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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: ssapach on May 31, 2011, 10:49:54 pm

Title: 8.1L....will it fit?
Post by: ssapach on May 31, 2011, 10:49:54 pm
I've been told that an 8100 vortec will fit with ease under the hood of my 1986 GMC.

Now, simply fitting under the hood is one thing, but there are a few more considerations:
-will the oil pan clear my front differential with stock suspension?
-will it fit between the frame rails?
-will the motor mounts bolt up to where the current 454 sits?
-will there be any interference with the passenger side head/valve cover/exhaust and the HVAC box on the firewall?  (truck is equipped with a/c)

I'm curious because I discovered an 8.1 for sale close to home.  Seller is asking $1000 and it comes as a complete motor, all accessories, wiring and ECM and has about 205 000 km on it.

Any help or suggestions would be appreciated.  When I'm home I might try to drive out and have a look at the beast.
Title: Re: 8.1L....will it fit?
Post by: 1980c10 on May 31, 2011, 11:10:12 pm
I don't have an answer but you should give some more info about your truck auch as 2wd or 4wd or any other info that might be helpful.
Title: Re: 8.1L....will it fit?
Post by: 1979C20 on May 31, 2011, 11:22:13 pm
I don't have an answer but you should give some more info about your truck auch as 2wd or 4wd or any other info that might be helpful.
I've been told that an 8100 vortec will fit with ease under the hood of my 1986 GMC.

Now, simply fitting under the hood is one thing, but there are a few more considerations:
-will the oil pan clear my front differential with stock suspension?
-will it fit between the frame rails?
-will the motor mounts bolt up to where the current 454 sits?
-will there be any interference with the passenger side head/valve cover/exhaust and the HVAC box on the firewall?  (truck is equipped with a/c)

I'm curious because I discovered an 8.1 for sale close to home.  Seller is asking $1000 and it comes as a complete motor, all accessories, wiring and ECM and has about 205 000 km on it.

Any help or suggestions would be appreciated.  When I'm home I might try to drive out and have a look at the beast.
I don't have an answer but you should give some more info about your truck auch as 2wd or 4wd or any other info that might be helpful.

1986 GMC 4x4 stock height with a 454 and ac. Not too much more you need to know.
Title: Re: 8.1L....will it fit?
Post by: Irish_Alley on June 01, 2011, 12:31:48 am
whats the vin and your ss#? ::)
Title: Re: 8.1L....will it fit?
Post by: Irish_Alley on June 01, 2011, 12:34:10 am
not sure but what year is the 8100v tec. will it mate to currant transmission?
Title: Re: 8.1L....will it fit?
Post by: ssapach on June 01, 2011, 07:25:50 am
The 8100 is out of a 2002, which happens to be the very year of truck my transmission came out of.

My understanding was that it would even have the same bellhousing bolt pattern as the 454/SM465 currently in the old truck.
Title: Re: 8.1L....will it fit?
Post by: 1980c10 on June 01, 2011, 06:33:58 pm
I didn't need to know any of that as i don't have the answer, however more information will get faster answers.
Title: Re: 8.1L....will it fit?
Post by: 1979C20 on June 01, 2011, 06:55:26 pm
If people are talking about shoehorning one into a firebird, i bet it will fit in our truck. Especially since you already have a big block.
http://www.thirdgen.org/techboard/engine-swap/471013-8-1-vortec-swap.html (http://www.thirdgen.org/techboard/engine-swap/471013-8-1-vortec-swap.html)
Title: Re: 8.1L....will it fit?
Post by: 1979C20 on June 01, 2011, 08:08:01 pm
http://www.youtube.com/watch?v=5LhzgJUMjCs&feature=youtube_gdata_player (http://www.youtube.com/watch?v=5LhzgJUMjCs&feature=youtube_gdata_player)
done/doable. But apparently you have to notch the crap out of the frame for ac unless you buy a bracket to raise it on the engine.
Title: Re: 8.1L....will it fit?
Post by: big bear on June 01, 2011, 09:49:55 pm
thats sick.  i love the 8.1
Title: Re: 8.1L....will it fit?
Post by: ssapach on June 01, 2011, 10:24:35 pm
I think I should go have a look at the motor first, make sure it comes with everything I'm expecting it to and make sure it's not covered in oil.

Thanks for the input everyone.

That video is even more inspiring too.....that engine would look at home under the hood of my truck.
Title: Re: 8.1L....will it fit?
Post by: Captkaos on June 23, 2011, 05:08:55 pm
little info here:
http://forum.73-87chevytrucks.com/smforum/index.php?topic=9192.0
Title: Re: 8.1L....will it fit?
Post by: nucknoel89 on June 23, 2011, 09:49:13 pm
Here's a step by step, it's for an 88 but it's acrew cab so the same style as 73-87s.
http://www.hotrodlane.cc/Streetstories/81%20swap.pdf
Title: Re: 8.1L....will it fit?
Post by: ssapach on June 24, 2011, 07:59:40 am
Thanks for the links guys.

All that frame notching and reinforcing scares me a little.  Not so much that I'm incapable of doing it, but it's more work than I need for what the truck will be used for.
Title: Re: 8.1L....will it fit?
Post by: 1979C20 on June 24, 2011, 01:42:22 pm
You dont have to notch it. You could either run no ac, or there are after market brackets that move the ac pump higher on the engine.
Title: Re: 8.1L....will it fit?
Post by: beastie_3 on June 24, 2011, 03:02:40 pm
the frame needs to be notched for the exhaust...per nuck's link
Title: Re: 8.1L....will it fit?
Post by: 1979C20 on June 24, 2011, 03:54:09 pm
It will need notching, but you wont have to notch and reinforce it.
Title: Re: 8.1L....will it fit?
Post by: roadrage41 on June 25, 2011, 04:52:06 am
The plasma, it is your friend.
Title: Re: 8.1L....will it fit?
Post by: big bear on June 25, 2011, 09:14:10 am
it may not be required and or necessary, and maybe its just in my head, but whenever i notch things i always support them. somehow or another.
Title: Re: 8.1L....will it fit?
Post by: ssapach on June 25, 2011, 10:53:54 am
I agree with reinforcing.  When I'm removing material I still want it to be as strong or stronger than it ever was.

Title: Re: 8.1L....will it fit?
Post by: slammed79 on June 27, 2011, 10:49:32 pm
If mini truckers can fit big blocks into s-10's I'd say an 8.1 will fit our trucks, that is just an opinion statement :)
Title: Re: 8.1L....will it fit?
Post by: big bear on June 28, 2011, 04:11:13 pm
If mini truckers can fit big blocks into s-10's I'd say an 8.1 will fit our trucks, that is just an opinion statement :)

true story man.  what can i say, us mini truckers are a crazy breed.  but serioussly,  ive seen the 454 in many s10s its crazy.  i thought having a small block in my sonoma was asking for trouble haha
Title: Re: 8.1L....will it fit?
Post by: Captkaos on June 28, 2011, 04:22:04 pm
The 8.1L is just like a tall deck BBC, many of the frame notching is not necessary.
AC = Just move it back up top
8.1L manifolds, just don't use them, measure for "normal" BBC headers and find a set that will fit, keep in mind the tall deck difference makes the heads sit out 1/2" wider.
The Front of the oil pan will have to be clearanced.
Title: Re: 8.1L....will it fit?
Post by: bohrer54 on July 07, 2011, 07:27:38 am
You could also use a ord front crossmember to give you the needed clearance for the oil pan. I am right in the middle of putting my 8.1/s6-650 6 speed into my 86' crew right now and with headers the frame looks ok other than the a/c. i dont have the brackets for the ac/alternator yet.

As for the wire harness, i would ditch the stock one and go with an aftermarket one like howell engine dev. inc.. Much simpler to install, just send em your pcm and they reprogram it and your done.

Let us know what you come up with, or if you need more info.
Title: Re: 8.1L....will it fit?
Post by: ssapach on July 07, 2011, 01:33:41 pm
You could also use a ord front crossmember to give you the needed clearance for the oil pan. I am right in the middle of putting my 8.1/s6-650 6 speed into my 86' crew right now and with headers the frame looks ok other than the a/c. i dont have the brackets for the ac/alternator yet.

As for the wire harness, i would ditch the stock one and go with an aftermarket one like howell engine dev. inc.. Much simpler to install, just send em your pcm and they reprogram it and your done.

Let us know what you come up with, or if you need more info.

It sounds like you're doing something identical to what I was planning.  Is your truck a 4x4 as well? 

I'm curious how that 6 speed fits under the cab, if there is any reworking of the transmission tunnel required for it to fit or if it has enough room???

I would ultimately like a good used Duramax for my truck, but everyone wants way too much for a good used engine, not including other essentials to run the motor (rad, intercooler, etc.)  but if another 8.1 comes up close to home i might have to consider it.  The one I was previously eyeing up has since been sold.
Title: Re: 8.1L....will it fit?
Post by: bohrer54 on July 08, 2011, 12:00:36 pm
Yep my crew is a 4x4.

I havent put the tranny under it yet, just the motor to see how that fits. just from looking i think it is going to be tight, but it may fit. i am going to do a bunch of floor pan work anyways so i thought if i need to i may just raise the tunnel a little if i need too.

I am really looking forward to seeing how the 8.1/6speed pulls. that will mainly be what my truck is used for. I had howell engine del. put there ho tune in it, along with removing all emissions and torque mang. stuff.
Title: Re: 8.1L....will it fit?
Post by: ssapach on July 08, 2011, 03:11:21 pm
I looked at the Howell website.  I may have to rethink this 8.1 engine option as they make everything look so nice and easy, and for about half the price of what PPE told me for a plug and play Duramax wiring harness.

Thanks for bringing that one up, I probably wouldn't have found that any time soon!

Title: Re: 8.1L....will it fit?
Post by: bohrer54 on July 09, 2011, 11:23:55 am
no prob. ;)