As one of the plain folk who had little faith in oil coolers on street bikes I have reconsidered my opinion. They do radiate heat when you are not moving and someting is better than nothing. Until I started using an IR thermometer I just didn`t think they would help much without a fan.
Most of what I knew about oil coolers came from working on air cooled VW engines. These engines came with an oil cooler that was mounted inside or just outside of the fan shroud and air was forced through the cooler. The only accurate temp gauge was a dip stick type and the factory cooler made a major difference. The aftermarket oil coolers gave little benefit because of the difficulty in mounting one. When these engines were pushed to produce 90hp they would overheat with or without an aftermarket cooler.
Sometimes there are slight changes that can make significant improvements. Sometimes performance changes push things too far. The CVO110 problems should have been discovered at the factory since the leaks and overheating show up in less than 10k miles. I was always looking for tuning secrets and got one from Gene Berg. Heat is the result of combustion not friction within the engine. Lowering comp ratio from 9.1 to 8.8 lowered head temp temp by nearly 60deg. Power loss less than 2hp . Is there a similar opportunity on a Twin Cam ? Sure. When converting an 88 to a 95 inch go with lower comp.
Pick up 6-8hp AND lower engine temp. With an oil cooler and careful tuning even bigger engines can be reliable. The only thing that bothers me is that HD knows this.
Quig. I believe Frisco was giving us a clue about heat dissipation from the oil cooler. It might not dissipate as fast as when air is moving across the cooler fins but it still adds surface area to dissipate additional heat before returning to the engine.
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2006 Low Rider
USMC '71-'77 Semper Fi
NRA Member
While I'm posting in the thread "Overheating Big Bores", I have a question about Donnie's article in the last AI issue.
I read every word twice and might have still missed something. He emphasized more than once that he dragged his fingernail across junction of the rear cylinder liner and the cylinder on the machined head surface of the cylinder and felt a perceptible difference in the level of the liner to the cylinder surface.
Then they tried to press the spiny locked liner out of the cylinder with a hydraulic press and it did not move .001".
I might have missed the explanation of how the spiny locked liners are moving in the first place when it is locked so tight into the cylinder. I might have missed that he is going to explain this in the next issue.
If someone knows I would appreciate the explanation. Or that I need to wait for next months issue.
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2006 Low Rider
USMC '71-'77 Semper Fi
NRA Member
As mentioned by others here correct tuning is definitely a require'mt. But, so far,no-body's specifically mentioned the lowly spark plug's effect on tuning/cooling...by as much as 70 to 100 degrees of internal cylinder/combustion temps (dissipated via cyl. head) per each colder heat range...vise-verse.
__________________ "If at first you don't succeed, try again...then swear"
Mark Twain
As mentioned by others here correct tuning is definitely a require'mt. But, so far,no-body's specifically mentioned the lowly spark plug's effect on tuning/cooling...by as much as 70 to 100 degrees of internal cylinder/combustion temps (dissipated via cyl. head) per each colder heat range...vise-verse.
Just so I understand evo, you are saying that with the right spark plug I can lower my engine temps? If so what are these spark plugs?
Hey,sgt
Nothing magical about spark plugs...simply put, a plug's heat range (nothing to do with spark) is determined by it's ability to retain heat (hotter plug) to keep from fouling...or to dissipate heat (colder plug) via the cyl. head to avoid detonation/pre-ignition...and all "name-brand" manufacturers offer their plugs in a variety of heat ranges.
For more information on this and the spark plug in general check out this link:
That and there's an excellent 2 part article by Donnie Peterson on the largely misunderstood spark plug in the July & Aug '08 issues of AIM if you have them.
__________________ "If at first you don't succeed, try again...then swear"
Mark Twain
That and there's an excellent 2 part article by Donnie Peterson on the largely misunderstood spark plug in the July & Aug '08 issues of AIM if you have them.
Must have missed those articles. Will pull out copys of AIM for those 2 months and read again!
Silly me, whenever I sugg correct tuning I just always suppose that everybody knows that Proper plug heat range is part of correct Tuning..
Good call though..
If there's a "controlled" scientific study of plug heat range affecting over-all motor temp,,,, man,, I like to see it..
Surely they Retain or Dissapate heat as designed but for Over-all Motor Temp and Oil Temp I don't think they make a tinkers damn..
Of course, plugs that are waaay too cold and crusty and possibly mis-firing, allowing hit-n-miss cumbustion, might overwork the motor producing HEAT---- and waaay too hot might allow Pre-ignition/detonation producing, ah, well, heat again,,,,hmmm, there IS no combo where they produce Cold..
Bottom line-- whatever heat (70 - 100????) that's transfered to the head by the plug is Normal IF the correct plug is used..
I will forever shout from the tree-tops that proper tuning and oil coolers are the only remedy for keeping motors & motor oil temps in line..
__________________ "Fill your hands you son of a bitch"
Rooster Cogburn
This is only to reassure you that I have not intended to "correct" you/others here...and am just touching on a basically simple yet important part of "proper tuning" rarely mentioned...that all too many guys seem to over-look and/or have no real understanding of.
As you say..dropping combustion-chamber temp by 70-100 degrees (per Champion Spark Plug data) is'nt going to drop an engines over-all temp.by quite that much,alone. But,as you know,every bit helps. And,all I'm attempting to remind/inform some folks of is that (example) any time they add a bore kit and/or higher comp. pistons,etc.(increasing combustion chamber heat) it's time to go to a colder plug than they had been running (decreasing combustion chamber heat) to a CORRECTED heat range, and do their "proper tuning" from there...noting that up-grading to a bigger bore is what this whole thread started out about...and that if I for one had ('nuther example) an excessively hot running stock TC engine from the EPA minded Mo-Co (loco?) I'd be looking into at least one heat range colder plugs to start "proper-tuning" with (especially after adding freer flowing air cleaner & exh.) and then adding an oil-cooler,etc, if needed.
__________________ "If at first you don't succeed, try again...then swear"
Mark Twain
Last edited by evoKENevo; 02-24-2009 at 12:51 PM.
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Oil coolers 
Re: Overheating Big Bores 
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Re: Overheating Big Bores 
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