8.1 motor swap in 67 chassis

[Vince Putt]

Anybody ever put one of these monsters in the 67-72 chassis?
I understand that firewall clearance may be a problem, or so I think so because I've heard that the standard big block is mighty close. The 8.1 is a taller deck block socommon sense tell me....

Are the motor mounts same as a conventional BB?

[DirtyLarry]

I actually have a fully dressed 8.1L sitting in my garage waiting to replace my bored and whored 396 in my 68 GMC. Yes, the 8.1L bolts in the same as a 454. Same motor mounts, flex plate and all……but accessory brackets are exclusive to the 8.1L so 454 brackets will not work.

The bad news is there is virtually no aftermarket support for an 8.1L as far as a wiring harness, hop up goodies, etc. I have exchanged several emails with Howell Engine Development and Turbo City on a wiring harness and they both claim to have one on the market very soon. A few months ago one of the magazines did project Baja Suburban that ran an 8.1L on a GM Marine controller and wiring harness so there are alternatives to hacking up OEM harness. Just have to hack up a boat harness instead and change the electronic throttle control to a 80mm F-body cable operated throttle body.

As far as firewall clearance, starting in 2004 the 8.1L did not have the huge EGR valve at the rear of the engine (where a distributor usually would be on older engines) so clearance should not be an issue. I doubt it would be an issue with the EGR engines either.

If you learn more on this swap…let me know because I have done a lot of research that lead to a lot of dead ends but would like to know more myself.

[Vince Putt]

HI Larry,
Street and performance has a harness, page 63 of their PDF catalog.

http://www.hotrodlane.cc/onlinecatal...005catalog.pdf

$950 ouch What did you pay for your engine and what all did you get?

From looking at your sig line I'd say you are a man that thinks BIG!!!

[qksilver]

I read some where that the marine stuff just needs a few power and ground wires. It is a stand alone harness but from what I remember doesn't not include a trans controller. It would be a great swap.

[72gord]

Hey guys, keep us posted on any progress with the swap...I have an 8.1 in my 2001HD and love the driveability and torque, would make a great swap!
P.S. It also gets about the same gas mileage as any 350 I've had.

[DirtyLarry]

Thanks for the info Vince

I have never heard of Hotrodlane. They seem to have their late model engine retrofits down to a science. I will defiantly keep their link in my part contact list. I will not be tackling this project for a while as I just built a new house and have tons of landscaping chores to tend to that will cost me more than my lunch money, plus my 78 K10 takes priority over my 68. When I redo my 68, I want to start from the ground up even though it is already a clean ride….but it is not perfect.

I scored my 8.1 back in early 2001 from a 2000 model year vehicle when the 8.1’s were first being introduced. It was purchased through my company (auto manufacturer) for the core cost as it needs head gaskets (early production known failure) and service parts were not yet available for the new gen BB at that time so complete engines were installed for warrantable failures.

I have seen 8.1’s on Ebay ranging from $1000 to $4000 so I am not sure what you would expect to pay for one today. Mine has less than 2000 miles on it.
Yes, I like big blocks. No replacement for displacement.

[miket]

Aftermarket heads and intake are available for the 8.1's but they are expensive.

[DirtyLarry]

Your correct, Tbyrne Motor Sports who constantly whores parts on another GM forum has some goodies but wants ridicules amounts of money for them.

I’ll pass on their stuff and will most likely run a GM Marine controller that can produce as much power on a stock 8.1 as what their stuff can do on a production emission controlled Silverado/Sierra 8.1L

[miket]

Originally Posted by DirtyLarry

Your correct, Tbyrne Motor Sports who constantly whores parts on another GM forum has some goodies but wants ridicules amounts of money for them.

I’ll pass on their stuff and will most likely run a GM Marine controller that can produce as much power on a stock 8.1 as what their stuff can do on a production emission controlled Silverado/Sierra 8.1L

A new pcm will provide as much power increase as a set of aftermarket performance heads and intake? Please post proof.

I know what you mean about TByrne, but a good set of heads with a matched intake and cam being outdone by a different pcm...boy I don't know about that. . These heads and intake might be available elsewhere---have you checked?

But, I would like to be corrected/educated as I have an 8.1 too. So let me know where tests have been done with that marine controller...

[DirtyLarry]

Well, you may have me there as I have not really studied Tybrne’s HP numbers in dept but I am confident a Marine controller, possibly a Marine cam, a set of nice headers and higher flow rate marine injectors could run pretty close numbers to Tybrne’s offerings if not more.....for a fraction of the cost. Especially since marine pieces are not governed by the same strict emissions constraints of production vehicles in terms of burning down catalytic converters or sending OBD II into a confused orbit. Don’t know for sure as I have a lot more research to do on this project.

I know sure my bored and whored balanced 396 with a .555 lift cam is certainly not a easy driver around town but it makes stop light to stop lights go by pretty fast so even a stock 8.1 with 340 HP and 455 lb ft of torque would be pretty impressive in a 67- 72 without all of the idiosyncrasies of big cams and cranky carburetors.

[Alvin]

I have looked into the 8100 swap a little bit, mostly to pass time. One thing I did come across, there is a series of high performance 8100 vortec engines used in offshore racing boats. The designations are HP1 8100, HP2 8100, and HP3 8100. GM Performance parts was supposed to offer a crate version of the HP3 sometime last year, but it never happened. It is listed on page 46 of the 2003 GMPP catalog. They spec'd it at "over 525hp @ 5200rpm, and 560 ft-lbs @ 4000rpm". All that accomplished on a 9.1:1 compression ratio. Hopefully GM will step up to the plate and offer this, I can see there is definitely some demand.