Max Rpm 3b

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Zekester

Zekester

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This one's easy...and I'm sure will get lots of opinions : )

I'm putting a 3B in my '80 BJ40 next week...I have installed an aftermarket tach, what is the max rpm the 3B should pull, max peak and max at sustained speed. What RPM am I looking for at cruise speed (60 mph/96 km/hr). Right now I'm running 33X9.5 thru 4.11s...
 
I personally dont like to keep my 3b sustained over 2500 rpm, and dont like to max over 3100-3200 . Might be low, but thats where I like it.
Cheers,
J
 
max rpms are 4100 but you will never see it with out a turbo...
most like to shift a NA 3B at about 2700 rpm (or less)(you need to get up there for the shift from 2nd to 3rd in a H55F)...
 
Peak HP is @ 3500. I've has mine up to just over 3k.. 3200 maybe.

I usually don't go past 3k. Normal shifting like Wayne mentions is more realisitic at 2600-2700 but on hills I take it up to 3. You probably will too with 33's if not it drops you down in the rpm range too low to build up speed.

my .02
 
crushers said:
max rpms are 4100 but you will never see it with out a turbo...
most like to shift a NA 3B at about 2700 rpm (or less)(you need to get up there for the shift from 2nd to 3rd in a H55F)...
Click to expand...

Wow, 2700RPM? I tend to shift around 1,600-1,800RPM..

If it's not lugging during the shift, is there any harm in doing so?
 
no problem, you might trap some more heat in the exhaust and raise the EGTs but people have been driving like you do for decades...
 
1600? i'd get run over by the 10 year old kid next door on his bike if I shifted that low ;)

as wayne noted if you lug an idi diesel your going to build heat big time.
 
Max RPM for my 2b is 4,000rpm and it will do no more even with it in neutral. Before I had lockers a lot of the trails were 1st gear 4lo and 4,000 rpms to the floor to get out. Three diffs later and it still runs 4,000 without a problem. Is it a good thing? Probably not, I have spare engines but it won't die. Keep er under 4,000 and you'll be fine:cool::beer: So in other words if you baby it or beat on it but service it it will be fine.
 
BJ-44 said:
Max RPM for my 2b is 4,000rpm and it will do no more even with it in neutral. Before I had lockers a lot of the trails were 1st gear 4lo and 4,000 rpms to the floor to get out. Three diffs later and it still runs 4,000 without a problem. Is it a good thing? Probably not, I have spare engines but it won't die. Keep er under 4,000 and you'll be fine:cool::beer: So in other words if you baby it or beat on it but service it it will be fine.
Click to expand...

I done babied the B motor, but she blowed up...

hence the 3B, and the tach...I didn't over rev ( I don't think so) but don't want to take the chance
 
x2 on the blowed up b motor, i too now have a 3b w/ tach
 
ummm, the few 2Bs i have driven seemed quite torquey... and better on fuel than the 3B...
but the B and 2B seemed to die early or so it seems...
 
If your fuel is set to where it doesn't run lean under a heavy load and the cooling /oiling systems are taken care of it would not meet an early death. If you have ever seen the bottom end of one of the engine the engines are beefy as hell, the connecting rods are twice the size of my Big block Ford. It does have twice the compression but it doesn't rev as high.
"You'll find the 3B will have a whole lot more torque than the old B motor ever had!"
If you look at the specs a 2b has more HP/torque than a 3B due to the higher compression. Some of the trail we go through here you won't get out of it running below 3,000 rpms. even with a 13B-T. It's not the power sometimes you just need wheel speed to get enough traction on a slippery slope. Now if your running sustained high RPM's going through the mountains then you are going to blow it up unless you drive slower. If I was in the mountains regions I would adjust up the fuel a bit so it wouldn't run lean and have a bit more power.
 
yep, i have torn quite a few "B", "3B" engines apart and they are very beefy... it seems the oiling system on the "B" was faulty... is the 2B the same?
 
If I had to choose between rev'ing it up or lugging it, I would just drop a gear and lte it rev a bit.

I like keeping below 3500. If a gear is too much and I have to downshift to maintain the hill then I keep the throttle below 3500. But more times than not in a BJ60 the weight overcomes the engine and it pulls down your rpm too.'

Just drive it :)
 
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