ENGINE - Time Slips

[Guest]

Well the verdict is in, not quite what I was hoping for but I did say I would post results. Made three runs and my best time was 13.27@106.10. For sure not a terrible time but I am sure with just a bit of tweaking I,m in the mid 12's, the car had tons more potetial but it didn't seem like I was doing much(making power wise ) until mid track and then I would just start flying. Didn't even come close to maxing rpm, so I,m pretty sure that next time I will drop another .5 to 1 second.

Solid mounts are great, not 1/2 the extra vibration that I thought would occur and it hooked up faily well, and best of all.... no breakage.

Brad

[Guest]

Hey Brad,

Hope you had fun at the track over the weekend.

What size gears do you have the rear-end,

open diff. or posi??

[Guest]

Quote:

<font face="Verdana, Arial" size="2">Originally posted by David72:
Hey Brad,
Hope you had fun at the track over the weekend.
What size gears do you have the rear-end,
open diff. or posi??</font>

I have 3:73.1 and it,s a posi, zoom gears and moroso brute strenght carrier. 4:10.1,s would be more appropriate for the set up that I have but I wasn,t sure if I wanted to give up the streetability so I went with the lower ( numerically) gears. I bought the gears about 18 years ago so I didn,t know much about the motor then.
Brad

[Guest]

Nice rearend set up. I put 3.90:1 gears,

and an Eaton posi in my 72. With the 2.73

open diff I ran a 14.630 my first time at

the track then I change to the new gears and

posi and went to the track with the same

set up on the motor and ran a 13.651. The

3.90 gears are deep but not to deep the are

great for cruising around town, and not really all that bad on the highway. I run

the car at 3000rpm on the highway, which is

somewhere between 55 and 60 mph.

I had another question.....What kind of ignition to you have on your car?

[Guest]

Quote:

<font face="Verdana, Arial" size="2">Originally posted by David72:
Nice rearend set up. I put 3.90:1 gears,
and an Eaton posi in my 72. With the 2.73
open diff I ran a 14.630 my first time at
the track then I change to the new gears and
posi and went to the track with the same
set up on the motor and ran a 13.651. The
3.90 gears are deep but not to deep the are
great for cruising around town, and not really all that bad on the highway. I run
the car at 3000rpm on the highway, which is
somewhere between 55 and 60 mph.
I had another question.....What kind of ignition to you have on your car?</font>

I have a MSD6AL, with an HEI distributor,and a msd coil, 8.5 mm wires. I run fairly close to the same rpm on the hwy. about 3100 @ 60 mph on 27" tires. If I can,t get mid 12,s with these gears I will be stepping up....gotta have the 12,s.
Brad

[Guest]

What are your 60" times??? Are you hazing

the tires??? That ride should easily be in

the low 12's. Have fun gettin her tuned in..

[Monte]

To answer your other post there is a calculation for correcting E.T.'s for elevation. However you need a degree in calculus to figure it so, try this in stead. From 6000' to 5000' add .20, from 5000' to 4000' add .19, from 4000' to 3000' add .19, from 3000' to 2000' add .19, from 2000' to 1000' add .18, and from 1000' to 0' add .17, these times very to correct for air density. This formula applies to most street/strip vehicles out there with engines capable of achieving approx. 90% to 105% volumetric efficiency. Also I second David72 check those 60' times. 106 MPH should put you about 12.6 to 12.8.One other thing, most people focus on the quarter mile time. I would start by tuning to get the best MPH first ( unless your just blowing the tires off the car) then figure out how to get the E.T. down. MPH=Horsepower. What did you have for tires?

[Guest]

I like my 3.73s, they are very streetable and low enough for a decent 1/4 mile run. I'd look elsewhere for some ET before going to 4.11s.

My 12.77 @ 110 was with stock HEI ignition, stock 12 bolt.

Did you advance the timing? I got a few tenths there.

 

 

 

------------------

Dave Kase

"Desmo888"

'70 SS454

[Guest]

Yes , I like the 3:73 ,s as well and don't plan on changing them just yet. I am confident that I will get at least .5-1 second just with tuning. The 60' time on the best run was 2.053 which needs to be tidied up a bit.I was using an old set of hoosier slicks that I didn,t heat up very well cuz I was a little worried they might not last the day, however they did hook fairly well in their defence and next time I will be heating them up a whole lot more. I also believe that if I lauch a bit harder it will help. Keep the tips coming guys, mid to low 12,s is my goal.

Brad

[Guest]

Don't forget to remove the power steering belt...

 

------------------

Dave Kase

"Desmo888"

'70 SS454

[Guest]

Hey Brad,

I concur with Monte.....I'd say that part of

ET dilema is that 2.053 60' time. Work on

getting the car to MPH, then you need to get

her to hook up and get that 60' time down,

it's amazing how much the ET improves with a

good 60' time. I haven't a clue what you

should shoot for. I have a friend with a

73 Omega (his very first car, bought in high

school) he has a big block chevy in it and it runs 11.88 on the motor and has run a 10.93 on the bottle at 122mph. The car hooks

up really good and his 60' times are where it

all begins. I'll find out what his average

60' time is and post it for you.

[Guest]

Quote:

<font face="Verdana, Arial" size="2">Originally posted by David72:
Hey Brad,
I concur with Monte.....I'd say that part of
ET dilema is that 2.053 60' time. Work on
getting the car to MPH, then you need to get
her to hook up and get that 60' time down,
it's amazing how much the ET improves with a
good 60' time. I haven't a clue what you
should shoot for. I have a friend with a
73 Omega (his very first car, bought in high
school) he has a big block chevy in it and it runs 11.88 on the motor and has run a 10.93 on the bottle at 122mph. The car hooks
up really good and his 60' times are where it
all begins. I'll find out what his average
60' time is and post it for you.</font>

Yes I think you are right, I mean I have to start somewhere and cutting that 60' time to something like 1.800 would be a great start. The motor certainly doesn,t lack power, but the way I worked it out I was only pulling 5100 rpm at the end of the track, and it pulls really hard at the big end. Going to California on Friday so it will be two weeks or more till I get back to the track (damn holidays).

[Monte]

That 60' time is hurting you a bit. There is a big difference between 2's for 60' times and the 1's. 2.2 to a 1.6 makes a difference not only in E.T. but also changes MPH a as well. Also Desmo is right, play with timing. Advancing the timing can help kill a little bottom end which may help the hook up but also help make it pull harder at higher RPM. Also the mechanical curve on the distributor and vacuum advance can also make a difference. Most street/track cars work well with full advance at 3000 RPM. Many HEI distributors get max advance at 4500 or higher, that can sometimes make a car pull harder at mid track. However 3000 max advance may not be the best for driving around town. You will have to experiment. How much total advance do you get and at what RPM? How much total timing on the balancer do you get? Also one other thing is proper jetting. You need to get your timing dialed in first before you do your jetting. Get your carb idle dialed in and then go after jetting. If your timing is set for max power, then get your carb set up correct. You can pull a plug anytime to see how the overall jetting is. However power jetting should be done at the track. Champion spark plugs are made to be read for jetting. Most copper plus work well. I personally do not like champion but I do tune with them because they are so easy to read. Champion also has a good web site with photos of how a plug should look and a heat range chart. Try to use as cold a plug as possible with out fouling. Many people go out and get a "hot" plug thinking that it will increase power, however with a big compression engine you already have plenty of heat. Running the combustion chamber cooler will help keep away detonation and create more horsepower. No matter which area you go after first, do things one at a time and write down what you did and what the result was. Always keep a record. I see guys all the time do things like change jets by going up or down 4 sizes. Or change jets and then timing at the same time and then go for a run. If there is an improvement which did it? The jets or the timing? If you change anything do just one thing at a time and stick with it. Go with the 2 rule. Never change jets by more than 2 sizes at a time, never change timing more than 2deg at a time, and never change heat range on plugs more than ranges at a time. Have fun Monte.

 

[This message has been edited by Monte (edited 03-16-2003).]

[Guest]

Thanks guys for all your info and advice, next time I will be going with notepad to document everything from tire pressures to jet and timing changes and everthing in between.