Auto Racing: power band, sarasota florida usa, piston crowns

Question
QUESTION: Hi, i race a lightning rod 1/4 mile oval in england. thanks to the experts help getting my suspension set up correct. i now have another problem ,because i can get the power down much earlier i run out of power to early on the straight. can i move my power band. i have a vernier cam fitted .can i adjust this to give me power later or possibly the ignition timing i am running 28 at 3000 rpm.( there is no lower ratio diff available to me,i use a 3.92 at moment the next diff is 3.62. ) many thanks mark england

ANSWER: Hello Mark:

You can alter your power band somewhat with changing your camshaft timing, retarding it a few degrees will give you more high end power, advancing it will give a bit more torque for hauling it out of the corners. ALWAYS turn the engine over a few wtimes once you've changed it, to make sure there's no interference between piston crowns and valves. Actually it's best to inspect the cylinders with a boroscope while rotating the assembly. Make sure thare'a .100" or 2.5 mm clearance between the two. Never change the cam timing more than about 10 degres!

I'm not familiar with the quality of petrol you have in the UK, but with the 93 octane we have here, I run about 34 degrees of ignition timing at 2500.  It makes the car a bit more difficult to start but it pulls well. (Datsun 1600 Sunny Sedan from the 70's )

So you might see if you can get one of the 3.62:1 rear end gears, andchange the cam timing for added torque.  You'll lose a bit at the top but hopefully by that time you'll be at thte next turn.  

I'm amazed, I didn't know there was any oval track racing in Merry Olde- -  

Cheers

Dan Liddy
Sarasota, Florida , USA

---------- FOLLOW-UP ----------

QUESTION: Hi dan, Thanks we use 89 oct fuel(unleaded) i use a 24v starting system so i will try a bit more timing and see how it goes. i have a 3.62 diff i just need to weld it up to lock it. looks like ive got a busy day at the track testing. i will let you no the outcome thanks again mark, if you have a minute to spare the tracks web site is arenaessex.com my formula lightning rod(1980s ford siera 2.0ltre)

ANSWER: Hello again Mark:

I suggest you try to find a limited slip device for your differential.  They add a bit of weight (3-4 Lbs. ) but the car rolls much easier.  With the welded rear end, cars are even hard to push, and in a corner, they get tail happy.

My Datsun racers are virtually undrivable with a welded rear in them. And it takes at least two people to get one rolling when pushing.  I tried one at Daytona once and couldn't get the car through the Internatioanl Horseshoe at all.

With the 89 octane , try about 34 Deg. of timing advance at 3000 RPM but watch your pllugs carefully. Pure white insulators with little specks on them indicate too much advnace, or a too lean mixture. Either one will cost you an engine. What's your water temp on a warm night ? (Farneheit would be easier for this addled old Yank !)

Go get 'em !!

Dan Liddy
Sarasota, Florida USA

PS:  It may interest you  to know that there is another Dan Liddy much closer to you, in Wheatley Hill, Durham,UK we ocasionally exchange e-mails.  Small world.

---------- FOLLOW-UP ----------

QUESTION: Hi dan, temp 210 deg f  normal. on the one hot day we have i hit 226 deg,i run a 50/50 mix water -antifreeze.. i run a modified twinchoke webber carb and i run rich (ON TICKOVER)1500 revs..
Not allowed to run slip or locker diffs hence the welded locked diff.(yes a nightmare to move)
I also use an oil cooler via a sandwich plate at filter

Cheers mark england


Answer
OK  the water temp is OK  What about oil temp ? You shouldn't let it get over about 250 to 275 F . and do you use synthetic? I hope the numbers are the same in UK, we mostly use a 20W-50 racing oil, Amzoil is a brand I use, but you probably have access to Rotella, and certainly Castrol Syntech.

Don't tell me- - - the miserable Weber 32-36 DGAV or DGEV ??  I call it the Weber Toilet. We have to use them in the semi-stock classes which we call "Improved Touring" Make darn sure your secondary venturies are rock solid in the bores. Shim them if necessary, and I'm working on a way to seal the fuel circuit so they draw better.

Hummmn- - - I just thought of something - - -I'm going to look into drilling out the secondary circuits - - - I wonder- - - - ?

All for now, tax man is after my wrinkled old arse.

Dan Liddy
Sarasota, Fl. US>