I6 to V8 swap questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

sjarrett71 · 10-22-2008, 09:01 PM

My uncle recently spun a rod bearing in his 81 Chevy 2wd with an inline 6 cylinder. He is thinking about swapping over to a V8 and since I am the family mechanic he wants me to do it. My questions are:

1. What is entailed in the swap? I understand I will have to get the complete v8 motor, accessory brackets and everything.

2. Will I have to change the crossmember or just the motor mounts?

3. Would it be easier to just rebuild the I6? If so, how easy is it? I heard from a friend I could do it with the engine still in the truck.

I did use the search feature but found nothing dealing with my questions. Any threads that you know of would be great.

**old Rusty C10** · 10-22-2008, 09:35 PM

its a direct bolt in unless its a big block you dont have to do a thing to the motor mounts.. you will need the accessories and mounts for them as some are different (power steering and AC)
to rebuild a motor you need to pull it if you can rebuild a 6 you can do an 8 its not much different

bucket · 10-22-2008, 09:39 PM

the mounts will be different if the 6 is a 292. 292's had offset mounts.

**Captkaos** · 10-23-2008, 09:47 AM

You need V8 mounts for the engine, I6's use a completely different engine mount. V8's regardless of size (SBC or BBC) use the same mount.

You also need to move the frame mount to the "8" position for a V8.

What transmission you currently have vs what you plan to go to (if you are going to change) will possibly require moving your trans crossmember.

Cherub · 10-23-2008, 01:11 PM

Did this swap in my dads 82. The motor mounts needed to be changed. The 3 speed tranny bolted up but as you can imagine the 350 was under geared.

sjarrett71 · 10-24-2008, 11:12 AM

So from the replies I am guessing I have to move the frame mounted motor mounts forward? It has an automatic tranny. Does anyone know of a thread that already deals with this so I can research it better? I'm sure I can figure it out I just want to go into this project informed.

**Captkaos** · 10-24-2008, 11:22 AM

no, the frame mount smove up or down depending which direction you are going.
The holes are actually marked on the frame support with a 6 and an 8. V8's mount in the upper holes.

sjarrett71 · 10-24-2008, 04:36 PM

So it's actually a pretty easy swap then? I just need to make sure I get all the brackets and everything from the v8? Anything else I should watch out for?

rigon4 · 10-24-2008, 07:29 PM

I have a 81 2wd blazer with a 250 i6 aka 4.1L and put in a 350 3 weeks ago you need the clam shell mounts and pullys off the sb and move the mounts on the frame to the top holes.

10-22-2008, 09:01 PM	#1
sjarrett71 Registered User Join Date: Dec 2006 Location: Rolla, MO Posts: 2,463	I6 to V8 swap questions My uncle recently spun a rod bearing in his 81 Chevy 2wd with an inline 6 cylinder. He is thinking about swapping over to a V8 and since I am the family mechanic he wants me to do it. My questions are: 1. What is entailed in the swap? I understand I will have to get the complete v8 motor, accessory brackets and everything. 2. Will I have to change the crossmember or just the motor mounts? 3. Would it be easier to just rebuild the I6? If so, how easy is it? I heard from a friend I could do it with the engine still in the truck. I did use the search feature but found nothing dealing with my questions. Any threads that you know of would be great. __________________ -Scott-

10-22-2008, 09:35 PM	#2
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,310	Re: I6 to V8 swap questions its a direct bolt in unless its a big block you dont have to do a thing to the motor mounts.. you will need the accessories and mounts for them as some are different (power steering and AC) to rebuild a motor you need to pull it if you can rebuild a 6 you can do an 8 its not much different __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

10-22-2008, 09:39 PM	#3
bucket Registered User Join Date: Aug 2001 Location: Shawnee, KS Posts: 923	Re: I6 to V8 swap questions the mounts will be different if the 6 is a 292. 292's had offset mounts. __________________ 79 K10 77 MGB 79 Kawasaki KZ1000

10-23-2008, 09:47 AM	#4
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	Re: I6 to V8 swap questions You need V8 mounts for the engine, I6's use a completely different engine mount. V8's regardless of size (SBC or BBC) use the same mount. You also need to move the frame mount to the "8" position for a V8. What transmission you currently have vs what you plan to go to (if you are going to change) will possibly require moving your trans crossmember. __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com

10-23-2008, 01:11 PM	#5
Cherub Registered User Join Date: Feb 2008 Location: Houston Posts: 970	Re: I6 to V8 swap questions Did this swap in my dads 82. The motor mounts needed to be changed. The 3 speed tranny bolted up but as you can imagine the 350 was under geared.

10-24-2008, 11:12 AM	#6
sjarrett71 Registered User Join Date: Dec 2006 Location: Rolla, MO Posts: 2,463	Re: I6 to V8 swap questions So from the replies I am guessing I have to move the frame mounted motor mounts forward? It has an automatic tranny. Does anyone know of a thread that already deals with this so I can research it better? I'm sure I can figure it out I just want to go into this project informed. __________________ -Scott-

10-24-2008, 11:22 AM	#7
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	Re: I6 to V8 swap questions no, the frame mount smove up or down depending which direction you are going. The holes are actually marked on the frame support with a 6 and an 8. V8's mount in the upper holes. __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com

10-24-2008, 04:36 PM	#8
sjarrett71 Registered User Join Date: Dec 2006 Location: Rolla, MO Posts: 2,463	Re: I6 to V8 swap questions So it's actually a pretty easy swap then? I just need to make sure I get all the brackets and everything from the v8? Anything else I should watch out for? __________________ -Scott-

10-24-2008, 07:29 PM	#9
rigon4 Registered User Join Date: Mar 2006 Location: east syracuse ny Posts: 371	Re: I6 to V8 swap questions I have a 81 2wd blazer with a 250 i6 aka 4.1L and put in a 350 3 weeks ago you need the clam shell mounts and pullys off the sb and move the mounts on the frame to the top holes. __________________ 1981 K-5 Blazer 2wd 1985 C-10 Short step 1988 C-10 Suburban

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