i would definitely go to another shop, most people report around 25-30% loss in economy. and what kind of "oiling problems" were they telling you about?

the reason for higher compression is that it raises the volumetric efficiency, and the fuel can handle it without detonation, and the better volumetric efficiency turns into a reduced loss in mileage so that even if your getting one or two mpg less, its still worth it because the fuel is cheaper.

sounds like your 302 needs a head gasket.

if you don't go over 65 mph very often, i wouldn't bother with the m5r2. I have it in my 88 and while its not a bad tranny, its not great. and it doesn't sound like you will be doing heavy enough work to warrant a zf5. if your t18 doesn't have the reeeaaally low first gear(there was two made, my sister 2x4 73 has a t18 w/ usable 1st gear, and it has 3.89's), i would go with a set of 3.00:1 (w/351) or 3.25(w/302) gears out back. if it does have the low 1st gear, i would run 3.55's, a great all-around gear.

overdrives have their own set of issues that follow them, and are a band-aid to poor engineering. for example I have a doug nash 4+1 (nowadays they are richmonds 5 speeds) which is basically the same gears as a close ratio t10 for 2-5 gears, but with a lower first gear added on. I can run 3.00:1 gears in the rearend and have the same launching performance and cruise rpm's as i did with the AOD and 3.73's. and a direct drive is stronger and more efficient than an over will ever be, but overdrive's became the thing to have, so there are barely any options for a properly geared direct drive anymore. if you want another example, there are millions of semi's out there with direct drive trannys and high gear ratios. they just have a really low first.

ok, my rant is over...

I will leave the 302 vs 351 up to you though, I have always seen high mpg's from 302s, but the 351 will give you more oomph.

however, if it was me... I would go with the 351 with a good rebuild, 12:1 compression, a set of gt40p heads, with small tube headers that fit them, stock roller cam (or if you had the money, call a cam company with excruciating detail of what you want, and ask them for a suggestion. they might just surprise you), an eldy performer intake and 500cfm carb (and being setup for e85/propane). 2wd t18 and 3.00:1 gears. run all synthetics, get a really good alignment (tell the tech beforehand you want it to be rather precise and hand him a 10 note) and cover the bed. if it was with the 302 the only thing i would change is 3.25 gears.

hows that for a mental circle!

edit: I'm glad that posted, I lost my internet connection and almost lost it!

 

the shop told me to get a high volume / high pressure oil pump and a bigger pan. Also that when they had it apart they would chamfer the oil ports and leave the crank to bearing clearance on the loose side to allow more oil to flow through. and again i find my self thinking "this is not a 600+ hp monster" i've heard these engines go for 150k with proper maintenance.

my t18 does have the granny gear, i tried it once on the street when i first got the truck, 0-2.25 mph instantly, then stay at 2.25 mph. with no seat belt. almost had to change my pants after that one. hahaha

i have no worrys about over working that trans, if they can handle the early diesels the small block is nothing. i was more worried about spinning it to fast trying to get to speeds no one saw when it came out. but i was thinking 45-50 mph would be my top speed, i don't want to go 65 in the truck (yet).

the m5r2 did worry me. ford never put it behind the 351. i like to think ford knows what there parts can handle and not. espically if i'm going to wake up the 351 with a cam. i don't want to risk cracking the trans in half or what ever would happen.

as for mpg everyone here seems to say the 300-6, 302-8, 351-8 get simmilar mileage if driven right. obviously the 351 has more opprotunity to burn more fuel.

fun story my 2005 mustang gt 5 speed manual gets the same mpg as my wifes 2011 kia sorento 4 cyl, 6 speed auto. so i know older bigger technology can keep up with these new little high tech engines. :-)

also i looked at the fuel comparison charts you posted. i really like the charts and graphs buy the way. but it really makes sense and seemed to back up my thought that a dual fuel engine optimized for e85 or LP would make the most out of either option. it looks like you just leave a lot on the table throwing e85 in a gasoline engine. every chart looks like e85 and LP are maybe 2% apart, which to me means they should run simmilarly and give simmilar performance.

if range becomes an issue i could just throw an aux tank under the bed or more propane tanks.

ps i'm glad that posted too. thanks

 

chamfering the oil ports on the crank is legit, although its more of a good practice than anything else, it removes any burrs that might contact the bearings and give a little more oil surface area to the bearing. but there is no need to build it "loose" or for a high volume oil pump, standard rebuild clearances and and a standard pump do indeed last a long, long time.

and yeah, like i said the m5r2 isn't a great tranny, but its not bad. I pulled a buddies 2500 dodge cummins on a 16 foot flatbed once...

the biggest thing that does, or ever will affect your mileage, is your driving. I used to squeeze an 18mpg average out of my 88 (an extended cab long bed 4x4) just by paying very close to my driving habits.

 

well thats good news on the crank. at least he wasn't blowing total smoke. but he hasn't called back yet either.

i like the once...

don't imiagine that will be happening again.

as its getting warmer out i am much more inclined to giddy up after work. so ill be looking through the junk yards and trying not to blow up both motors. ;-)