Let's talk cams.

[DAN 05]

Since building my engine with ported heads and Hot Rod cams, I've had three different throttle bodies on it and the surging idle is not because of the throttle body.

I'm just repeating what they told me.

 

[AutoXRacer]

Figured I'd post it here. Not trying to highjack the thread or anything, but figured, lets include all things cams... lol

Hope yall don't mind.

If one were to go with Comp Cams 127450, what springs would you go with?
Would you go with lockers or limiters?

Would going all Comp Cams be better, springs, retainers, etc...?

Any benefit in going with titanium retainers vs steel on a street/strip car in the 600-700 rwhp range on pump and +800HP on E85/race fuel?

 

[martinr69]

the FRPP hot rod cams do sound good. I ran the comp cam mutha thumper in mine. I had o/r h pipe, sct 93 octane tune, delete plates, under drive pulleys, frpp 411 gears, and it was a DD.
Great sound and horse power for a DD. price prob was alittle more but worth it.

 

[BruceH]

Figured I'd post it here. Not trying to highjack the thread or anything, but figured, lets include all things cams... lol

Hope yall don't mind.

If one were to go with Comp Cams 127450, what springs would you go with?
Would you go with lockers or limiters?

Would going all Comp Cams be better, springs, retainers, etc...?

Any benefit in going with titanium retainers vs steel on a street/strip car in the 600-700 rwhp range on pump and +800HP on E85/race fuel?

You could get away with 26113 or 26125 springs. I'm running a cam that is very close to the 450 with 26113 springs and have revved it past 7200 without issue.

The rule of thumb is to lock out anything above a 26113 spring. Sometimes the 26125 work with limiters and sometimes they don't. The tfs springs usually need lockouts. If you do lock them out then set the intake centerline between 108 and 110 with tfs crank gears or by timing one tooth off which equals 8.6 degrees. IIRC the 450 and 550 both have an intake centerline of 102 degrees.

 

[05stroker]

If you do lock them out then set the intake centerline between 108 and 110 with tfs crank gears or by timing one tooth off which equals 8.6 degrees. IIRC the 450 and 550 both have an intake centerline of 102 degrees.

Why 8.6* Bruce?

Reason I ask is I have 127550 cams now heads up with the cams locked full adv. and plan to degree them -4* on the new setup with the tfs gears with 11.6:1 C/R and 20 psi. Manuel had asked me about -6* and I was leery.

School me please.

 

[BruceH]

Why 8.6* Bruce?

Reason I ask is I have 127550 cams now heads up with the cams locked full adv. and plan to degree them -4* on the new setup with the tfs gears with 11.6:1 C/R and 20 psi. Manuel had asked me about -6* and I was leery.

School me please.

8.6 is what one tooth is on the phaser. 360 degrees divided by 42 teeth comes in at 8.57. It's an easy way to get a good retard without having tfs gears.

I've done a lot of airflow testing with different combos of cams and retard. I'll tell you that lito is spot on with his recommendation based on the 102 centerline. You won't feel much difference down low but it will increase your top end airflow past about 3500 rpm.

My current cams are basically 127500 with a 113 lsa and 6 degrees of retard ground in. This makes the intake centerline 108 degrees. I took the time to plot valve events, degrees, and the corresponding airflows from logs. My tests were done at 0, 5, 10, 15, and 20 degrees of retard with 127400 cams. I verified that the cams were retarding as commanded. It can be a little tricky as there are some other parameters that affect cam retard and the tables don't behave like the others with imrc deletes.

The thing that I learned was my cams with a 108 centerline cover the best low and high rpm retards that I had with 127400. In other words someone really knew what they were doing by building in 6 degrees of retard. It can't be coincidence that my prior findings confirmed that these custom ground cams are optimized for max airflow at all rpms when locked out.

I don't know if any of that makes sense to anyone but me. I'm sure that there are differences in motors that might change the results a little but I'd say that -6 or a 108 intake centerline with the 550 lift and duration is going to help your top end while not affecting your bottom or mid by much if at all.

 

[DAN 05]

All that knowledge hurts my brain.

 

[05stroker]

8.6 is what one tooth is on the phaser. 360 degrees divided by 42 teeth comes in at 8.57. It's an easy way to get a good retard without having tfs gears.

I've done a lot of airflow testing with different combos of cams and retard. I'll tell you that lito is spot on with his recommendation based on the 102 centerline. You won't feel much difference down low but it will increase your top end airflow past about 3500 rpm.

My current cams are basically 127500 with a 113 lsa and 6 degrees of retard ground in. This makes the intake centerline 108 degrees. I took the time to plot valve events, degrees, and the corresponding airflows from logs. My tests were done at 0, 5, 10, 15, and 20 degrees of retard with 127400 cams. I verified that the cams were retarding as commanded. It can be a little tricky as there are some other parameters that affect cam retard and the tables don't behave like the others with imrc deletes.

The thing that I learned was my cams with a 108 centerline cover the best low and high rpm retards that I had with 127400. In other words someone really knew what they were doing by building in 6 degrees of retard. It can't be coincidence that my prior findings confirmed that these custom ground cams are optimized for max airflow at all rpms when locked out.

I don't know if any of that makes sense to anyone but me. I'm sure that there are differences in motors that might change the results a little but I'd say that -6 or a 108 intake centerline with the 550 lift and duration is going to help your top end while not affecting your bottom or mid by much if at all.

Thanks for the GREAT explanation! I will talk to Manuel more about the 6 degrees then.

Can I assume the 108 centerline is the goal above and beyond the 6* when degreeing the 550s, or the other other way around?

 

[BruceH]

Thanks for the GREAT explanation! I will talk to Manuel more about the 6 degrees then.

Can I assume the 108 centerline is the goal above and beyond the 6* when degreeing the 550s, or the other other way around?

That's a good question and brings up another point. All of my data might be off by a degree or two because I didn't degree the cams, lol. With that said I'd shoot for the 108 intake centerline.

 

[AutoXRacer]

You could get away with 26113 or 26125 springs. I'm running a cam that is very close to the 450 with 26113 springs and have revved it past 7200 without issue.

The rule of thumb is to lock out anything above a 26113 spring. Sometimes the 26125 work with limiters and sometimes they don't. The tfs springs usually need lockouts. If you do lock them out then set the intake centerline between 108 and 110 with tfs crank gears or by timing one tooth off which equals 8.6 degrees. IIRC the 450 and 550 both have an intake centerline of 102 degrees.

So in my configuration, I can only run the 26125 type springs since the 450 has .555 lift; the 25113 are speced at .550 max lift.

Comp Cams still specs limiters to use with the 26125...?????

Not sure what do you here, I like the limiter concept...but we couldn't control the cams with limiters with the 127300s. So with 127450 and stronger springs, I doubt we'll be able to control them.

 

[BruceH]

So in my configuration, I can only run the 26125 type springs since the 450 has .555 lift; the 25113 are speced at .550 max lift.

Comp Cams still specs limiters to use with the 26125...?????

Not sure what do you here, I like the limiter concept...but we couldn't control the cams with limiters with the 127300s. So with 127450 and stronger springs, I doubt we'll be able to control them.

Comp only makes limiters. I was able to command retard just fine with the 127400 cams but decided to lock them out with the increased lift of my custom 127500. I'm still using the 26113 springs though. Many people have used them with 550 cams.

You can lock yours out just fine though. I doubt you will ever notice any difference with a pd blower. Just be sure to retard them so your top end doesn't suffer.

 

[AutoXRacer]

Comp only makes limiters. I was able to command retard just fine with the 127400 cams but decided to lock them out with the increased lift of my custom 127500. I'm still using the 26113 springs though. Many people have used them with 550 cams.

You can lock yours out just fine though. I doubt you will ever notice any difference with a pd blower. Just be sure to retard them so your top end doesn't suffer.

So there won't be a noticeable difference between limiters and lockouts?

 

[BruceH]

So there won't be a noticeable difference between limiters and lockouts?

Not with your setup. Retarding the cams will take some low end power away but because you have a pd blower you will never notice imo.

 

[AutoXRacer]

Not with your setup. Retarding the cams will take some low end power away but because you have a pd blower you will never notice imo.

I guess going with the 10 degree lockouts is also pointless...???
What are these applications for?
20 degree limiter
10 degree lockout
Full lockout

Sorry for all my questions. I just like to consider all the options.

 

[BruceH]

I guess going with the 10 degree lockouts is also pointless...???
What are these applications for?
20 degree limiter
10 degree lockout
Full lockout

Sorry for all my questions. I just like to consider all the options.

Not at all pointless. 10 degrees of retard locked out isn't a bad place to be with some cams. If you are going to degree the cams you will need the tfs crank gears anyway so then the 10 degree lockouts don't make much sense.

A 20 degree limiter allows you to use a higher lift cam and ensure that there won't be valve to piston contact. Lockouts lock the cams out at 0 degrees for the same reason.

 

[AutoXRacer]

Not at all pointless. 10 degrees of retard locked out isn't a bad place to be with some cams. If you are going to degree the cams you will need the tfs crank gears anyway so then the 10 degree lockouts don't make much sense.

A 20 degree limiter allows you to use a higher lift cam and ensure that there won't be valve to piston contact. Lockouts lock the cams out at 0 degrees for the same reason.

At what point do you lose control of the cam timing?

For example, with 127300 cams, PAC 3V springs (still not sure what their spec is), and Comp Cams limiters (20 degrees), we were not able to control the cam. When you commanded 1 degree, they when 10-15 over; it was impossible to ramp them.

 

[BruceH]

At what point do you lose control of the cam timing?

For example, with 127300 cams, PAC 3V springs (still not sure what their spec is), and Comp Cams limiters (20 degrees), we were not able to control the cam. When you commanded 1 degree, they when 10-15 over; it was impossible to ramp them.

More than likely it was due to the springs. I had 127300 with 26113 springs and was able to command retard and see it in the data logs. Same result with 127400.

Almost everyone with the pac or tfs, or livernois springs ends up locking out the phasers because the springs are stronger than the phasers ability to control the cams.

 

[wht67]

More than likely it was due to the springs. I had 127300 with 26113 springs and was able to command retard and see it in the data logs. Same result with 127400.

Almost everyone with the pac or tfs, or livernois springs ends up locking out the phasers because the springs are stronger than the phasers ability to control the cams.

Been lurking in this thread since I am about to start my build. I bought used big valve ported heads that I had checked out by Modular Head Shop. They said I have heavy PAC springs on the heads. I have new Detroit Rockers for supercharged applications that I had planned to use but based on your information I am thinking about getting 127550 cams and locking them out. I have a FRPP Whipple HO and my build will include a IW 10% OD balancer so I will probably be good on the low end, what would be the best way to get the 127550 set to 108 centerline?

 

[RED09GT]

Something I haven't seen tried is to use the 26113 springs on the lighter intake valves and the PAC springs on the exhaust valve. Since the exhaust lobes have bigger lift and duration on most of these cams and the single exhaust valve is heavier than each individual intake valve, it would make sense to have more control with a stiffer spring on the exhaust valve. This would also put less strain on the phasers and may be enough to keep them happy with limiters.
I wish I had the budget to test this theory.

awesome autocorrect malfunctions brought to you by tapatalk

 

[retfr8flyr]

I have the Livernois springs and custom cams with the 127500 lift. I am using the Livernois limiters and haven't had any problems with the phasers. I had lockouts previously and I like the street manners with the limiters much better.


Earl