Factory B Pipe Tuning - Optimal Head Pipe Temperature?

Ben Fredenburg

Ben Fredenburg

Location
Michigan
Hi Guys,

Curious to what temperature the head pipe should be. I recently did a motor swap freestyle ported 701 to a Dasa 850 stock stroke. The B pipe mani has dual cooling.

When I was running the 701, I had the top two water screws closed and the bottom open 1/4 turn. However, with the Dasa running the same - I melted the top cooling line that runs from the top of the head pipe to the flow control valve then to the chamber. I used my temp gun after riding for a couple of minutes and the top of the head pipe was reading close to 300 degrees F. Motor was around 120.

Obviously I need to open the top screws up to allow more water to cool, but does anyone know the optimum temperature for exhaust flow?

Thanks,
Ben
 
Harbor

Harbor

Location
Stockton
Ben Fredenburg said:
Hi Guys,

Curious to what temperature the head pipe should be. I recently did a motor swap freestyle ported 701 to a Dasa 850 stock stroke. The B pipe mani has dual cooling.

When I was running the 701, I had the top two water screws closed and the bottom open 1/4 turn. However, with the Dasa running the same - I melted the top cooling line that runs from the top of the head pipe to the flow control valve then to the chamber. I used my temp gun after riding for a couple of minutes and the top of the head pipe was reading close to 300 degrees F. Motor was around 120.

Obviously I need to open the top screws up to allow more water to cool, but does anyone know the optimum temperature for exhaust flow?

Thanks,
Ben
Click to expand...

The 3 head pipe adjusters are for dialing in & cooling your pipe chamber.

The head pipe is cooled via water flow in and out the 2 barbed fitting on the head pipe. Like nucleus said above you may have a flow issue in or out of your head pipe. Unless you ment to say the chamber is 300, then you'd adjust those adjusters to cool it more.

Edit: I do remember helping a buddy claiming to have a head pipe issue ( hot to the touch) he said. Top head pipe out hose hot too also. We went thru his head pipe adjustments and He had 2 adjusters out about 1 turn each.
 
Last edited:
Ben Fredenburg

Ben Fredenburg

Location
Michigan
The chamber isn't very hot. Just the head pipe. I'm going to run the cooling line to the top of the head pipe and run the stinger line to the bottom.

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Ben Fredenburg

Ben Fredenburg

Location
Michigan
The head has 4 cooling fittings. 3 are straight out of the hull through pissers. 1 is going into the bottom of the head pipe for cooling. I have the top if the pipe exit going into the stinger. I have the bottom tunning screw open 3/4 of a turn (not 1/4 like in my original post).

I don't think the top of the head pipe is getting any cooling since water is going into the bottom then into the chamber.

Factory states to cool through the top fitting then exit out the bottom (stinger).


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Harbor

Harbor

Location
Stockton
Try plugging the 2 center outs on your head with pipe plugs or for quick test temporarily connect the 2 together with hose. That will push more water thru the head pipe, I run my engines that way. Leave hose from head to bottom of head pipe like you have it, most run that way. Leave other line off head to pisser like you have it. Go top of head pipe to a T, water goes straight thru T to pisser, T off the T (90 degrees) to Fcv then to stinger, or to stinger if no Fcv, if you already have it set this way great..
 
MTRHEAD

MTRHEAD

Location
MotorCity
My b-pipe header pipe casting sizzles water immediately up top. On the area where the three bolts are to the cylinder manifold. This is due to NO water for about 3/4” on both the head pipe and the manifold. This is on a stock boat. The casting water jacket has to stop and solid aluminum is what is left. I’m assuming there is some variation in the aluminum thickness hence some get very vey hot. Also ones that are opened up to 49mm probably see more heat too. Anyways I’m going to swap my line around this weekend and see what putting water in at the top does versus the bottom. I’ve always had dry pipes and noticed this just by chance one day recently
 
fastgtfairlane

fastgtfairlane

Location
Charlotte, NC
if youre having issues with the headpipe sizzling, id recommend running a dedicated line to the bottom of your headpipe, that way youre getting constant cool water flow directly from the pump instead of being preheated through the engine first. you also need to open your screws more on the headpipe to allow more water into the exhaust stream. that dasa puts out lots more heat than that 701 did and also the bpipe is more restrictive on the dasa than the 701 which will also create more heat. the top screw on the head pipe will have a more dramatic affect on your pipe tuning than any other screw as its closest to the engine.
 
U

undieingbreed

Location
Pa
I have the 701, other guy has the dasa. I think I will be trying dual cooling this winter as a project. I noticed the pistons are .50 over as well "first time this motor is apart" so dual cooling with the pipe probably won't hurt. I mainly only use the top adjuster as well,. Had it appx 1 turn out. I'm just confused how this sizzling issue happened all of a sudden with no other mods. I'm even going to rebuild the carb this week for giggles even though plugs look ok.
 
Harbor

Harbor

Location
Stockton
undieingbreed said:
I have the 701, other guy has the dasa. I think I will be trying dual cooling this winter as a project. I noticed the pistons are .50 over as well "first time this motor is apart" so dual cooling with the pipe probably won't hurt. I mainly only use the top adjuster as well,. Had it appx 1 turn out. I'm just confused how this sizzling issue happened all of a sudden with no other mods. I'm even going to rebuild the carb this week for giggles even though plugs look ok.
Click to expand...

Have you taken the hose off the pump and checked it visually for any internal debri, visually ? Also leak check your thru hull cooling tube ?
 
U

undieingbreed

Location
Pa
I pulled the line from the block to hull fitting nice and clean, I blew through it with 60psi from block to pump and can blow through easily by mouth. Also straightened the hoses I could go look through them.
 
Harbor

Harbor

Location
Stockton
undieingbreed said:
I pulled the line from the block to hull fitting nice and clean, I blew through it with 60psi from block to pump and can blow through easily by mouth. Also straightened the hoses I could go look through them.
Click to expand...

Saw you’ve done a lot already, that’s good.. just keep in mine a hole in a thru hull tube Or hole/rotting hose Back at the pump itself Would bleed off your water.... that all, carry on
 
fastgtfairlane

fastgtfairlane

Location
Charlotte, NC
someone else mentioned it earlier. it sounds like you have too much water exiting the head and not enough going to the headpipe. try plugging off 2 of the exits on the head so more will flow through the headpipe and see what that does. 4 outlets with 2 inlets is too much flow which will not allow enough heat transfer to actually remove the heat. personally still a fan of a dedicated exhaust cooling line going into the bottom of the headpipe right from the pump.
 
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