Don Terrill’s Speed-Talk

I would like to improve my 60' and hopefully my 1/4 time
currently running a 3.73 rear end gear with a spool and a 28" tire
debating if i should change gear or tire size or even both
engine/trans is 383sbc &Th400 standard gears
car is approx 3100# and around 800bhp
best 60' has been 1.51
multi leaf with dble adjustables on rear and Koni coil overs on front
approx trap rpm has been around 6300rpm
I have been thinking of using a 26" tire as that should give me around a 4.02 overall ratio
also can anyone explain startline ratio and how it effects performance.
any suggestions welcomed
Thanks

There could be a lot of different ways to get a little more launch out of the car. Probably the most informative thing you could do is to borrow a video camera (hopefully one with a high speed mode) and capture some launches from several angles. You'll want to get a good view of the whole car as it transfers weight and the tires. Post it on youtube and link it here.

And what have you tried adjusting so far? Tire pressure, shocks, launch rpm, etc?

My best run 10.307@133 was after i set the rear shock compression on very hard and the extension on soft
MT drag radial tire pressure @ 14#
launch rpm 3000 on a 3800rpm convertor
car leaves very flat hardly any seperation or front end lift .
The rear gear was already installed in the 9" and as it had the strange Alum center it was a great price but obviously that ratio is hurting
I have had the convertor re stalled approx 4200rpm expected
have a video cam for this year and interested in comments about the combo being way off.
Thanks

The first question that needs to be answered is "are the tires spinning on launch now?" The old shoe polish and an observer work well to answer this. Video cam even better.
If you're getting near 800hp out of that 383, I can't believe it would want to leave at any less than 5500 to 6K on launch, and with your size tire, at least a 4.30 or so gear. THEN you're going to have to figure out how to plant that HP. IMO, properly set up, that car should 60' in the mid to high 1.30's.

on my own when at track but several observers said no spin but also no movement in suspension
actual hp was 757@6900 tq 648 @5000 engine dyno
I realise my gear is hurting et & 60' so before spending $ on gears I was thinking smaller 26" tire
convertor i have is all i can afford at present
when scaled car was 51% front but have removed all i can think of and blower put a bunch of weight back in there
i also changed from dropped spindles to stock on the front end and it made no difference .

Hope this doesn't sound crass, but if you have about 800 HP and you're 60' is 1.50's I'd say you're spinning or something is very wrong with your car?

I'd go to a taller tire to get a bigger foot-print.
My street TA gets about 1.50's 60 ' times with 250 HP. Stock suspension, 3.08 gear.

no problem only too thankfull to hear views from more experienced racers
I also think some of the slow 60' is my lack of experience
so i will work on that and also general consnsus seems i should go larger on the tire not smaller then maybe look at rear gears
appreciate the help
Royz

biggest tire you can on there, more gear to match the tire size, and more convertor, say around a 6000. youve got alot of motor there, my buddy runs a 625 hp sbc, and runs a 6400 stall. runs a 9.80 w/2700 # car. so you shud be just as fast with 750 hp and he runs a 1.42 60' . theres lots of changes you can make,,but just my ideas..

Novaz wrote:
actual hp was 757@6900 tq 648 @5000 engine dyno

WOW!! Kaase's engine won the 2009 Engine masters challenge with 403 CI making "only" 597 LBs TQ @ 5400 rpm, and 677 HP @ 6400 rpm.(solid roller cams, tunnel rams, 2 carbs, were legal in 09) What a dismal performing engine compared to your 20 CI smaller engine making 51 more LBs TQ, and at a lower rpm, and you made 80!!! more HP @ 6900 rpm, less than the 7000 rpm limit for 2009.
You'd have won hands down, probably embarrassing Kaase in the process!!
Kaase's 597/403=1.48 Lbs TQ per cubic inch. (1st place engine in 2009)
Novaz 648/383=1.69 Lbs TQ per cubic inch. (and at a lower rpm)
NHRA prostock 835/500=1.67 LBs TQ per cubic inch.

Of course there's always the chance that the dyno you used was VERY lofty, and your engine really makes less than 600HP like the ET/MPH would suggest. I just have this funny fealing that if Kaase's lower power engine was installed in your car, you'd find that lower et your looking for.

If it don't run the number, it don't make the power.

Randy

I think this 383 has a blower on it, hence the good TQ and HP figures
Cheers Steve

redsmokin57 wrote:I think this 383 has a blower on it, hence the good TQ and HP figures
Cheers Steve

Sorry, I didn't know that if you made 757HP with a blower, it would run the same as 565 naturaly aspirated HP!

Randy