The Stovebolt Site Forums The Shop Area General Truck Talk 23mpg

during the winter i pulled the 350 motor from my 52 an made a 383 stroker out of it got rid of the 350 tranny an picked up a 700r from summit put it back together drove it to c my momma 212 miles away on 9 gallons of gas could not beleive it it runs saaweeeeettt just want to thank the fellers at this website 4 all the answered questions because i dont think i would of tried to tackle it if it wasnt 4 all the positive feedback

thanks again
the kid

I get about 10 mpg. and am very jelous. are you sure you wern't towed or trailered part way.

I'm a newbie ... my 66 'burb has a 250 inline 6 with 3 speed. What kind of mileage can I expect? The gas gauge doesn't work, so the answer might mean me not getting stranded

Sounds like you have her SUPER TUNED ! ...congrats !

52chevykid: way to go man. I put the 700r4 in my pickup and while I have not checked the mileage I can tell I'm not fueling up as regular!!

52chevykid/others: while I am ashamed to admit this I have made a badddd mistake. I have disasembled the 52panel and did NOT make enough "reference points" for putting in the V8. I did make a mark where the front of the cab was in relation to the chassis. NOW, while I have the chassis off I want to blast it and put the engine,tranny on the chassis but need to know where to sit it. SO, can anyone measure me a "point to point" for locating the chev small block in my chassis and it be good when I bolt the body back on???? Please???? OK, I admit I made a mistake so don't crucify me to bad!!!!!

The 700R4 is the reason for your good mileage.I am running a 350SB,with a 700R4 and 3:90 rear,and getting 20 MPG.The 4 th gear in a 700R4 is about .78 to 1 ratio,whereas the 350 turbo hydramatic is 1 to 1 in high or 3rd gear.What is the gear ratio in your rearend?Nothing like an overdrive tranny for fuel economy.

Achipmunk,
Do you still have your transmission crossmember still in place? You can measure from the bellhousing mounting holes forward to the block to tell you where the rear edge of the engine will be. Just set the old bellhousing down over the holes to find the back edge of the block would work too,
Scott

Scott, I understand what your saying. Right now the chassis is out from under the body and sitting in the yard. The original cross memeber is still on the chassis. Why didn't I think of that :hammering: So, as I understand it, the back of the old 6 cyl would be good for the back of the V8 and the distributor sitting in a good place. Thanks

The V-8 bell is very close, if not the same, in thickness as the 6's. If you run GM's HEI, you will still have firewall clearance problems. If you use a small cap aftermarket distributor, it should fit without modification.
Good luck,
Scott

i believe the rear end gear is 373 not real sure cause i never knew what i was doin an no truck wasnt attached to anything on my trip i couldnt believe the mileage either

52 Chevy Kid,That 23 MPG sounds about right with that gear ratio.Along with the fuel economy you should still be getting good performance.With a 700R4 you can go up to a 4:11 rear and still have good fuel economy and good pickup.when I put mine together I was gonna put in a 3:73 rear,but after the way the truck performed and the gas mileage,I just left the 3:90 in there.Way too many people changing engines,to get good perfomance and economy,when the real secret lies in the gearing.

I don't know squat about transmissions or gearing, etc. Is a 700r4 a manual transmission? Will it help my 62 c-30 get better mileage? Will I need to change my differential? ??????? :confused: :confused:

The 700R4 is an automatic overdrive transmission.If you have a C30 you probably have a very high rearend,probably somewhere around 4:56.Anyway you can get that rear gear down to maybe a 3:42 will help on mileage,or better yet a 3:08.With the 700R4 it is about.78 to 1 ratio,whereas a regular 350 or 400 Hydramatic is 1 to 1 ratio.

A C30 will more likely have a 5.14 gear, which is a low gear, not high (higher the #, lower the gear). 4.56 was used in the 3/4 tons, though it did become an option on the later 1 tons. About the highest you can get for that diff is a 4.10, using a center chunk from a '68-'72 3/4 ton. If you want a higher gear, like a 3.42, you'll need to swap out to a later diff, like a GM corporate 14 bolt 10.5" ring gear, or possibly the Dana/Spicer 70. If you're looking to keep it manual, and want an overdrive, consider either the NV4500 or a Ranger or Gear Vendors add on overdrive.
BTW-I only get about 12 mpg, IF I keep my size 14 out of it!!!

I changed my rear ratio from 5.14 to 4.10, and was planning to go to an NV 5-speed as well, for the overdrive. But, having driven the auld girl for a while now with the new ratio, I've decided that I won't need the O/D unless I was to start logging a lot of miles on Epic #2. She's completely driveable now, where before she was screaming at anywhere over about 40 - 45 mph. Now, I could cruise at 55 - 60 all day. And while I haven't gauged fuel economy yet, I know there's a BIG difference.