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Re: roller vs mechanical flat tappet cam?
[Re: jyrki]
#1260972
07/04/12 05:16 PM
07/04/12 05:16 PM
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Joined: Jan 2003
Posts: 6,840
The Swamp
Sixpak
master
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master
Joined: Jan 2003
Posts: 6,840
The Swamp
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Quote:
I converted to a roller in a street car around 1994. The reason was that I wiped out three MP cams during a short period. I have used dozens of different cams since then in different build ups. In my opinion, there isn't an absolute truth here. There really is a reason why the OEM manufacturers use rollers nowadays too, it just makes more power than a similar flat tappet. It also accepts way more aggressive grinds, which requires and can use way stiffer valve springs etc. That of course stresses the other valvetrain components alot more than a flat tappet will ever do. However, a similar flat tappet would kill everything + itself there immediately. In a race car with frequent checking and maintenance, I would say go for it. And with an aggressive race grind. In a streeter, if you pick a "street roller" that doesn't require extreme spring pressures etc., I would say that the relaibility is at least as good as with a flat tappet, but the manners and power better. The real question is, that is the advantage for you worth the 1000$ or so you have to spend upgrading?
What I understood for the switch to roller cams by the OE's was that in the mid 70's when Catalytic converters and unleaded gas became the norm in the US, the converters started getting contaminated by the zinc and other oil additives that promoted better wear on bearing surfaces. When they started cutting the zinc in the oils to save the converters the cams and lifters started failing. I remember a rash of bad cam and lifter failures in a lot of 305 Chevy's in the early 80's that may have been partially due to this. So to get around the loss of wear additives, the OEs switched to rollers.
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Re: roller vs mechanical flat tappet cam?
[Re: cheapstreetdustr]
#1260974
07/04/12 07:48 PM
07/04/12 07:48 PM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
master
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master
Joined: Oct 2003
Posts: 7,506
Az
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Thanks, but I didn't really need an explaination of why a roller is better than a flat tappet cam. point is, if your application can't utilize the extra area under the curve, it's a waste of $. Yes, there is a point of no return in regards to aggressive lobe ramps, and it applies to roller cams also. With flat tappet cams, that point is usually determined by the lifter diameter. With rollers, the point is usually determined by how strong you can make the rest of the valve train. I still contend that if you are running a cam under .650 lift, the negatives to running a roller outweigh the positives. You pays yo money and you takes yo chances. 
Fastest 300
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Re: roller vs mechanical flat tappet cam?
[Re: Crizila]
#1260975
07/05/12 03:28 AM
07/05/12 03:28 AM
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Joined: Jan 2003
Posts: 2,932
Finalnd, Perkele
jyrki
master
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master
Joined: Jan 2003
Posts: 2,932
Finalnd, Perkele
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for me, running a flat tappet gave three negatives in one summer, wiped out cams and the consenquences. After that rollers in my own use, some occasional harm either from own stupidity or from the parts getting tired. I think I have hade maybe ten lifter failures, a couple from wearing out and some others loosing pushrods etc. The cams may have gotten some scars, but nothing you can't fix yourslef. Some rocker failures too, the aluminum ones get tired if you stress them and break after a lot of cycles, just like aluminum rods. Our stuff has been relatively low rpm, so the weight is not a huge factor. Although the current one has a red line of 7700, it has been together for three summers without problems. Forgot a couple of hurt valvepsrings during this time, but since switching to endurance springs, there hasn't been any problems. In an old Hot Rod magazine they compared similar grinds on hyd flat tappet, solid flat tappet and roller designs. The roller won clearly, they produced a broader tq curve. And that's also the reason the OEM went with rollers; while having the cam adv. degrees low to meet emissions, you still get more area under the curve and retain, or increase the performance. Like I wrote before, there is an advantage, but is it worth the 1000 or so in your case is the hard question. You might spend it elsewhere for even bigger advantage. My next engine, a 340 W2, will most likely use a flat tappet because it's a budget build. We'll see wether the decision is right or wrong.
Plynouth VIP '67 TT IC EFI
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Re: roller vs mechanical flat tappet cam?
[Re: A57_RT ]
#1260977
05/31/13 01:09 AM
05/31/13 01:09 AM
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Joined: May 2013
Posts: 80
new york
68HEMIRR
member
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member
Joined: May 2013
Posts: 80
new york
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Quote:
One set of these and you will never buy another set of solid lifters again and never eat a lobe.
These SM are the heavy ones at 73 grams vs a std old 828 comp at 88 grams and then the pig comp lightweight edm-s at 101 grams, just right with a johnson hylift hydro.
I use modest springs, middle of the road rockers, .116 walled pushrods and bang these to 7600 over and over.
As I posted one set is going on 4 flawless years in a street/strip car with comp rockers,springs and they are on there 5th camshaft.
So there are some flawless solid cam setups in use.
The only thing ive seen with these lifters is if you get near .700 more the spring pressure needed calls for a roller core with solid lobes, at least thats what the class racers are doing.
UNTIL THE GLUE SEPARATES AND THE LIFTER FAILS WHICH MINE DID.....700 SPRING PRESSURE I DID AND BLEW OUT 8 LIFTER CUPS.MY STAGE V HEADS WHERE BUILT BY FORHEMISONLY AND HE THOUGHT I HAD A ROLLER CAM....SO FORGET THAT IDEA
Last edited by 68HEMIRR; 06/01/13 10:28 PM.
BORN TO BE WILD
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