Vintage Mustang Forums banner
  • Hey everyone! Enter your ride HERE to be a part of this month's Ride of the Month Challenge!

61 - 71 of 71 Posts

·
Premium Member
Joined
·
404 Posts
Read all the post. I feel just running some roller Rockers in a flat tappet engine gets you a little bit more revs and won’t break the bank. I am running a 347 stroker. In my ride. It revs crazy I shift at 6500 Rs no issues. That’s my 2 cents. Never lost a cam in my life time. Been running small blocks since mid 80s
789993
 

·
Registered
Joined
·
6,581 Posts
Read all the post. I feel just running some roller Rockers in a flat tappet engine gets you a little bit more revs and won’t break the bank. I am running a 347 stroker. In my ride. It revs crazy I shift at 6500 Rs no issues. That’s my 2 cents. Never lost a cam in my life time. Been running small blocks since mid 80s View attachment 789993
SWEET ride!

Allen
 

·
Premium Member
Joined
·
13,885 Posts
Read all the post. I feel just running some roller Rockers in a flat tappet engine gets you a little bit more revs and won’t break the bank. I am running a 347 stroker. In my ride. It revs crazy I shift at 6500 Rs no issues. ......”
For what’s worth, Carroll Shelby had the 260 and then 289 HiPo engines in his first generation Cobra They were, of course, solid flat tappet engines and he red lined them at 7,000 rpm with the power dropping off around 6,500..

He advised new Cobra owners that if they needed to regularly hit 8,000 rpm to get what was then referred to as a “roller kit”, meaning roller lifters.

But most of the Cobra’s were 100% good to go at 7,000 rpm for as long as needed, in 100% stock form.

This photo is from my high school yearbook and was taken in front of our local Ford dealer sometime during the fall of 1965, just as the new 1966 models hit the showroom. I got to ride in both cars pictured. I was at this photo shoot, but behind the camera, heckling my classmates, especially the gals !

Z


789996
 

·
Registered
Joined
·
1,558 Posts
Your sketch illustrates the problem with flat tappet lifters and aggressive cam lobes. The lobe ramp angle cannot exceed the lifter “flat” such that the edge of the lifter digs into the cam lobe. That would equal instant cam/lifter destruction. Sure, the lifter will contact the lobe across its entire face as the lobe goes round and round, but if the contact patch between the cam lobe and lifter gets too small, say goodnight to the cam!

With a roller lifter, you can increase the ramp angle immensely pushing that lifter up to max lift in no time, more aggressively than you show in your sketch.
Absolutely. Although that situation is not yet reached in the sketch, it is easy to see that if the lift were increased, you'd reach the point where the lifter would dig into the lobe. But my main point was that you can't compare the "aggressiveness" of flat tappet and roller cam lobes by just looking at how rounded or pointy they are shaped.

And yes, the roller profile can be made more aggressive than in my example. But there's a limit to roller cam lobes too. Too aggressive a profile would result in too much side forces on the lifter and too high forces in the rest of the valve train. The increase in lift of a roller vs a flat tappet for a given duration is probably 0.050-0.075" I would say (e.g. .550 instead of .500 for a [email protected] cam)?
 

·
Registered
Joined
·
1,848 Posts
Absolutely. Although that situation is not yet reached in the sketch, it is easy to see that if the lift were increased, you'd reach the point where the lifter would dig into the lobe. But my main point was that you can't compare the "aggressiveness" of flat tappet and roller cam lobes by just looking at how rounded or pointy they are shaped.

And yes, the roller profile can be made more aggressive than in my example. But there's a limit to roller cam lobes too. Too aggressive a profile would result in too much side forces on the lifter and too high forces in the rest of the valve train. The increase in lift of a roller vs a flat tappet for a given duration is probably 0.050-0.075" I would say (e.g. .550 instead of .500 for a [email protected] cam)?
Totally agree. I would imagine too that you could get a higher gross lift with a roller than a flat tappet, given a flat tappet can only ramp up so fast. Most of us though do not require .600”+ of valve lift for our street driven cars (I don’t know the ramp limits of a flat tappet, just throwing a number out there), so a flat tappet most definitely serves the purpose of the masses.

Another thing I am curious about the differences between roller and flat tappet... for an engine application that will see extended high RPM use, be it 1/4 mile runs or roundy round a track or cones (something beyond the occasional stop light race or parking lot donut), will there be a benefit? Lower oil temps due to less friction?

I know roller setups tend to require higher spring rates to keep the heavier valve components from bouncing around uncontrollably, but I am curious if there is a side benefit to that higher spring rate with the operation of the engine/valve components.

There has to be some other benefits of a roller setup besides possible lift limits or marginally less friction. Although, it wouldn’t be the first time a car part manufacturer has duped its customers into buying something they didn’t need. 🙃
 

·
Registered
Joined
·
8,006 Posts
Just one more data point. My car's engine was rebuilt (upgraded) in about 1985. It has a high performance Crane flat tappet cam. It regularly exceeds 6,000 rpm, and I've never had a problem with it.

That said, if money were no object, I would undertake further upgrades and one of those would be a roller set-up.
 

·
Registered
Joined
·
51 Posts
I will throw out my experience with cam failure. Several years ago I changed the oil in our boat (460 ford, flat tappet cam) in the middle of the summer. It had been running fine, no problems, no noise. The boat had about 350 hours on it.
The next time on the water it lost a lobe on the cam about halfway across the lake.
I used a high quality synthetic oil and did not add any zinc.
I am a firm believer in roller cams now.
 

·
Premium Member
Joined
·
7,444 Posts
LSG mentioned a good point that struck me......What are the cam profiles considered "aggressive"? This can be a helpful point to consider.
 
61 - 71 of 71 Posts
Top