Flat v Roller Cams not what you may think.

[shane_3800]

Some interesting points by a man with lots of experience.

 

[someguy360]

A lot of engine builders in the know with Holden engines still prefer flat tappet over roller.

Both Frank from Dandy engines and Tony Knight from Knight engines who are both very respected in the industry both favour solid/mechanical flat tappet cams over rollers for their builds.

Pretty sure TK uses exclusively F280 and F288 crane cams for 355 builds these days unless the customer specifically wants something different. He swears by them as a good reliable way of getting 400hp from a 355.

I would have gone solid for mine but I already have a set of $700 YT non adjustable roller rockers that I don't want to replace.

The only time in Aus I've heard of flat tappet lobe failure with new/aftermarket cams in the past decade is:
A. Haven't used the correct oils to suit a flat tappet cam.
B. Had some sort of defect from the factory (theres been a few companies that havew started making FT lifters in china and some haven't passed break in).
C. People that haven't performed cam break in and just treat them like a Roller cam and fit them and let them idle (or spend 40 minutes trying to get them started).

If you look after FT engines and maintain them properly and don'tbuy into the fact that you need the latest and greatest synthetic oils with little zinc like modern engines, they'll last as long as any other valve train.

Lobe failure in the US is much more common as the EPA has banned zinc of any kind in engine oils. So people with flat tappet cams have to buy separate zinc addatives for every oil change, which doesn't happen if you take a car to your local mechanic or dealer. Also some just straight up aren't educated in oiling requirements for older engines or are unaware zinc is no longer in oils.

Oils ain't oils.

 

[shane_3800]

A lot of engine builders in the know with Holden engines still prefer flat tappet over roller.

Both Frank from Dandy engines and Tony Knight from Knight engines who are both very respected in the industry both favour solid/mechanical flat tappet cams over rollers for their builds.

Pretty sure TK uses exclusively F280 and F288 crane cams for 355 builds these days unless the customer specifically wants something different. He swears by them as a good reliable way of getting 400hp from a 355.

I would have gone solid for mine but I already have a set of $700 YT non adjustable roller rockers that I don't want to replace.

The only time in Aus I've heard of flat tappet lobe failure with new/aftermarket cams in the past decade is:
A. Haven't used the correct oils to suit a flat tappet cam.
B. Had some sort of defect from the factory (theres been a few companies that havew started making FT lifters in china and some haven't passed break in).
C. People that haven't performed cam break in and just treat them like a Roller cam and fit them and let them idle (or spend 40 minutes trying to get them started).

If you look after FT engines and maintain them properly and don'tbuy into the fact that you need the latest and greatest synthetic oils with little zinc like modern engines, they'll last as long as any other valve train.

Lobe failure in the US is much more common as the EPA has banned zinc of any kind in engine oils. So people with flat tappet cams have to buy separate zinc addatives for every oil change, which doesn't happen if you take a car to your local mechanic or dealer. Also some just straight up aren't educated in oiling requirements for older engines or are unaware zinc is no longer in oils.

Oils ain't oils.

I sort of beat you to the punch with the video I posted.

Another fact with flat tappets is with that initial burst of acceleration, you get a choppy pulse that, when used with a carb, not EFI gives you a very lumpy note, as the booster signal is pulsated more than with a kinder ramp rate roller.
You can hear the difference with street hydraulic roller cams they open and close the valve very gently, helping with the engine running smoothly.
Also, solid cams sound crankier, and you run into an issue using solid rollers on the street with wheel skid, because hydraulic roller cams always have pressure on the wheel you can run them at low speed, but solid rollers don't like low engine speeds for continuous periods like highway driving as the wheels start to skid and can flatten the cam/wheel. So for a street solid a flat tappet can be a good choice, but yes you risk flattening lobes.

 

[someguy360]

solid cams sound crankier, and you run into an issue using solid rollers on the street with wheel skid, because hydraulic roller cams always have pressure on the wheel you can run them at low speed, but solid rollers don't like low engine speeds for continuous periods like highway driving as the wheels start to skid and can flatten the cam/wheel. So for a street solid a flat tappet can be a good choice, but yes you risk flattening lobes.

I know probably 30-40 people running solid FT and solid roller cams on street cruisers without issue, most of which would be seeing low RPM/idle conditions 90% of their life

Lots in daily driving start stop traffic, I haven't heard of any failures specific to driving conditions.

I've not heard of any street engines wiht solid flat tappets wiping lobes for any reason other than incorrect maintenance or installation.

 

[shane_3800]

I know probably 30-40 people running solid FT and solid roller cams on street cruisers without issue, most of which would be seeing low RPM/idle conditions 90% of their life

Lots in daily driving start stop traffic, I haven't heard of any failures specific to driving conditions.

I've not heard of any street engines wiht solid flat tappets wiping lobes for any reason other than incorrect maintenance or installation.

I know these days both flat and roller you can get harder surface finishes that may be a contributing factor in the life of certain cam designs.

 

[Immortality]

I had a mate loose a cam on his 350 chev, basically every other lobe. Cam came from the US, big name supplier. Conclusion was the cam was ground wrong (taper on the lobe). A new cam was fitted by a NZ supplier along with matching lifters and fancy Joe Gibb break in oil used but that also resulted in the loss of a couple of lobes, this was put down to the engine not been stripped and cleaned well enough. 3rd time the charm and it lived.

The quality of the lifter/cam lobe machining finish is critical. I have only bought cams from NZ suppliers who grind their own. When the cam goes in on the 304 I'll mike up the lobes and see what sort of taper they have.

I believe TK used to recommend Camtech cam profiles ground to his specification but that unfortunately that is no longer an option.

Oils definitely ain't oils. It's been a long time since I believed the hype that modern fancy synthetic oils are backwards compatible with older engines.

DV also covers cam lobe failures in some of his books, big cams don't like low idle RPM. DV explains it quiet well so I won't regurgitate it here for you.

I know these days both flat and roller you can get harder surface finishes that may be a contributing factor in the life of certain cam designs.

Also different cam core materials are used depending on cam type.

 

[Immortality]

These might be of interest with regard to cam/valve train issues/failures.

and

 

[shane_3800]

These might be of interest with regard to cam/valve train issues/failures.

and

When Steve Morris talks about cams you listen, this is because he cut his teeth in Pro Stock racing; he doesn't do N/A now but he used to.

 

[Deuce]

When Steve Morris talks about cams you listen, this is because he cut his teeth in Pro Stock racing; he doesn't do N/A now but he used to.

Boost fixes everything (or breaks everything)

I believe that is his current motto

 

[Deuce]

These might be of interest with regard to cam/valve train issues/failures.

and

Yeah watched them the other day as they came out.
Was very cool and good though provoking material.