'55 Chevy 3800 Cummins - Page 7

nblehm · 03-13-2021, 10:45 AM

That frame is coming out so good. i could look at that rear crossmember/link mount pic all day.

6DoF · 03-14-2021, 10:42 AM

Quote:

Originally Posted by nblehm

That frame is coming out so good. i could look at that rear crossmember/link mount pic all day.

Thanks!

Sir Sam · 03-14-2021, 02:42 PM

Looks good. I still think it should be galvanized.

xj_man_646 · 03-15-2021, 08:02 AM

Matt, I suggest 4" exhaust. There is no reason to struggle to package a full 5" turbo back system. You won't have the power to use that much flow.

6DoF · 03-15-2021, 08:16 AM

Quote:

Originally Posted by xj_man_646

Matt, I suggest 4" exhaust. There is no reason to struggle to package a full 5" turbo back system. You won't have the power to use that much flow.

right now i won't ... but eventually i fully intent to.

6DoF · 03-15-2021, 08:17 AM

this next bit of fab is going to make a few of you twitch. off road fab'd some drive shafts for test fitting and set-up this weekend. i have actually had very good success doing this with perfect balance at 80mph, and living years under jeeps being beat off road. so i'm sure this is a long-term temporary solution.

had to make a little clearance on the fwd shaft to the crossmember. held a sharpie on a pc of 1/4" plate and spun the shaft to get about 1/2" clearance. if the chassis twists enough to get that to contact, the solution isn't more clearance but adding a roll cage

this shaft is 1410 joints, and will eventually just get a new professionally balanced pc.

the rear shaft helped me set the rear pinion angle and check it thru travel. at full droop i set the pinion 2deg below the shaft to allow for a little motion up under torque loading. at full compression the pinion is only 1.2deg below the pinion, so ride will be somewhere in the middle. axle perches are officially tacked in place, making the axle DONE and ready for final weld/paint. this shaft is a junkyard 1350 cv, eventually i'll get a new 1410 cv unit and have to change the yoke on the axle at the same time. that's probably also a good time to get better gears and limited slip installed.

i'm quickly running out of things to fab and procrastinate doing the floor ...

xj_man_646 · 03-15-2021, 10:04 AM

Quote:

Originally Posted by 6DoF

right now i won't ... but eventually i fully intent to.

No, Matt, you won't. 5" is capable of so much flow that you will not reliably make that much power out of a 12v tow rig.

It will also help with noise.

nblehm · 03-15-2021, 11:03 AM

I made a driveshaft with old shafts when I ls swapped my j-10. It was ok enough to drive under 60 but it wasnt any where close to square. I didnt put much effort into it though.

jeepkid05 · 03-15-2021, 01:36 PM

This is super sick. What welder are you running?

6DoF · 03-15-2021, 01:40 PM

Quote:

Originally Posted by jeepkid05

This is super sick. What welder are you running?

thanks!

welder is the same Lincoln Sp175+ i bought in college with my student loan

was the cheapest 220 welder at the time with both infinite voltage and wire control.

xj_man_646 · 03-15-2021, 01:46 PM

Are there no 'upper control arms' with a truck arm suspension?

Cobound · 03-15-2021, 01:47 PM

Holy Christ this is moving along nicely...so many small details you're hitting, too.

That said, all that nice frame fabbing and welding and you're just going to cover it up w/ some old patina body panels

6DoF · 03-15-2021, 02:33 PM

Quote:

Originally Posted by xj_man_646

Are there no 'upper control arms' with a truck arm suspension?

no sir, they are radius arms. but because of the triangulation and reduced deflection thru articulation the axle is bolted directly to them vs with bushings. also creates a little bit of a sway bar effect.

6DoF · 03-15-2021, 02:36 PM

Quote:

Originally Posted by Cobound

Holy Christ this is moving along nicely...so many small details you're hitting, too.

That said, all that nice frame fabbing and welding and you're just going to cover it up w/ some old patina body panels

thanks!

and yes i am! maybe one day i'll make a bed floor hatch to show off the rear end, but probably not. also maybe one day i'll make the whole truck shinny, but not for a while.

xj_man_646 · 03-15-2021, 03:33 PM

Quote:

Originally Posted by 6DoF

no sir, they are radius arms. but because of the triangulation and reduced deflection thru articulation the axle is bolted directly to them vs with bushings. also creates a little bit of a sway bar effect.

Interesting. I had never really looked into it much.

6DoF · 03-15-2021, 04:45 PM

Quote:

Originally Posted by xj_man_646

No, Matt, you won't. 5" is capable of so much flow that you will not reliably make that much power out of a 12v tow rig.

It will also help with noise.

you might be right ... but still doing it. my research says that the 5" has a deeper tone, and generally less raspy like i want. i've also ordered a muffler to go behind the resonator to try and even take out a bit more noise. as for power, everyone on average seamed to think that it would help on an engine making 600+hp, especially at higher RPM when using the 4k+ gov spring. and i intend to do both of those things.

xj_man_646 · 03-15-2021, 06:36 PM

Quote:

Originally Posted by 6DoF

as for power, everyone on average seamed to think that it would help on an engine making 600+hp, especially at higher RPM when using the 4k+ gov spring. and i intend to do both of those things.

I fully believe it'll still be overkill. Unless the turbo outlet is 5" or larger you're restricted from the get-go anyway, and that seems huge, at least in my mind compared to what I'm used to seeing on trucks. Just something to consider if it becomes tough to package exhaust. You do you, as they say. I'm enjoying watching the progress! Seeing stuff like this kinda / sorta makes me wish I had kept up with CAD or gotten a job that uses it. I've also seen some of the wheeler alumni use CAD for their cage designs to great success.

6DoF · 03-15-2021, 10:10 PM

Quote:

Originally Posted by xj_man_646

Seeing stuff like this kinda / sorta makes me wish I had kept up with CAD or gotten a job that uses it. I've also seen some of the wheeler alumni use CAD for their cage designs to great success.

oh man, i'll never go back! i love it!

jeepkid05 · 03-15-2021, 10:39 PM

IMHO 5” is the only way to go on a Cummins. It sounds like a big rig.

6DoF · 03-15-2021, 11:00 PM

the best thing you can do is run open, zero back pressure at all. i can fit it down the side, so why not!

i'll probably have to 3" the first 3 ft

03-15-2021, 08:02 AM	#124
xj_man_646 Senior Member Join Date: Oct 2004 Location: MN Posts: 27,743	Matt, I suggest 4" exhaust. There is no reason to struggle to package a full 5" turbo back system. You won't have the power to use that much flow. __________________ - James I like diesels

03-15-2021, 08:17 AM	#126
6DoF AKA: jeepnski Join Date: Sep 2002 Location: Pittsburgh, PA Posts: 16,870	this next bit of fab is going to make a few of you twitch. off road fab'd some drive shafts for test fitting and set-up this weekend. i have actually had very good success doing this with perfect balance at 80mph, and living years under jeeps being beat off road. so i'm sure this is a long-term temporary solution. had to make a little clearance on the fwd shaft to the crossmember. held a sharpie on a pc of 1/4" plate and spun the shaft to get about 1/2" clearance. if the chassis twists enough to get that to contact, the solution isn't more clearance but adding a roll cage this shaft is 1410 joints, and will eventually just get a new professionally balanced pc. the rear shaft helped me set the rear pinion angle and check it thru travel. at full droop i set the pinion 2deg below the shaft to allow for a little motion up under torque loading. at full compression the pinion is only 1.2deg below the pinion, so ride will be somewhere in the middle. axle perches are officially tacked in place, making the axle DONE and ready for final weld/paint. this shaft is a junkyard 1350 cv, eventually i'll get a new 1410 cv unit and have to change the yoke on the axle at the same time. that's probably also a good time to get better gears and limited slip installed. i'm quickly running out of things to fab and procrastinate doing the floor ... Last edited by 6DoF; 03-15-2021 at 08:20 AM.

03-15-2021, 01:46 PM	#131
xj_man_646 Senior Member Join Date: Oct 2004 Location: MN Posts: 27,743	Are there no 'upper control arms' with a truck arm suspension? __________________ - James I like diesels

03-15-2021, 01:47 PM	#132
Cobound - The Don - Join Date: Sep 2002 Location: MN Posts: 49,171	Holy Christ this is moving along nicely...so many small details you're hitting, too. That said, all that nice frame fabbing and welding and you're just going to cover it up w/ some old patina body panels __________________ To each his own. Not all those who wander are lost. The great irony - triggered snowflakes accusing triggered snowflakes of being triggered snowflakes

03-13-2021, 10:45 AM	#121
nblehm Needs moar dagger Join Date: Feb 2004 Posts: 26,783	That frame is coming out so good. i could look at that rear crossmember/link mount pic all day.

03-14-2021, 02:42 PM	#123
Sir Sam Working Mother Join Date: Mar 2004 Posts: 19,918	Looks good. I still think it should be galvanized.

03-15-2021, 11:03 AM	#128
nblehm Needs moar dagger Join Date: Feb 2004 Posts: 26,783	I made a driveshaft with old shafts when I ls swapped my j-10. It was ok enough to drive under 60 but it wasnt any where close to square. I didnt put much effort into it though.

03-15-2021, 01:36 PM	#129
jeepkid05 pee pee pants Join Date: May 2005 Posts: 16,378	This is super sick. What welder are you running?

03-15-2021, 10:39 PM	#139
jeepkid05 pee pee pants Join Date: May 2005 Posts: 16,378	IMHO 5” is the only way to go on a Cummins. It sounds like a big rig.

03-15-2021, 11:00 PM	#140
6DoF AKA: jeepnski Join Date: Sep 2002 Location: Pittsburgh, PA Posts: 16,870	the best thing you can do is run open, zero back pressure at all. i can fit it down the side, so why not! i'll probably have to 3" the first 3 ft