HFT vs SFT Cam Identification

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gzig5

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Can I determine if a cam is a solid or hydraulic by some feature on the lobes or something else? I have a cam that came in a 65 273 Commando short block but there were no lifters or heads, just the cam, pistons, rods, and crank. It looks like it is in pretty good condition and from measuring the intake lobe it seems to have .313" lobe lift, which would be .470" lift with 1.5 rocker. That's a bit more lift than stock and if I can figure out whether it is SFT or HFT I might use it in my 340 with J-heads, depending on the other specs. I have a gut feeling that it is a SFT because it came from an engine that originally would have had SFT, has the high compression Commando pistons, and the cam is higher lift than stock. But how do I tell? I have a degree wheel, V-blocks or lathe to mount it in, and plenty of dial and test indicators. I've googled but haven't found a method to determine if the lobe is for a SFT or HFT lifter.
 
The easiest way by far is to find a shop that has a Cam Master machine
and put it on it!
The hard way is to put it in you block with a mag base on your lifter and
a pointer (clothes hanger or similar) and a degree wheel. That will give you
a idea of duration @ 50 and rate of lift on the ramp of the camshaft starting
to open.
Boy I wish there was a easier way = I know because I have 100 plus camshafts
and 1/2 do not have the card and no # on the back or it is obsolete.
 
Years and years, decades ago; I read that;
Solid lifter cams have two ramps; a clearance ramp and the usual acceleration ramp.
By degreeing the ramps below .050, and analyzing the data as to lift per degree/per degree/ you can find the switch point. or not. If you find it, it's a solid. If you don't, it's not.
IDK if that's true, but that's how I remember it.

The thing is, the lobes are not flat across, so IDK how accurate V-blocks would be. To find the wear on my used 340 cams, I chucked them in a lathe and rubbed the indicator down the center of the lobes.
There is a lot of tedious math involved ............
 
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Yes on the ramps. the solids had a run up ramp and then the lift, same long ramp on the back end. the Hydro cant have a run up (they just pop up and down and then flat line for ~220 degrees of cam rotation) as the lifters will pump up to lowest point of lobe and stay pumped at that point so a run up ramp will bleed cylinder pressure with a very slight valve opening.
 
You do not need to go as high as 050 tappet lift to determine if it is SFT or HFT, will not tell you anything. You measure from zero lift to about 0.020 lift. It can be really difficult to get a definite answer because the line between sol & hyd has become blurred over the years, with some companies making cams that can be used with hyd or sol lifters; these cams have longer ramps than more conventional hyd cams & shorter ramps than conventional sol cams.
A couple of guidelines may help.
Here are some cams that I have degreed. Durations @ 002 & 012 lift: 296,264; 294,264; 295,265. These were all conventional hyd FT cams, not the hybrid above.

These are sol cams: 338, 293; 318, 290; 334, 298.
You can see the ramps are longer with the sol lifter lobes.
 
Bewy said:
You do not need to go as high as 050 tappet lift to determine if it is SFT or HFT, will not tell you anything. You measure from zero lift to about 0.020 lift. It can be really difficult to get a definite answer because the line between sol & hyd has become blurred over the years, with some companies making cahe ms that can be used with hyd or sol lifters; these cams have longer ramps than more conventional hyd cams & shorter ramps than conventional sol cams.
A couple of guidelines may help.
Here are some cams that I have degreed. Durations @ 002 & 012 lift: 296,264; 294,264; 295,265. These were all conventional hyd FT cams, not the hybrid above.

These are sol cams: 338, 293; 318, 290; 334, 298.
You can see the ramps are longer with the sol lifter lobes.
Click to expand...

I agree the ramps are over well before .050 but it would probably would also
be useful to check the duration @ .050 to see if the cam would be effective
for his application. It appears that he does not know much about it at all.
 
OK, a parallel (sort of) question. I may need to have a cam reground. Reading the above posts suggests if the cam was originally a SFT, it could be reground for a HFT profile, yes? Or is there something else that differentiates solid from hyd cams beyond the 3-bolt solid face? As a follow up, I've read somewhere there are occasions when some mismatched lifters/cams can be used (i.e. hyd lifters on a solid cam). Is this true and, if so, what are the combos that cannot be used? Are there advantages or disadvantages to doing this? I prefer to keep same with same but would like to know for my education. Appreciate any technical help on this. Thanks.
 
mayhem said:
OK, a parallel (sort of) question. I may need to have a cam reground. Reading the above posts suggests if the cam was originally a SFT, it could be reground for a HFT profile, yes? Or is there something else that differentiates solid from hyd cams beyond the 3-bolt solid face? As a follow up, I've read somewhere there are occasions when some mismatched lifters/cams can be used (i.e. hyd lifters on a solid cam). Is this true and, if so, what are the combos that cannot be used? Are there advantages or disadvantages to doing this? I prefer to keep same with same but would like to know for my education. Appreciate any technical help on this. Thanks.
Click to expand...

Yes, you can take a SFT cam and grind HFT lobes on it, but like any regrind you can only change the profile a small amount.

I never use hydraulic lifters on a solid lobe, but I will use a solid roller lifter on a hydraulic roller lobe.
 
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