Flat vs. Roller Lifters?

szicree · #1 06-02-2007, 08:34 PM

I'm going to Texas in a couple of weeks to build up a Superior O360. Originally I had selected flat lifters, but am aware they offer a roller version. Their website claims better durability, but gives no hard data. It also seems to imply that the cam on the roller engine is less "rampy" than the conventional model. This is the opposite from how things work on cars, so I'm a bit confused. Anybody have any factual data on the pros and cons?

KPmarc · #2 06-02-2007, 08:59 PM

My understanding is that the cam profile is different to accommodate the roller lifters but the actual valve events are the same: Identical timing, lift, overlap.

The theoretical benefit is reduced friction and reduced *potential* of cam/lifter spalling. But the fleet is still too new for both Superior's and Lycoming's version of the roller lifter to bear this out.

FWIW, so far everything about my roller-lifter IO-390 is nominal save for the oil analysis. It got flagged for too LOW an iron count compared to the IO-360 fleet. But it has only 220 hours on it, so it's waaayyy too early to know if they'll be a benefit or not.

--Marc

gmcjetpilot · #3 06-03-2007, 11:54 AM

Quote:

Originally Posted by szicree

I'm going to Texas in a couple of weeks to build up a Superior O360. Originally I had selected flat lifters, but am aware they offer a roller version. Their website claims better durability, but gives no hard data. It also seems to imply that the cam on the roller engine is less "rampy" than the conventional model. This is the opposite from how things work on cars, so I'm a bit confused. Anybody have any factual data on the pros and cons?

My opinion, if starting from scratch today I would go for it. Factual data is a little thin right now except in the deep dark dungeons of Lycs R&D, but I did talk to them.

Lycoming service guys could not shut-up about roller cam. They said they wish (as a company) they had gone to it sooner and think it's a real improvement. What improvement?

Like all things "roller" it does free up some HP, but from what they said it seems that they love the way it wears and solves any and all existing/potential cam problems we now have.

Not that Lyc flat tappets are bad, but we all know cams and tappets wear. They make TBO all the time consistently, but the design relies on splash lubrication only as you know. With the cam sitting top center in the case, it drys out if it sits too long. The work around (besides flying often) for cam lubrication is the aftermarket cam oil squirter mod, but really the problem is still dry start-up's after a long periods of sitting. In GA planes those periods of non use are the problem.

I recall from what I was told, you can not convert a Lyc Non-roller case to a roller cam case. I'm not 100%, but I think its a unique case and conversion of older cases is not possible. Lycoming did the roller thing not to increase power but increase wearability. I think that is the main advantage, wear and may be a few HP as a bonus.

Aftermarket roller cams where widely coming out for cars in the late 70's. They had their issues with cam walking, especially with some engine blocks that where not perfectly square with respect to the lifter bores, cam and crank.

Rollers cams allow you to run massive valve spring forces which enhances the RPM potential, lowering valve float at high RPM. That does not apply to Lycs, plugging along at 2,500 rpm with a red line of 2.7k. I'm not sure what you mean by "rampy", but assume more aggressive lifts and profiles. Ya, I don't think Lyc did anything radical, but the roller allows valve train and valve forces to be "smoother". The engine designers, engineers call it valve train "jerk".

"Although high accelerations are needed to give rapid opening and closing, too rapid a change in acceleration - the 'jerk' or 'jerk rate' - will give rough operation due to the sudden changes in forces. For this reason cam profiles are designed not to give very rapid changes in accelerations."

It's the acceleration of acceleration if you will, inertial loads. Clearly not slamming the valve down would have some anti-wear-n-tear pay off, as well as opening it quicker, with less overall "jerk". Roller cams have more options for the designer of the cam profile. Again most of that is for high rpm applications, but I see some practical advantage for the whole valve train.

Is it worth it? Don't know, but if you fly rarely it would have a clear advantage. I have flat tappets and don't have roller cam envy. However building the dream engine, sure why not. It's only money.

RV8RIVETER · #4 06-03-2007, 12:56 PM

George is correct. Needs special case, lifters, and cam.

cytoxin · #5 06-03-2007, 05:27 PM

ive taken apart engines for cars that the quick lubes have a habit of not putting oil in. the roller motors with w/o oil show little or no wear. 25-miles or less. i watched a 3000gt twin turbo go back together with a rusted cam that was cleaned off with a roloc wheel and the car never had any issues (solid red rust cause it sat in the trunk for a month and the customer wouldn not buy new cams.....4 of them. the only roller failure ive seen was on a v8 and it broke the guide and turned sideways in the guide. technician to my amazement just installed a new guide and lifter on off they went. saw this truck for regular maintenance and it was not ever a problem.
the cam lobes on a roller look way different (wider lobes) but then the tappets have rollers which are obviously narrower. roller valve trains can go for ever. my last lt 1 had 228000 miles at overhaul and i put the same cam back in it. absoluteley no measureable wear.

i would without a doubt go with the roller setup.

rgbewley · #6 06-04-2007, 07:57 AM

The Lycoming engines do require different cases, cam, lifters, push rod tubes and a few other parts. All new Lycomings, whether certified or experimental are roller tappet engines. Superior offers the choice of flat or roller. Their modification involves using the same cases, but drilling a hole through the case and using a screw to keep the roller tappet from rotating in the case.

There is not hp increase by going with the roller cam/tappets. I would suspect that part of the reason for going with roller tappets is the lack of producers of the flat iron tappets. There are only three places in the US that make them, and the cost will get to be prohibitive as time goes on. They had to do something now or be in a crunch later.

The materials in the roller tappets should prove less corrosive than the iron tappets and should help eliminate the camshaft problems that have plagued the engines for years. For every engine that doesn't make TBO, there is another one that does. But, if you live in high humidity and don't fly more than 80 hours a year, roller tappets should be on your list for consideration.

szicree · #7 06-04-2007, 09:05 AM

Thanks for the good info. I guess my biggest concern about the rollers is that they can turn sideways and really make a mess of things, but it sounds like they're becoming the standard. I guess it's gonna be rollers for me.

yakdriver · #8 06-04-2007, 09:17 AM

Steve, If you go the roller Superior gives you a 3 year warranty for free. You have to pay extra (about the same price as the roller) for the 3 year warranty if you go the solid lifters. Don

gmcjetpilot · #9 06-04-2007, 12:51 PM

UPDATE: If you send your old flat tappet engine into Lyc they will rebuild it (remanufacture zero-time or overhaul) with roller tappets. There is no extra charge it is automatic. Of course a Lyc overhaul is more money than a new ECI/Superior. The case mod can only be done at Lyc not in the field. Apparently Lyc is making it their new standard.

Rick_A · #10 06-04-2007, 02:10 PM

I had planned on getting a roller tappet engine from Mattituck but changed my mind after attending their engine building working shop. I discussed this in length during one of the breaks and it seems to me the main benefit was stated in the previous post from Barrett "if you live in high humidity and don't fly more than 80 hours a year, roller tappets should be on your list for consideration".

The gist of the conversation that I had was that flat tappets are simple and proven in Lyc's and if you fly on a regular basis the benefits of the roller tappets are minimal. So I decided so save a few grand and get the old technology.