High rear cylinder CHT temps.

[RFazio]

I read some posts here about high cylinder head temps on climb. I've got a new skyview installed in my 6 and I'm seeing stuff I never saw nefore. One thing I'm noticing is high cylinder head temps on the two rear cylinders. They are at least 75 degrees higher than the front two. Only in climb is this a problem. My front cylinders never get above 375 or so. I have seen some installations on pushers where they would block a few fins on one set of cylinders tryng to even out temps. I was thinking of blocking a few fins on the front two cylinders and hoping for more flow to the rear two. Is this a crazy idea? Will I only heat up the two fronts and do nothing for the rears? I was thinking of blocking them with some duct tap just to try it.

[Jamie]

I had a fairly early baffle kit with my -7, which was the same as the kit provided on the -6. Van has since improved the baffle kit. Our early baffle kits did not have plans for angles/ramps to push air up and over the front cylinders to the back. My understanding is that the new baffle kits do include the material and instructions for building these ramps.

Lots of folks on the older baffle kits just use "speed tape"...i.e. aluminum tape on the front cylinders to push air up and over to the rear cylinders. I think mine are about 1/2 inch up the fins and it spreads the airflow fairly evenly.

[frazitl]

when first wringing out my 7A / Superior 180. Problem I has was too large deflectors in front of the front cyl fins. My recommendation is to use some aluminum foil sticky tape covering about 1/2 to 1/3 of the front cylinder fins (assuming you have no deflectors installed). It's very easy to work up or down in size with the aluminum tape until you get the distribution you want. I still have tape on #3 a year later waiting to get around to removing the baffles so I can install proper aluminum deflectors.

[RFazio]

Thanks for the quick responces guys. I have not seen or heard of these deflectors. What do they look like? Does anyone have a picture?

[chipf]

You can see these deflectors in this picture:

http://picasaweb.google.com/lh/photo...t=embedwebsite

They just block the incoming air from much of the two front cylinders. I expect they will need some trimming to get the temps balanced nicely. I will find out soon!
I ordered this O320 baffle kit about a year ago.

This on this page of my build log.

[frazitl]

but quickly found them to be too high for effective cooling in 100 degree Las Vegas heat. YMMV of course, but I'd start with tape about half the hight Chip is showing.

[cwreeves]

Richard,
I used aluminum tape on my front cycl due to cool temps on the fwd cyclinders. The tape works very good for me. I fly in the southern AZ and temps very about 25 degrees AT cruise. 325 on the front and 350 on the back. My plan was to build the aluminum air dams as seen in the previous posted picture, however, the tape works and I've not taken the time to install the dams.
Charlie, RV-7, Tucson AZ

[RFazio]

Thanks for all the responces. I think I'll try the tape first just to see what kind of difference I can get.

[vasrv7a]

I have the same issue and want to try using aluminum tape. Is there a particular spec to use? High heat? extra strong adhesion? is there an aircraft grade I should try, or will a standard product from Home Depot be acceptable?

Any advice on this issue would be very helpful...

Thanx.

Victor

[kiwipete]

Richard

It's worth while putting a washer between the rear of #3 cylinder and the baffle to create a gap which gives better cooling.

Peter