Small block vs big block questions

[Sniper X]

So, I have two trucks. one is the 78 Camper Special with a 454, all stock, and the other is a all stock 350 both are 4 speeds. The 350 truck is a 74. If I do do what I want to this winter as a project, which is remove the 454 and rebuild it, with rebuilt heads, bore and new bearings, mild street cam and headers. I already know It will never get more than 9mpg probably less.

If I pump up the 350, which would be kinda stupid now since it was rebuilt 7K miles ago by the PO....and do a 383 or something, what kind of mileage should I expect?

I am not "really after mileage"....more after good solid but streetable power and reliability. Just a little more than a stock 454 that is this old has.

I guess I am basically asking what you guys have for HP and mileage on some mild or wild motors, and how the reliability is on both the big and small blocks that are bilt up a bit or a lot...

[glock35ipsc]

Hard to say what kind of mileage a SB would get unless we knew all the build details, trans info, gearing, tire size, etc. But chances are the answer would be either great, good, or terrible. No one can answer the numbers question until it's built, broke in and manually figured out after a couple tanks of fuel.

Another factor is how much $$ you have to spend. My truck is getting low to mid 20's for mileage at around 300hp. But it's not a small block or a big block, and it wasn't necessarily cheap either.

[Sniper X]

Yeah, when I bought my 1973 which was a C20, TH400, 350, it had been a 454, but had had a 350 swapped in. The PO said he had done it to get bettrer mileage. He owned a construction company and towed a long flatbed trailer to and from Santa fe a lot. He said he wanted better mileage than the 454 gave but still wanted the pwoer. He said he was pissed because even thugh the 350 was putting out about 325hp, he said it neither got better mileage while towing, nor did it pull the hills as well as the mild 454 which he figured at about the same HP but way more tq. he said the 454 got 9 or 10mpg doing anything, and the 350 got 7 towing and about 12 while unloaded. trouble was, it was NEVER unloaded.

[glock35ipsc]

Originally Posted by Sniper X

it had been a 454, but had had a 350 swapped in.......... He said he wanted better mileage than the 454 gave but still wanted the pwoer.

And no one told him this was a really dumb idea?

Originally Posted by Sniper X

nor did it pull the hills as well as the mild 454 which he figured at about the same HP but way more tq.

Another DUH moment for the PO! Torque pulls the heavy trailer.

A mild 350 wild probably give you the best performance with the best possible mileage. But again, it all comes down to how much you want to spend. I've got 323 cubic inches, can smoke most ricers around here, pull my trailer, and get over 20 mpg. All at once! But it wasn't cheap.

[Sniper X]

Exactly! I might just do a simple rebuild on the 454 and put in a middle of the road cam and headers since it will be swapped into the 74 which never again needs smog.
I wil then put the recently rebuilt in the last 5k miles, 350 in the 78 and give it to my GF to drive to and from 4h when we take the kids and animals. I think my 74 will boogie with a 375horse 454 in it. I know it will pull my trailer down the road no problem! I don't really care about the mileage because I have two other cars that get great mileage and a motorcycle.

[glock35ipsc]

Well there ya go! Sounds like a great plan.

[von guido]

i get 12-13 mpg outta my 454 on the hwy. stock motor except a crane high energy cam, aluminum dual plane intake,670 speed demon carb, and full lenghth headers into xpipe and flowmasters. 3.08 gear and a 30.1 inch rear tyre. My small block gets 18mpg and its same recipe as the big block but with a voodoo cam. both trucks have th350 transmissions.

[BIG KRIS]

Not sure what type of mileage cause there toys and we not really looking for best mpg,but i have a 83 with a 355 making 425hp and my dad has a 85 with a 468 both have head/cam/intake/carb.My sb it hauls but the bb is crazy power all over the place in the street on the highway that thing just pulls and melt rubber as long as the gas is on man what a fun truck to drive.