Top "speed" in my BJ40? (1 Viewer)

Rusto

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Took my new to me BJ40 out for an extended spin yesterday after changing all my filters and putting in some fuel system treatment. Runs much better with just fluid and filter change. PO was worthless. most likely years since the oil and coolant had been changed, same with the fuel filters.

First time I've really been able to stretch it's legs in good weather. I'm at 6,500 feet and coming back into town I was driving into a stiff wind. The ol' B engine topped out around 55 mph and didn't seem to have the oomph to push the gears more than that. Half way down on the accelerator was the same speed as all the way down, if you get my drift.

I know the B engine is super slow and I'm cool with that, but curious if that's about what I should expect and what else could do to ensure the engine performance is optimized.
One thing I need to do is drain and clean the fuel tank as there is a little rust sediment in my clear inline filter I added.

What else should I do? (please, no turbo suggestions for now :) ) Rebuild/Replace the Injection pump? "Tune" the IP to the high elevation?

Overall, the 40 did have some more pep in its step which is nice.

Thanks, Russ
 

GTSSportCoupe

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If you install a pyrometer you can get an idea of the AFR it's at. If its running lean, you may be able to add more fuel for more power.

Maybe check compression and have the valves adjusted.

Not sure if a larger diameter exhaust on these helps? Maybe upgrade to 2 1/4" exhaust from the header back with a good free flowing muffler?

Probably due for an injector rebuild also.
 
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Shy of differential possibilities wouldn't larger tires contribute some top end (affects low end negatively if you need the torque) if there is room for it?
 

Rusto

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Good stuff. Thanks @GTSSportCoupe and @traveldud It has slightly larger than stock tires on it right now. I think the larger tires could actually be hurting it at top end as it's preventing the RPMs from getting where the need to be, like a shifting too early kind of feel.

Being at 6,500 feet, I doubt it's running lean, but knowing one way or the other would be a good thing. I'm sure the compression is low.
That should probably be next on my list while I'm also getting the fuel system clean.
What I really need to do is go through every contributing part of the power delivery chain and make sure they are all in fairly good working order.
 
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It is a B series engine? You want blistering acceleration with your 30 miles to imperial gallon too?

Life in the slow lane passed by air cooled VW's.

you want better performance? Simplest is a 13b-t if you can find one.
 

Rusto

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I don't necessarily want more than the B is capable of giving. I know it's slow.. I just want to know what it should be. The engine looks as if it's never been opened up in 45 years of service, so there's that...
I do need to do a compression check and adjust the valves, along with cleaning the fuel system.

Is 55MPH at 6,500' driving into a 20MPH wind about all I can ask for? That's really my question. If that's what it is, then fine.
 

Rusto

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There we go. Thanks everybody. I figured 55 wasn't too shabby all things considered.

Next big challenge will be the 10,000' mountain passes. I believe I'll check the compression and adjust the valves before I go there.
 

Rusto

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No wind to speak of and cool, this morning provided optimal conditions for a new land speed record* attempt.
100 kph / 62 MPH. Felt comfortable at 90/56 with smooth "acceleration" and responsiveness throughout the powerband.

I'm good with that.

*for this particular 1975 BJ40
 
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Massachusetts
No wind to speak of and cool, this morning provided optimal conditions for a new land speed record* attempt.
100 kph / 62 MPH. Felt comfortable at 90/56 with smooth "acceleration" and responsiveness throughout the powerband.

I'm good with that.

*for this particular 1975 BJ40


That’s all a get out of mine... at sea level.
 
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San Jose, CA
I have driven my BJ41V about 500miles from San Diego to San Jose along hwy 1.

I am cruising at 63mph with the engine running @3000 RPM. It can go faster, 66~67mph depending on the total load but, I don't feel comfortable with the engine revving
at 3300 RPM, its very noisy and stressful. I have a B2 engine
 
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Victoria BC Canada
I am very happy with 55 mph (90 kph) in my BJ40 with a newly rebuilt B engine. Considering I have owned this since 1987 and this is the best it has ever done, I am pleased. I like to think of my truck as a Rolls-Hardly (rolls downhill just fine, but hardly goes up them)

Something else to consider is making sure that all the wheel bearings, axles, transfer case & transmission are well lubed.
 
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My '78 was clocked doing 76mph in a 70mph zone by SCHP. Now, I had come down a hill into a flat spot, but apparently it was there. Normally, I'm around 65mph top end.

To be honest, I don't expect much, but I've been surprised.

I didn't get a ticket, though.
 
Joined
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Victoria BC Canada
I have driven my BJ41V about 500miles from San Diego to San Jose along hwy 1.

I am cruising at 63mph with the engine running @3000 RPM. It can go faster, 66~67mph depending on the total load but, I don't feel comfortable with the engine revving
at 3300 RPM, its very noisy and stressful. I have a B2 engine
Something to consider when going 60+ mph is the stability of BJ40s - they are notoriously unstable at "High" speeds.
 
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@OTBT I was worried about the stability of my BJ41 at 60mph but it wasn't an issue at all. Suspension was doing well and even when I went over some dips it felt stable. Making turns, however, was a bit uneasy at high speeds on the off-ramps especially. But going in a straight line, I could easily do 70mph downhill without issues (in neutral).

I'd really hate to roll over in this vehicle without any air bags or other safety features :skull: Most of the time I'm cruising at 2700RPM and that gives me a comfortable 90km/h. If you could only ignore other cars overtaking you on left and right
 
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Is 55MPH at 6,500' driving into a 20MPH wind about all I can ask for? If that's what it is, then fine.

No wind to speak of and cool...
100 kph / 62 MPH.

Yes, sounds normal.
I remember reading about a mostly stock BJ60 on a dyno seeing about 35hp at the wheels. There just isn't reserve power. Cruising flat ground in calm conditions the BJ40 would theoretically have the same top speed as a stock FJ40. Limited by 4.11 axle gears, no overdrive, fairly low engine output, rolling resistance and aerodynamics. Add a stiff head wind or a a slight hill and you will be struggling. Keep in mind that some people have added pyrometers to their naturally aspirated B/3B, and found stock they were set to max fuel at dangerously high EGTs. So sustained foot to the floor trying to overcome headwind could be bad for that engines health.
Not a bj40 but I had a similar result returning north west from moab in my BJ60 years ago; hours upon hours of stiff headwind across idaho and a truck struggling at 55-60mph on the interstate. my 3B got a turbo because of that trip
 

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