New Tech Note - Measuring Head Clearance on Nitro Engines

[Marty Davis]

Occasionally I see something that should be shared with the racing community to make things easier for them. Just such a thing, I have written about in a new Technical Notes published over the weekend.

I have been running some of the newer engines that have domed and dished pistons and I thought that I had a great way to measure head clearance. I have a nice height guage that will measure things to half a thousandth. Problem is, how to probe this type piston to get the correct measurement.

So, I decided that there had to be a better way. I found it in using an old product (PlastiGage). When I went back and checked the engines that I used the height guage on, I found that my head clearance was .014". The engine ran well, but I was imagining how well it might run at my preferred .006"-.007". I was amazed at the performance increase. I checked some of my buddies engines and found the same thing and after changing clearance, they also found amazing performance gains.

One thing I forgot to mention in the Tech Notes is that when you close up the head clearance you gain HP and this makes the engine not have to work nearly as hard. That saves plugs, and all the other gains.

Check out the Tech Note at: http://1nitrorc.com/PlastiGage.html

 

[Brian Sorgente]

Nice write up Marty. Thank you for sharing all of the great articles you've written over the years.

It is pretty tricky to figure out your head clearance with the new domed/ dished pistons (until you use plasti-gauge of course). A little tough to figure out your compression ratio too. Maybe someone can move this to the "how to" motors forum so it doesn't get lost in the general one.

Brian

 

[Jerry Betke]

Thanks for the info. It will help a lot of guys get the head clearance correct. Jer

 

[steve wood]

I have been doing this for a few years on the "hemi" motors.

Something else I have started doing, I made a dummy liner out of aluminum, so I can put the piston and head in it and have the head contact the piston, then fill the cavity with alky through the plug hole. This will give a better volume reading with the domed/dished Pistons

 

[Kevin Krogness]

Only way I've ever done it. Works great and cheap!!

 

[Brian Schymik]

so, the measurement is taken on how wide the plastic gets squished laterally?

How does this compare to squishing a thin piece of solder and measuring it with a caliper?

Or to Keeley head gauges?

 

[SayMikey]

Plastigauge is softer and will make an accurate measurement every time

 

[KenOlvis]

I bought some today was wondering same thing can i measure the thickness of the plastic with calipers are is it best to use the chart

Thxs

Ken

 

[SayMikey]

Use the chart/sleeve that came with it. You can clean it right off with brakekleen

 

[KenOlvis]

Thxs Mike

Happy boater

Ken