Building a 372XP Big Bore With 272XP Piston

[Mastermind]

Here's a few pics......I'll be adding to this one.

Opened up the transfer inlets a bit since the 272XP piston is a windowed design.





Here we are test fitting to the case. The match is worse than you can see here.....



Here it is after being case matched.......



Like I said......I'll post more as I set the squish and port it.

 

[ELECT6845]

That 372 looks clean. Did some idiot power wash it for you?

 

[barneyrb]

Randy, who built the big bore kit?????

Thanks.....

 

[Mastermind]

That 372 looks clean. Did some idiot power wash it for you?

Sure enough. :msp_sneaky:

Randy, who built the big bore kit?????

Thanks.....

It's a no name kit from Weedeaterman. Very nice ones these are.

 

[Jacob J.]

Interesting how Husqvarna chose to shroud the lower transfers on the 372 jug, but chose not to on the 385/390...

 

[Mastermind]

Interesting how Husqvarna chose to shroud the lower transfers on the 372 jug, but chose not to on the 385/390...

I think it's because of the relationship with the bottom of the piston at BDC......

 

[Rudolf73]

Woohoo a 372BB hotrod build! :cool2:

 

[workshop]

Here's a few pics......I'll be adding to this one.

Opened up the transfer inlets a bit since the 272XP piston is a windowed design.





Here we are test fitting to the case. The match is worse than you can see here.....



Here it is after being case matched.......



Like I said......I'll post more as I set the squish and port it.

It's time for a dumb question now. What is squish?:msp_confused: Besides what a bug makes when you step on it.

 

[Mastermind]

Woohoo a 372BB hotrod build! :cool2:

It's gonna get a big assed carb and stuff too.

 

[Mastermind]

It's time for a dumb question now. What is squish?:msp_confused: Besides what a bug makes when you step on it.

Squish is the clearance between the top of the piston and the head.....

 

[Jacob J.]

I think it's because of the relationship with the bottom of the piston at BDC......

That and desired base volume when the piston starts back up I always figured...

 

[workshop]

Ah! I understand. Thanks for answering Mastermind. I see others talking about proper squish clearance. Is there a rule of thumb standard for it? Also have seen others talk about removing the gasket at the bottom of the cylinder. Does this put squish in danger of being too close?

 

[Mastermind]

Ah! I understand. Thanks for answering Mastermind. I see others talking about proper squish clearance. Is there a rule of thumb standard for it? Also have seen others talk about removing the gasket at the bottom of the cylinder. Does this put squish in danger of being too close?

I try to shoot for .022 - .024

On some saws removing the base gasket will make it way too tight. Always check it to be sure......

 

[mt.stalker]

It's gonna get a big assed carb and stuff too.

That thing's gonna scream :msp_thumbup:

 

[Rudolf73]

That thing's gonna scream :msp_thumbup:

Literally and metaphorically :eek2:

 

[bryanr2]

been real boring on here lately. Glad to see something worth reading.

 

[greg storms]

squish

so, would not using a base gasket yet maintaining the deck clearance you mention be the same as raising the compression ratio? I'm trying to comprehend....

 

[Mastermind]

so, would not using a base gasket yet maintaining the deck clearance you mention be the same as raising the compression ratio? I'm trying to comprehend....

You'll see us talk about cutting the squish band in these engines. That decreases the volume of the combustion chamber......then we turn the base of the jug to set the squish clearance which raises compression. At times lowering the jug also allows us more control over the port heights.

 

[watsonr]

You'll see us talk about cutting the squish band in these engines. That decreases the volume of the combustion chamber......then we turn the base of the jug to set the squish clearance which raises compression. At times lowering the jug also allows us more control over the port heights.

Come back from your retreat and be all technical and stuff.... welcome home:msp_wink:

 

[Mastermind]

Come back from your retreat and be all technical and stuff.... welcome home:msp_wink:

Bonnaroo was a blast..........Sundance in two weeks. That's my last getaway till next spring.