29cc Cylinder Squish question

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, and others.
M

medic05

New Member
Messages
4
Reaction score
0
Location
Gander, NL
Hello everyone.
I know that this has been beat from dog to devil. I have also searched here and the HPI Baja forum.
I know that most say a proper squish is .015" to .020". I have seen some people say they have run .010" on certain engines.

I have a rovan(yes I know, mistake) baja 5b. It has a 29cc engine in it. From the first tank to now(3rd tank) I have blown 2 head gaskets. I have replaced them after finding the problem on the second one, I have that corrected. It was the crankcase halves not lined up.

When I put it back together I measured the squish. The squish is at 0.011" Is this going to create a problem for me?
The gasket is a stock steel CY Gasket (.020"). It is the same thickness as the stock gasket that was on the engine. I do have a spare gasket but, I really don't want to have to take this darned thing apart for the third time to put yet another gasket in. But, if I do have to take it apart to double up the gaskets, can i use the gasket I just installed over again? It has not yet been ran(because of my squish).

Thanks everyone for your help.
 
Most engine builders run .020 to .025 squish. I checked my Squish on my OBR race ported 30.5 and my race ported ESP 28.5 and both are between .020 and .022. If you squish is to small you can have problems with spark nock. Yes some run it as low as .015 but you are in the danger zone. From what I have read recommend squish is .019 to .031. Did you check it right near the cylinder wall?

Yes .011 is not good. I all so torque all my engine fasteners to book specification.
 
Last edited:
Got the second gasket added. Squish is now about .022" .
I used the first gasket over again as it didn't seem to to squished too much from the head. I also didn't run the thing with it on so there shouldn't be a problem I hope. Being the third head gasket in 3 tanks, if it leaks this time, I'm putting a real fuelie in. Thank you 46u for your help.
 
I didn't think of that one. The stock is .020 and I just had to double up. Maybe I'll order a .040 to have on hand just in case. I need to soften the copper up before I install them don't I? I didn't soften the metal ones because I was affraid to burn the carbon off of them. Because I am new to it and have only bad luck.
When I run it for the first time should I tight the head bolts down while it is still warm, or should I wait until it is cooled down?
 
Yes it is a good idea to anneal the copper gaskets. Been doing this on motorcycles for 40 plus years with copper gaskets.

All I have ever done with paper gaskets is torque the cylinder bolts to book specifications and have never re-torqued them. On a copper gasket might not hurt to re-torque them after getting up to temperature and let them cool down all the way.
 
Back
Top