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350 sbc with a 3.73 rear end.

9K views 21 replies 12 participants last post by  painted jester 
#1 ·
Who is running this?

What car/truck?

What carb? Efi? Tbi?

Headers, cold air intake, cam, gear drive?

How do you feel about it? Fun? Quick? To much?

How's your mpg?

Thanks for your time! -dave
 
#2 ·
I have a 350 sbc / 3.73 rear gear combo in my '65 C10 with an Edelbrock carb and a Muncie M-21 manual. trans. Long tube headers, open element air cleaner.

You left "Tire Diameter" & "Transmission" out of your query.

My truck has 33" dia. rear tires and turns 2250 RPM at 60 MPH with the M-21 1:1 ratio trans.

Overall it's a good compromise set-up for old school drive line technology.

I was running 31" tall tires. It was more peppy around town, turned more rpm's on the highway.

Ideally a higher rear gear ratio, like a 4.56, with an overdrive transmission would be a lot more fun in town and better on the highway.

Hope that helps :thumbup:

 
#3 ·
your right, my bad!


love that truck btw!

was just trying to get a feel for whats out there.
I`m deciding on what to do with mine right now.

if i run 3.73 rear end with a th700r4 on p225/70/r14 tires my rpm at 72 mph should be at roughly 2393 in 4th gear, if i did 4.11 rear end it would be roughly 2637rpm

for fun factor i would love to run 4.11 but that doesn`t seam like tolerable mpg.

we have a real good transmission specialist here in town i want to go talk to and see what we can do in the way of custom.

my knowledge on transmissions are not exactly pro obviously but if there is a way to get that 4th gear down from a 0.70 and closer to a 0.55 that would be perfect. but i have no idea how possible or impossible that is.

i`ve always heard there are mechanics and then there are transmission guys.

then further more i understand how you want the engine to be cruising at a "comfortable" rpm range meaning the power/torque is pushing it nicely rather then struggling against the atmosphere. but then from that higher rpm is more fuel consumption.

2k rpm is my ...educated guess? fun factor for around town and be able to cruise down to L.A. with out having to take out a loan for fuel price.

any feedback would be GREATLY appreciated, i`ve built and helped build quit a few classics but this is my first time behind the wheel here its always for me been " can you put these in? " or " can you install this? "

again i would really appreciate the feedback thank you for taking the time! -Dave
 
#4 ·
do you have more info???


make/model of vehicle???
vehicle weight???
engine/parts specs???
what mph you will be at MOST of the time?? please don't say 95 mph 90% of the time.
what gear is in it now???


you don't want a engine that starts making power at 2500, when you're always cruising at 1700 rpm. or the other way around.


those tires are only 25"- 25.5" tall. bigger tires will need more gear.
 
#9 ·
79 C 10 350/350 with 3.73 225/60/15 .Tons of fun. Brother had it for years.
Cruise rpm was a bit high , but expected. Ran great. Pulled a 21 foot Pro line center console/open bow around to the keys and back to Bradenton many times. Awesome ratio.
The Q jet would really come alive and the surprise on peoples faces was great.
 
#13 ·
with out getting Richard in an uproar and having him toss the gear drive over the fence,,,lol.

They make a horrible sound,but more importantly can cause spark scatter at high rpm.The best cam timing of course comes from a belt,but expensive and needs to be replaced frequently.The chain is reliable and quiet and rarely fails.
 
#14 ·
I run a 350 with a lunati voodoo 231/239 @ 50 535/550 lift roller cam with a turbo 350,3000rpm stall and 3.73 rear posi unit on a 86 chevy s10 with a 650 holley double pumper and I get 19 mpg highway at 65 mph cruising around 3000 rpm. I have full length headers and run dart iron eagle 200cc heads fully ported and gasket matched. Truck runs plenty strong and I don't know the weight but I am guessing about 3500 lbs.
 
#15 ·
your getting 19mpg running at 3krpm? whoa that seams like a lot...

unfortunately the insides of the block/heads are where my intelligence is very limited.

i know most people tend to build a over the top, top end and there bottom end suffers/breaks.
 
#16 ·
Yes believe it or not I do get 19 mpg highway. I used a Proform 650 vacuum secondary carb and it was jetted 68/74 and then I switched over to the 650 holley double pumper and have it jetted 65/72 and I could not believe it but I filled up my gas tank and took a long 45 minute drive out of town in two different areas and used about 4 gallons of fuel and calculated it and got 19 mpg. With such a loose stall and ported heads a decent size cam I am surprised but it does that good. That was a steady drive at about 65 to 70 mph and no getting on it though.
 
#17 ·
well that being said if i did the 4.11 rear end it would be roughly 2637rpm at 72 mph thats still less rpm then yours and your getting 19 roughly.

same carb i`ll be putting on aswell so...

i found that the 69 camaro runs 4.10s with disc brakes, it would be swell to acquire a used axle to replace with. -Dave
 
#18 ·
. The 200-4R tranny has more overdrive (49%) and better ratios for a 350" V8 engine...

. The typical Chevy 350" V8 built with early 1970's tech was a gas hog... like 9 MPG city and 11 MPG hiway... depending on what 350 you have, you may want to make some basic internal changes that will get it more like 15+ city and 20+ hiway...

http://www.f-body.org/gears (hit 'clear right' button before doing anything)
.
 
#19 ·
My setup is a 355 SBC with twin 450 Holleys on a Dominator tunnel ram, with 10.25:1 compression, and old 2.02"/1.60" camel hump heads, Crower 280 cam, and fenderwell headers. Rear is 3.73 gears, TH350, and tires are 28" tall 275-60-15 M&H drag radials. I can cruise at 65 mph and get over 21 mpg, but my car only weighs about 2500 lbs.
Of course around town I have trouble keeping my foot out of it, and mileage really suffers whenever I stick my foot in it!
 
#20 ·
to the best of my knowledge the 350 I have is a recently rebuilt actually it doesn't even have 20,000 on the rebuild,

LS 48 it came out of a 1973 Corvette.

23 gm 3970010. 2 bolt main

are the numbers on the back of the block.

the Original owner has way way too much money he put that engine in a beautiful El Camino ,he found it didn't have enough power so he had it rebuilt and put on a triple deuce that still didn't have enough power he drove it for about five thousand miles then gave that engine 2 a great friend of mine so he could put in a 502.

my buddy threw it in his 56 drove it for maybe 20,000 he then got handed a 454 with the LT80 transmission and gave me the 350.

my buddy sold the intake with the carbs.-Dave
 
#21 ·
to the best of my knowledge the 350 I have is a recently rebuilt LS 48 it came out of a 1973 Corvette. 3970010. 2 bolt main
the Original owner found it didn't have enough power
. The 1970's 'Dark Ages of Engines' L48 is one of the 350's I was referring to above... lowest power, worst MPG... that design rated 125 HP in some California-spec Chevy Monzas... a little higher in 'Vettes... prolly from better exhaust system and 4 bbl. carb... it can be improved upon immensely using the right parts... but a stock-spec rebuild doesn't help it... except for reducing oil burning... the -010 block is a good block to build on, though...
.
 
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