POLL: Why use a flat tappet over a roller cam?

Would it be acceptable to have a roller cam with Edelbrock heads and just roller tip rockers?

 

Hello Jim, the Lunati cam you tested gave up 75 hp because it was not able control the valvetrain dynamics . I was thinking that the valve seat pressure was some 30# low (correct me if I am wrong) I do remember that you used comp cams lifters & custom pushrods. I would like to see a dyno test with differant springs & mech. lifters . It would be interesting to see what the hp numbers are with the valvetrain was under control.
I have a NIB cam of the same p/n I would donate if interested

 

I really do not see a problem with a hyd flat tappet cam lasting 100K miles with the correct oil as I am sure a lot of these older cars have that many miles on them. <o></o>
Looking at all the posting I think someone running mostly stock parts is as good off with hyd flat tappet cam, especially if staying 5500 or under. I see the roller really shines as the RPMS rise above the 5500 mark. I think that most people making power in that range and above have changed heads, rods and other Buick stock weak parts.

One of the very important things I see is to pick the correct cam for the application and Not to over cam.
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I think this is a good informative post for all.

Thanks to all you guys for this info.<o></o>
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Nelson<o></o>

 

a stock flat tappet cam doesnt have the spring pressure that flattens lobes.

 

Do roller rockers have to be used when running a hydraulic roller cam?

 

Using TA's catalog as a reference, a trend seems to emerge: anything .500" lift and over TA 'recommends' using their roller rockers. .499" and below states 'stock rockers ok'.

One might be able to 'cheat' a little here and go a little over .500" lift with stock rockers (or at least the extra thick stock type rocker shafts), but where the safety threshold is, who's to say.

 

Would someone point me to that link..

 

one other aspect everyone seems to be overlooking is that with a roller cam, you can do a cam swap later down the road if you want and you only need to buy a cam, reuse the lifters and everything else. Also, No cam breakin. Maybe you decide somewhere down the road to step up the motor or to tone it down, or whatever. Simply swap the stick. Guarantee you down the road soon you will see guys selling roller cams by themselves because they made a change out. No more asking, do you have the lifters with that.? I know plenty of people who have wanted to change up , or down their cam , but did not want to go through the hassle of new cam, new lifters , and new breakin proceedure hoping they don't kill the new cam. Just saying.

 

Very good point. One I was thinking about the other day. I would LOVE to use a mild roller cam setup for a mild engine. Just have to overcome the initial cost is all, which is pretty much the only drawback to using a roller setup. Well, the cam (from TA) would have to be .465" or larger, which to many would not be an issue.

Not sure how long the lifters would last over a mild flat tappet. As long as the needle bearings held up, I imagine you could get well over 100,000 miles out of it, possibly over 150,000...but there'd have to be some preventive maintenance to replace the lifters after so many miles to ensure the needle bearings don't take a dump all throughout the rest of your engine.

Not sure how much I'd trust that, knowing that aftermarket vendors don't want things to last a long time, they want things to perform and wear out.

 

I'm sure their have been hiccups here and there but generally speaking TA Performance is not prone to selling junk. I imagine their roller lifters would fall in the same category..their roller rockers are built for war..

---------- Post added at 08:04 PM ---------- Previous post was at 07:59 PM ----------

With the lifts the roller cams are easily capable of it would be a smart move to get the roller rockers. Is a Hydraulic roller cam perfectly quiet? Or is there a little bit of the sewing machine noise? Not worried about a little bit of noise but a quiet valve train would be nice for a change.

 

By all means, get the roller cam, lifters, and rockers.

No one ever said TA sold junk.

I'm also quite certain that if one were in the business of selling things, one would not discourage others from buying their products.

TA says 'some customers have reported over 100,000 miles on these rockers' talking about their rollers.

So figure on a rebuild every 100k miles, which isn't so bad, for preventive maintenance.

Most racers won't worry about miles on an engine anyway, since their wallets will burn yet another hole figuring out where to upgrade their machine next. If it manages to last 100k miles, I guess you got your money's worth! :TU:

 

I'm with you, I think long term roller lifter durability is still a valid concern. Brought the subject up on page 1.

Devon

 

I am not really cocerned about the roller lifters,Th eOEM has been running roller lifters for years now . Th eonly time I would worry about the roller lifter failing is for the guy who rarely changed the oil, but if you do that, the engine aint gonna last anuway so what is the difference.? The roller bearings do not like dirt or grit, so normal maintenance should be fine.I have seen many many many stock engines go 200,000 miles with no rebuild, no lifter problems and no cam failures.

 

I guess I have to ask..

Who drives a classic car 100K miles????

No one I have ever known.

 

Just thinking about it again after the idea about lifter reuse was brought up. And I have no idea whether the roller/bearing design was borrowed from OEM, or just piggybacked from the typical race solid roller, which certainly would not likely see high mileage, thus the "unknown".

Devon

 

100,000 was just a round number I pulled out of the air. Racing engines surely will not see this before needing some attention, but if you think about it, it's all relative. Everything needs maintenance eventually, and preventive maintenance is the best way to ensure something lasts as long as it can.

It's not uncommon for a stock engine, even the old flat tappet ones, to see over 100k-150k miles before needing a rebuild. Most classic cars have odometers that have flipped at least once already, yes? And if not, then it's considered low miles for a car so old.

We all have to change oil at certain intervals, tune-ups, etc. when things wear out. Tires need replacing, gas tank needs refilling. For those who are racing enthusiasts, it is expected that these intervals will occur more frequently. However, for a daily driven street machine designed to be mild and conservative, with enough power on tap to do the occasional goofball burnout or even to just get out of its own way, longevity and durability are paramount.

The biggest concern for roller lifters isn't so much how long they'll last, but when to change them for maintenance. It's something that won't exist with a flat tappet cam, and if it wears out the engine at least limps along until the next rebuild, without needle bearings scattering throughout the engine...

So I suppose everyone who uses a roller cam setup has a ticking time bomb on their hands. It works great until the lifters fail, then it's time for a rebuild for sure! Just how long it takes for that to happen, who knows? The lifters may work like new one day and fail the next. There's inherent risk to running any engine beyond the factory designed parameters, of course, but the closer to stock you can leave one, the longer it would last I'd imagine.

So my issue here isn't so much performance oriented as it is longevity oriented, which not many consider to be an issue with roller cams since they're typically set up to give as much power as possible.

Seems the bearings on roller lifters would last a while under lighter spring pressures and lower lifts/RPMs though. It would be a nice setup, though it would be even nicer to know about when to change the lifters for preventive maintenance.

Cars with timing belts....last a certain length of miles, and sure they can go a bit further after that, but you never know when they're going to turn loose, and when they do, catastrophic failure occurs. Knowing when to change them ensures that the engine will live a nice, long life.

 

Yeah, but one thing that does exist with flat tappets is wiping out cam lobes. I know because I wiped one out about 3 and a half years ago. The end of the lifter was chewed up too. Having hundreds or thousands of little flakes of iron and steel floating in around in your motor is every bit as bad for it as some needle bearings. Had to replace all the cam/rod/main bearings and everything had to be disassembled/inspected/cleaned to get it all out. A big PIA is what it was

It wasn't available at the time but I would have absolutely went with the roller cam if it had been. The roller rockers are also quieter than the flat tappet cams and throw in the fact I don't have to worry about wiping out cam lobes its a win/win in my book.

As for the rollers I wouldn't worry one bit about them, they've been in use since the 80's. I've heard and read of a lot more flat tappet problems than I have roller rockers.