Head Temperature top five, *** Give me the top five reasons head temps run high ***** Options

[wndsnd]

Oil temp is cool, heads are running hot.

What are the top five .....

[ThePaintedMan]

A couple things here, IMHO:

1) What kind of CHT gauge are you using? If it's a VDO type, then it's non-compensating type. Up where you guys are, you've been having cold weather, which means that it likely is reading quite a few degrees higher than the actual CHT is. Read more here:

http://www.ratwell.com/technical/VDOGauges.html

2) Timing is probably one of the biggest drivers of CHT temps, especially under load. However, you know your stuff and as long as you're pretty confident you have it set correctly, you're probably pretty close and can rule that out as you main concern.

3) Jetting, especially under load. If you've got the temps way down, then you were probably way lean previously. What mains and idle jets are in it now, and what size engine are we talking about?

4) Sync of the carbs. If one carb is open more than the other, that side of the engine is doing far more work. If that happens to be the side you have the CHT lead on, then the higher temps you're seeing are a good indication that the other side might not be pulling it's weight. Verify your sync tomorrow before you get on the road with the gauge (you have a synchrometer, correct?) Might even try checking it at several different RPMS - idle, 2k and 3k.

5) Valves - if you've got a tight valve lash on the #3 cylinder (where your CHT lead should be), especially an exhaust, you're not letting the valve do it's secondary, but important role of sinking heat away from the head. Check your valve lash adjustment before you start it up in the morning. Keep it on the loose side instead of tight if you're concerned, especially on the exhaust valves.

When in doubt, run it pig rich with jets if you're just trying to get to Chris' shop. Doing it for too long can be harmful, but if it's far too lean, you're risking really high temps which could do more damage quicker. Also, if you being to see the temps spike, slow down a little and downshift. The less "lugging" you put the engine through, the lower the temps should be. After that, let Chris help you figure the rest out - I learned a lot from him, and he is truly one of the Obi-Wans here. (IMG:style_emoticons/default/beerchug.gif)