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Workshop => Engine and Bottom End => Topic started by: stroberts22 on November 29, 2013, 04:39:33 PM

Title: pro design cool head failure
Post by: stroberts22 on November 29, 2013, 04:39:33 PM
I noticed I was losing coolant and the water jacket was getting pressure from the combustion chamber so I thought I had a bad head gasket but when I tore it down the head had a huge crack in the dome. Is this common for these heads? It's a 22cc so compression wasn't to crazy. I put a stock head back on for the time being but if this is a problem with these heads I might just keep the stock one on the machine.
Title: pro design cool head failure
Post by: C-Leigh Racing on November 29, 2013, 08:09:43 PM
I would have to say, in all my years of dealing with 2 strokes & 250R engines, a cracked dome in a Pro Design head, that would be a first one I've ever heard of.

Now if you were asking about a high compression 250R build, with a tight fitted to the bore cast piston & it cracked right across the top from one side to the other, now I would say I've seen that before & believe it or not the engine was running good, won the main the Saturday night before it was found.
Cracked Pro Design dome, you have the first man I know of.

I wouldnt be surprised, if you was to send it to Pro Design, they probably would replace it free if you had a nice sounding letter along with it.
Just like an Apple for the teacher, guess whos the teacher pet afterwards.
Neil
Title: pro design cool head failure
Post by: stroberts22 on November 29, 2013, 10:48:08 PM
Here's a picture of the crack. I try to contact them but with my luck I'll just buy another dome myself.
(http://i811.photobucket.com/albums/zz40/stroberts22/DSC03326_zps60c188ac.jpg) (http://s811.photobucket.com/user/stroberts22/media/DSC03326_zps60c188ac.jpg.html)
Title: pro design cool head failure
Post by: Jerry Hall on November 30, 2013, 11:14:31 AM
Quote from: stroberts22;18753
Here's a picture of the crack. I try to contact them but with my luck I'll just buy another dome myself.
(http://i811.photobucket.com/albums/zz40/stroberts22/DSC03326_zps60c188ac.jpg) (http://s811.photobucket.com/user/stroberts22/media/DSC03326_zps60c188ac.jpg.html)

This is not uncommon on the low compression domes.  The dimensions of the "wet" side of the dome is the same as the high compression domes making the dome thickness to thin in key areas.  The fins are not necessary for cooling.  The fins trap steam bubbles, add unnecessary weight and cause a stress risers to occur  between the fins when the engine fires.


We see a similar problem on the piston crown of many of the aftermarket low-compression forged four-stroke pistons.  The piston companies usually use the same forging blank and machine the top of the piston to lower the compression.  Guys buy the low compression pistons to make their engine more reliable but the pistons are not as strong as the high compression pistons due to the thin piston crown.
Title: pro design cool head failure
Post by: C-Leigh Racing on November 30, 2013, 01:25:30 PM
Good point there Mr Hall.
With that being as it is, sounds like another good reason to stay away from low compression & pump gas to keep the thickness of the dome thicker.

Man, you cant win with those 4 pokers, either pay me now or pay me later, but in some cases, it pay now & pay later as well.
Neil
Title: pro design cool head failure
Post by: rsss396 on November 30, 2013, 04:50:23 PM
I did that on a pro design cr500 dome and I know of another guy a prodesign coolhead that did the same.
I would be best if pro design would just quit making the head insert with the fins since it is of no advantage.
Title: pro design cool head failure
Post by: stroberts22 on December 21, 2013, 03:40:20 PM
I'm going to reuse this head and was wondering what cc of insert in need for around 190 psi with 69.5 piston? Plus with this big of piston does the head need to be modified any?
Title: pro design cool head failure
Post by: traxman on December 21, 2013, 04:13:48 PM
I have had 2 or 3 Coolhead domes fail in the same place but these were 295 domes set up @ 17:1 and 15:1 ratio's and they failed very quick.. I agree with rsss that fin design needs to go, everyone broke in the same spot the trade off for what little extra cooling there might be is not worth the additional strength. For you info, that motor made it 4 years with a stock head with a recut dome set-up @ 15:1 before a failure.
Title: pro design cool head failure
Post by: Jerry Hall on December 22, 2013, 05:03:18 PM
Quote from: traxman;20415
I have had 2 or 3 Coolhead domes fail in the same place but these were 295 domes set up @ 17:1 and 15:1 ratio's and they failed very quick.. I agree with rsss that fin design needs to go, everyone broke in the same spot the trade off for what little extra cooling there might be is not worth the additional strength. For you info, that motor made it 4 years with a stock head with a recut dome set-up @ 15:1 before a failure.

The horizontal fins on domes do not help when liquid cooled.  The fins trap steam bubbles and keep the water from making full contact with the hot surfaces.  This is just another example of what happens when layman's logic/common sense is used to design parts that should have be done by those that have training and understanding in convective heat transfer when liquid is used as the cooling medium.  

Design errors are becoming more common in the aftermarket performance parts industry as aerospace machine shops are losing machining contracts with cuts in the defense budget. Aerospace machine shops have made a living biding on making high tech parts from blueprints of parts that have already been designed and tested.  The majority of the design errors like the fins on the dome inserts occur when the machine shops step outside their field of expertise which is machine work and start designing and making their own parts.  Poorly designed parts are created when designed by those that obviously did not have the necessary experience or training in the areas of science required.
Title: pro design cool head failure
Post by: poli250 on December 22, 2013, 05:21:16 PM
first you talk flow bench and dyno as tools. now you rip on poor design cool heads. you sound like carlos bud. sure you are not carlos imaginary friend- jerry? just ribbing you man. sitting here bored wifes shopping. lol
Title: pro design cool head failure
Post by: Jerry Hall on December 22, 2013, 06:21:49 PM
Quote from: poli250;20502
first you talk flow bench and dyno as tools. now you rip on poor design cool heads. you sound like carlos bud. sure you are not carlos imaginary friend- jerry? just ribbing you man. sitting here bored wifes shopping. lol


I am on the phone most of my work day taking calls from guys that have spent their hard earned money on parts that do not perform as advertised.  For some reason, guys in the off road industry are real suckers for anything that has the words CNC,  Billet,  6061 T6,  Titanium,  CAD/CAM designed, 304 stainless, 316 stainless, carbon fiber etc. in the advertisement for the part.  

I do not like to see someone spend the same amount of money two or three times to finally get the results they were expecting had they done their home work.  Reading all of the stuff on all of the forums and watching Utube videos is only a small portion of "doing your research" or "doing your homework".

Because someone has a website or a big add in a magazine, does not guarantee the business is reputable or has the experience needed to help you with your project.  There are a lot of "impostors" on many of the forums that are not real people but persons employed to pump certain companies products and services.  Before you spend your money, talk to a lot guys in person or on the phone about their personal experiences, satisfaction or dissatisfaction with products and services from parts manufactures and engine builders.


Sorry or the rant, just venting a little.   .............I listen to too many grown men cry on a daily basis.  I am a engine builder and not a grief counselor for guys experiencing buyers remorse.
Title: pro design cool head failure
Post by: traxman on December 23, 2013, 02:43:35 AM
Quote from: Jerry Hall;20507
I am on the phone most of my work day taking calls from guys that have spent their hard earned money on parts that do not perform as advertised.  For some reason, guys in the off road industry are real suckers for anything that has the words CNC,  Billet,  6061T6,  Titanium,  CAD/CAM designed, 304 stainless, 316 stainless, carbon fiber etc. in the advertisement for the part.  

Oh &$^*!!! You just described my drag bike... :frown-new:
Title: pro design cool head failure
Post by: poli250 on December 23, 2013, 04:30:57 PM
so pro deign who makes cool heads is a cnc aircraft shop makes billet parts, advertises, web site, mags, has been around for ever, makes a poor design head? not crying, trying to learn.
Title: pro design cool head failure
Post by: udontknowme on December 23, 2013, 05:24:10 PM
if the dome cracks that would suggest a crap design.  or so it seems
Title: pro design cool head failure
Post by: poli250 on December 23, 2013, 06:05:17 PM
Quote from: udontknowme;20610
if the dome cracks that would suggest a crap design.  or so it seems
hear you. i wont be buying a cool head.
Title: pro design cool head failure
Post by: sameltoe on December 23, 2013, 11:20:01 PM
So...what do you guys run?? I guess I relly don't know, but who else makes heads? Esr?
Title: pro design cool head failure
Post by: Jerry Hall on December 24, 2013, 12:33:36 AM
Quote from: sameltoe;20624
So...what do you guys run?? I guess I relly don't know, but who else makes heads? Esr?

Why not just run an OEM head that has the "right" modifications done to it.  The engine does not care if it is a billet head or anodized or made of unobtanium.


The engine wants a the right shape combustion chamber with the right piston to head clearance.  It needs a volume that will give the exhaust pipe the exhaust temperature it was designed for.  The cylinder wants the head to control the coolant flowing through it in a manner that will cool the cylinder, the combustion chamber and keep the spark plug base temperature correct for long hard runs.

The engine wants a head design that will compliment the rest of the engine.  The engine does not care if the optimum head design it gets is the result of millions of dollars of research and testing or the design was purely accidental.
Title: pro design cool head failure
Post by: udontknowme on December 24, 2013, 01:20:56 AM
rk tek makes a head. never tried it though

i dont see much point in using aftermarket unless your wanting a dome profile that cant be accomplished with the oe head

if you want to chop up alot of blank inserts for experimentation then aftermarket would be handy
Title: pro design cool head failure
Post by: rsss396 on December 24, 2013, 08:07:14 AM
One appeal is the o-rings cut are in the head so its a bolt on upgrade to close the very large squish on 250r motors, plus I prefer o-rings over head gaskets. Its also much easier to chuck up a coolhead dome in a lathe to cut then it is to setup a factory head on a plate.
If Pro-design would just stop putting the cooling fins on the domes and left more material for strength then they would not have the problems they sometimes have.
The lower compression heads are thinner due to more material cut away for the larger combustion area and heads that are run under frequent detonation conditions are the ones failing.
The other coolhead down side is the water passages are not sized to direct flow like the factory gasket does,so filling the water passage on the head with epoxy and sizing them like a factory head gasket is a worth while effort
Title: pro design cool head failure
Post by: udontknowme on December 24, 2013, 12:14:26 PM
http://phatheadracing.com/trx250.html
http://2strokeheads.com/

i like orings but on the other hand i never had a problem with a gasket. im sure all the aftermarket stuff will be full open design. its probly not a bad idea to 'partially' plug off the frontal area. you can see on this head the rear is open and front is pretty well plugged

(http://i1081.photobucket.com/albums/j357/doddledo/headr_zpsaa770330.jpg) (http://s1081.photobucket.com/user/doddledo/media/headr_zpsaa770330.jpg.html)
Title: pro design cool head failure
Post by: chrisr on December 24, 2013, 12:33:03 PM
Quote from: udontknowme;20650
http://phatheadracing.com/trx250.html
http://2strokeheads.com/

I ran across the phathead racing billet heads one time on a different board.  I always wondered about them.
Title: pro design cool head failure
Post by: etccb on December 24, 2013, 12:43:47 PM
The esr head body has the passages cut to flow more to the ex side and less on the intake side. The intake side may still be larger then what some may want to see but they have addressed coolant flow on thier oring heads.
Title: pro design cool head failure
Post by: rsss396 on December 24, 2013, 03:24:10 PM
Quote from: udontknowme;20650
http://phatheadracing.com/trx250.html
http://2strokeheads.com/

i like orings but on the other hand i never had a problem with a gasket. im sure all the aftermarket stuff will be full open design. its probly not a bad idea to 'partially' plug off the frontal area. you can see on this head the rear is open and front is pretty well plugged

(http://i1081.photobucket.com/albums/j357/doddledo/headr_zpsaa770330.jpg) (http://s1081.photobucket.com/user/doddledo/media/headr_zpsaa770330.jpg.html)

Trx250r's have water inlets on the rear of the cylinder so it's best to restrict flow on the intake side and improve flow over the exhaust port where cooling is most important.
Title: pro design cool head failure
Post by: udontknowme on December 24, 2013, 04:13:54 PM
yes of course. i didnt take into consideration the water path. the pic shown water goes through the case and to the exh bottom very first thing then to cylinder rear. 250r sounds like the opposite
Title: pro design cool head failure
Post by: udontknowme on December 25, 2013, 09:46:22 PM
i never seen this kind of insert before. looks like some sort of copper or brass alloy mixture. does anybody know of it ?


(http://i1081.photobucket.com/albums/j357/doddledo/sxs13125050_zps00663513.jpg) (http://s1081.photobucket.com/user/doddledo/media/sxs13125050_zps00663513.jpg.html)