Van's Air Force
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320/360 roller cam and lifter conversion
- Thread starter 659JR
- Start date
rocketbob
Well Known Member
No. There is no performance gain. Its only beneficial if you don't fly often.
David-aviator
Well Known Member
DakotaHawk
Well Known Member
David - nice (but useless) statement
. Care to continue on and give reasons why you wouldn't do it?Not trying to be snarky. Just wonder what your opinion is based on.
David-aviator
Well Known Member
David - nice (but useless) statement
Not trying to be snarky. Just wonder what your opinion is based on.
Lycoming spent a ton of money to get the roller cam system certified. It is designed into new engines and is not available as an upgrade to older engines.
I do not believe anyone has successfully upgraded the older engines to roller technology. A system was offered some years ago but nothing came of it. To jump into this deal has questionable benefits and certainly would place the buyer in a beta test mode.
That's why I would not do it.
Here's the questions I asked various engine builders last year when we were looking at engines for the clown car. After many years in aviation, these are the prime drivers for me:
1) Does it make more HP? A-minimal to none
2) Do they cost less? A-no, they cost more
3) Do they weigh less? A-no, they weigh more
4) Do the markedly increase the TBO? A-probably not.
There could arguably be advantages for engies that sit, or are abused maintenance wise, but overal no demonstrable benefit....only incremental at best for the 99th percentile of us that don't have radical cam grinds or rebuild our engines yearly.
That's just my 2 cents as usual!
Cheers,
Stein
1) Does it make more HP? A-minimal to none
2) Do they cost less? A-no, they cost more
3) Do they weigh less? A-no, they weigh more
4) Do the markedly increase the TBO? A-probably not.
There could arguably be advantages for engies that sit, or are abused maintenance wise, but overal no demonstrable benefit....only incremental at best for the 99th percentile of us that don't have radical cam grinds or rebuild our engines yearly.
That's just my 2 cents as usual!
Cheers,
Stein
roller lifters
At this time they are more money than the flat tappets but with the problems that the flat tappets have had over the years it is a nice improvement. I have yet to find a shop that has seen a failure or a roller lifter or cam. In fact most engine shops are able to polish and reuse the cams at overhaul without having to grind them. ECI now has a repair process for the lifters that will decrease the cost as well.
As for converting older engines to the rollers that has been done to both the wide and narrow deck engines. They are doing them for both the experimental and Reno racers.
Jesse
At this time they are more money than the flat tappets but with the problems that the flat tappets have had over the years it is a nice improvement. I have yet to find a shop that has seen a failure or a roller lifter or cam. In fact most engine shops are able to polish and reuse the cams at overhaul without having to grind them. ECI now has a repair process for the lifters that will decrease the cost as well.
As for converting older engines to the rollers that has been done to both the wide and narrow deck engines. They are doing them for both the experimental and Reno racers.
Jesse
DakotaHawk
Well Known Member
Thanks! Now I feel more informed.
rocketbob
Well Known Member
Learned some new things about roller lifter setups that I thought I'd share.
When Lycoming originally developed the roller lifter setup they found that there was a significant gain in HP due to the reduction of internal friction losses. To keep within certification HP that they had to dial back the cam timing so the engine power would remain constant.
So if one deviated from this and was able to make a stock cam work with a roller lifter setup (which is possible) then there would be a significant benefit in power and volumemetric efficiency.
When Lycoming originally developed the roller lifter setup they found that there was a significant gain in HP due to the reduction of internal friction losses. To keep within certification HP that they had to dial back the cam timing so the engine power would remain constant.
So if one deviated from this and was able to make a stock cam work with a roller lifter setup (which is possible) then there would be a significant benefit in power and volumemetric efficiency.
Bob,
What is your source for this info? It is exactly what Garry at Ly-Con has told me, with the added bit that 15% was the reduction. Now the question becomes how many ponies @ 2,700 rpm are consumed overcoming internal friction on a flat tappet engine? When pressed for a number, an indirect answer from several builders is that 2Gs plus for a conversion can buy more horsepower in other ways than rollers.
John Siebold
rocketbob
Well Known Member
Same source, Garry.
The Lycoming roller tappets look an awful lot like a Chevy or Ford roller tappets. I would be interested in doing the machining if I could find a stock roller tappet body that would work, because a full set for a small-block Chevy costs about the same as a single unit for a Lycoming.
The Lycoming roller tappets look an awful lot like a Chevy or Ford roller tappets. I would be interested in doing the machining if I could find a stock roller tappet body that would work, because a full set for a small-block Chevy costs about the same as a single unit for a Lycoming.
az_gila
Well Known Member
It would seem to me that the same cam timing would actually be a different cam profile. Surely the geometry of a flat object sliding on a cam is different from that of a point contact....
On Windsor (small) block Fords, the only roller setup I'm familiar with, when Ford went roller they switched cam material from iron to steel. I presume, though I don't know for a fact, that it was done for wear reasons. Are Lycoming flat tappet and roller cams made from the same metal? Just curious.
rocketbob
Well Known Member
Certainly a different cam profile would be desired when using a roller cam with higher lift and longer duration, which the stock Lycoming roller tappet cams don't do. Most automotive cams have a small angle ground into the profile to make the tappet rotate and I'm not sure that Lycoming cams are this way. I would guess not. But with a stock cam assuming that it is flat used with a roller tappet, you would get more lift on either side of the cam profile but the duration at the top would be shorter.
This is very true. Roller lifters allow for a very different / more flexible cam profile. I have the first version of Superiors roller lifters. Not ideal if I ever needed to remove them, but when I do a simple case mod will allow me to use their newer version.
I have seen a lot of ruined cams for a number of reasons. Why not go with something new?
