Need Help in Rear gear Selection OR

[darrin75]

Rebuilt Mopar 383 Engine & Transmmission Note:
OK here is the scoop on the 383 and trans.There will be all NEW PARTS unless stated,I will start at the top of the motor,750 Holley carb,Used single plane intake painted nice,Chrome valve covers,chrome air cleaner,452 heads with a 3 angle valve job and hardened seats for unleaded premium,509 cam and lifters,pushrods,timing chain,pistons 10 to 1 compression so you can still drive arround town on unleaded premium,pistons Keith Black,with there rings,chrome pan,Crank turned 20 and 20,rods rebuilt,water pump,fuel pump,filters and synthetic 10W40 oil after the break-in run,and of course all new gaskets.Only thing used is the intake I keep them in stock and new holley carbs for customers all the time.727 trans Fresh and stock convertor


This what I have.  Firefigter says use a 4.30 gear, which is maybe the way to go?  If I switch the 509 cam down to a engle 56k How much horsepower do I lose.  Any?  if I don't switch the cam I am looking Into 3.55,3.91 or 4.10 gears, to try and get in between?  going from 3.23 to 3.55 really make much of difference?  Is there any benifit to running taller tires etc.  Any opinion needed?  Open to all suggestions?  I currently have 235 60 15 tires, small.  The most this car will be driven is 50 miles out.  No long trips here?  I have enclosed car hauler.  Want to smoke some people, but still drive the car on the street SOME?  My car is fast as hell top end.  I have had it around 135 mph, and more to go, but when will I ever need that much power up there?

[Nacho-RT74]

thinking on actually gas prices ( for you, not for me LOL, I still fill the tank with US$2.5 95 octane ) for good street won't go more than 3:91 and less than 28" diameter tires.

Then if you go with bigger tires I would go with same step up gears ratio.

you can see also on this way:

3:23 to 3:55 change does mean 10% less top speed and 10% more Rpms keeping same size tires. In my numbers 10% is a lot for highway of course, however not that much on street. 3:91 is the same relationship but around 25%, what makes bigger diff on street use.

[darrin75]

So I get what you are saying, so going from 3.23 to 3.55 is about 10% gain on bottom and minus 10% on top end, but Are you saying 3.91 is 25% gain on bottom end, If thats the case, this si most  what I am looking for.

[Nacho-RT74]

pretty much... keeping same tires size of course. Bigger tires change will make closer step up relationship.

Similar relationship with gas consumption LOL depending of course also about Torque converter you go. I was worried about driveability. I wanted a CLOSER TO STOCK driveability feel keeping on some performance numbers. PPl say I'm nuts, and maybe I am, but I'm not on FUN TO DRIVE reving up stuff and just advancing couple of feet... sorry wasn't my goal. IS MY DRIVER!!! Caracas is a REALLY HEAVY TRANSIT city on rush hours, specially between 5 pm and 8 pm... you won't believe how hard is here drive on those hours.

I finally went with KB240 pistons, 280/474 cam, 2250-2350 stall converter, and deciding about 3:23 or 3:55 gears ( SG unit, mostly sure will go with 3:55 ) on 27" tires, searching for taller tires, but not wider... hard to find on 15". Stock TQ carb ( 850 cfm... more than any stock carb ) and stock everything, just sligth mill down heads and metallic gasket.

being the cam powerband starting on 2000, and torque converter slightly above that... I think I'll get what I wanted... I know lower bottom end that going with higher stall, but as stated is just an upgrade, not a racing car. I'm increasing compresion thought

That is IF I find my Standart bore engine ( sleeved ) is still on good numbers bore to mount standart KB240 pistons. My engine just have around 18K-20K unabused miles, so my guess is will need just to be honed.

[darrin75]

One last ?.  If I go with a 489 case, switching from 742 case.  Driveshaft length any problems??/Yoke Size problems???Just curious before I buy One?

[Nacho-RT74]

no, everything keeps the same... just need to keep eyes on yoke size ( 7260 or 7290 joint )... however both should it be the big one I think.

BTW, my combo is just an experiment!!! don't take it as example!!!!

[darrin75]

One final question here.  With the set up I have now, Can not do burn outs at all.  Will the 3.23 to 3.91 fix this problem with 509 cam and the 3000-3500 stall I have or will the 4.10 do the job?  If the 3.91 will do the job I am looking for then thats what I want, if not the 4.10 maybe?

[Rolling_Thunder]

cant smoke the 235 tires with that combo       hmmmm.....        3.91s should be able to

[firefighter3931]

One final question here.  With the set up I have now, Can not do burn outs at all.  Will the 3.23 to 3.91 fix this problem with 509 cam and the 3000-3500 stall I have or will the 4.10 do the job?  If the 3.91 will do the job I am looking for then thats what I want, if not the 4.10 maybe?

The 509 cam in a 383 won't begin to pull hard until 4000 rpm....your stall is still too small. If you were still insistent on keeping that cam, my recommendation would be to degree it in and install it on a 100* intake centerline which would be 8* advanced. The go to a 4.10 gear and tune the heck out of it with a lot of initial timing, proper advance curve and a double pumper carb. It won't be easy but it can be done.

Or, you could just swap out the cam to something more appropriate. 



Ron

[0X01B8]

There's a topic on the Performance section, somehthing like 'post 1/4 times.'  There's a guy with a 383/727/3.23 Satellite who gets sub 14 second times out of his car.  Don't know anything else about his setup, but I bet it's tuned pretty well.    My 440 was over-cammed and the carb was outta whack, but now it's got a nice streetable cam (k56), good tune, and moderate parts in every other category.  It's jeckyl and hyde.  I'd let me mother drive it (shes 83) it's so smooth, but step on the gas and all hell breaks loose.  Guess I'm just saying to err on the side of less not more.   

[Purple440]

There's a topic on the Performance section, somehthing like 'post 1/4 times.'  There's a guy with a 383/727/3.23 Satellite who gets sub 14 second times out of his car.  Don't know anything else about his setup, but I bet it's tuned pretty well.    My 440 was over-cammed and the carb was outta whack, but now it's got a nice streetable cam (k56), good tune, and moderate parts in every other category.  It's jeckyl and hyde.  I'd let me mother drive it (shes 83) it's so smooth, but step on the gas and all hell breaks loose.  Guess I'm just saying to err on the side of less not more.   

What are you running for a carb now?  I've got issues with my cam and carb and I'm looking for solutions.  Ron's helped a ton of course but I'd like to hear what you did.

- Doug

[darrin75]

http://www.dodgecharger.com/forum/index.php/topic,31888.msg348246.html#msg348246

I think some one told me "firefighter maybe" that I had a vac secondary carb, what really is the difference in the one I have a a double pumper?  For some reason I always thought I had DP?  Also firefighter The cam will probably get changed this winter, do to the problems I am having.

[darrin75]

bump

[0X01B8]

What are you running for a carb now?  I've got issues with my cam and carb and I'm looking for solutions.  Ron's helped a ton of course but I'd like to hear what you did.

- Doug

It's a Carter 750 AFB pre-Edelbrock, but basically the same as performer.  I had to lean it out a bit.  Looks stock and pretty easy to work on.