I took the chevelle out to the track for the first time with the new engine.
My question is that my MPH regardless of my time was the same at 99.60 or 99.XXX, for example
I had a run of 14.018 with my MPH 99.7 and another at 13.660 at 99.5.
My overall quarter mile time dropped when I my 60 foot time finally got within the 2.2 and a best
of 2.063. I now I can leave the line harder if I stall about 2400 so I wonder what the MPH indicate?

Best time
reaction time .244
60 foot time .2068
some number 79.82 MPH
final time 13.6608
final MPH 99.426


I did no tunning or jetting at the track and used street Nitto 555R tires, I wanted to drive the
car in my every day trim and run it. I think this is a great baseline for tunning and I hope
that my car is a 13.1 or 13.4 car respectfully and this would be without slicks. After all
a 2004 cobra was running off 12.7 and 12.6 in street trims also. If you can please give me your
input on my times I would appreciate your opinions.

The 14 second was a 14 second run due to the 2.2 60 ft. and the 13 second run was because of the better 2.06 60 ft..your 99 MPH indicates a low 13 if you improve the 60 ft. even more than a 2.06
What is your combo? What tires?

Your speed will always be consistent within 1-2 mph (depending on atmospheric conditions) and is a reflection of horsepower and weight. ET is more a reflection of gearing and traction. I expect that your MPH will not change much as you continue to tune, but you can bring the ET down by experimneting with traction and shift points. 2.06 60' is not bad for street radials. I never did better than 2.01 on street tires. I have gone as low as 1.91 with Mickey Thompson Sportsman Pro DOT-legal sticky tires. I doubt you will go quicker than 13.4 unless you can get the MPH over 100. Nice times! What size engine do you have?

Depending on how you are jetted, you could gain some mph by changing jets. My car was quite lean at first. I picked up 4 mph with jetting up (that's around 40hp!). Timing is a factor, too. Try changing it a degree or two both ways. When making tuning changes look the mph. As said, it is an indicator of hp. Keep going in the direction that increases mph until it stays the same or falls off, then backup to the previous settings. Do only one change at a time.

Pat my current combo is as follow

Engine 350 bored .60
Cam: Comp Cam 274xe with 1.6 roller rockers
Heads: Stock GM cast with port work and valve 2.02
Carburetor: Speed Demon 650 mechanical Secondaries
Intake: Edelbrock Air Gap RPM
Ignition: MSD 6AL with Pro Billet Distributor
Headers: Flowtech
Transmission: 700r4 with 2400 stall lock-up
Rear End: 10 bolt posi 3.73 gears

Pat the engine made great power on the engine Dyno at 410 Hp and 448 lbs torque, but I have not done any tunning to the carburetor or timing since installing the new engine. The Demon Carburetor has the orginal setting from the factory and the timing I am not sure but I think its at 35 degree.

I agree that I need to get my MPH in the 100 to get to lower numbers and possible 13.00 flat, but I feel that I can still get a 13.5 or 13.4 because I know I can leave the line harder and at a higher RPM then what is shown on the slips.

99mph in a street-trim Chevelle with a 350 is pretty stout. Congrats.

if you get some sticky tires on that thing i would say 1.80 60ft times should be obtainable, maybe even high 1.70's. that would knock another 4 tenths off your 1/4mi time. i could see 13.20's being within reach with some traction. graemlins/thumbsup.gif

The tires I use are Nitto 555R which are probably the best street/drag tires you can buy and they are sticky when they are warmed up. I don't think I had a traction problem at the track but I will be looking at my fuel curve and rev limiter, on one of my runs I hit a 13.7 while hitting the rev limiter. I am going to have it chassis dyno tomorrow so hopefully I can take it back to the track and get those MPH into the 100 + range, maybe 13.0 flat?

100 mph should, with good traction, give you about 13.25. 2.0 60' shows that you are spinning. With what you have in the engine, I'd expect you to be pushing 13.0 or better.

I suggest using 1.5 rockers on the exhaust and keeping the 1.6s on the intake. Most engines make more power this way. You might try bumping the total timing to 38º. On the dyno, several years ago, my engine picked up 27hp with a three degree increase. That was worth almost 2.7 mph.

Shift points have a big impact on performance. With your cam I'd expect them to be around 6000 rpm probably a bit more. I've found, in my car, a higher shift point leads to a higher finish line rpm, which is a higher mph. Are you locking the convertor? This will stop any convertor slippage. You can wire the 700 to lock in third. I'd do this. You shouldn't be close to going into 4th.

Pat I found out some critical information while tunning my car, well as it goes I wanted to shift my car from 6000-6200 RPM with a 6400 chip in the 6AL, but for some reason its seemed like the rev limiters cam on way before 6400 RMP. While at the track I would have to short shift from second to third, 5800 RMP because of what I thought was the rev limiter which as stated before is set at 6400RPM coming on. Come to find out it was not my rev limiter coming on but the engine is running out of fuel under 5800+ loads its like the car dies then it comes back after I shift into the third gear which I thought at the time was my rev limiter coming on but I watched as the engine started to cut out around 5800/5900 RPM's. Now the next step is to find out how to fix this fuel situation because if I can shift at 6000K with out the engine starting to cut off then I should get my MPH into the 100+ farily easily. Question is it my jets in the carburetor to lean or is it the fuel pump? The fuel line from the tank to the carburetor is 3/8 and not the 5/16. Any suggestion?

Do you have a pressure gauge you can see while driving? Mostly, in my experence, the car lays down in 3rd but pulls well in 1st and 2nd when the fuel system is lacking. I'd try richening up. I think it is best to richen up first rather than lean first. A lean condition can destroy an engine. Go up two jet sizes. What you are feeling could be detonation. Does the sound of the engine change when it loses power? That would, to my ear, indicate a lean condition. It's possible that the springs are not up to the task. Once they float, they will only get worse. Try richening up, though, and see if that fixes it.

Pat the engine does not produce a ping or detonation sound but more like a sputter sound like the engine is bogging or cutting out, I thought it was the rev limiter, but it feels like it is running out of juice at high RMP. The question is would the carburetor be the cause or is it the fuel pump not supplying enough fuel therefore resulting in dry bowls? My current fuel pump is a stock I believe there is no marking on the fuel pump other than made in the U.S. Don’t you think I should like at the fuel pump itself first because I don’t think running smaller jets would make your engine sputter. The springs are z28 which are not the best but on the dyno it did not experience any valve float during the 10 pulls and 3 pulls at 6400 RMP. I think the problem never the less is a fuel problem, not enough fuel being supplied to meet the engine demand.

I think it is the jets. That pretty much describes the sound I had when running lean. Usually if the fuel supply is too small the engine will lay down in high gear but pull strong in lower gears. The fuel line is probably big enough. I ran well into the 12's with the stock lines. You could put a better pump in (mechanical is fine) but I'd bet the problem is jetting. I suggest looking at the plugs for tiny black specs on the porcelain. If you find any, that is aluminum blown from the piston by detonation. You'll need a strong magnifying glass and very good light.

Pat I am going to test your theory and go up to sizes in the jets, I am not sure what your combo is but if your experiencing the same thing I am experiencing then I can only assume that you are correct. I will let you know!

What I found was jetting up moved up the rpm that that the sound started at. I just kept going up on jets and the car kept going faster. A some point, it will stop going faster or slow down a bit. Back up a couple sizes and if the engine sounds clean, you've got it. Otherwise, bump up one size and see what happens. Do both ends of the carb. I hope it works out.

Originally posted by Spawn22:
Pat my current combo is as follow

Engine 350 bored .60
Cam: Comp Cam 274xe with 1.6 roller rockers
Heads: Stock GM cast with port work and valve 2.02
Carburetor: Speed Demon 650 mechanical Secondaries
Intake: Edelbrock Air Gap RPM
Ignition: MSD 6AL with Pro Billet Distributor
Headers: Flowtech
Transmission: 700r4 with 2400 stall lock-up
Rear End: 10 bolt posi 3.73 gears

Pat the engine made great power on the engine Dyno at 410 Hp and 448 lbs torque, but I have not done any tunning to the carburetor or timing since installing the new engine. The Demon Carburetor has the orginal setting from the factory and the timing I am not sure but I think its at 35 degree.

I agree that I need to get my MPH in the 100 to get to lower numbers and possible 13.00 flat, but I feel that I can still get a 13.5 or 13.4 because I know I can leave the line harder and at a higher RPM then what is shown on the slips. Nice HP and Torque numbers! graemlins/thumbsup.gif I have a friend who had a 383 in a bit lighter car than yours with pretty much the same parts including gears and tranny. He did have RPM heads. His car ran a 12.38 E.T.. I posted (http://www.chevelles.com/cgi-bin/forum/ultimatebb.cgi?ubb=get_topic;f=4;t=017068) about it last fall. I think you should be able to get a couple more mph out of it and low 13's with more tuning and traction.

Rod

First I rejetted my secondary from the stock #78 to #80 and I was going to change my primary
from stock #70 to #73 but for some reason the carburetor had #71's in the front, go figure,
anyhow I am going to leave the fronts at #71 which is one size up from stock and go two up
in the secondary to see if the engine will not sputter at high RMP's. I will test it tonight
and let you know what the outcome is, I purchased a Holley mechanical fuel pump also, but
I want to see if the rejets will fix the problem first.

I'd go ahead and bump the front up two sizes from what is there.

What kind of numbers did you end up pulling on the chassis dyno??

I will be doing the chassis dyno next month I decided to fix my fuel problem first.

Pat you are right on it it was not my fuel pump it was the jets, I went up two sizes only in the rear and the car will continously pull up to 6K with out cutting out Now I can shift the car at 6200 RPM rather then 5900 graemlins/hurray.gif The car feels much faster than the 13.6 it ran last week and I would not be suprised if it went 13.2 or 13.00 flat with the one adjustment I made however I will take it to the track maybe tomorrow and do more tunning and possible timing adjustment graemlins/beers.gif

Great!!! Take some jets with you. You might find more power, yet.

graemlins/beers.gif graemlins/hurray.gif Nice quick fix:) Now you tell them mustangs that if GM had thrown a supercharger on the chevelle (or camaros if that is their argument) from the factory that it'd be a whole new ball game, don't compare your shiney apple to a rotten orange:) Good luck!

Did you make it to the strip? Just wondering how it went.

Yes Pat here is the thread I started
Update track results (http://www.chevelles.com/forum/ultimatebb.php?ubb=get_topic;f=4;t=020444)

Got 13.2 at 103 MPH and 60 foot time of 2.033 but was only allowed 4 runs because of race. Pat I think I could have got it 13.00 flat or 12.9 because the previous run was 14.2 with a 3.047 60 foot time at 104.079MPH