Landracing Forum

Bonneville Salt Flats Discussion => Build Diaries => Topic started by: so cal racer on December 17, 2007, 05:36:44 AM

Title: 74 corvette for l.s.r.???
Post by: so cal racer on December 17, 2007, 05:36:44 AM
o,k, i have just been given an option of getting a 74 vette  i am sure this is a better option than my previous 92 1/2 ton ext cab pu. but what about the rear end?? do i need to change it to possibly a 9'' ford and what about a trans it has a turbo 400  do i need a manual trans??? sorry for all the questions but just starting out here. need lot's of help!!!!   so cal racer  in long beach calif.
Title: Re: 74 corvette for l.s.r.???
Post by: Carl Johansson on December 17, 2007, 11:02:57 AM
o,k, i have just been given an option of getting a 74 vette  i am sure this is a better option than my previous 92 1/2 ton ext cab pu. but what about the rear end?? do i need to change it to possibly a 9'' ford and what about a trans it has a turbo 400  do i need a manual trans??? sorry for all the questions but just starting out here. need lot's of help!!!!   so cal racer  in long beach calif.
Pretty high CD on the C-3's  something like 0.43 -  as compared to 0.32 or so on the C-4's & 5's.  Also the flat rear window causes a huge "suction" due to turbulance.

That being said -  the sundowner car -  the Banks car etc have all run in excess of 200 mph -  some well in excess -  but be prepared to spend cubic dollars to get horsepower!

Carl Johansson
Btw we run an 82 C-3 -  with the bubbled back window -  so significantly better aero -  and with 450 hp -  we are running 175 mph on the short course!
Title: Re: 74 corvette for l.s.r.???
Post by: Jonny Hotnuts on December 17, 2007, 12:47:39 PM
I agree with CJ.

The choice of the initial project is IMO the most important decision for a successful project.
This means if you choose a project that is bad from the start it will always be hindered, at a disadvantage to other better chosen cars and IF made competitive much more expensive in the end.

Many of the rule classes have fairly restrictive rules pertaining to what can be done to the body. These rules as I have found out change and is something in the future you need to consider. The difference between a body with a good CdA and an ok CdA is THOUSANDS of dollars difference and less headache to achieve the same speed.


This is what I recommend you do, if you seriously want to break a record:


1st- find an obtainable record in an obtainable class.
This means that if you say you want to build an AABFS you need to have big pockets to break the big numbers. Search the rule book for a record that is low for the engine size compared to the same displacement in other classes. And if the project interest you....personally I am not into roadsters....I didn’t grow up around them and never owned one....just not my cup of tea.

2nd- after you decide what cherry record you want to pick find a car in that class that has the best foundation for the project....even if it cost a little more money now it will save you in the end not having to continually pump $$$ into the motor to get a brick to go fast.


Here is an example, just picked quickly in the book.

H/BGAC set in 00 @ 140

The H/GALT is 148.....same class and motor LESS a blower and over 8 mph faster.....makes ya think dont it!!!


Now that I found a record I think I can break I went to the Mayfield car aero page and found a car with good ###.

http://www.mayfco.com/tbls.htm

I choose the 92 civic SI for example with a Cd of .31 and a CdA of 6.34....
If I looked for a while and did some research I KNOW I could find better....this is only an example of a good car I found.

The Honda I chose with a CdA of 6.34 will need approximately 150 (Bonneville wheel HP) to do 150 mph......is that obtainable from a 1.5K motor with a blower.....I would think I could get 150HP from a 1.5K Honda without a blower!!!!!

The difference in body to a bad car is:
A 93 600SL has a Cd of .45 and CdA of 9.54....this means a 150 HP motor will take SL to a blistering 130 mph.


Title: Re: 74 corvette for l.s.r.???
Post by: jimmy six on December 17, 2007, 01:29:36 PM
I don't know your size but some Corvettes are hard to cage correctly. Many are done and you should look at them before starting on yours. Good Luck
Title: Re: 74 corvette for l.s.r.???
Post by: Sumner on December 17, 2007, 01:45:33 PM
I agree with CJ.

The choice of the initial project is IMO the most important decision for a successful project.
This means if you choose a project that is bad from the start it will always be hindered, at a disadvantage to other better chosen cars and IF made competitive much more expensive in the end.

Many of the rule classes have fairly restrictive rules pertaining to what can be done to the body. These rules as I have found out change and is something in the future you need to consider. The difference between a body with a good CdA and an ok CdA is THOUSANDS of dollars difference and less headache to achieve the same speed.


This is what I recommend you do, if you seriously want to break a record:


1st- find an obtainable record in an obtainable class.
This means that if you say you want to build an AABFS you need to have big pockets to break the big numbers. Search the rule book for a record that is low for the engine size compared to the same displacement in other classes. And if the project interest you....personally I am not into roadsters....I didn’t grow up around them and never owned one....just not my cup of tea.

2nd- after you decide what cherry record you want to pick find a car in that class that has the best foundation for the project....even if it cost a little more money now it will save you in the end not having to continually pump $$$ into the motor to get a brick to go fast.


Here is an example, just picked quickly in the book.

H/BGAC set in 00 @ 140

The H/GALT is 148.....same class and motor LESS a blower and over 8 mph faster.....makes ya think dont it!!!


Now that I found a record I think I can break I went to the Mayfield car aero page and found a car with good ###.

http://www.mayfco.com/tbls.htm

I choose the 92 civic SI for example with a Cd of .31 and a CdA of 6.34....
If I looked for a while and did some research I KNOW I could find better....this is only an example of a good car I found.

The Honda I chose with a CdA of 6.34 will need approximately 150 (Bonneville wheel HP) to do 150 mph......is that obtainable from a 1.5K motor with a blower.....I would think I could get 150HP from a 1.5K Honda without a blower!!!!!

The difference in body to a bad car is:
A 93 600SL has a Cd of .45 and CdA of 9.54....this means a 150 HP motor will take SL to a blistering 130 mph.

Good advice, the only hiccup is for those of us that take generations to finish a car the record might not be soft when it is completed  :cry:.  Seriously though, JH is completly right about if you are serious about breaking a record don't have any ties to any one car.  The car that might be best might be one that you wouldn't normally be found dead in  8-).

To figure the HP needed once you have the CdA (Cd and area) you might find the Drag Force-HP-Thrust-Weight spreadsheet here helpful:

http://purplesagetradingpost.com/sumner/bvillecar/bville-spreadsheet-index.html

Good luck,

Sum
Title: Re: 74 corvette for l.s.r.???
Post by: Jonny Hotnuts on December 17, 2007, 06:59:31 PM
Quote
Good advice, the only hiccup is for those of us that take generations to finish a car the record might not be soft when it is completed
 

Funny thing Sum, I couldn’t agree more.....in fact I would like to think that our car is a perfect example of this. My pop and I knew our car would and could go much faster than it did last year...but decided to not push a dangerous handling condition to prove nothing on a test year. And it would be somewhat naive for someone to see our first year’s numbers as an easy mark.

The age of the record, numbers of teams competing in that class for the record and what the original record was set by are all important factors to consider. 
Title: Re: 74 corvette for l.s.r.???
Post by: Stan Back on December 17, 2007, 07:44:13 PM
JH --

"The age of the record, numbers of teams competing in that class for the record and what the original record was set by are all important factors to consider."

That's another reason to not like roadsters!

Stan 
Title: Re: 74 corvette for l.s.r.???
Post by: bvillercr on December 17, 2007, 07:55:35 PM
Good advice, the only hiccup is for those of us that take generations to finish a car the record might not be soft when it is completed  :cry:. 

Just remember that some of the soft records that are out there could have been set on a return run when there engine or vehicle broke.(Bonneville anyway)  Records are not that easy to come by for many, but for the few it's a piece of cake.(not us)
Title: Re: 74 corvette for l.s.r.???
Post by: SPARKY on December 25, 2007, 08:31:46 PM
THE 92 Chevy PICKUP is the better choice...its Aero is as good as any---just doesnt have an optional WING like dodge :-D---you will have to use LEAD for traction control-- :-o-lol