Comp XFI Lobes for Carbureted Application?

[M_Body_Coupe]

Have any of you guys run Comp XFI hydraulic roller lobes in a carbureted application? I've read that they're designed for fuel injected applications, whatever that means.

Are these lobes relatively hard on valve train components in an application that's driven quite a bit?

What a superb timing to ask this question!!!

So I've been running a custom ground Comp Cams hydraulic roller cam (see attached spec sheet) in a 408 W2 stroker build here. Car is a summer cruiser though, so far from a daily drivers. However, I have put on a serious amount of engine RPMs given the rest of the drivetrain setup - 727 with 4.10 gearing, so this thing buzzes at cruise.

This grind is using a 13084B intake and 3039B exhaust lobes.

My setup is an Edelbrock Victor single plane intake with a Carter TQ 9800 series carb feeding "da beast"! lol Using their beehive springs, Harland Sharp W2 rockers, and B3 geometry correction kit.

I did not custom spec this cam, bought it new when someone passed on it...and before anyone cringes I picked that up b/c it was a nearly the same specs duration wise as my old Hughes Engine HE3844AL hydraulic flat tappet, and this was my first trip into the "roller territory". The CompCam piece though is 112 LSA while Hughes was a 108 grind.

So what can I tell you? In short, I wish I had gone with a larger cam (the stroker easily eats this up and there is just way too much torque on the bottom end with a 4K converter and 4.10 gearing anyways).

What I do particularly like here is that the hydraulic roller cam actually gets me about 1-2" of vacuum more at idle (9-10" at 850-900 RPM) compared to the flat tappet. Granted though, that's 112 LSA (with 4 deg ground into it) compared to a 108 LSA cam, so it's hard to tell WHAT actually netted me the better behaviour: the wider LSA or the roller lobes?

Here is a bit of a toot-my-own-horn move:

Anyways...I did a bunch of research into this to try to understand the whole XFI lobe theory. CompCams doesn't seem to publish any other details on these, although I have spotted multiple mentions of "...Xtreme Engergy is the more suitable lobe for carbureted applications...", alas, no explanation what so ever for why that is, and guessing about the actual lobe design is...well, pure speculation!

For my part the next step is to move to the QXI lobes because these have much more lift and my W2 heads flow well all the way up to .700", so I might as well take advantage of that capability.

Subsequently, my follow-up question is: has anyone used the QXI lobes??? LOL

...oh, and if I can push my luck further: given the current 240/248 @0.050 duration, what would you consider the be the next step-up size to move to?

 

[360duster]

Thanks, that's interesting. Yeah, I'd like to see a picture if you've got one. I was told by the guy at Comp (whatever that's worth) that their iron roller shelf grinds are all SADI. Like this one I had acquired and sold earlier this year. Sounds like it isn't?

View attachment 1716489054

View attachment 1716489055

Here's a photo of the cam, the right one is the one we are talking about:

 

[Newbomb Turk]

SADI = Selectively Austempered Ductile Iron

Yeah, there was a name for the cores that were billet with the pressed on iron gear.

I’ll say it again. I don’t care what heat treatment they use I won’t use a roller on an iron core. Not even a Hyde roller unless it’s damn small.

 

[mopowers]

What a superb timing to ask this question!!!

So I've been running a custom ground Comp Cams hydraulic roller cam (see attached spec sheet) in a 408 W2 stroker build here. Car is a summer cruiser though, so far from a daily drivers. However, I have put on a serious amount of engine RPMs given the rest of the drivetrain setup - 727 with 4.10 gearing, so this thing buzzes at cruise.

This grind is using a 13084B intake and 3039B exhaust lobes.

My setup is an Edelbrock Victor single plane intake with a Carter TQ 9800 series carb feeding "da beast"! lol Using their beehive springs, Harland Sharp W2 rockers, and B3 geometry correction kit.

I did not custom spec this cam, bought it new when someone passed on it...and before anyone cringes I picked that up b/c it was a nearly the same specs duration wise as my old Hughes Engine HE3844AL hydraulic flat tappet, and this was my first trip into the "roller territory". The CompCam piece though is 112 LSA while Hughes was a 108 grind.

So what can I tell you? In short, I wish I had gone with a larger cam (the stroker easily eats this up and there is just way too much torque on the bottom end with a 4K converter and 4.10 gearing anyways).

What I do particularly like here is that the hydraulic roller cam actually gets me about 1-2" of vacuum more at idle (9-10" at 850-900 RPM) compared to the flat tappet. Granted though, that's 112 LSA (with 4 deg ground into it) compared to a 108 LSA cam, so it's hard to tell WHAT actually netted me the better behaviour: the wider LSA or the roller lobes?

Here is a bit of a toot-my-own-horn move:

Anyways...I did a bunch of research into this to try to understand the whole XFI lobe theory. CompCams doesn't seem to publish any other details on these, although I have spotted multiple mentions of "...Xtreme Engergy is the more suitable lobe for carbureted applications...", alas, no explanation what so ever for why that is, and guessing about the actual lobe design is...well, pure speculation!

For my part the next step is to move to the QXI lobes because these have much more lift and my W2 heads flow well all the way up to .700", so I might as well take advantage of that capability.

Subsequently, my follow-up question is: has anyone used the QXI lobes??? LOL

...oh, and if I can push my luck further: given the current 240/248 @0.050 duration, what would you consider the be the next step-up size to move to?

View attachment 1716489126

View attachment 1716489127

Thanks. That's a pretty mean idle. I'm shooting for something quite a bit more tame so I can comfortably cruise it on the road and have it last a long time. I'm just not sure if the XFI profiles are the right choice for that application. That said, the BluePrint 408's have the shelf 236/242 comp that uses the XFI lobes, so who knows.

Here's a photo of the cam, the right one is the one we are talking about:

View attachment 1716489176

Thank you. Are you sure the cam on the right isn't a billet piece? Do you have a close up picture?

 

[360duster]

have to check the old computer.....will do this evening.

here we go:

 

[BSB67]

Have not used the XFI lobe. If I was building a HR motor and thought that the lifter could keep up, I would use them without a second thought.

 

[MadScientistMat]

Typically, a so-called EFI cam is designed to work well with a factory ECU and a factory tune. With Comp being Comp, they probably are thinking more of Chevy mass airflow sensors. The main problems these can have are with intake reversion or fuel being sucked out the exhaust during overlap. Vacuum signal is less of a concern than on a carb, but if you have the intake valve opening late to limit reversion and low overlap, you're not going to have a cam that's especially rough at idle anyway. Not anything I would worry about.

 

[mopowers]

have to check the old computer.....will do this evening.

here we go:
View attachment 1716489398

I'm no pro by any means - not even close, but that looks like 8620 billet steel to me. Hopefully someone who knows better can chime in.