I6 or 350?
 

i have a 68 chev 2wd and right now its got a 292 I6 in it that burns oil and this truck is soon goin to be my daily driver
i have a 350 that is complete and ran when the 68 gmc its in was parked about 17 years ago, i havent had time to get it started due to where im storing the truck but i know it wont take much effort
now my question is will the 350 with a rochester quad get better mpg then the oil burning 292
the 350 would get a new set of gasgets andwhatever else it needs to be in perfect running condition before it gets any use
so would the 350 with the th350tranny be the best gas millage combo versus the oil burning 292 with the same tranny
i dont know was the gears r but its pretty low gearsim shure cause the truck was a 2wd c/20 with a 350 originaly and a 3speed granny shifter
tell me your thoughts about it thanks

Re: I6 or 350?
 

it proly wont be the big of a gas milage difference
and there are pro s and cons for both engines

Re: I6 or 350?
 

When you say the 6 burns oil, how much?

If it's one quart of oil per 1000 miles..fugetaboutit. Drive the truck until it blows.

If it is one quart per full tank of gas, first try a adding a can of STP to the oil.

If it is still one quart per full tank of gas, swap out the o-ring valve seals with rubber umbrella valve seals for a small block f*rd (289/302). A lot less work than swapping engines.

If the truck has a continueous fog of burnt oil making the truck look like crop duster going down the road, then... good luck with the quicky fresh-up and swap of your V8.

Re: I6 or 350?
 

[QUOTE=Willy Prost;2309092]If it is still one quart per full tank of gas, swap out the o-ring valve seals with rubber umbrella valve seals for a small block f*rd (289/302). A lot less work than swapping engines.
QUOTE]

Willy, can you expand on this? Can you use them on any six?

Also, what year 289/302?

Thanks.

Re: I6 or 350?
 

292s get terrible mileage.

Re: I6 or 350?
 

When I first bought my 71 with a 250 in 1996, among the other small problems the truck had was that it was burning alot of oil (2 quarts during a 250 mile trip from Washington,DC to Topsail Isliand, NC. Another 2 quarts along the way back).

Upon returning home, I asked the guy I bought all my auto parts at the time what should I do. He is the one that suggested that I try using rubber umbrella style valve seals for a f*rd 289/302. Plain rubber umbrella seals do not need machining like teflon valve seals. The valve stem is the same size as the chevy six. The 250 and 292 use the same basic head design. The 292 may have a bigger combustion chamber size, but I'm not sure. The valves are the same.

Chevy engines of that era used o-ring seals located near the valve spring keepers. Over time, the rubber deterioates, alowing oil to escape into the combustion chamber and the exhaust. The valve guides wear too, but the rubber seal is what keeps the oil losses low.

You do not have to remove the cylinder head to swap out the valve seals.

Tools that you do need to do the job are:

A valve spring compressor to get to the valve guide seals. I used a K-D model 2078 Universal Overhead Valve Spring Compressor. It is small enough to fit over the valves without getting in the way.

If you have access to compressed air, you can use a fitting that screws into the spark plug hole to inject compressed air into the combustion chamber to keep the valves from falling down into the combustion chamber preventing you from putting the valve spring and valve retainer back together after replacing the valve seal.

Don't have compressed air? No problem. You just need some old clothesline. Just feed the clothesline into the spark plug hole until you can't anymore. That will be enough to keep the valves from falling into the combustion chamber. That is what I used.

How to do the swap:

rotate engine to TDC for cylinder #1.

Either feed clothesline or install air feed to spark plug hole.

Compress valve spring. Remove valve keeper. Remove valve spring. Remove traces of old valve seal.

Place umbrella seal cylinder over valve. replace valve spring. replace valve keeper.

repeat for other valve for that cylinder.

After #1 cylinder is finished, rotate crank to next cylinder in firing order until finished.

This cheapo repair has lasted 11 years and 70,000 miles later. I can't complain. Today the engine uses ~ 1 quart per 1200 miles. The cylinder head could use a valve job someday, but that day isn't today.

update: I don't remember what year(s) 289/302seals. This was done 11 years ago. I don't have the reciepts from the parts store. I just remember that the cost for enough seals to do the 6 cost less than 10 bucks in 1996.

Re: I6 or 350?
 

willy, good write up on how to do it... may buy drivethechevy some time to fix his 350 if his oil burning is due to worn valve guides.

I'll stop by my local napa and ask about those seals.

Re: I6 or 350?
 

:agree:

The 350 will get MUCH better mileage