tire size,rearend,and carb Q's...

[chevy355s10]

Here are the tires sizes that are on my s-10.

The front tires are 205/65-R16's..= 8" wide and 24" tall. Tread patch = 6" wide.

The rear tires are 275/60-R15...= 10" wide and 27-28" tall. Tread patch = 9 1/4" wide.

http://tire-size-conversion.com/tire-size-chart/

http://www.miata.net/garage/tirecalc.html

the rear end i have now(2.73's and a peg leg) is gonna be taken out soon to be replaced by one with 3.73's and a posi unit. but as of now....it sucks off the line,but i dont have any traction problems....but i have a feeling all that will change with the new rearend. my cruise rpm as of now is about 2500rpm's at around 65mph. what i need to know is this....

should i get a set of wider back tires?
would yall change the rear tire size?
what will be my cruising rpm ith the 3.73's at 65mph?
How many mpg's will i lose with the rearend change?
will my truck have a lot more "balls" off the line with the 3.73's? because...as of now,im really dissapointed.


oh yeah...one more thing...My truck will not idel at anything under 1100-1250 rpms.If i try to get it any lower...the truck coughs,laughs, and dies.

is this my carb? cuz ive checked everything else.i dont have a can of carb cleaner,so that test is outta the picture and the only one i havent done.

The carb is a 600cfm vac sec holley.

 

[chevy355s10]

and the transition from idle to part throtle operation is...well...it stumbles for a sec then it takes off. even out of gear and just giving it a little pedal,it does this.

the engine is as follows...

350 bored .030 over,
9.8:1 compression,
lunati bracket master II cam.specs are .515/.515 lift 300*/300* duration 246*/246* duration at .050",
dual plane intake and 600 vac secondary holley.

 

[grumpyvette]

ok, lets take things one at a time
you've currently got a badly mis-matched cam and rear gear ratio, a combo that screams for a 3000 rpm stall converter if its an auto trans, and your long over due for that 3.73:1 rear gear ratio change.
your engine wants to run between about 3500rpm-and 6000rpm with that cam but the rear gear ratio keeps you below 3000rpm for easily 1/3rd of the time,
we all started out making similar mis matched parts combos, but trust me , swap to the 3.73:1 rear gear ratio and if its an auto trans a 3000rpm stall converter and life will be far easier


should i get a set of wider back tires?

it won,t hurt, but you should be ok with the current tires for now

http://tire-size-conversion.com/tire-size-chart/

OBVIOUSLY KNOWING YOUR TIRE HEIGHT HELPS IN CALCULATIONS

would yall change the rear tire size?

that depends on the engine,gearing etc but l would keep the current tires for a while

How many mpg's will i lose with the rear end change?
about 25% from current would be my guess

what will be my cruising rpm ith the 3.73's at 65mph?

about 3000rpm

this thread below will allow you to find the speeds/rpms and gear ratios

viewtopic.php?f=71&t=555

will my truck have a lot more "balls" off the line with the 3.73's? because...as of now,im really disappointed.

you'll notice a big difference, once you get the engine tuned correctly with the new gearing, but with that cam you REALLY NEED A 3000RPM STALL CONVERTER ALSO


oh yeah...one more thing...My truck will not idel at anything under 1100-1250 rpms.If i try to get it any lower...the truck coughs,laughs, and dies.

its mostly the cam youve selected and a badly mis-matched rear gear ratio currently, once the gear ratio is changed to a 3.73, you get a 3000rpm stall converter and you get the carb tuned correctly you'll be much happier

viewtopic.php?f=44&t=1788

viewtopic.php?f=44&t=773

viewtopic.php?f=44&t=745

viewtopic.php?f=55&t=1639

viewtopic.php?f=70&t=202

viewtopic.php?f=70&t=1411

 

[chevy355s10]

the cam powerband is 2500-6500.

is there anything else you see wrong grumpy?

 

[grumpyvette]

you don,t list enough details about the engine,components , trans , exhaust system,and car to get a very detailed idea of your combo, but that was the only major factor that sticks out like a roman candle, the, heads, intake,manifold, headers,exhaust system, ignition,and carb might need tweaking, to produce better power, but they probably could be made to function fairly well as they are, you really didn,t post enough detailed info to tell.