To "Hybrid-ize" with Solid Rollers or Not This XFI Lobed Hydraulic Cam ?
 

Hey guys , I am the one who bought JLMounce's old custom KRE HR comp cam.

This cam was custom ground for KRE using 232-238 dur @050 lobes from from Comp's XFI , respectively the intake and exhaust lobes are #13081 b and #13141 b.

Got tired of searching for a used magnum lobed Stump puller, want to run hydrid set-up using Comp's Endure-X solid roller lifters I already have. I just want to finish my engine so pulled the trigger on this one.

This is going in my new 461 Stroker, 9.5 CR and 260 CFM @ .600 SD performance CNC #46 Irons. Cleaned up Holley SD intake and Q-jet. ( while I wait for my aluminum 71' HO intake to get done)

I plan on running HS 1.65 rockers .

So you cam and valvetrain gurus in the house:

-Do you consider the XFI TOO aggressive to run it Hydrid ?

-Should I just buy garden variety Hydraulic roller lifters for this somewhat mild street cam?

Its just that I have the Endure X lifters already and really dont mind setting valve lash since most my other cars are running Solid flats.

BTW here you have the cam specs and two screen shots of Comp's catalog for XFI lobes , My lobes are the one at the bottom at the page , (red arrow) intensity @ 200 are 156 and 160 respectively.

Thanks

The XFI is a bit aggressive for aluminum heads as a hybrid. It will work fine with your 46 iron heads, the expansion rate on the engine won’t effect the lash as much.

Looking at garden variety hydraulic roller lifters is where people get into trouble.
If you go the hydraulic route spend the dough and get hylift Johnson's.
Right now they are hard to obtain of course and be prepared for sticker shock, but if you want something durable with consistent bleed down rates that don't cause lash problems it's what ya need. Other wise you'll just be another guy in here complaining about sewing machine noise, tickers, and the like.

Or you can try the Comp Evolution HR lifters - they seem to be a good part.

Yes forgot to mention those. Not only are they priced more in line with everything else they also (so far) have excellent reviews. Plus they are readily available unlike the hylifts.

Agree on the Comp Evolution lifters. Had them installed on my 433 and they are quiet and smoothed out the engine.

I don’t want to derail the op too much.

What heads do you have and what length pushrods did you end up with? My adjustable PR is based on iron heads with flat tappets, so not sure if I’d need a different one if going to the evo’s. Thx

RMP,
I answered this for someone else and I be darned if I can find it. I'm doing this from memory hope it's right. My mechanic indicated he started with 8.5 inch PR and didn't like it and went with 9 inch PR. PR has a .008 thousandths wall chrome moly. The heads are cast iron and the cam is HR. Hope the info helps out, but have many variables involved.

After looking atbthe cam lobes in detail I really think such baby lobe can take solid rollers on a iron headed engine. Ill jeep an eye on em regularly dor the first year and mostly loosen them all each winters to save the springs.

Speaking of springs what you guys think , mu current springs are 1.700 installed height. Something like 170 on the seat and 370-390 on the nose once broken in?

I may explore the beehive world also if someone has played with this already. That engine should be done by 5500-5600.

Peter

After looking at the lobes in detail I really think such baby lobe can take solid rollers on a iron headed engine. Ill jeep an eye on em regularly dor the first year and mostly loosen them all each winters to save the springs.

Speaking of springs what you guys think , mu current springs are 1.700 installed height. Something like 170 on the seat and 370-390 on the nose once broken in?

I may explore the beehive world also if someone has played with this already. That engine should be done by 5500-5600.

Peter

If you take a look at the data overview of the XFI lobes from the master lobe catalog, Comp does state the lobes were developed specifically for beehive springs.

That said, I did not have beehives on my engine and I typically spun it to around 5600 rpm. I never appeared to have any stability issues with the hydraulic roller lifters in place.

Do you remember what springs, and installed height you ran? But If I run solid lifter Ill need a bit stiffer springs compred to your Hydraulic lifters.

This is really a baby cam

Comp told me 200 on a he seats with solid rollers.Tom

Thanks Tom.

I would not consider beehives unless you use HR lifters.

You only need to increase the seat pressure as a hybrid if you want to run a lot of lash, more lash, more seat pressure, and your not going to want to run much lash with that XFI cam, it is too aggressive off the seat, the lash ramp on the closing side is pretty short, and not that big of a cam. You loose duration with more lash.

On one of my hybrids with iron heads I run 150 on the seat and just over 410 over the nose (413 spring rate) .630”lift. I zero lash the intakes when cold, just have some friction when you turn the pushrods, then I run .005” lash on the exhausts. It tightens up some when hot. It operated very quietly, you can not tell it has a roller cam in it, the red line on it is 7500. It is pretty high strung, and a much less aggressive cam profile than an XFI.

For that small XFI cam I would shoot for 160 lbs and just under 400 over the nose and 1.65 rocker as a hybrid, and use a dual spring. With HR lifters you would be happier with beehives.

They are the springs that KRE setup for me. Don't quote me on this but I believe that they use Crower springs with something like 140 on the seat. No idea on install height, but I would assume somewhere around 1.7" My pushrods were on the shorter side at 8.7"

And yes, it's a baby cam.

I truly appreciate the insignt Jay, My heads have Comp's 995 springs currently installed at 1.700, installed at 1.600 they would be more like 150-155 lbs but maybe run into coil bind and they are probably a little tired.

What would you recommend for valvesprings, for 80% street.

Peter.

FWI,first of all the cam makers suggest if you want solid rollers get a tight lash solid roller cam and NOT use a hyd roller cam.Its a crutch.Also to error on the high side of spring pressures.Your choice.Tom

You would probably be on the high end of pressures like Tom is saying anyway, because the 1.7 IH isn’t really enough room to run 1.65HS rockers on that cam. It will end up around .610” lift with those rockers. There are some nice street springs you could run but they are near $500, used on LS platforms and gen3 hemi’s. About the cheapest spring at a 1.7 IH I can think of is a PAC-1200, would be plenty of spring on that, more than it needs. I think about 150 seat and 425 max.

An ideal spring with the 1.65HS rockers and that cam as a hybrid for the steeet is something like a compcams 26925 or Howard’s 98441 with the installed height set at 1.75”. I suppose you could adjust that with a +.050” keeper or retainer.

I am not trying to push this either way, Hybrid or HR lifter. Just offering info. My hybrids are not worth even comparing, to much is different.

I have a nice set of 2347 Hylift Johnson HR lifters if you could keep it on a budget with an decent HR lifter. I’d gladly work out something trade them for comp SR’s, I do a lot more SR’s than HR’s. I have extra sets of HR’s.

The 995s with that cam would definitely not work with 1.65s, would be past coil bind. But shimmed like described 995s could be set to work good with 1.5 rockers as a hybrid or HR lifters.