I have a question for you,

I was running an autocross today and there was a large sweeper one end of the course. Mid corner my engine seemed to be starved of fuel because of the g's during the corner. Have you run into this problem? If so how did you solve it?

Overall my day was pretty good, I ended up running a better time than a 5.0 that was running slicks and I was only .2 of a second off the time of a '01 Trans Am. I am sure I could easily knock off another second or so if I had slicks or decent tires.

I also had alot of oversteer during through the whole course. Part of it I contribute to my crappy rear tires. I didn't have my rear sway bar hooked up, would this help or hurt me with my oversteer problem?

Everyone should be required to track their Corvette because it is just that fun.

 

Rear sway bars increase oversteer.

BigBlockk

Later.....

 

crossedflags77
The only way I could fix the fuel problem was with a fuel cell that had a sump. I didn't want to spend the money for a pre-made one, so I made one myself. In hind sight I should have just bought a lite weight one. At the time I thought a little weight in the rear would help with the oversteer. Now that I'm trying to get weight out I might have to get a lighter cell. The key is the sump it needs to be centered and of a good capacity. I run a full flow system (not dead head) so capacity is important in the really big sweepers. So far so good.

Great news on your track time.

In my experience the cone type parking lot events are very hard for c-3's without mods and tires. I recommend the road courses for more enjoyment.

As far as suspension is concerned it depends on what you have and therefore what you can do. As a rule the sway-bar in the rear is not necessary.
That being said it totally depends on where your car is now.

(This is for Everyone)
Suspension setup is an art. To get very good at setup takes years of experience. For any one of us to say this will work or that is actually pretty rediculous.
That doesn't mean there are not things in general that will improve the performance of the suspension. The reality is the more adjustabilty you have the better. You have to approach the setup as an extension of yourself and car. Your driving style is just as important as this part or that part.
For me the best modification I made to reduce oversteer was to learn better throttle management and how I entered and exited the corners.
Which goes back to seat time. In other words as you improve you should improve your suspension. (unless your like Twin Turbo, build a race car then learn to drive it. LOL )
I remember a few years back Rupert Bragg Smith saying to me: The key to sucessful driving is to quickly learn the mechaniacl abilitys of the car and not drive beyond them. He said it was up to the mechanics to make the car faster. The Moral is drive your car to it's limit and have fun. As you upgrade so will your times. (if you want to go that route).
Be careful of the DIHLEMA (race or street). It can bite ya!!



WOW I'm rambling here guy's. Sorry!

I will get to the point. Spend as much time as you can learning about how suspension works. As you build a vocabulary you can more effectively communicate your needs to anyone you are trying to gather info from. Also know exactly where your car is now with setup. So when you try something you can record the result. READ, STUDY, LEARN, DRIVE, DRIVE, DRIVE. By the way the DRIVE part is the funnest.
Later!

 

I have the same problem. I don't think it's a fuel tank issue with the pickup going dry cause I've encountered it with a full tank. I figure it's the carb metering...it's a gravity/vacuum feed system and during a tight fast corner with good rubber the g-forces upset the fuel bowl level and creates a rich condition in one venturi and a lean condition in the other, but the lean condition wins so power will fade. I've decided to upgrade to a multi-port fuel injection system when I'm cleared for the cash outlay. That's the only thing that will fix the old carb-in-the-corner problem.

 

Yea I was running with an almost full tank, so I figured it was carb issues. Thanks for the help 72 Ray and Rockn-Roll. Looks like fuel injection is in order, but I don't see it anytime soon .

 

Is it a Holley? Check your float levels. If you're not running sticky tires I find it suprising that you could be experiencing fuel starvation mid corner.

edit: now I see the edelbrock 600 in your sig. Don't know anything about em, so I can't really help!

 

69autoXr, your car is one of my favorites! Could you tell me what size wheels are on your car and what the back spacing is?
72Ray is the pride of this forum, whipping *** and supplying the related videos for our enjoyment. Those small econo cars were able to stay in front of him because the track was so tight. I think he would have overpowered them if there were a nice straightaway.

 

CrossedFlags77, see if you can borrow a small Holley with center-pivot floats. I believe that Edelbrock carb is like the old Carter ABS/AVS models and they had fuel starvation problems in hard turns.

 

Yeah! the carb thing. Forgot about that. I never really drove my car much with stock stuff. I forget not everyone has the the same setup. I do know that the tank will be an issue at some point. I run a Holly HP carb. I went with the full flow system to keep the heat down at the carb. Also put a phenolic carb spacer to help with the heat. You don't have to fuel inject to correct the problem. A good carb will do the trick for 1/4 the price.

 

16x11" about 4 1/4 backspace. I use a 5/16" spacer in the back to clear the caliper, but that is ok because the tires still don't completely fill up the rear flares.

 

69autoxR, what about the front? What size and back spacing? Do the tires hit at all on the inner fender when you turn the wheel all the way?

 

Same size, front and rear, and same backspace. I don't need the spacer in the front to clear the caliper. No rubbing on full lock, and I haven't seen any during suspension travel.

 

I run the ultra hp series like in my avatar

 

Good stuff 72 Ray, thanks for sharing

 

After many years of fwd VW's I autocrossed my '75 this weekend. Amazing how little transfers from FWD to RWD in terms of set-up. I was chasing understeer all morning. (I run 255/60-15 front and rear). In the VW higher pressures in the front and no front sway bar were the norm. After thinking about it at lunch I dropped 10 psi from the fronts to get the sidewalls to roll a little and pumped the rears up to 40 psi. It still understeered but not nearly as bad and I think it was much closer to neutral--much more driveable. I wasn't chasing the car anymore! Needless to say, I'm hooked. Next A-X is October second. Any recommendations on actual tire pressures? I have to go out and check the tires cold. I think a ten psi differential front to rear would be best!?!?
BTW, L-48, TH400, Headers, dual cats, dual exhaust. Edelbrock performer intake, Edelbrock 600 cfm carb, K&N filter with extreme top.

 

I did it in the 80's with 255-60-15's shaved to 1/8"...ran 34 front and 32 rear..78 stick...FE7 suspension and some "weird" shocks (old story there)..still plowed if I went in to a tight corner to fast..concentrate on being smooth..good luck..it all comes together with seat time..

 

Yeah,

Seat time. Hard to get much up here in Vermont. Need to unlearn some FWD habits too! Should I resist the temptation to put a rear bar on it?? I'm not intending to go roadcoursing anytime soon, so big changes aren't a necessity, I think?

Thanks for any advice.

George

 

72 Ray,
I think I read that you run 15" tires due to availability and price. I'd bet you'd go much faster with some 17 or 18 inch racing rubber. Imagine your times if you could take some weight off the car and run some steamroller tires. I'd love to see the look from those rice rockets when you passed them in a corner with your 33 year old Chevy! You've got an incredible car, 2 thumbs up!

 

I don't know if that's really the case. Why do the NASCAR boys still run 15" tires? The shorter sidewalls tires are so stiff they might not maintain contact patch during hard cornering with our more compliant suspensions.

 

I think the only reason NASCAR guys run 15's is the rule book. They'd drop 15's in a second if they could. Yeah, they tune their cars using air pressure, but they'd have to do a lot less of that if the tire sidewalls weren't so tall. That's the advantage of short sidewall - they take some of the guesswork out of suspension setup. That, and the larger rim diameter allow the use of huge brakes. I do think there is a limit to the shorter-is-better sidewall argument, but I think 17's or 18's would be an improvement.
By the way, both you and 'Ray have awesome vettes and I won't take away anything you both accomplish while holding up the C3 end on the track! I'm now inspired to tweak my '70 with some road racing in mind. My wife is gonna kill me - if she finds out!