Cummins 4BT & Diesel Conversions Forums banner

1 - 13 of 13 Posts

·
Registered
Joined
·
275 Posts
Discussion Starter #1
sorry for the silly question here but what's a safe redline for a 4bt cpl 858 bone stock motor?

Thanks, Dan
 

·
Registered
Joined
·
72 Posts
Bone stock the Gov spring should make it a moot point.
or are you refering to bone stock fuel settings, injectors, turbo, and a wild gov spring?
I have heard 3600-3800 the valves may start floating.
It also depends on how many miles are on the engine, if the valve springs are getting a little weak from age, how good all the beargins are, oil pump in good shape. If you are going to go to the time and expense of replacing all of those parts to bring it back to a new 858 build, might as well replace with better parts so you can spin it a litttle harder.
BTW, I am not an expert on this engine by any means, and hopefully someone posts with better info.
 

·
Registered
Joined
·
1,203 Posts
look up governor information.

vehicle motors in stock config will spin to 2500 and defuel, might get 2700 rpms out of them, but not easily.

Changing the gov spring to the 366 spring will give you 3200 rpms.
 

·
Registered
Joined
·
275 Posts
Discussion Starter #4
It's a used motor I got from a local junk yard. They pulled a good running motor out of a P-30. I'm assuming it's all stock including the gov spring but I really don't know. I have not fired it up yet. I'm building some mounts and buying filters etc. I hope to fire it up in a couple weeks.

Thanks for the info. I'll check and see if the governor is working when I fire it up. I'm assuming if it revs beyond 2500 to 2700 that something is either modified or not working normally.
 

·
Registered
Joined
·
1,203 Posts
it's the 3200 rpm spring that everyone always talks about...well some people. I got mine from piers diesel research. I was very intimidated about the install, but it is quite easy and didn't take very long at all. i could do it again really quickly now that I know what i'm doing...
 

·
Administrator
Joined
·
4,164 Posts

·
Premium Member
Joined
·
1,660 Posts
spring is only $17 or so (or $5 or so from a local supplier) and lets the engine spin up freely as high as 3200 rpms. Mileage goes way down though too... Good for accelerating and some other nice perks, but not needed. There is a 4000 rpms kit too but you need valve springs (not hard to do at all). My 4BT was governed around 2300-2500 rpms and that seems to be how they are set up out of the package...
 

·
Registered
Joined
·
34 Posts
spring is only $17 or so (or $5 or so from a local supplier) and lets the engine spin up freely as high as 3200 rpms. Mileage goes way down though too... Good for accelerating and some other nice perks, but not needed. There is a 4000 rpms kit too but you need valve springs (not hard to do at all). My 4BT was governed around 2300-2500 rpms and that seems to be how they are set up out of the package...

Who is the local source you speak of Andre?
 

·
Premium Member
Joined
·
1,660 Posts
diesel injection service over near the Napa. you need the Bosch part number, it is the same a Dodge Gen 1 3200 rpm spring. If you want to pick one up for me when you are there..!
 

·
Registered
Joined
·
34 Posts
diesel injection service over near the Napa. you need the Bosch part number, it is the same a Dodge Gen 1 3200 rpm spring. If you want to pick one up for me when you are there..!
Are you talking about Industrial Injection? (on ~1250 South and 7th west) There is also Desco (on 17th So and 5th west). I'm not familiar with Diesel Injection Service but I'll look them up.
 

·
Registered
Joined
·
1,203 Posts
my mileage hasn't gone down. I don't rev up to 3200 all the time, rarely probably, but i can if i need to, merging etc... I need a tach, but i probably only rev a few hundred over 2500 most of the time, helps with not lugging the engine too much when shifting.
 
1 - 13 of 13 Posts
Top