engine swap

[bigdadddychevy]

I just bought a 1970 chevy c-10 out of georgia and im shipping it to where i live in the bahamas.. problem is its a 350 and we have on goin traffic and gas is gone up to $5.50 a freakin gallon here.... now my question is can i swap it out easily to put a 235 in the truck to save myself some money at the pump? this truck is costing me a fortune as it is because im paying for the cost of the truck, shipping it down to west palm beach, shipping it across the water and on top of all that im paying 57% custom duty on all of those figures combined! thats why this hobby is a big expense here because the government is trying to make up for all of the money they loose. so please can someone brighten up my day by telling me it can be done! Also is the front grill interchangable with the 71 & 72 models?

[Jtrux]

First, grill is exchangeable.

Second, unless you have everything to swap in I don't think it would be worth it. I thought the bahamas was just a little place, how much gas do you think you'll be spending. If you have some decent gears like 3.07's or maybe 3.73's and you take it easy on it, I think 15 mpg can be expected which isn't bad.

[Longhorn Man]

From what I've seen on here, the most cost efective way t0o get decent MPG is with a 307 engine and 3.07 gears. Inline guys only seem to get 10 - 14 MPG, and it seems the 307 guys are bragging of 13 - 15.
Plus, when you figure EVERYTHING that is bolted to your 350 will swap right over to the 307... NOTHING to convert, no drive shaft mods, no linkage mods... just a simple engine swap, the cost is kept to a minimum. (whats the point in spending more money than you have to, if the whole goal is to save money?
You could go with an LS engine, but that kinda goes against the last paragraph.
And, believe it or not, the caddy big blocks get outstanding MPG in these trucks.
Grill swap. you'll need the 71/72 bumper and then the inner/outer grill, and I think the hood release handle assembly too.

[Wrenchbender Ret]

Like the other guys say I would find out what gear ratio the rear end is & consider changing the ratio. You could put a 250 6 cyl. in it without much trouble, as it was the basic engine in that model.but weather it would be cost effective is another thing to consider.

[68gmsee]

Terrible how the cost to own a classic is so high over there.

Here's my .02

Don't waste your time and money going to a 250 or 235. Your gas mileage won't improve that much. You best bet is to make sure your 350 is at optimum performance -rings, valve job, cam, ignition, carb, etc.

As was mentioned, find out what rear end you have and go with a lighter version. For instance a 3.07/3.08 instead of a 3.73/4.11.

You didn't say if you had an automatic or 3 speed. A good 4 speed automatic would help or even a 4 speed floor shift.

But don't expect 20 plus mpg. You'll do good to get 12-15 combined, whether it's a 6 or a V8. My old tired 350 got 14-15 highway and my overhauled 250 gets 15-16 highway. And it all depends on whether I have a tailwind or how fast I go...

[mr48chev]

A 235 isn't a proper swap for that truck.

I think I would work on optimizing the mileage from the 350.

That would include:
A cam designed for fuel mileage rather than high performance.
An HEI ignition. I picked up up 2.5 mpg with an aftermarket HEI, good plug wires and good plugs.
I also swapped to dual exhaust at the same time but I am not sure that had that much effect. Sure sounds sweet though.
An intake and carb geared more towards economy than hot dog performance.
If you are running the stock Quadrajet it can be tuned for better mileage by someone who knows what he is doing.

I got 16 on the freeway with the 70 C-10 with a 307 that had a Z28 cam and power pack heads running a truck 4 speed and 3.72 gears but that was a combination that just seemed to work.

I honestly think you can get better mileage (somewhere around 15/16) out of the truck if you work at it a bit with the 350 than you would if you put in a 6 in it's place.

I do have a friend who owns a tune up shop who made some dramatic gains in fuel mileage a few years ago by installing aftermarket fuel injection and I am thinking seriously about going that way with the next engine I build for the 71.