Cummins 4BT & Diesel Conversions Forums banner

61 - 70 of 70 Posts

·
Registered
Joined
·
115 Posts
I was definitely joking.
Blocks are the same, but if you're going to rebuild one, go with the 4bd1t. Direct is usually more desired than indirect. But both are good. Not sure how much H.P. you can get out of it, but you’ll maybe get close to that, best case scenario. I don’t think your transmission will hold up to that though. If you start pumping up H.P., get some better cooling on the transmission. That will help it last some.
 

·
Registered
Joined
·
30 Posts
Discussion Starter #62
You asked about a fusible link. It looks just like a piece of wire, but possibly a tad smaller than the wire it protected. They are often added onto the end of a wire at a junction point. On the power issue, you can certainly get more power. Must remember you're driving a cement block on wheels, not a sports car. Their typical road speed was 35-45 MPH and probably topped out around 50-55. The feeling of more power under load is normal because the turbo is starting to put out more boost and the injection pump is adding more fuel. One issue you may have is gearing. These delivery vans were geared low and transmissions often didn't have overdrive. What transmission is in this unit? Don't remember you every saying.
Thanks for the information! I'll try to find the fuseable link!

As far as the truck it doesn't seem more Powerful with a Load! It Feels Like a Turd! Going Uphill on Molasses!

Also going down the Freeway it's Screaming RPM Wise! I can Cruise at 65 mayne more but usually keep it at 60! It's just turning to many RPM!

Also noticed the TURBO Must Be Laboring ??? Because the More I hear the TURBO Whistle! The more the Temp Needle Rises! ???

But I Noticed that if I stay out of the TURBO! The Temp Stays Good! Now to be Fair I Just gor it Running Less than a Month ago and its only Been on a Few Trips! And to be totally Honest I'm to Low on Cash to have the Radiator Rebuilt and the Intercooler Replaced or Refurbished and Maybe All the Fluids Flushes and Changed!

Either way I'm gonna Grab Both a 4bd1 & 4bd2 as I'm not sure what Block to Start with ??? And then I'm gonna start Slowing Acquiring the things I Need to Rebuilt the Engine with More HP ( at Least Double )

Now it was Mention by someone else in the thread that once I Build the Engine I'll just Wipe Out the Transmission ?? ( Please Advise )

My Theory was More HP Change Rear end Gears ( for Higher Top End ) and Rebuild Transmission with Whatever UPGRADES ( if there are Any Available!

BTW the Transmission I have is a ( Jatco jr403e )

Please Advise!
 

·
Registered
Joined
·
11,259 Posts
Generally more heat in a diesel is caused by an imbalance of fuel and air. Too much fuel and not enough air to burn it creates heat and very little power. Timing retarded can also cause a heat build up. Also makes the power like a dead dog. You could have a couple issues at work there. I believe that engine has the Bosch A injection pump. Drive gear on those is held on by tension without a key way and should it slip the timing is screwed up. You could check the pump timing and that wouldn't cost you much. Do you have a boost gauge to see how much the turbo is putting out?
 

·
Registered
Joined
·
30 Posts
Discussion Starter #64
Timing seems Spot On! But I'm a Chevy Dude! ( Gas ) this is my First Diesel Venture! But the Timing seems Good! As Far as Power it's there just under Load! You can tell the Difference ? And especially Going up a Hill! And Not even a Big One! Just even Going up like a Long Freeway Grade Hill! I got From 60-65 to About 35-40 but the Engine Never loose Power! Or Chugs it Just Slows and Won't Pull Hard! But never Stops or Quits ? Its just way Under Powered! Stock the engine is Rated at 135hp ( Brand New from Factory ) I figure after 25 Years its more like 80-100hp

Either Way its got a Chevy Logo! And I'm a Proud Papa!

I Just want to Make it Pull Like a Freight Train!

Engine = 4BD2

Trans = jr403e

Please Advise!
 

·
Registered
Joined
·
147 Posts
A good next step would be to install a boost gauge to see of you're getting enough. A combo vacuum/pressure gauge from the auto parts stores can be used temporarily. The injection pump has a built in boost compensator: low boost=low fuel rate=low power. This helps prevents excessive smoke. My 4BD2T has noticeably less power with the boost compensator disconnected.
 

·
Registered
Joined
·
11,259 Posts
Did a little looking. The 4bd2t engine has a torque curve that hits its peak around 1900 RPM and only drops maybe 4 lb ft all the way to 2800 RPM. That peak torque number looks to be around 254 lb ft. Peak HP is also at 2800 RPM. By comparison, a Cummins 3.9 engine with a P7100 injection pump hits 325 lb ft of torque @ 1700 RPM but starts to drop right just above 2000 RPM. That's reason most try to tune their drive train for a Cummins to operate in the 1700-2000 RPM range. Peak HP on that one is 130 @ 2500 RPM. A 4bt with 71 lb ft more torque would definitely pull harder than the Isuzu. The fact that you run out of steam just going up a service ramp tends indicate there are problems. You mentioned it getting hotter on hard pulls. Do you have a pyro gauge and if so what was it showing? Typically you want to keep your maximum level under 1200 deg F. Cummins generally recommends around 1000 deg F before the turbo. Must remember aluminum melts at 1221 deg F and the in cylinder temp is a good deal hotter than the measurement taken at the turbo. The oil cooling nozzles aimed at the bottom of the pistons help compensate for that. Don't know a lot about the Jatco JR403E other than it is computer controlled. It's gear ratios show it has a .724 OD in 4th gear. In theory that steep OD gear would keep a diesel in the lower RPM range where the peak torque is but at the same time the HP down there is pretty low.
 

·
Registered
Joined
·
115 Posts
Timing seems Spot On! But I'm a Chevy Dude! ( Gas ) this is my First Diesel Venture! But the Timing seems Good! As Far as Power it's there just under Load! You can tell the Difference ? And especially Going up a Hill! And Not even a Big One! Just even Going up like a Long Freeway Grade Hill! I got From 60-65 to About 35-40 but the Engine Never loose Power! Or Chugs it Just Slows and Won't Pull Hard! But never Stops or Quits ? Its just way Under Powered! Stock the engine is Rated at 135hp ( Brand New from Factory ) I figure after 25 Years its more like 80-100hp

Either Way its got a Chevy Logo! And I'm a Proud Papa!

I Just want to Make it Pull Like a Freight Train!

Engine = 4BD2

Trans = jr403e

Please Advise!
Hey, which turbo do you have? That year could go either way. Does it have a wastegate? If it’s that one, a good intermediate step before turbo replacement is cranking the wastegate shut. If I remember right, you can get the stock wastegated turbo to about 20psi. Then bump the fuel a bit. But... don’t bump the fuel until you’ve got an EGT gauge. You’re probably fine to crank the preload on the wastegate with stuck gauges.
 

·
Registered
Joined
·
30 Posts
Discussion Starter #68
Thanks for all the Help but im starting with a Fresh Block and I'm gonna Build that Engine! On the Stand and I'm Looking for Guidance! To Gain way More HP, Torque for Pull and Gear the Rear end for Higher Freeway Speed at Less RPM!

I want it to Pull Like a Freight Train
 

·
Registered
Joined
·
11,259 Posts
Not sure how much power the Isuzu engine is capable of. A 4bt Cummins can get near 250 HP on a single turbo and do 300 HP with twins. If you got it tuned to 200 HP the difference would probably be shocking. To pull like a freight train takes torque. The Isuzu's torque is around 1.85 times HP while a Cummins is 2.50 times. Probably a combination of several factors such a pump timing, cam profiles, etc. Your engine and a Cummins have essentially the same bore and stroke, but yours has a higher CR, 20:1 vs 17.5:1, which is normal on IDI engines. Usually, with a higher CR you can't run as much boost. The 4bd1t is essentially a clone of the Cummins. Same bore, stroke, and CR but only has 243 lb ft peak torque vs 325 on the Cummins. The Isuzu is setup as a higher revving engine and it's lower torque sort of fits the bill of higher revving diesels. Don't know if you could get a different cam grind to change that HP and Torque curve. Companies do all kinds of cam grinds for Cummins but haven't seen much for Isuzu.
 

·
Registered
Joined
·
115 Posts
DON’T grind the cam. It will go through the hardening layer. The 4bd engines aren’t the torque monster that the Cummins is. It’s torque is steep and drops off quickly. The Isuzu climbs smoothly, and maintains near max for longer. Not a clone, it’s much smoother and more drivable, IMO a more refined engine. It won’t shake you to death. If you have a 4bd1/2 that’s in good shape, you should be able to get around 250hp/500lbs/ft without any mods other than better turbo, good intercooler, and cranking the fuel. 4bd2t will he slightly less, but smoother and rev higher with power further up in the rpms. If you’re rebuilding, balance the rotating assembly.
 
61 - 70 of 70 Posts
Top