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O-320 Cylinder Head Temps

W

Will Bentley

Active Member
I have an RV6-A with an O-320 D2J and fixed pitch prop. On climb out my number 3 cyl will go to around 430 degs until I reduce climb. Once cruising it stays in the neighborhood of 340 to 360 degs F along with the other 3 cyls.

I was recently told by a friend that the GAMI guys say the temps should NEVER get above 400 degs unless I'm looking to buy a new jug soon.

Your input on this would be more than appreciated. Do I need to start working on the engine baffles??

Thanks,

Bill
 
Bill, how much time is on the engine? If it's new, then that's not out of line. After break in, then you should be able to see less than 400 on an O-320 on climb out.
If it's not new, then make certain you have the carb jetted properly. Plenty of information on that if you search the forums.
What climb speeds are you using? REducing power with a fixed pitch prop takes away some of the cooling effect of the enrichment valve in the carb at full power. Try lowering the nose and let the speed build up.

Vic
 
Vic,

Thanks. The engine has 400 SMOH. Great point about keeping the throttle advanced and speed up on climb out. I'll increase my forward speed and see if that doesn't cool that cylinder some. I'll search the forums on properly jetting the carb. I will generally climb out around 110k.
Is there any chance I have done damage by allowing that cylinder to go into the 400 deg F range? My oil samples always come back looking good and my compressions are good.

Do most of the RVs out there stay below 400 on climb out? Should I be concerned? I try to do everything by the book and this one has me concerned. Why is it we treat our RV's better than our kids???

Bill
 
No prob there.. I believe some of the info got distorted by the time it got to you.. Keep in mnd that the red line is 500 deg.. I'm not a proponent of high CHTs, but to suggest that the moment you hit 400 that jug is trashed is absolutely ridiculous ...
 
Sure....I know what you're talking about but I've been around a while :D. I'm also sure that the poster that asked the question won't have a clue as to WHAT you're talking about and WHY he should add the washer :eek:.

If you have time you might volunteer some additional info and elaborate on your (worthwhile) suggestion. This way the poster can get an education and be on the road to solving his issue.

I'd add to it myself but I wouldn't want to steal your thunder :).


LifeofReiley said:
Try adding one washer to the back side of the #3 baffle... should solve your issue.

-d-
Click to expand...
 
That's a hoot! Sure nuff...I didn't know why I was going to add a washer to the backside of my nr3 baffle...but I was definitely going to do it. Thanks to the both of you for the suggestion...I'm gonna wait and find out where this washer goes, exactly...and why.

I think I really enjoy troubleshooting this way!

Bill
 
I'm heading to the airport now to try this. I'm not precisely sure what to look for, but from your description I'll bet it will be easy. Thanks a lot...think I'll go do some night flying and see what the temps are "down" to...

Thanks again...
Bill
 
Will Bentley said:
I'm heading to the airport now to try this. I'm not precisely sure what to look for, but from your description I'll bet it will be easy. Thanks a lot...think I'll go do some night flying and see what the temps are "down" to...

Thanks again...
Bill
Click to expand...

On my 0-320 D2J I saw the exact same issue. I added the washer as discussed in this thread and also installed a small cylinder blocker in front of the #1 cylinder. Measured from the inlet ramp, I think it covers an additional 1 or 1.5" of the cylinder head height.

Works like a charm.
 
Vic, Rick & Kyle

I've been out changing the oil/filter on my 6A. I placed a washer behind each location where the baffle attaches to the cyl. I flew it and found
all to be the same. I also climbed out at around 120 kts & full throttle but it still went to around 410F..the other 3 cyls were in the mid to high 300s.

Kyle, can you amplifly a bit on the fix you were talking about regarding
the nr1 cyl blocker. And anyone else wanting to input...I'd be very receptive.

Bill
 
Will Bentley said:
Vic, Rick & Kyle

I've been out changing the oil/filter on my 6A. I placed a washer behind each location where the baffle attaches to the cyl. I flew it and found
all to be the same. I also climbed out at around 120 kts & full throttle but it still went to around 410F..the other 3 cyls were in the mid to high 300s.

Kyle, can you amplifly a bit on the fix you were talking about regarding
the nr1 cyl blocker. And anyone else wanting to input...I'd be very receptive.

Bill
Click to expand...

Your symptoms may be explained by a couple of things that are easy to check:
1) Induction leak on cylinder 3 causing it to run lean. Check Intake runner for leaks.
2) Cylinder casting flashing on the cylinder fins between the spark plugs. Look down between the plugs and see if the airflow is being blocked in this area. Compare it to your other cylinders. I cleaned out these flashings and saw a 30-40F reduction in measured cylinder temps.

Vern
 
Will Bentley said:
Vic, Rick & Kyle

I've been out changing the oil/filter on my 6A. I placed a washer behind each location where the baffle attaches to the cyl. I flew it and found
all to be the same. I also climbed out at around 120 kts & full throttle but it still went to around 410F..the other 3 cyls were in the mid to high 300s.

Kyle, can you amplifly a bit on the fix you were talking about regarding
the nr1 cyl blocker. And anyone else wanting to input...I'd be very receptive.

Bill
Click to expand...

The cylinder blocker is a little piece of bent aluminum that you pop rivet to the top of the inlet ramp in front of the #1 cylinder. It goes right against the cylinder fins and shields the first 1 - 1.5" of the cylinder head fins from direct air impingement. It deflects a little more air off of the #1 cylinder and results in a surprising reduction in temperature on #3 with little increase on #1.

I was very skeptical of how effective a cylinder blocker would be and was extremely pleased with the results, particularly considering how easy it is to take a 4" x 3" (approx) piece of aluminum, put a 90 degree bend in it and pop rivet it in front of the cylinder.
 
What Kyle said :)....but for trial purposes you can just take a piece of aluminum tape, reach through the cowl, and and stick it where you'd put the metal piece....just above the 'floor' of the inlet and against the cylinder fins of #1 cylinder. Saves you from pulling the cowl each time. Matter of fact the tape will last quite a while.

Kyle Boatright said:
The cylinder blocker is a little piece of bent aluminum that you pop rivet to the top of the inlet ramp in front of the #1 cylinder. It goes right against the cylinder fins and shields the first 1 - 1.5" of the cylinder head fins from direct air impingement. It deflects a little more air off of the #1 cylinder and results in a surprising reduction in temperature on #3 with little increase on #1.

I was very skeptical of how effective a cylinder blocker would be and was extremely pleased with the results, particularly considering how easy it is to take a 4" x 3" (approx) piece of aluminum, put a 90 degree bend in it and pop rivet it in front of the cylinder.
Click to expand...
 
Kyle Boatright said:
I was very skeptical of how effective a cylinder blocker would be and was extremely pleased with the results, particularly considering how easy it is to take a 4" x 3" (approx) piece of aluminum, put a 90 degree bend in it and pop rivet it in front of the cylinder.
Click to expand...

I installed the cylinder blocker, during baffle installation, based on measurements from others. It has been very effective for the #3 CHT's. I rarely see it get to 400 in a climb, and is usually around 325 in cruise.

L.Adamson --- RV6A, 0360, Hartzell C/S
 
Vern, Kyle, Rick & L.Adamson...


Incredible that u guys r right there for me! Okay, I'll give these ideas
a shot in the morning. Amazing how many flyers have the same problems.
Many thanks to you. Will get back with the results as soon as I try them.
(Great idea about not having to remove the cowling each time and I happen to have some aluminum tape right on my workbench...)

Thanks again!
Bill
 
Well, I cut out a 6 inch by 1.5 inch piece of aluminum tape and placed it on the nr1 cylinder baffles as suggested. I saw a slight difference in climb out temps but still in the low 400s. Nbr 3 and nr1 cylinders are now reading almost exactly the same temps now. 2 and 4 are about 20 degs cooler.

I was really expecting an appreciable drop in temps, especially since the OAT was reading in the mid 30s this morning when I flew instead of the typical
70s. I climbed at 110k to 4000'. As soon as I leveled off all of the temps dropped to the low to mid 300s but during climb temps refuse to get below around 410 or so.

Should I try and cut different sizes of aluminum to see if there is a combination that might work, or would that be a wasted effort?
Also, I did check to see if there were any blockages below the spark plugs or any where else, for that matter. None found.

Bill
 
Will, have you had the airplane since new? Is this a change in characteristics, or is this a different engine ( you said it has 400 smoh)?
Do check the intake tubes for leaks as someone else mentioned. I change the intake gaskets every 2 years anyway. They're cheap, and they do leak.
If at all possible, swap a couple of probes around just to make sure it's not the probe. It seems odd that only #3 is running hot on climbout, and then close to the others in cruise. Have you checked the lower cylinder baffles that wrap around on the bottom to make sure they are still tight to the cylinder? I've seen those break over time, especially if they are saftied instead of using a threaded rod.
I didn't look where you live, but if Atlanta is convenient, fly down to Mallard's Landing on the week end and we'll take a look at it together (no cost to you other than fuel).

Vic
 
Will

Have you checked that the ramps on the upper cowl have the ends closed off. This has been a problem for some people.
Also that you have a good baffle to cowl seal and air isn't escaping anywhere else.

Peter
 
cylinder temps

I also had high temps as you have described, and I am running a full pressure plenum on my o-320. The washer behind no. 3 helped a lot. I ended up installing 2 louvers in the bottom of the cowl, and the results were amazing. I dropped 30 degrees overall immediately. Oil temps were unchanged, and run at 195 max. I cruise at 330 CHT average, and climbs rarely go higher than 390 CHT.

Regards, Chris
 
Vic, Peter & Reiley

Peter, yep, checked that...ok.
Reiley, thanks anyhow.

Vic...Actually, nbr1 and nbr3 are now almost identical on climbout. When I placed the aluminum on nr1 it brought the climbout temps up on nr1 and slightly decreased nr3. When leveling off nr1 & 3 both cooled off evenly.
Once I leveled off, all 4 temps seem to be pretty close, which indicates
to me that the temp probes are functional (my guess anyway).

I willl check the lower cyl baffles to make sure they are tight.

Your offer is tempting. I am 500nm from Atlanta...if the weather isn't hard IFR (icing/thunder storms)..I may just take you up on your kind offer to take
a look at my problem.

Thanks,
Bill
 
Chris...

That's really amazing. I was beginning to think that louvers or some type of mod would be necessary. Thanks for your input. If necessary I may just do the same thing you did. Where did you get the louvers? I assume they are metal and you fiberglassed them to a cutout in the lower cowl?

Bill
 
If you research a bit, you'll find that the 6's don't generally have the heating issues that the 9's have. Apparently ( I haven't measured) the 6's have more outlet area on the bottom of the cowl.

Just something to think about, since I've never seen 6's with Lycoming type engines, and cowl louvers.

L.Adamon --- RV6A
 
Think I've solved it...thanks to VERN!!!!

Looks like Vern wins the jackpot for solving my problem! Vic, Rick, Kyle, L.Adamson, Reiley, Peter and Chris...THANKS for you interest and help.

Vern mentioned that I should look at the fins near the spark plugs and see if that area is blocked from good air flow. I looked earlier and didn't see anything. This morning, however, I pulled out my big spot lights and guess what I beheld??? Beads! I use desicants in place of my spark plugs while I'm overseas..apparently a couple of these spilled some of the beads and they stuck in between several of the fins. After removing this material I test flew
the plane and saw about a 20 to 30 deg F drop in the nr3 cyl. On climb out to 6000' my hottest temps were cyl 3= 408F, cyl 1= 405, cyl 2=402 and
cyl 4= 381.

Don't know why cyl nr4 stays so cool. When I leveled off all temps went to
within 2 degrees of each other...around 305 degs F.

I'm going to guess that with the hottest temp being 408 that that really isn't all that bad. Vic (or anyone else), do these temps pretty well seem to be in order? They are definitely an improvement from what I was getting earlier.

Shall I try to get them cooler or be happy with what I have...?

Many thanks...Bill

PS...Vic, your invitation to fly to your place in Atlanta in an attempt to resolve my problem was just WAYYYY too kind. My deepest thanks for
you generosity.
 
Will

Glad to hear you've found the problem. Thanks for sharing your findings. Thats how we all learn from these things.

Happy Flying

Peter
 
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