The material was free, so I may have went overboard with thicknesses.
Another 1991 Suburban
- Thread starter sean257
- Start date
The material was free, so I may have went overboard with thicknesses.
Larry, I have another question that I have not been able to find a definitive answer for through search. We ordered a harness and ecm from Howell. I am using the stock NP241 transfer case with a 32 spline shaft swapped in. Since it a 91 it has an electronic speedometer and we are using the stock transfer case will this work electronically? The guys at Howell said something about we may need an adapter for 40 pulse vs 2 pulse, but I am confused. Best I can tell the transfer case I have should be 40 pulse, and that should be fine. I also understand that there will need to be a switch installed so that when it is in 4 low, the transmission knows it is in 4 Low. That part seems fairly well explained though.
Last edited:
Larry
Bigassgas Explorer
Sean, sorry for the late reply on this as I just noticed your note to me this morning. Hope you got your speedo pulse deal figured out. I sure do not have your answer on that one. I have not messed with one of these with electronic speedo, only mechanical speedos. As a far as a 4low switch to tell the ECM the truck is in 4 low isn’t necessary. I don’t run one on my 8.1L K10 and no plans to use one on my Burb either.
The engine looks great. Looks like it even may have the correct brackets for the high mount A/C compressor to avoid any frame hacking for compressor clearance. Did your supplier advise what the engine came out of? Looks like a 2000-2003 medium duty truck engine. I dig the flares too. The cutouts are the best looking flares on the market, I just don’t think I would ever be brave enough to take a sawzall to the fenders of one of these old trucks.
Look forward to the updates :ylsmoke:
The engine looks great. Looks like it even may have the correct brackets for the high mount A/C compressor to avoid any frame hacking for compressor clearance. Did your supplier advise what the engine came out of? Looks like a 2000-2003 medium duty truck engine. I dig the flares too. The cutouts are the best looking flares on the market, I just don’t think I would ever be brave enough to take a sawzall to the fenders of one of these old trucks.
Look forward to the updates :ylsmoke:
beags86
Adventurer
Contrary to popular belief there are zero frame modifications to be done to install an 8.1L when using the proper accessory brackets and exhaust manifolds. If you Google 8.1L swap you will find a swap article from a WyoTech Instructor that installed an 8.1L in an 80's GM crew cab. The guy did not research his swap very well or he would have discovered the frame did not need to be hacked up to make room for the A/C compressor and exhaust manifolds. Using GM Medium Duty Truck or G-Van accessory brackets allow the A/C compressor to mount up on top the engine opposed to the side of the engine where the frame interference occurs. He would have also discovered the 8.1L will accept any older BBC exhaust manifold or header. A set of 454 exhaust manifolds would have saved him from cutting the frame for exhaust clearance. Lastly, he would have discovered the firewall doesn't need to be hackup either to make room for the EGR valve as the valve can be removed and the EGR function tuned out of the ECM as well as about 10 other things he wasted time and money doing. If you look at my swap pictures there are zero frame mods. I pulled a 7.4L out in the morning and stuffed the 8.1L in that same afternoon. The 8.1L is a straight drop in to the existing small block or big block mounts as well so no modifications there although there will be some oil pan clearance issues to deal with, which the ORD HD engine cross member can fix. You can't say all of that for a Gen III small block. You will also play hell finding the proper exhaust manifold or header to fit a Gen III small block in an old truck without cutting the frame. In my opinion the 8.1L is a much easier swap than any Gen III 5.3L, 6.0L or 6.2L with much greater rewards.
I have gotten overwhelmed with PM's and emails from various forums where people want to know how to go about an 8.1L swap. Given my worn-out enthusiasm to address every PM from people that just want to pick my brain to death without doing any research of their own I created this thread to help people with their 8.1L curiosities. Check it out :ylsmoke:
I don't have a build thread on my 8.1L swap but I do have all of the pictures here. I think you will agree it is a sanitary swap with no. The plan for my Polar Bear Suburban will even be cleaner :elkgrin:
Larry, I have to speak up a bit here. The Wyotech instructor you are talking about here was my instructor while I was at Wyotech. So I have to stick up a bit for him. This truck he built was simply awesome. Crew cab short bed. He was building this thing while I was in school. This was back in 05-06. There was very little knowledge of the 8.1 and what parts work and don't. Very little Internet support if you will. Gary is a very smart and talented mechanic and fabricator.
So he did what he needed to get the swap done. At the time this was done it was some groundbreaking work. (I never heard or read at the time of anyone doing this) last if you look closely you can see the frame is fully boxed. This truck also started out as a crew cab dually that was shorted for the short box. So frame mods were not really a bid deal. It would never go back to stock. Here's a pic of it finished.
I did not think until after I asked, but with you running the nv4500 manual, it does not need to know if you are in 4 low, or how fast you are going.
Interesting perspective beags. I was thinking, if it was not for the internet I would not know that the frame could be left in tact. That being said, it is kind of misleading now when you do a google search and your instructors frame cutting recipe for the swap is among the top results. As such, if Larry hadn't set me right, I would have been putting in a 6.0 right now because of the Wyotech pdf.
Interesting perspective beags. I was thinking, if it was not for the internet I would not know that the frame could be left in tact. That being said, it is kind of misleading now when you do a google search and your instructors frame cutting recipe for the swap is among the top results. As such, if Larry hadn't set me right, I would have been putting in a 6.0 right now because of the Wyotech pdf.
Larry
Bigassgas Explorer
Don’t get me wrong, I didn’t say the truck wasn’t nicely built with great details to craftsmanship. There is also no doubt he is a talented guy but what I’ve said all along is there was a lot of unnecessary work done with his engine swap by not doing more research and by research, I don’t mean surfing forums to find someone else that has done it to ask them questions. Research is popping hoods, combing through service manuals, comparing part numbers in catalogs, etc. to see what all is out there. Napa and AC Delco’s websites are awesome for researching part pictures and model usage. When I did the serpentine belt conversion on the truck back in 1995, there was no internet. Same with when I did the 3/4 axle swap. Research was done the old fashion way by opening books, comparing vehicles, and opening hoods. When I did my 8.1L in 2008 there were no internet hits on such a swap either. As far as I know I was one of the first to do this swap if not, the first in a street legal truck. The only other I knew of that that time was the 8.1L swap Peterson’s 4-Wheel & Off-Road did into a desert race truck and it was pretty much all GM marine stuff. Although, I work for a truck manufacturer where we use GM Powertrain to power our RV and some commercial stripped chassis and had a bit more 8.1L experience that most people.
Correct, with mine being a manual transmission the ECM in my truck has no idea how fast the truck is going (no speed input to the ECM) nor any inputs from the tcase. I could see where an automatic transmission would need a VSS signal to shift properly but I don’t see where the ECM needs to know the tcase range. Sure, late model trucks have tcase range inputs into the ECM but for the purpose of torque management to prevent the engine overtorqing the driveline. Old carbureted vehicles didn’t care what range the tcase was in nor did the TBI EFI rigs. Late model ECMs really don’t need to know either. Along with Howell’s suggestions you can also pick and choose what inputs you want Howell to build into or delete from the harness and ECM tuning. I had them delete EGR, APP (drive by wire), Torque Management and add a performance tune although I do have an electric fan relay and powerlead if I ever choose to move to an electric fan. The harness they built for me only had 4 connections to the truck itself….Keyed on power, constant battery power, fuel pump and tachometer. I don’t even have an A/C request signal going to the ECM, as the MAP senses the load and adjusts the idle as needed when the compressor comes on. The air compressor, cluster oil pressure and temp gauge signals still work with the original 1978 harness with no inputs to or from the ECM.
Al_Santos
New member
I have 4.56 gears with 35 inch tires. I think it runs great now. I haven't towed anything real heavy with it though
I have not noticed any sag, but I can hear the whole door rattle when I hit big bumps. I'll have to take pictures of the ladder to door connection, I don't have any on my computer.
On another note, if anyone knows where to wire up my TSS to brake wire that would be great. I need 12v when the brake is not pressed and 0v when the brake is pressed. This wire is for the torque converter lockup control. I do not have cruise control.
I am really liking the new grill and headlights (even though it is a Chevy/GMC mix now)
On another note, if anyone knows where to wire up my TSS to brake wire that would be great. I need 12v when the brake is not pressed and 0v when the brake is pressed. This wire is for the torque converter lockup control. I do not have cruise control.
I am really liking the new grill and headlights (even though it is a Chevy/GMC mix now)
