Straight 6 guidance - The 1947 - Present Chevrolet & GMC Truck Message Board Network

1972CST · 01-22-2016, 10:22 AM

Hey guys, need a little help in an area that I'm not so fimiliar with. I have a 1979 GMC high Sierra with a bad (4.1 I think) straight 6 in it. I'm looking for the most economical way to get it going again. I have ran across a 250 straight 6 out of a 1969 c-10 on Craigslist for a decent price.
My question is will the 250 be a direct bolt in replacement for the 4.1?

Thanks for your help!

manimal · 01-22-2016, 11:07 AM

Same engine.... The only thing I dont remember is when GM used the integral head(late 70's early 80's). But a 69 will drop right in. use your HEI distributor.

Dead Parrot · 01-22-2016, 12:40 PM

You didn't mention if you were locked on staying with a 6. Lots of folks pull out perfectly serviceable 305s or 350s because they want to install MORE power and they wind up with the used engine cluttering up their garage. IIRC, there isn't any difference between 6 and 8 as far as the bell housings are concerned. As long as you get the accessory brackets and manifolds with the motor, you shouldn't have a lot of issues. Exhaust will be the main difference. See if the 'more power' person will toss in the Y pipe cluttering up their yard.

barry1982 · 01-23-2016, 12:10 AM

I agree with Dead Parrot...... you can probably grab a 305/350 cheaper than a 6 . Pickup a few parts at the wrecker from a donor truck (motor mounts etc)
I have swapped V8's into three 6 cyl trucks over the years, its not too bad.

1970pelle · 01-23-2016, 12:35 AM

Is your county a emissions test county? I know Mecklenburg county is a emission test county. Does that effect you?
If not think about the V8 swap, like a 305 or 350. You will like the truck better.

Ken

**MikeB** · 01-23-2016, 08:09 PM

Quote:

Originally Posted by Dead Parrot

You didn't mention if you were locked on staying with a 6. Lots of folks pull out perfectly serviceable 305s or 350s because they want to install MORE power and they wind up with the used engine cluttering up their garage. IIRC, there isn't any difference between 6 and 8 as far as the bell housings are concerned. As long as you get the accessory brackets and manifolds with the motor, you shouldn't have a lot of issues. Exhaust will be the main difference. See if the 'more power' person will toss in the Y pipe cluttering up their yard.

I did this swap on my 82 C10 last year. Biggest issues were:

Finding the proper V-8 motor count "clam shells"
Engine wiring harness mods (some wires are shorter, some longer)
Alternator and PS pump brackets
Fan shroud and radiator (There are at least 3 different radiator and fan shroud sizes for an 82 model small block V-8.)

lilpoindexter · 01-23-2016, 01:06 AM

As a straight six / integrated head '78 owner, i will tell you...you will like a V-8 better...even a 305. It's cool showing people my odd ball straight 6...but it's kind of a lethargic boat anchor. If smog wasn't an issue for me, i would put in a 350 with a small carb and small cam to get decent mpg, but still have a little grunt.

manimal · 01-23-2016, 07:55 PM

If you go with a V8, you'll be just like everyone else! The inline six is a sweet running engine. Are you building your truck as a driver? Hauler? Race car? If you answered either of the last 2 then yes, be all means go V8...BUT if you a reliable driver and occasional hauler, that 250 will be a GREAT engine.
V8's are old hat and boring......

RANDY COX · 01-23-2016, 10:19 PM

Quote:

Originally Posted by manimal

If you go with a V8, you'll be just like everyone else! The inline six is a sweet running engine. Are you building your truck as a driver? Hauler? Race car? If you answered either of the last 2 then yes, be all means go V8...BUT if you a reliable driver and occasional hauler, that 250 will be a GREAT engine.
V8's are old hat and boring......

x2^^^^^

1972CST · 01-24-2016, 02:35 AM

Wow! Thanks for all of the input! It seems like I have wrestled with all of the suggestions you are bringing and they all have good points.

Long story short- I was given my grandfathers 79 High Sierra long bed, 2wd, 6 cyl, auto, bone stock truck. The truck has been sitting over 10 years and needs some major attention, like another engine (original uses oil like crazy) and trans rebuild ( slipping when parked).
My ambition is to get the truck to a "useable" condition so it's not just going down hill sitting. Seems like everyone wants to borrow a truck and this one would make a better "loaner" than my z71 LOL.

My long term plan is to swap in a 350 and make it appear factory. This truck is NC state inspection exempt due to its age so no one will be poking around under the hood.
In the short term, a good running $250 6 cyl Craigslist special seems attractive and I am in the middle of restoring my 72 k5 so money and time is tight.

Sorry for the long post, I felt your replies deserved a little more background info

From what I am hearing the 69 model 250 should be a simple, quick and cheap way to get things moving again.

Are there any particular things I should keep in mind when I go take a look at the used 250?

01-22-2016, 10:22 AM	#1
1972CST Registered User Join Date: Mar 2008 Location: Concord NC Posts: 511	Straight 6 guidance Hey guys, need a little help in an area that I'm not so fimiliar with. I have a 1979 GMC high Sierra with a bad (4.1 I think) straight 6 in it. I'm looking for the most economical way to get it going again. I have ran across a 250 straight 6 out of a 1969 c-10 on Craigslist for a decent price. My question is will the 250 be a direct bolt in replacement for the 4.1? Thanks for your help!

01-22-2016, 11:07 AM	#2
manimal Registered User Join Date: Oct 2006 Location: Southern Kalifornia Posts: 3,066	Re: Straight 6 guidance Same engine.... The only thing I dont remember is when GM used the integral head(late 70's early 80's). But a 69 will drop right in. use your HEI distributor. __________________ ------------------------------------------------------ -Lance 2000 Chevy C2500, 5.7, 4L80e 1999 Suburban K2500, 7.4, 4L80e 1980 Camaro..son's car...PROJECT

01-22-2016, 12:40 PM	#3
Dead Parrot Registered User Join Date: Aug 2012 Location: Oklahoma City, OK Posts: 2,620	Re: Straight 6 guidance You didn't mention if you were locked on staying with a 6. Lots of folks pull out perfectly serviceable 305s or 350s because they want to install MORE power and they wind up with the used engine cluttering up their garage. IIRC, there isn't any difference between 6 and 8 as far as the bell housings are concerned. As long as you get the accessory brackets and manifolds with the motor, you shouldn't have a lot of issues. Exhaust will be the main difference. See if the 'more power' person will toss in the Y pipe cluttering up their yard.

01-23-2016, 12:10 AM	#4
barry1982 Registered User Join Date: Oct 2015 Location: Waskatenau, Alberta Posts: 259	Re: Straight 6 guidance I agree with Dead Parrot...... you can probably grab a 305/350 cheaper than a 6 . Pickup a few parts at the wrecker from a donor truck (motor mounts etc) I have swapped V8's into three 6 cyl trucks over the years, its not too bad.

01-23-2016, 12:35 AM	#5
1970pelle Registered User Join Date: Sep 2007 Location: N.E. Florida Posts: 500	Re: Straight 6 guidance Is your county a emissions test county? I know Mecklenburg county is a emission test county. Does that effect you? If not think about the V8 swap, like a 305 or 350. You will like the truck better. Ken __________________ 1985 IROC Z28 190HP TPI 305,700r4,T-tops,rear trac lock, Black on lite gray, 16in Z28 wheels 2007 Lexus ES350 (wifes) 1984 CJ7 with 1995 HO4.0L MPI, 2 1/2 OME YJ Lift “There is no limit to the amount of good you can do if you don't care who gets the credit.” ― Ronald Reagan

01-23-2016, 01:06 AM	#7
lilpoindexter Registered User Join Date: Sep 2010 Location: los angeles Posts: 1,134	Re: Straight 6 guidance As a straight six / integrated head '78 owner, i will tell you...you will like a V-8 better...even a 305. It's cool showing people my odd ball straight 6...but it's kind of a lethargic boat anchor. If smog wasn't an issue for me, i would put in a 350 with a small carb and small cam to get decent mpg, but still have a little grunt.

01-23-2016, 07:55 PM	#8
manimal Registered User Join Date: Oct 2006 Location: Southern Kalifornia Posts: 3,066	Re: Straight 6 guidance If you go with a V8, you'll be just like everyone else! The inline six is a sweet running engine. Are you building your truck as a driver? Hauler? Race car? If you answered either of the last 2 then yes, be all means go V8...BUT if you a reliable driver and occasional hauler, that 250 will be a GREAT engine. V8's are old hat and boring...... __________________ ------------------------------------------------------ -Lance 2000 Chevy C2500, 5.7, 4L80e 1999 Suburban K2500, 7.4, 4L80e 1980 Camaro..son's car...PROJECT

01-24-2016, 02:35 AM	#10
1972CST Registered User Join Date: Mar 2008 Location: Concord NC Posts: 511	Re: Straight 6 guidance Wow! Thanks for all of the input! It seems like I have wrestled with all of the suggestions you are bringing and they all have good points. Long story short- I was given my grandfathers 79 High Sierra long bed, 2wd, 6 cyl, auto, bone stock truck. The truck has been sitting over 10 years and needs some major attention, like another engine (original uses oil like crazy) and trans rebuild ( slipping when parked). My ambition is to get the truck to a "useable" condition so it's not just going down hill sitting. Seems like everyone wants to borrow a truck and this one would make a better "loaner" than my z71 LOL. My long term plan is to swap in a 350 and make it appear factory. This truck is NC state inspection exempt due to its age so no one will be poking around under the hood. In the short term, a good running $250 6 cyl Craigslist special seems attractive and I am in the middle of restoring my 72 k5 so money and time is tight. Sorry for the long post, I felt your replies deserved a little more background info From what I am hearing the 69 model 250 should be a simple, quick and cheap way to get things moving again. Are there any particular things I should keep in mind when I go take a look at the used 250?



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