finish line rpm vs launch
 

I am in the process of going from 5.38 to 4.88 gears in a j/sa 70 Sport Sattelite wagon 383 is shifted at 6400 goes thru traps at 7400. Building a trans with a lower first 2.45 to a 2.77. Thoughts keeping the same basic gear multiplication down low and more in power band down track. Does this seem like a move in the right direction or is it normal to "over rev" a stocker that much? It sure seems out of breath last 300 ft. Is that to much of a jump?:confused:

Re: finish line rpm vs launch
 

I made about the same move last year, The car had a better 60ft and ran faster with less RPM at the stripe.

Re: finish line rpm vs launch
 

What MPH does it run now?

I'd guess it needs a 5.13

Re: finish line rpm vs launch
 

You may find short shifting the 2.77 out of first will help ET.
I would GUESS 5.13's as Mark suggested. Better to have not enough rear gear than too much rear gear.
4speed Johnny needs to put a stick behind that 383! That would be an awesome wagon!

Re: finish line rpm vs launch
 

Thanks Phillip, gives me a little confidence!

Mark, I have a set of 4.88's to try since I'm expirementing didn't wanna pop for new and 5.13 just seem like such a small change?

Jeff, I agree and in fact originally intended on putting 4spd in wagon but now my 16 year old son is racing it and we aren't quite sure if he inherited 4spd gene! rest assured my road runner is still a stick and am building another 70 road runner 440-6pak 4spd combo for stock eliminator. When you say short shift you would shift 1-2 even lower like 5800?

Re: finish line rpm vs launch
 

Sorry Mark, 12.70, 1.69 60 ft 102.8 mph in 3600 ft air with a 25 mile an hour cross wind (I'm sure doesnt effect this aerodynamically superior race car at all!) Brakes were also slightly dragging that day (Strange disc all corners) have since installed adjustable pushrod and springs inbetween pads in calipers seems to have cured. have also switched the car to cal-tracs now so we wil see. Nothing like changing 6 things at once in a combo but I think all right direction also took weight out to move from k to j since those time slips

Re: finish line rpm vs launch
 

Yes, shift 1-2 at a lower RPM than the other gears.
That 16 year old needs to start racing the right way. Give him the 4-speed and put the 2.77 trans in your wife's grocery getter! :)

Re: finish line rpm vs launch
 

Turn Junior loose w stick, the stick gene seems to be passed to each generation,if he can't drive stick,then I would go for paternity test then.LOL
My son was driving FWD nova w/stick @ 9 years old,took his 25 year old uncle for ride uncle told him he could'nt drive stick shift,he told his uncle I'll teach you.LOL
Mike Taylor 3601

Re: finish line rpm vs launch
 

You guys are making me feel so ashamed! I feel like I've betrayed the 4spd brotherhood. He raced our old 79 St Regis cop car when he was 14 and 15 in our local tracks "teen championship race" and actually won once and runnerup twice he's a pretty good light cutter but :( had to leave it in drive so he wouldnt forget to shift! Last year he blew up the old farm truck driving it to town in low lock! This car was supposed to be a spend no $ and drive it deal and now I'm buyin slush box parts... how'd this happed that could have went towards jerico! Sons tow truck is a 93 cummins with 350,000+ on it with a 5 spd (pistol grip shifter out of road runner of course) if he gets through year getting 4spd trained with that then we'll consider J/S no A!:)

Re: finish line rpm vs launch
 

Maybe you need the shift point shock collar I just don't understand why I have'nt had any luck selling them. If you need shift light they work better than light driver can stare at light and wonder what is that light for,but the shock collar eliminates any daydreaming and missing shift points.
Mike Taylor 3601

Re: finish line rpm vs launch
 

I agree, the 5.13 I think would work better. Lower the shift point by 200 and with the 5.13 should put you in the sweet spot. My Volare has a 4.88 and it weighs in at 3500+ with normal trap rpms at 7200-7400. That is using the 30" radial. I'm thinking that 383 was all out of steam before the 1000' mark at 7400. Jim

Re: finish line rpm vs launch
 

my 383 stocker motor(old school 1993 motor) with 2.45 727 and 4.56 would go through the traps at 6200.......by comparison....4speed jericho, 5.13 7000-7200.....109-111 mph either way.....not running out of steam, but with the 4.56 seemed like it wanted it to be a 1/3 mile race! With the 70 you are limited by your 600 cfm holley a bit.

Exhaust with 4.56 dead hooker supercomps, and dynomax ultraflow, with stick TTI's.....nothing sexy.

My vote for the combo with a auto would be 4.88....unless you have done work to the motor and carb and exhaust system to let it make hp that much higher.

Or you could just put the stick in it and not have to learn all about the automatics!

Eric

Re: finish line rpm vs launch
 

While you were in the Garage, I would leak down the engine and make sure it is in top shape. I have seen similar big block mopar with that head and compression spin easily that high ( As I recall Steve Wann told me
he rouitinely spun his big block 383/440 stockers to 7700 and laughed at me by being a Sissy).

I do agree that a 488/513 gear would be better unless you are at altitude
like Denver for example.

If I read your posting correctly @ 102 Mph.....I would be also check you
valve train and spring pressure. At 12.70 and 102 8 your speed/ET is about
what I would expect in a Heavy Stocker that was not real high HP.
My kids wagon @ 4000 ft when it ran 12.8 would run 102/03. @ 3700 Lbs
when it was making in the low 310-320 Hp range and it appears you big block
is a bit high torque and maybe a bit better midrange on the track.

I can not recommend enough putting a light low drag racing transmission with
straight cut gears (Probably a 263 low or so) like Pro Trans (Palmdale Calif.) is a heavy lower class stocker.
It is expensive but it Really makes a big difference (Dave does not pay me to say that).
It helped Jr.'s stocker 06/07 in 60 and about a tenth a Half. the 727 with 904 guts is
Even more Dramatic in performance difference. It sounds like you car is struggling on
the index and it is no fun to get in bad Summer air and not be able to play .
I know very well...... it hurts to spend to money, but if you can swing it---Buy the
Best and Only Cry Once.

Re: finish line rpm vs launch
 

Would this be the red Satellite stocker wagon that was on Racing Junk a while back ???

Re: finish line rpm vs launch
 

That would be the one according to what Johnny told me.

Re: finish line rpm vs launch
 

From experience,I think the 4.88 is the right way to go.We used a 29.5" Firestone/Phoenix in a 70 Road Runner with 383,both 4-speed and 727 were used,4.88 gear was perfect for that combo.I know the wagon is a bit heavier,but with the 2.77 first,I think that will work great.

Re: finish line rpm vs launch
 

I checked my #1 son Robbie who runs a H/I/J SA Roadrunner with a low compression 400. He runs 488 @ Sea Level and has run 513 at altitude sometimes (4000plus ft. ) He shifts around 6200 and goes thru lights @7200.
He normally runs 11.3/11.4 @115 to 116 at sea level(Usual showing 2000ft.)with the 4.88 @3650LBs. He thinks the 513 are probable a push at sea level ......but a littleharder on the engine.

Again I would look at condition of your engine and maybe try another converter. 102/103 Mph is not a lot of speed for a big block car even with a 625 carb. I believe you might be able to run the 735 Holley on that combo as I have seen Don Wann's 70 383 Roadrunner run the Holley some years ago............................................... ............
and it was (Like all their stuff) way FAST!.