Hey guys i just bought an 89 RS that was converted to a 350 carbed engine. I know that my cam is not matched to my gears or converter. Right now i have a stcok converter with 2.73 rear end. My uncle told me that when i match all three up i will burn the fuel more efficiently and get better MPG. Is this true? (i think it is)
Also what would be a good gear and coverter to go with when i get the money. My cam has a 268" lift with 218 duration and 110 degrees lobe seperation.
For the gears i was thinking of the equivalant to a TH350 trans with 3.73. so i was think with a 700r4 that 3.55's might be good. what do you guys think.
thanks
Tom

 

top gear with a th350 and 3.73's is equivalent to about 5.20's with the 700r4 overdrive. 3.73's will work great with your combination. A performance converter won't help mileage. It will hurt mileage if it doesn't lock-up and/or slips alot.



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82 camaro--original steering wheel, brake/gas pedals, seats--everything else modified
82camaro

 

That's not a lot of lift on that cam You sure that isn't the duration? It should be a number closer to .470 if you are using a CC268 grind...

Anywho, going with different gears and converter will definately wake up that car. As for milage... not a good thing. I don't know what kind of rear you have, but I think you can get 3.45 for a 10-bolt which work very good with a 700R4. You would definately want a locking converter for a 700R4... especially if MPG is a concern.

I use a 3000 stall and 3.27 gears and get about 25 mpg on the highway.

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

 

268" of lift, Hmm, You may have some piston To valve Clearance Problems


realistically Now tho, Going to a Deeper Gear Will hurt Milage, why ?> cause you have to turn more RPM to go the same speed.

Going to a Deeper stall, as long as its a lockup stall, Wont.

700R4 and 342's ( thats what Biochem meant Is What Im going with, and seems to be the best Option For street performance with MPG in mind )


373 would prolly get me closer to redline at the traps ( theoretically, havent run it yet ) But Would cut down the milage.


TH 350 has a final drive ratio Of 1:1

With 3.73' that means that your Final drive ratio is 3.73:1 Crank revolutions to Wheel revolutions.


700R4's OD ratio is .7:1

Soo that means what, to get a 3.73:1 ratio you wanna hmm, math time....

ouch, my head...

duh...

.7*x:1 = 3.73:1

3.73/.7 = well ****... No calc here....

Same as mutiplying by the reciprocal...


3.73 * 10/7


ahh dammit, that dosent help...


373/7 =, well appromiately 7 goes into 37 like, 5ish times


So about 5.33's Should take care of You.


Not Good For gas Milage.


hmm, that dosent sound right, Im gonna confirm that when I get home with a calc, hahaha



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60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver
Reader's ride -> My Ride

Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype

 

Sorry guys i guess i made a little mistake. the lift is 468". Ok guys i understand what you have said and i appreciate it, but i have heard if your cruising RPM is to low and the engine is bogging then you are actually using more gas. I am not going to go with a huge stall, maybe 2500. and i was thinking of 3.42 rear like you guys have suggested. well i guess i will have to wait and find out when i get the money to do this.
Thanks
Tom

 

Yeah, Sounds like a Good Plan.

With the Locking Converter, What your describing isnt really a factor.


Specially with our Motors, Maybe a uberweak 4banger, that couldnt tow the car along at low RPM at high speed, any of our motors makes sufficent torque, even at idle, To keep our cars goin.




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60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver
Reader's ride -> My Ride

Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype

 

I don't see 3.73's with a Th350 good for gas though.

Maybe 3.08 with the 350 and 327 with the 700r4 for good milage.