Big Cam 400

Bobus

Bobus

Powerstroked
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Nov 6, 2007
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What's your thoughts on a Big Cam 400 Cummins. It's in a '81 Freightliner backed by a 13 speed. Going to look at the truck this afternoon or tomorrow morning. Anything to watch out for? Do they make good power and can more be made safe and reliably?
 
Look for antifreeze around the heads and any fuel leaks on the injection pump, see if the owner knows how many miles are on the bearings too. Everything on them is comparatively cheap for a class 8 diesel but they can still eat thousands pretty easily.



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Went looked at it, truck is a little rough but it is 34 years old. Engine was almost completely dry except for oil on the front driver side where head/block meet. Engine sounds great idling, hazes a fair bit though. The tag on the engine says it's a '84 model year. That make it a BC III?
 
Big cams were out. Good engines but not by much. They only noticeable difference between a 3 and a 4 is the injection pump. 4's do tend to run a little hotter so I would watch the egts. But I wouldn't worry about it if I was you.
 
Big cams haze at idle that's no new thing. Most if not all (can't remember) 3's and all 4's had low flow cooking which is not a good thing.
 
Lol, low flow cooking. Bc4 was the low flow.

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Like what is a fair amount of haze, like this?

982F18F7-6DBF-4F05-BD85-7F28FC152516_zpscbiuk73f.jpg
 
LOL
Man I can remember those days. Fire one of those up in the shop and get it outside asap. Those old engine will pump raw fuel out the pipes until they get up around 160 degrees.

That big cam 3 will not be low flow cooling.
 
This one was until I got the injectors set right, accessory drive was out of time so the set was completely off, it would have wet streaks on the block even after it was up to temp.

People can't leave well enough alone, that is the second engine I have dealt with that has been put together with the accessory drive out of time.
 
SmokinCAT said:
People can't leave well enough alone, that is the second engine I have dealt with that has been put together with the accessory drive out of time.
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Yep, we've seen that a lot here too.
 
Snedge said:
LOL
Man I can remember those days. Fire one of those up in the shop and get it outside asap. Those old engine will pump raw fuel out the pipes until they get up around 160 degrees.

That big cam 3 will not be low flow cooling.
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Yea I couldn't remember for sure on the 3. Re-reading my post I think it sounded like I was sure on the 3 and I wasn't. That was my bad.
 
Big Cam 400's had lower compression and slower cam timing than other Big Cam engines to help control egt's. This made them harder to start and with a fair amount of haze when temps were low until the engine warmed up. They wont produce the power and torque of today's electronic controlled engines but will handle a big load quite well.
I've owned a few of these engines and consider them to be one of the easiest semi class diesel engines to work on and maintain. Still have the sig timing tool for setting cam timing along with extra deep 5/8 socket for jake brakes and a couple other tools that helped when working on these engines.
 
If it's a Big Cam 3 the CPL should be either a 625 with a 3969 fuel cal (lots of torque and a fair amount of black smoke) or a 531, and a 614.. All are great CPL's. I just got through going through mine, it's collage of Big Cam 1/2 parts and a 3 oil pan, turbo and N14 exhuast manifold. The early Big Cam 2 blocks are thee best block to use for high h.p applications, here's why.. Take a head bolt out of a Big Cam 1/2, they're about 3/4" longer than later 2,3,4's. The main bolt diameter in the early 2's were the last of the mohican big bolt bottom ends.. After that everything went 3/4 inch main bolts and you guessed it cap walk. I had mine line bored by Mike Denning and we replaced 3 main caps and this engine had already been through the recon center. I put the updated wide cam bearings in it, timed it a .70 and let er rip.. DO NOT follow the timing charts in quickserve, that is epa crap, use what's in the ole manuals and it'll be fine. Use lots of fuel treatment and they'll run like a top. Any thing else just ask.
 
Snedge said:
73-74 would have been much better.
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If you want it to start decent under 40 degrees leave it at .70, that was thee original nominal timing back in the early 80s.. Pittsburg Powa has had everyone on this whole lazy timing thing.. The first 400s CPL 267, 310, 324 and 393 were actually a 14.5/1 engine while the next CPL 449 was a 14.0/1. BUT the 454 CPL with MVT ran 14.5/1 pistons due to the retard. Almost all timing codes were right at .70, and plenty of people have made 500+ and got decent fuel mileage with .70 timing.. The 3969 fuel cal was the one to have, it had a much broader torque curve than any other calibration, you can time a 449 cpl engine to lazy timing and change the button, but the engine won't do what you want it to do until the springs are changed.. Yeah you can back your rail pressure screw out but still, your torque will not be felt, the difference is in the spring set up and how much fuel pressure it takes to move the plunger from the main circuit to the supply fuel circuit...
 
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