willaduncan Posted March 15, 2014 Report Share Posted March 15, 2014 Seeing as there is no recent good topic on how to correctly measure squish I ran across some good pics and info out there and figured I would post it on here for those that may have questions in the future. When setting up your solder make sure that the ends of the solder touch the cylinder wall on both sides directly above the wrist pins and that both ends are cut smooth. These are examples of how your test solders should look. The reason for the small hump is to allow you to either pull the ends farther apart or push the ends closer together. This will allow you to get both ends of the solder to touch and rub on the cylinder wall. The hump shape of the solder is to lay flat on top of the piston, also this will keep the solder from moving around and help keep it in place. It is also very important that the hump shape of the solder does not come in contact with the squish band area. One last note before you go on to the actual Measuring Squish, make sure that the ends of the solder touch the cylinder wall on both sides and that both ends are cut smooth. The test solder below were done improperly. These are some examples of poorly done solder tests. You must keep the hump shape of the solder small enough, so it will not come in contact with the squish band. If this hump shape comes in contact with the squish band, it may rock the piston and may give an incorrect reading on the ends of the solder. It is very important that the ends of the test solder are cut clean and blunt. This is a very critical area to be measured. Now it's time to Measure Squish Band Clearance The best and easiest way to do this is by using a piece of rosin-core or acid core-solder (Do not use a solid, core-less type of solder). You can buy the rosin or acid core solder from your local hardware store, auto parts stores or places like radio shack. The solder needs to be thick enough to smash slightly but not so thick as to bind the engine (after you do it a few times you will get the hang of it). Places to get your test solder .050" Rosin Core Solder = Radio Shack PN # 64-006 E .062" Rosin Core Solder = Radio Shack PN # 64-002 E .093" Rosin Core Solder = NAPA Auto Parts PN # 777-1862 .125" Acid Core Solder = NAPA Auto Parts PN # 777-1857 You need to remove the flywheel cover, this will allow you to turn the engine by hand. Next you will need to remove the head and save the old head gasket if it uses one (some engines do not use a head gasket, they use o-rings and the o-rings are not necessary for this test). You will then need to bend the solder into a hump shape shown in the pic’s above and replace the head torquing it to spec. Now turn the flywheel by hand or use a wrench on the flywheel nut and rotate the motor so both cylinders pass TDC. The solder needs to lay right across the center line of the wrist pin. Make sure the ends of the solder touch the bore of the cylinder on both sides. You can use a small dab of grease on the hump shape that should be laying flat on the top of the piston also, this help hold it into place. DO NOT USE THE KICK STARTER TO ROTATE THE ENGINE, TURN THE FLYWHEEL BY HAND. Once both cylinders have passed TDC remove the head. You will see where the solder was smashed and this is your current squish band clearance. Another option is using molding clay or machinist wax but most all builders recommend the solder technique, again this was not my work simply some info I came across while searching the topic. Hope this will end up helping someone out! 3 Quote Link to comment Share on other sites More sharing options...
2004LEBanshee Posted March 15, 2014 Report Share Posted March 15, 2014 Good write up. Never relized how inaccurate just sticking the solder through the spark plug hole was until i took the time to do it this way. This is the only way to get an acccurate result. I think i was measuring . 056ish the half ass way and .051ish laying the solder accross the whole piston. This was the difference of me needing differnet domes. I was also told to try to use solder the does not have the flux core. Quote Link to comment Share on other sites More sharing options...
RadarRacing Posted March 15, 2014 Report Share Posted March 15, 2014 Great write up. I use flux core as well. Some worry about the acid in the flux core but I dont get it everywhere so dont worry about it. Quote Link to comment Share on other sites More sharing options...
willaduncan Posted March 16, 2014 Author Report Share Posted March 16, 2014 Thanks guys like I said this is a compilation of info I found during some searches for machinist wax that trickedcarbine had told me about and know that I've never found a decent write up on here for this important step of engine assembly. I had to change some stuff since some of it didn't apply to measuring squish but I hope this helps people out in the future Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted March 17, 2014 Report Share Posted March 17, 2014 Teuche'^ It's pretty cool when someone learns something new and takes the time to do a good write up. 1 Quote Link to comment Share on other sites More sharing options...
Strm Trpr Posted June 22, 2015 Report Share Posted June 22, 2015 Here's some more info too. http://www.rb-designs.com/rb_designs_llc_017.htm Quote Link to comment Share on other sites More sharing options...
sheerider1026 Posted June 23, 2015 Report Share Posted June 23, 2015 So why not discuss squish clearance. What's acceptable. It's different effects. Etc. Carry on 1 Quote Link to comment Share on other sites More sharing options...
possum Posted June 23, 2015 Report Share Posted June 23, 2015 Actually the orings do matter. You need to put them in. Quote Link to comment Share on other sites More sharing options...
Strm Trpr Posted June 23, 2015 Report Share Posted June 23, 2015 Actually the orings do matter. You need to put them in. Just curious, have you actually measured squish with and w/out o-rings in the head and were the results different? Correct me if I'm wrong. But, I'd imagine the o-ring in the groove of the dome allows the dome to actually seat and seal on the cylinders, metal to metal contact. The primary function of that o-ring in that groove is to not allow combustion gases/pressures past the o-ring and lose compression. Quote Link to comment Share on other sites More sharing options...
willaduncan Posted June 28, 2015 Author Report Share Posted June 28, 2015 Yes you are correct the o-rings do not matter you are only risking pinching the o rings Sent from my iPhone using Tapatalk 1 Quote Link to comment Share on other sites More sharing options...
willaduncan Posted June 28, 2015 Author Report Share Posted June 28, 2015 And sheerider1026 I didn't want to get into acceptable squish clearances since every builder will say something different, I want their builder to say what their squish clearance should be Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
willaduncan Posted June 28, 2015 Author Report Share Posted June 28, 2015 Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
registered user Posted June 28, 2015 Report Share Posted June 28, 2015 excessive piston to head clearance is of no value as you only increase the chance for deto with stagnent fuel sitting at the outer edge of the head. problem is since parts grow with heat and rods stretch at high rpm it can be tricky to find the point just before the piston contacts the head Quote Link to comment Share on other sites More sharing options...
possum Posted June 29, 2015 Report Share Posted June 29, 2015 Yes Ive done it with and without orings. Orings do change the dimension. How would you pinch an oring when you put the head on the same way as you would any other time? Quote Link to comment Share on other sites More sharing options...
willaduncan Posted June 30, 2015 Author Report Share Posted June 30, 2015 Funny because I have done it with and with out the orings with no change in value... But if you want to measure with them on go ahead there is more than 1 way to do this. If an o-ring slips out of the groove while installing you would pinch an o-ring Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
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