4BT and "Tonys Tips" coolant upgrades

[Francis Valerio]

I have twin 4BT in my Bertram 28.  I am very happy with the set up for my recreational activities.  Good on fuel and pretty dirt simple.  Last september I unfortunately had catastrophic failure when the rear (#4) exhaust valve disintegrated and the rest is history.

Now, I have new block and new cylinder head new pistons etc….

After all this work (doin myself) I want to be sure that I make the colling system as good as I can and would like to implement the upgrades that are on Tony suggested on the old 6BT applications.

My engine are 1988 vintage and think I could benefit and at the very least I dont think any could hurt.

For Turbo I got a 1″ Banjo and am gonna plug the rear head fitting and instead add a billet aluminum expansion plug kit and drill and tap a 3/4 NPT hole and then add a 3/4″ by 1″ barb to mate with the banjo on turbo.

That leaves me with the connection on the side front at the coolant inlet elbow that connects with the exhaust manifold (both are 1/2″ NPT now). The exhaust manifold on the 4BT has no threaded hole on the side like the 6BT. Cummins makes this connection via the  “water transfer connection” part #3904971 that is bolted to the top of the exhaust manifold.   The threaded connection on part #3904971 is only 1/2NPT as well as where it leads to on the aluminum inlet elbow. I was considering drilling and then retapping both of these parts to 3/4″ NPT to open them up a bit. There is def enough “meat” on the inlet elbow and would be simple to drill and tap.  Not so sure on the cast steel part 390497 though.  I do think it is doable but looking for some input.

What do you think?

I only had 100 hrs on the rebuild and then dropped a #4 exhaust valve that took out the block and the head. Just want to do all I can to make it better.

Frank

Massapequa Park, NY

 

Topic

[Tony Athens]

Check your tachs under no-load at the dock and write down the numbers.. Assume your CAV pumps are set correctly that will limit the max RPM’s to 3050 -ish ………….. So , what ever they say, use that as your standard..

If you get to within 150 of what ever that RPM is, then you are getting all they have to offer.. ( example= 2950 on your tachs no load, would mean you are probably making a real 2900)

[Francis Valerio]

I am going to revive this thread.

2020 “overslept” is back in the water, 1st time since this thread was started.

I am happy with the coolant modifications and upgrades that I installed. Thanks sbmar!
The vessel has the modified cooling system on the new engine (4BT 150hp) I built (new block, head, actually everything except the crankshaft and bolt on stuff is brand new). Running hard @ say 2700rpm she is staying about 7 degrees cooler than the port engine (which is stock cooling system).

I reworked the props and the jury is still out if they are getting me over the top.

I have gotten 2925 rpms but I am using diesel that is almost 4 years old. I do not get 2925 every time I try tho. I checked my tachs with strobe pointer and @ 1200rpm the tachs are on the money. I could not check at higher rpm, dont feel safe doing the test alone. The fuel has conditioner in it and I am multi-staging the filtration and use vacuum gauges. I am just making local runs for now to burn the old fuel so I can replenish with fresh diesel. I need to burn about 50 more gallons before I am ready to add fresh.

Getting rid of the fuel any other way is NOT an option.

Seems to be running real good but I am hoping that fresh fuel may give me another hundred rpms but I am not getting my hopes up. After I test with good new fuel I can then at least know where I am at.

Frank V

[Francis Valerio]

Do you think I should go with the 160F thermostat? 

How does this turbo (above) look?  The specs on the fins are dust etc…that the flash really highlighted.

Did you see the broken valve pic?

[Francis Valerio]

Turbo pics  Hard to get clear pic.  Spacing from fins to housing is consistant and even  mostly carbon you see  some pitting on housing.

[Francis Valerio]

Thank you!  Great pics. 

I have read your exhaust system section and my exhaust could use some improvements.  Notably a hump to prevent water from working its way back.  I dont have pics now and dealing with a knee injury so climbing a ladder is a no go for a while.  Gonna have to take some engineering I think.  Its a Bertram and sits pretty low with that deep vee.

I will get a pic of the Turbo as well (exhaust side).

When I say I dropped a valve maybe that is wrong terminology.  A valve BROKE but not at the stem. See pic. Not melted either.

 

[Tony Athens]

Factory 4BT 3.9 150 plumbing & possible upgrades

Frank,

 

Downlaod these pics and study them on a real screen.  This is current “factory plumbing” and did leave room for improvement, no doubt…

 

But with that said, I have a heck of a time understanding  why you dropped valve because it it..  I’d sure like to see your exhaust system as installed in the boat  and inside your turbo (exhaust outlet side)..

 

But with the said, I will help you on the upgrade as  VIABLE options that will help, but also stopping you from going overboard..

 

 

Tony

[Francis Valerio]

[Francis Valerio]

Here is a pic off of this site in the “Tips” section.  It is off an early 6bt I think.  The end cap has 2 (Two) threaded openings.  One is on the side (top of it as shown in photo) and the other is located in the top of it (where the red brass 90 degree elbow is). 

I was wondering if this was drilled and tapped?  It does not appear to be original.  I believe cummins usually has either a freeze out plug “OR” an exhaust port for a dry stack exhaust (I think) where the elbow is shown here.  Either way I believe that this opening would NOT be a thread as is shown in the picture.

This is what I was thinking about doing in my case but there is an expansion plug at this location (on mine) and would require a minimum of tapping a 1″ hole which is pretty big.  I dont have that size tap either.  Also I if I plumbed here I may run into clearance issues from hatch cover with a 90 degree elbow installed (not sure on that tho).

This is why I am thinking of tapping the other opening (where the brass straight fitting is in this pic.) from 1/2″ to 3/4″ like I mentioned earlier in this long winded thread.

 

[Rob Schepis]

Here’s an other shot showing the front coolant plumbing connections

[Rob Schepis]

Yes on that location, here’s two more pics that I have from when I photo-documented the thermostat change out for the website.

The adapter is 1/2″ npt into the manifold cap.

I know Tony is planning to respond to you on this as well with some additional guidance, probably over the weekend, he’s “fully loaded” with a few concurrent commercial repowers….

 

[Francis Valerio]

Thanks for sharing the pics.  Let me ask, on the picture with the manifold cap (w coolant alarm).  Below and to the right of that area on the side of the exhaust manifold is where the coolant return (or whatever you will call it) is located…correct? What size is the connection that is threaded into the manifold? 1/2NPT or 3/4NPT?   (I think it is 3/4). That is a superior design than the manifold cap, which is the only option on the 4BT.  This is part of my mind set on modifying the original design. 

 

btw: duly noted on the cap being the high point so no need to vent there.  I assume the 2nd vent goes to the intake manifold somewhere as the high point of the pressure side of the system that originates nearest the thermostat area where the water enters the engine via the water pump and T/Stat.

[Rob Schepis]

Frank, Nice job on the return of information.  Below is a link which you may or may not have seen, not all applicable to what you are doing but some is and good visuals too. Here’s my manifold cap (with coolant switch I added as part of my alarm system) which vent to the expansion tank.  And a shot of the turbo, no venting, the manifold cap is the highest point.     http://www.sbmar.com/articles/cummins-b-series-coolant-plumbing/

[Francis Valerio]

Tony Athans suggested to upgrade my cooling system referring to his B-series recommendations.

I realized that the 4BT is limited to the 1/2 NPT ports where the 6BT series has 3/4NPT bosses that are reduced with 3/4 x 1/2 bushings.  For the 6BT it is easy enough to just remove the bushing and add the 3/4NPT X 1″ barb fitting.

In my case it was also suggested to “underprop” and run the engine a bit harder and cruise @ 2700 and add a 160F theromstat and a bigger expansion tank mounter on the front or side.   This is why I am wanting to upgrade the coolant system.

I have not done any of this yet but if anyone has any suggestions or any input that they think I may be doing something that may not be a good idea please chime in.

Another thing that the 4BT seems to not utilize is “vents” that connect to the the expansion tank.  On the later series 6BT series they have a vent connected to the top of the turbo housing and another on top of the cylinder head area I believe.

I plan to add a vent to the turbo housing, the top of the exhaust manifold water transfer connection and possibly another “high point” in the system to be determined if necessary.

I also plan to plug the rear 1/2 water exit port at rear of the cylinder head (this normally connects to the hose that runs to the turbo) and then utilize the rear freeze out plug and add an aluminum billet expansion plug adapter that bolts in its place.  This will be drilled and tapped to 3/4NPT and the turbo rear banjo will be upgraded to 1″ and then 1″ID hose will connect these two connections.

I believe this will increase the flow and cooling capability of the engine and increase the capacity of coolant in the system as well that could possibly buy some time if an over heat did occur.

[Francis Valerio]

[Francis Valerio]

detail pics of 1/2npt ports

[Rob Schepis]

Yeah that is a considerable overload, especially if you like to run her up.  Pretty sure that’s the engine that was in Tony’s brother’s boat with 30K+ hours on it on original head.,,,

[Francis Valerio]

CPL 741

Thanks Rob,

CPL 741.

There were no signs of overheating or air trapping and the machine shop could not definitively determine the cause.  The local Cummins dealer concurred and added that sometimes it is unavoidable.  I do know for sure that I am slightly overpropped and will take care of that before she returns to the water. 

My rated RPM is 2800.  Could only muster 2650 to 2700@ WOT with clean bottom and good wheels.  I should muster about 2900 maybe 2950 at WOT.  This def could have contributed.

I will get some more pics up later or this evening.  I believe that the valve cracked before it let go.  I noticed the last trip out when I shut her down I had a sheen on the water that was fuel at the dock but I was not 100% sure it was from my boat. The next day we went out and I saw the sheen again while warming up the engines but it was very slight (in hindsight).   When we got into the channel and brought her up on plane within 10 seconds BOOM and that was it.  Immediate loss of power and smoke.  She ran but was obviously mortally wounded.  I had hoped it was an injector but it was the worst case scenario.  Hopefully that paints a picture.  Like I said I will get those pics soon.

Frank

[Rob Schepis]

Welcome aboard Frank.  Can you post your CPL’s and some good pictures of all – including what you are modifying and pictures of your exhaust setup —- Is your exhaust safe? —-  You lost the exhaust valve closest to the turbo….  When you had the failure was there any signs of an overheat or air trapping – ie. cracked exhaust manifold?

 

[Francis Valerio]

Photo 2

[Francis Valerio]

1/2 ports. Manifold and coolant elbow inlet

[Author]

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