LO206 head - any break-in needed?

B

bryant

Member
My engine is 3-4 years old now without anything other than regular oil changes. People tell me I should get my head serviced, but that costs maybe $75 in labor plus parts (springs, gaskets, etc), plus shipping both ways. At that point it's almost the same cost to just buy one brand new and have a spare. Similarly, the cost of a leakdown tester ($80) + crank clamp ($90) is prohibitive to finding out whether I even have a leak. I don't notice significant power loss, but who knows.

I guess the first question is whether I should just keep driving it, or if you'd agree it should be serviced? Second question, if I bolt a brand new cylinder head on, is there anything special to break it in or is it ready to race at that point? Thanks!
 
Leakage is power slipping away. If your head has never been serviced chances are it is leaking. I have seen up to 15% on an engine the age of yours with no head work. The seats, especially the exhaust, will show leakage mainly due to so many heat cycles. At my shop I have seen some new heads that had no leakage and some with significant leakage. If you remove the head you can check for leakage with the correct size rubber stopper, a small piece of copper tubing, and some fuel line. Simply squirt some WD or carb cleaner on the valve and blow through the fuel line and stopper attached to the port. Unless you have someone near you that has them, the investment in the tools will be worth it. For what it's worth, at my shop your head work would run $125-$150. New heads are in the $220 range and with the price increases we have seen in the last couple of years could rise even more. Install the new head, put some heat cycles on it and run it. My personal recommendation would be to find a 206 builder/tuner close that you like and have the head rebuilt. I have many customers with two heads so they always have one ready to go.
 
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IMO, the seal on a rebuilt head will last longer than on a new head. While there is significant variance, generally speaking, after a number of heat cycles the seal on a new head begins to break down. I attribute this to the seats and guides moving ever so slightly or possible the valve face and/or seat not being true.
 
Thanks everyone. So, what I'm hearing:

1. Pay for a rebuild even if it costs the same as a brand new head.
2. No need for break-in with a new head; just send it. But it will itself need a rebuild anyways fairly quickly when new.
 
All good info provided above.

It takes about two full race days to see the seats in the head "settle" from heat cycling. The exhaust is the most prone to this (obviously from the localized super heating.) It will get elliptical or egg shaped and should to be recut after this short amount of run time. Once the head has been thoroughly heat cycled and the seats have been cut, they pretty much take a set and minor cutting/lapping can maintain them from that point forward.

It looks like I need to raise my prices on cylinder head servicing though. :) I think we do a pretty fair job and you should not be spending nearly as much as some builders are demanding (in my opinion.) I posted an article on our Facebook page in our Tech Talk Tuesday column (maybe a year ago now) about servicing LO206 cylinder heads that you might want to take a look at.
FWIW, we charge $50 for cylinder head work (tear down, clean, inspect, cut seats, lap valves, etc) & $125 for a complete LO206 rebuild (including all cylinder head work.) (that's labor - parts are add'l.)

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🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
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33 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
Okay, I hate to open a pandoras box, but, aside from cutting the seats and lapping the valves, what head work can be done?
 
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