[Karck]

But if the cam lobe desings is same as flat tapped one? And one wants just the roller lifters?

[ponyakr]

Originally Posted by gtofreek

You cannot run hydraulic flat tappet cam springs on a roller cam of any sort that you can buy for a Pontiac...

So, are you saying that none of the cam companies will grind a custom Pontiac roller cam, with HFT spec lobes ?

If so, why can't a mild HFT lobe be ground on a roller cam core ? Most all the new vehicles have been running very mild roller cams, for many years now. So, is there something about a Pontiac roller cam core that won't allow the smaller HFT spec lobes ?

Yes, I know the aggressive roller lobes make more power. But, for those who just want the longevity and other advantages of the roller valve train, but neither need nor want the big power, why can't they get a roller, with HFT spec lobes, which can then run the lighter HFT springs ?

[Karck]

Actually why cant i just use roller lifters on flat tapped cam? Are pontiac Cams also Allingment in slight angle to reduce cam movement? Or are they stright, theres thrust plate after all in pontiacs.

[ponyakr]

Originally Posted by Karck

Actually why cant i just use roller lifters on flat tapped cam? Are pontiac Cams also Allingment in slight angle to reduce cam movement? Or are they stright, theres thrust plate after all in pontiacs.

HFT cam core material not compatible with roller lifters. Roller lifters can only be used on roller cam cores. At least that's what I've read. If I'm wrong, somebody please correct me.

[Karck]

Originally Posted by ponyakr

HFT cam core material not compatible with roller lifters. Roller lifters can only be used on roller cam cores. At least that's what I've read. If I'm wrong, somebody please correct me.

I fetched answer from Hot Rod forum, Yes HFT cams have lobes grinded on angle to turn the lifter. So it would break the roller in no time.
And ofcourse whit HFT you will loose the advantageous shape that rollers can use.

[pontiacman63383]

Wow this has turned into an interesting thread about roller vs flat. I'm learning a bunch from you guys. Keep the info flowing. Also does anyone have the grind specs for "old faithful" by change so I can get an idea on what kind of cam it is

[Will]

Check out SD Performane's website, I believe they have the basic specs there.

[lust4speed]

Originally Posted by ponyakr

So, are you saying that none of the cam companies will grind a custom Pontiac roller cam, with HFT spec lobes ?

If so, why can't a mild HFT lobe be ground on a roller cam core ? Most all the new vehicles have been running very mild roller cams, for many years now. So, is there something about a Pontiac roller cam core that won't allow the smaller HFT spec lobes ?

Yes, I know the aggressive roller lobes make more power. But, for those who just want the longevity and other advantages of the roller valve train, but neither need nor want the big power, why can't they get a roller, with HFT spec lobes, which can then run the lighter HFT springs ?

Also, there are plenty of very mild hydraulic roller cams - we just don't bother to talk about them much. In my Cruiser engine I've got a Crane hydraulic roller with 214/222 duration at .050" that idles pretty much like an old 067 Pontiac cam (this HR has .536/.560 lift with 1.65's). Very mild characteristics, but even running 87 octane with 8.4:1 compression, the engine produces 360 horsepower at the flywheel. It's a little quicker than my H.O. car was when new, and does it on regular fuel. Gotta love the roller cam characteristics.

[pontiacman63383]

alright guys, should be my last real question. It looks like I will be full roller hydo with the old faithful cam and 1.65 rockers. what length push rods would I need and what kind of valve spring pressure should I be looking for?

[Steve C.]

Keep in mind the heavier weight of a hydraulic roller lifter over a Hydraulic flat tappet lifter. Always run enough seat pressure to control the valve action as it returns to the seat. When in doubt, run slightly more seat pressure . . . not less.


.

[Steve C.]

The copy of the 'Old Faithful' cam card has been posted here on PY before on numerous occasions.
From them:

Part number 51-000-9
Grind number P8 3122B / 3120B HR112.0

Rated 289 / 306 at .006" tappet lift
236 / 245 at .050"
Lobe lift .3800" / .3830"
112 lobe separation / 108 ICL

Beware as noted here in this thread with a 1.65 rocker ratio in theory the valve lift will be 0.627" intake & 0.631" exhaust with that cam. I say in theory because depending on the manufacture the ratio could be less, or more.

Do your homework as to what might be required regarding the installed height on the cylinder heads to accommodate the increased valve lift. This in addition to enlarging the pushrod hole as already mentioned.


.

[Steve C.]

Asked previously here on PY within another thread:

"What is the seat pressure and installed height for the old faithful roller cam"

Answer posted by Dave Bisschop:

"To the OP, in most applications we use the Crane 99893 valve spring, installed at 1.790-1.810", I set the intakes on the tighter side of the tolerance, I test all the springs and always put the ones with the higher pressures on the intake valves, since the intake valves weigh more and also have the momentum of the charge pushing on the back side of the valve while the exhaust valve if anything has pressure pushing or drawing it closed and the valve is lighter. On my digital InterComp spring tester the seat pressures on a new set of springs will range from 147-157lbs typically @ 1.800" and 380-390lbs @ 1.200" open pressure."

Side note, regarding pushrod length. To be accurate you should measure and then order. Also, and important, the mention of the Crane 99893 valve spring is for conversation here, and not a recommendation by me. Personally I'd choose something else. And always remember valve springs typically lose some pressure after run in and over time.


.

[pontiacman63383]

Originally Posted by Steve C.

Asked previously here on PY within another thread:



Side note, regarding pushrod length. To be accurate you should measure and then order.

Personally I'd choose something else.

.

If you mean measure the old ones I don't have them, If not how do I measure. Also what would you personally choose?

[Steve C.]

Verifying Pushrod Length And Rocker Arm Geometry

http://www.compcams.com/Technical/In...20Geometry.pdf

Valve springs, two very good sources:

.http://www.racingsprings.com/

http://www.kmotion.biz/springsintro.htm


.

[Steve C.]

Also stated from someone within another thread:

"...the installed height in itself doesn't amount to a hill of beans. what you need to know in addition, is the COIL BIND HEIGHT, then you can calculate how much max lift you can run before reaching coil bind with the springs."

.

[ponyakr]

"...HFT cams have lobes grinded on angle to turn the lifter..."


I knew the lifters were not flat, and that the bores were offset, so that the lifters would spin in the bores. But, I never read or heard that the cam lobes were actually ground at an angle. So, thanks for that info. It was there online, all the time. But I just never saw it.

http://www.crankshaftcoalition.com/wiki/Lifters

[gtofreek]

It is impossible to grind a HFT lobe profile on a roller cam, for use with roller lifters. You can have one ground with the same @ .050" lift duration, but that would be the only similarity. Roller lobes need rounded noses so the lifter will stay in contact with the cam. If you try to grind it like a HFT lobe, the lifter will never stay on the lobe and destruction will happen very quickly. There is so much more to a cam lobe than just duration @ .050", advertised duration, and lift.

Originally Posted by ponyakr

So, are you saying that none of the cam companies will grind a custom Pontiac roller cam, with HFT spec lobes ?

If so, why can't a mild HFT lobe be ground on a roller cam core ? Most all the new vehicles have been running very mild roller cams, for many years now. So, is there something about a Pontiac roller cam core that won't allow the smaller HFT spec lobes ?

Yes, I know the aggressive roller lobes make more power. But, for those who just want the longevity and other advantages of the roller valve train, but neither need nor want the big power, why can't they get a roller, with HFT spec lobes, which can then run the lighter HFT springs ?

[ponyakr]

Don't know why I haven't thought about it sooner. But, Bullet Cams has a master list of HR lobes, which includes some VERY small spec lobes.

http://www.bulletcams.com/Masters/HRlobes.htm

So, even if they can not grind a HFT spec lobe(less the bevel) on a HR core, you can get a very mild roller cam, ground with your choice of any of the lobes on the list.

"... Roller lobes need rounded noses so the lifter will stay in contact with the cam..."

I never heard this either. I thought the roller lobes were round so that they would have more effective duration, above .050 lift. I assumed that with the high spring pressures, the lifters would stay on the lobes, regardless of their shape(within reason, of course).

I assume that there is a lobe shape, beyond which the roller lifter will not stay on the lobe, passed a certain rpm, with a given spring pressure. I also assume that you could increase the spring pressure to keep the roller in contact with the lobe, at a higher rpm. But at some point, the spring pressure necessary would be too high to be practical.

So, I reckin cam lobes are a compromise. You need the best compromise of lobe shape and necessary spring pressure, to provide the performance and/or longevity, fuel mileage, etc, you desire from your cam. Obviously, all out race engines, HP 500+hp street engines, and daily driver 400hp street engines, will require 3 completely different cam lobe grinds. But, the good news is, almost any grind you could need is available.

But, you may need a custom ground cam to get exactly what you need. I assume that many of the cam grinders charge quite a bit extra, for custom grinds. But, there are probably some who don't charge extra for custom grinds. So, will some of you guys who know, please post a list of all the cam grinders you know of, that will grind a Pontiac HR cam for a reasonable price. Please post info about those companies with whom you have had a good experience, ordering a custom grind. Please include contact info. This may help a lot of guys who read this thread. Thanks !

[gtofreek]

Plus, what would be the point of a roller cam ground to HFT specs? Might as well run HFT cam. I'm not convinced that aftermarket roller lifters are any more dependable than flat tappet lifters. Only thing is, when roller lifters go bad, they have the potential to do a lot more damage.

OEM's went to roller cams because they needed to in order to meet the current emission standards, and still make the power we want. Wasn't going to happen with FT cams. That's why these new 4 and 6 cylinder engines make as much or more power than the V-8's of the 70's.

Properly broken in FT cams run well over 100,000 miles generally, and some well over 200,000 miles. Anyone here seen an aftermarket roller cam and lifters go 100,000-200,000 miles in our Pontiacs? I've seen more roller cams or lifters fail than FT. The main reason people go to roller is for the roller cam power benefits, and better driveability.

[gtofreek]

There is a difference between a mild roller cam, and a roller cam ground with HFT cam specs. HFT cams can also be ground in very radical profiles, so just saying HFT cams specs, or profile doesn't necessarily mean "mild". Roller cams can be had in very gentle profiles, and they will make more power than a FT cam ground with the same duration @ .050" numbers, generally. There can always be exceptions to the rule, but generally speaking, if you have a roller cam with 214° @ .050", and a FT cam with 214° @ .050", the roller cam will make more power because it has more duration under the curve[at higher lift area where the head breaths better], than the FT cam.

FT cams, however, do open the valve faster in the first .050"-.100" of lift than a roller cam does. A good case in point is the 233/241 Voodoo cam. It has 233° @ .050" lift. At TDC it has the valve open .139" with a 1.65 rocker. BY comparison, I checked a roller cam[I believe it was the Old Faithful IIRC, which is 236° @ .050", but at TDC it had the valve open about .010" less than the smaller Voodoo cam did @ TDC.