-
Welcome to The Truck Stop! We see you haven't REGISTERED yet.
Your truck knowledge is missing!
- Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
- We have tons of knowledge here for your diesel truck!
- Post your own topics and reply to existing threads to help others out!
- NO ADS! The site is fully functional and ad free!
Problems registering? Click here to contact us!
Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!
GMT400 6.5 Swap Help
- Thread starter adventr
- Start date
Sent a message. Thanks again for the help and the phone call earlier.
I have always been set on standard compression ratio simply because I had read where lower compression is harder to start in the winter. But that may not be true or may be blown out of proportion. Will do some research on here.
Well I've built many, a few for folks here, not 1 single complaint .....
And just how much time is spent "starting" the motor vs working on the road ? a lot of folks spout stuff someone else says because they are followers, most have never had a lc motor...
And just how much time is spent "starting" the motor vs working on the road ? a lot of folks spout stuff someone else says because they are followers, most have never had a lc motor...
@DieselAmateur has one of my 18:1 P400's and lives upstate NY, maybe can offer his views.... I think it gets cold up that way LOL....
Will L.
Well-Known Member
Stock starter and low batteries, then you can tell it is harder to start- barely.
Using a powermaster starter, it spins so fast I think they actually start easier than Powermaster on the 21.1:1 compression.
Oh, you mentioned there IS rust on the camshaft. If it doesn’t wipe off with a little brake cleaner on a rag it is garbage.
unfortunately sounds like you bought a $2000 block.
Using a powermaster starter, it spins so fast I think they actually start easier than Powermaster on the 21.1:1 compression.
Oh, you mentioned there IS rust on the camshaft. If it doesn’t wipe off with a little brake cleaner on a rag it is garbage.
unfortunately sounds like you bought a $2000 block.
Thanks guys for the info on the 18:1 engines. I do have one more question about the p400. Dimensionally, is it of similar size to the standard 6.5?
Reason I ask, I saw a pic of a p400 bottom end. It appears that the oil pan flange sits either flush or below the main caps. As where on my 6.5, the oil pan flange sits at the top side of the main caps.
The main reason I didn't go duramax from the get-go is because when I dropped the cad model into my chassis model, I found that there would be no room for any suspension up travel with the duramax. Just curious if the p400 might be the same way there.
Reason I ask, I saw a pic of a p400 bottom end. It appears that the oil pan flange sits either flush or below the main caps. As where on my 6.5, the oil pan flange sits at the top side of the main caps.
The main reason I didn't go duramax from the get-go is because when I dropped the cad model into my chassis model, I found that there would be no room for any suspension up travel with the duramax. Just curious if the p400 might be the same way there.
If your truck is 4x4 you will need a different pan, Jody's already has a custom pan, will it work for you I don't know... The Dimension are the same, the pan is shorter to make up for the 3" girdle...
DieselAmateur
She ain't revved 'til the rods are thrown...
I've never had any starting issue running 18:1. Granted it's always been with a Powermaster starter, which I can't recommend enough. The engine is a little louder and smokes a little more on startup, but getting it to turn over has never been a concern of mine and we can have weeks here where the temperatures stay in the teens.
MrMarty51
Well-Known Member
I would think that with the lower compression ratio, it would spin over faster, even with a stock GM starter.
Will L.
Well-Known Member
It does spin faster but the fuel is harder to ignite if precups aren’t hot.
Anyone that knows enough to get compression down also knows enough to run self limiting plugs=AC Delco 60g. Cycle the plugs a second time if it is crazy cold is not unusual anyways.
My estimate that it starts faster is because the starter spins it faster with the lower compression.
getting a heads up comparison is not really easy- all things have to be exact and never will be. So it’s like “seat of the pants” judging. And I was being critical because I came from higher compression better theory. But years of loosing those arguments had me jump to the dark side...
Anyone that knows enough to get compression down also knows enough to run self limiting plugs=AC Delco 60g. Cycle the plugs a second time if it is crazy cold is not unusual anyways.
My estimate that it starts faster is because the starter spins it faster with the lower compression.
getting a heads up comparison is not really easy- all things have to be exact and never will be. So it’s like “seat of the pants” judging. And I was being critical because I came from higher compression better theory. But years of loosing those arguments had me jump to the dark side...
Thanks guys, definitely makes sense that it cranks faster due to the lower compression ratio. Sounds like it's a non-issue.
I'm still debating over the P400 motorhome. I've got a 45ft trailer, BUT.... The motorhome is 11ft tall so that would put me over-height. That and I don't believe the breakover angle on the motorhome would allow it to make it over the dove.
I'm also kicking around wiring ideas in my head and trying to determine the best way to approach that whole side of it. My tahoe has a lot of features that the crew cab truck does not have, so I don't believe just using the unmodified crewcab harness is the correct course of action.
I'm thinking that I'll need to cut out all of the non-engine related wiring from the crew cab harness and then combine it with my tahoe harness.
Few things that I'm wondering about (perhaps you guys might have some knowledge here):
I'm still debating over the P400 motorhome. I've got a 45ft trailer, BUT.... The motorhome is 11ft tall so that would put me over-height. That and I don't believe the breakover angle on the motorhome would allow it to make it over the dove.
I'm also kicking around wiring ideas in my head and trying to determine the best way to approach that whole side of it. My tahoe has a lot of features that the crew cab truck does not have, so I don't believe just using the unmodified crewcab harness is the correct course of action.
I'm thinking that I'll need to cut out all of the non-engine related wiring from the crew cab harness and then combine it with my tahoe harness.
Few things that I'm wondering about (perhaps you guys might have some knowledge here):
- Fuse blocks
- Main one under the hood
- Are they the same between gas and diesel? Obviously there will be added/different relays, but I'm wondering if I can add the diesel features to the tahoe block.
- Under dash (I think it's called the DIC)
- Same question here.
- Main one under the hood
- Engine harness
- When pulled from the crewcab truck, it looks as if the majority of engine-related wiring runs from engine over to passenger side firewall, then thru the firewall and to PCM behind the glove compartment.
- I know that the throttle pedal wiring has to get back to the PCM somehow, which I assume is thru the dash harness.
- When pulled from the crewcab truck, it looks as if the majority of engine-related wiring runs from engine over to passenger side firewall, then thru the firewall and to PCM behind the glove compartment.
Signed up for Alldata and looking at diagrams for the 98 K3500 and my 2000 Tahoe, it appears that most everything is a separate system.
Looks like I'll be able to split the dash harnesses and then pick/choose parts from each and combine into a new loom. Not as bad as I was thinking it was going to be.
Looks like I'll be able to split the dash harnesses and then pick/choose parts from each and combine into a new loom. Not as bad as I was thinking it was going to be.
Last edited:
P400 motorhome ... Sounds like there are some local people and places that would allow you to park and scrap it. We have no idea your time to do this or maybe pay them to pull/scrap it and just pick engine/trans up. Thinking out loud here.
Then the obsolete, outdated, and unreliable Passlock Security Theft Module goes off. Another headache to be aware of on the Tahoe.
Then the obsolete, outdated, and unreliable Passlock Security Theft Module goes off. Another headache to be aware of on the Tahoe.
Now would be a good time to convert to a DB2 pump, a lot less headache and much more reliable...
MrMarty51
Well-Known Member
It is a nightmare trying to separate the two fuse block halves and same with the connector that passes through the firewall.
I have thought of using one of those multitool, buzz tool devices, to keep from making sparks like a cut off wheel would do, and cutting a fairly large swath around the fuse block and around the engine harness block on the firewall of the harness that I want to keep from the donor vehicle, then, on the firewall of the vehicle I want to keep, cut a smaller swath around the fuse block and engine harness connector.
remove the complete harnesses along with the sections of firewall and arrange everything I want to keep from the non donor vehicle onto the donor vehicle harness, the harness can be shoved through the holes and then the fire wall sections can be placed over the holes and screwed back into position.
That way it saves having to release and plug each wire while curled under a dash unit.
I have thought of using one of those multitool, buzz tool devices, to keep from making sparks like a cut off wheel would do, and cutting a fairly large swath around the fuse block and around the engine harness block on the firewall of the harness that I want to keep from the donor vehicle, then, on the firewall of the vehicle I want to keep, cut a smaller swath around the fuse block and engine harness connector.
remove the complete harnesses along with the sections of firewall and arrange everything I want to keep from the non donor vehicle onto the donor vehicle harness, the harness can be shoved through the holes and then the fire wall sections can be placed over the holes and screwed back into position.
That way it saves having to release and plug each wire while curled under a dash unit.