]

I begin to think it is just the way it is. The L81 rear gears are very low and you have an cam that works at mid and high rpm. I think the low gears magnify the loss on low rpm torque.

You could hook up a vacuum gauge to see how much vacuum you have on your intake.

Besides that small intake runners isn't such a big problem, better have small runners then low air velocity through the runners.

Groeten Peter

 

[LannyL81]

I will re-check the timing again this weekend. I am sure I have valve lash correct, but when time available, will check again.

I think it's just me and not wanting to abuse the drive train. I do not rev up the engine and dump the clutch....just can't get myself to do it. Which is probably what it would take with the stock grearing.

The times I tried to spin the tires I took off from a stop slowly and then floored it...so I was rolling....only tried a couple of times. Like I said, this just does not have the "push you back in the seat" power like the 95 and 96 have.

 

[Sensei]

Well, as you know, my engine is not stock, but I do run the original carb (modified) and computer (with Hyperchip) and distributor. I have the stock rear gears and a TH700r4 transmission, which has a lower first gear. Without power braking or reving, I can take my foot off the brake and jam the gas pedal to the floor and float the rear end around in circles. I actually have to be careful pulling out in traffic because if I push the pedal too hard with the wheels turned, the rear of the car will get ahead of me.

I think the key is planning your components to work together, then properly tuning everything. My '81 is my main car, I drive it almost every day. In my neigborhood, I am turning about 1300 rpms, on the highway, about 2000-2500. At WOT, the transmission upshifts at 5200 rpms. I used these numbers to select head, cam, intake and exhaust components. I am always tweaking for a little extra power/ gas milage. When you drive it all the time, you find what works.

God bless, Sensei

 

[PMartin]

I'm running a stock setup and have no problem smoking the tires.

 

[LannyL81]

Not driving this car much does not help me at all, that is for sure. I have it insured as a collector's car so I cannot drive it all that much....mileage limit as well as day limit (not supposed to drive it to work).

Like this past weekend...did not even have a chance to start it...much less drive it. I end up thinking about things to try all week long and then the weekend comes around...and I end up doing house things and no Corvette activity. If only I didn't have to work.........

 

[Sensei]

If only I didn't have to work.........

Don't worry about working, Obama will take care of you.
:Wotflotfl:W:L:L

 

[PMartin]

Do you think we could get a corvette stimulus package?