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

First, I'm starting this thread to get different views or a list of pros and cons, not to start a heated argument.
It will also help those looking at future builds so keep that in mind.

So here is one of several observations:
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There are a few BBB street/strip engines that have been or are in the process of being built with ported heads, headers,
decent intake and carb combinations and they also included 1.6 roller rockers.
So in the quest for horsepower a flat tappet cam was chosen.
In one of these cases the person has previously had a flat tappet lobe failure.
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Again, these engines already have the roller rockers so it is about $500 to $600 difference to use a roller cam in place of a flat tappet.
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You can use a roller with a lot less duration to make the same power.
The decrease in overlap makes for a lot better engine for the street.
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Or you can use a roller with about the same duration and make a lot more power than the flat tappet equivalent
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JW estimated there is as much as 60 hp to be gained at this build level by using a roller cam over flat tappet. (that included changing from 1.55 stock to 1.6 roller rockers)
That figures out to be around $10/hp if you already have roller rockers and about $17/hp if you need to change to roller rockers.
In either case it is a good deal.

Then there is the matter of flat tappet lobe failure. There is always that chance and if it occurs
then the money difference is gone with the added inconvenience.

So I would like to know why a flat tappet cam would be chosen over a roller in the above cases?
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Paul

I'm adding that it doesn't have to be just the above case. It would be good to hear about all the reasons for staying with a flat tappet cam in all cases.

Thanks in advance for all your replies.
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I thought one of the more interesting statements Jim made, and I'm paraphrasing, was the $1,000 cost for 60 HP on the roller cam where people spend over $2500 for heads for a 40 HP gain or so. The roller cam was a better HP/$ as you mention it being a decent cost.

 

As a self-assembler (read middle-aged shade tree mechanic), I have no experience with rollers and I'm not wanting to be the pioneer/guinea pig. I realize several have bit the bullet but I don't know about what it takes and I've run flat tappet cams all my life. I know there needs to be something, a cam bumper/button to limit the cam longitudinal walking but I'm not clear on how it needs to be setup so I'm going to pass for now on this build and be happy with the TA212 unless there is convincing reasons not to. I've searched on here for pics of the cam button/bumper setup but all I've ever seen is V6 stuff.

The stuff on TA makes it look like a considerable effort that makes me doubt my ability to get it right.

http://www.taperformance.com/PDF/Roller_Cam_Installation.pdf

 

Don't fear the reaper. Ask questions. Also, those directions are way old. The directions come with the roller cam bumper are clear as day and it really is super super simple. I'm a geologist and shadetree hack/mechanic. Thank you for the data point for Paul :TU:



My thumb is holding the roller bearing/bumper in, so with the cam installed and the intake off, bolt on the timing cover with a gasket, then push the cam forward and backwards, and note the movement. Then little shims that come with the bearing/bumper can be installed in the hole the bearing/bumper go into until the forward/rearward movement is in spec. then you're done! No extra oiling tubes, or other stuff. I've got over 16,000 miles on mine and its still going strong.


You can see one of the shims in the distributor gear, it's like a washer but with a very large hole in the middle.

 

This isn't the case in your example, but I've considered going to a roller cam and the only reason I haven't is due to the difference in the ouiling system between the earlier BBB (67-69) and post 70 BBB.
Being a 69 400, I'd have to change how oil feeds my rockers and I can't justify puling it all apart and spending the money unless I'm ready for a full rebuild.

So wen the day comes to rebuild the entire engine, I'll go roller. For now, I'm very happy sticking with the flat tappet and if I want to change only the cam, I'll stick with a flat tappet.

Like I said, not the situation you've outlined.

 

If you can afford to go roller I'd do it. Technology advances, yes, flat tappet cams work, roller cams work better, BUT they cost more. I guess it all depends on how much you want to pay to update a traditional Buick V8 to modern day spark ignition engine technology.

 

Lifter gallery failure? They make lifter gallery girdles for a reason. Quick action can put a lot of stress on the gallery. Have enough been installed to know when the gallery is flirting with failure? Do we know the effects with enough engines over time? Physics may tell us one thing while our old cast iron lifter gallery's may tell us another.

There are better engines to build for the ultimate in power. I like four valves and four cams better with roller followers. They are engineered for the application, and are not a retrofit with a lot of questions. Why risk yours with technology that has not been proven with enough examples over time in the given application? I'd sit back and watch for a while first!

Cheryl

 

Looking at the Ta website I don't see anything about 455 rollers other than solids. Is the price 700 for the cam and 700 for the lifters? Or is it like the price of the 350 roller cam

---------- Post added at 07:30 AM ---------- Previous post was at 07:29 AM ----------

And the fact that if you still have iron heads don't it make all the extra lift from a roller useless???

 

The only negative for a roller cam I can think of that hasn't been mentioned yet is lifter failure. When a roller tipped lifter lets go it is usually catastrophic (small roller bearings and misc shrapnel going everywhere).

I have no idea about frequency of failure and imagine it would be less frequent with a mild grind compared to the radical race-only grinds of the past.

Devon

 

im saying. if you have an engine with 9 to 1 compression with stock heads dual plane intake and headers. would it be better to go roller cam with 550 lift or heads first. because the cost of the roller is cheaper. but with the heads and a flat tappet it costs more but there is more gain at the time. then go roller later. but of course if your building a buick its easier to do a head swap later than a cam swap. at least in a car with manual brakes and no ac box.

 

I think the mild versus wild is the key. How often have you heard of an OEM roller lifter trashing a whole engine? They've been in millions cars since the 80's. I'm not concerned about mine at all. It also touches on the lifter valley topic, no braces required for the mild profiles that significantly increase area under the lift and HP curve, not enough pressure to break the lifter bores and not enough pressures to significantly cause wear on the roller parts. I've got 16,000 miles on mine so far and counting.

The catalog doesn't say if the TA lifters are bushings or pins, but I'd expect pins.

---------- Post added at 06:56 AM ---------- Previous post was at 06:52 AM ----------

I will add to this one that is a good point and I kind of forgot about, is the roller cam is not a simple "bolt on" upgrade, the cam bearings need to be replaced with the dual grooved ones, so the engine more or less has to be out of the car unless you are a glutton for punishment. I forgot about that part due to I try and do all my internal engine work with the engine out of the car.

 

This may hold true for a off the shelf flat tappet cam but I'm sure it would be less HP difference with a custom ground piece and saving a little $$ too

 

OK, can someone put together a sticky about the prereqs for a roller cam and the requirement when installing a roller cam?

I'm up for a group buy if it happens in the next 30 days. I already have TA 1559 Dual grooved cam bearings and only have the pan and front cover on today. I'm going to be getting a little anxious as the weather warms up.

 

I agree with the many benefits of roller over flat.

So I'm playing devils advocate in argueing in favor of FT:

The obvious economic advantage. As stated, it may only be a few hundred $ but that amount may be enough to break ones budget.
Idle rump/lick/thump/whatever. Some folks (myself included) like a nice rumpity idle. A FT gets you there with a smaller cam. A roller would have to be bigger (see below).
Too much hp. Don't laugh. Those of us that don't have a girdle (i.e., budget) might not want to push the block hard enough to break it. So a FT can "limit" the hp to a block-safe level. A roller with enough duration to have the "sexy" idle (see above) may be too much for the block.

 

Yes and yes! I wish the price of the roller set up would drop $200-$250. I stated before, that is the difference between me putting the set up in my occassionally driven Centurion when I go to rebuild the engine and not putting it in. As the price sits now, the Centurion will get a flat tappet cam come re-build time (actually probably one I already have laying around.. but if I didn't!).

And the too much HP thing is 100% valid. I am genuinely worried I am up against that thresh hold and possibly past. My current Skylark block has not had any sonic testing, visual inspection makes it appear the casting is relatively centered (I've seen worse), and I'm the one that bolted it together, with main studs no less. And I still want to go to a higher lift cam, lol.

 

Scott

Don't forget that you can have the roller cam ground on any LSA you want.
If you want a more rumpity idle then just have the cam ground on a tighter LSA.

These are some great replies.

Paul