Hey everyone! I'm looking to change over from hyd. tappet to hyd. retro-roller this winter, so far I have lifters and pushrods. So-I'm looking at a roller cam. So I'm looking for opinons on which profile you think will work best with my combo (in sig).

70cc heads, -18cc dish pistons I believe puts my compression around 9.3:1. I'm also considering stepping up to a 750 cfm carb, although it seems to run great with the 650 I currently have. Oh, and maybe fab and install a "test pipe" in place of the CAT (just to test if there's any power increase of course...ahem.)

Even though I have a forged crank, I still want to keep power down low and not spin it past 6K. I was looking at this Lunati cam:

60111 N/A 270/278 219/227 .515"/.530" 112/106 Hyd/Hyd 1800-6000
60111 Description- Hydraulic Roller: Strong power increase in mildly modified engines with excellent throttle response. Will work with stock converter in 383-up cubic inch. Likes 2000 RPM converter in 350 or less cubic inch applications. Likes 3.23-3.73 gearing. Largest choice for inboard/outboard marine applications. Has noticeable idle and likes headers.

Not a daily driver, 90% street, but I don't want to be embarassed on "test and tune" days at the dragstrip. Am I in the ballpark with the above profile?

EDIT: I'll most likely have to get any cam I choose custom ground with a small base circle for clearance, so other cam profiles are "open season" so to speak.

 

well the recommended RPM range is probably based on 350 cubes, so with your 400, you can lower that 500RPM or something. Since it's not a daily driver, I might go higher. Maybe try 230* or so duration at .050" ?

 

on my daily driver i had a 224/230 duration cam, and my new engine im building for daily driving runs 230/236 duration

 

Wow! I really didn't notice the duration until tou pointed it out...that's shorter than the flat tappet I have now - the XE274 has 230-236 at .050! But- the lift is a bit higher on the Lunati.

So what would be a better duration? Something like 236-242 area? And on what LSA? I was thinking of going with a more idle freindly 112 because the 110 in it now seems a bit lopey.

 

ive never gone bigger then a 230ish duration cam so i cant tell ya what the 240's feel like. if one cam has less lift then the lunati, but more duration, 1.6'roller rockers would fix that.

really theirs not much difference between a 110 and 112.

 

Man...you can tell you haven't done much tuning

 

travis, he is comparing his flat tappet to roller, so that's the main duration/lift difference there.
If you think the 274 wasn't too "undriveable", shoot for the same duration specs (roughly), that way it'll have the same bad characteristics, but the power bonus will be there.

I don't think the LSA will affect your idle much, i'd go with a smaller one for the bigger peak power...
Dyno don, your thoughts on the recommended LSA?

 

If it's going in a 400 then I'd say yes you're definately in the ballpark. Not a bad choice at all.

 

What cylinder heads? I know you say the CC's, but what kind are they? Factory stuff? Heads and the amount of air they can flow play a fairly large role in cam selection....

 

Well, if you like the choppy idle for the street, then ok, 110, if not then stay with 112 and install intake center line at 108.(for more vacuum, or 106 with power brakes)
The bigger you go at .050 the more it's going to lope.
Usually you can go a little more with the stroker but not too much.

 

Sorry - I just posted my sig once....they're Dart Iron Eagles, 200cc intake runner.

And thanks for the replies so far!

-Another cam I was considering is the Comp cams XR288HR. It's range is 2500-6000 RPM's, Street/Strip, 9.1:1 compression ratio, 236/242 at .050, .520/.540 lift but have it ground on a 112 LSA instead of the 110 LSA advertised. How about that one?

 

wouldnt be too bad at all.
i would use that.


-Don, i ment between 110 and 112, their isnt much difference in idle quality.

 

MUCH better. Go with that one.

 

Confuzed,

FWIW, this is just my experience. I'm running a Comp grind in one of the LT1s. With the setup I have, it makes valve lifts of 0.535"/0.545", net durations of 220°/230°, and LSA of 114°. That feeds a standard (4") bore 350, 198cc ported LT1 iron heads, 2.02/1.60" valves, 10.4:1 compression, 1,800 RPM stall, 3.08 gears, and I can't hook up for diddly-squat on 10" street radials with reinforced stock LCAs and correct pinion angle. Zero hop - just a tad of rear lift. The axle just stays on the ground and roasts rubber to near self-ignition. With a real converter and decent rear gears, and tires that actually stick, the axles wouldn't stand a chance. The idle change is barely noticable. It idles at 650 RPM in the programming and doesn't even pant. If it weren't for the rumble from the Flow 40s under load, it would seem like any other stock 350 with 360HP and 390 ft/lb. When summer arrives, we should hook up so you can drive it. I'm guessing you'd make far better time than me and my "three-day" reaction and poor torque management abilities.

Your 400-ish engine with a carb instead of SFI and a higher stall RPM (it's just gonna happen because of the extra torque of the 400 compared to a "baseline" 350) will swallow up that kind of cam and ask for more. This is the second replacement cam in that LT1, since I "chickened out" the first time and went with a milder (.500/.510) Comp grind on their recommendation.

I'd suggest you call Comp's Tech Help Line. Depending on the tech person you get at the other end of the line, you should be able to list your specs, goals, and uses for the vehicle, and they should be able to give an honest suggestion. However, in two out of two cases, I've found that they tend to recommend a grind on the conservative side, but not by much. I had a similar experience with Crane several years ago. If they are adamant that you should not go to the next step, you may need to take that under serious consideration. Once you have a recommendation and teh reasons why particular features and parameters are suggested, base your furhter research on that. If someone else suggests something way off the map from that "baseline", you can ask specifically why, and determine by the response whether it is an off-the-wall "moroon" or someone that may have a clue about the subject. We've got both at TGO...

Either way, going roller is an excellent step.

My 2¢

 

Thanks for the reply Vader, Freebird, Travis and others!

Vader: I've already called Comp cams, and I gave them all the specs on my engine they asked for, and the XR288HR I mentioned above is what they recommended - but cut on a 112 LSA instead of the 110 LSA. The guy claims it's a "step up" from the XE274 flat tappet I have now, and I'll have a better idle (higher vacuum) with the 112 LSA - Like Dyno Don is also saying. The recommendation was also made by the Comp tech to get a larger carb also. But- I'm leary of what any tech guy recommends because the Demon rep talked me into going with a 650 cfm carb over a 750.....now they all say it's too small....so I get further opions here. Don't worry, I've been on the TGO board long enough to know who's done this before, and my "moroon" filter is on.

By reading your post, I concluded that you feel I shouldn't be afraid to go a bit bigger? Is that correct, or am I a bit slow? And I think I understand your reasoning....I have problems with traction as is right now too (due to bad torque management). I think it's because I'm presently getting my max of 490 ft lbs in at around 3400 RPM's, and max HP at around 4400 RPM's.

My thought is to find a profile that might move the max TQ and HP slightly up on the RPM scale, so maybe I'll be able to get a better launch without spinning, and have extra power at the higher end. The catch is, keeping it streetable with a decent idle, because remember, I don't have an SFI system I can program to idle this thing at 650 RPMs. I need a good enough vacuum signal to accomplish that with a carb right?

Thanks for the reassurance that going hyd roller is a good thing. If you do searches, many think solid roller is the only way to go, and hyd roller isn't worth it. But I'd rather keep hyd on the street.

Feel free to keep the advice comin!

 

Well, just got off the phone again with Comp cams.

I "bit the bullet" and ordered a cam, lifters, retainers and fuel pump push rod. I'll tell you right now, the retro roller route is an expensive one!

I finally settled on a custom cam, with Comp's help...I have the specs:
-236/242 duration at .050
-106 centerline
-112 LSA
-.510/.540 lift
-ground on a small base circle.

Now I just have to get a new timing cover with thrust button, and I should be set!!

Only bad part is that I'll need to check my pushrod length....I have some pushrods that I got with the used lifters I bought - but I doubt I can use them since they came off a roller engine with a cam that wasn't cut on a small base circle....figures...

I just hope I'll be happy with this cam, because it's too expensive to change now!!

 

Call Comp back and have them throw in an adjustable pushrod.
Big ole order maybe they will throw one in for free but they are only $20 or so. The only way to get the geometry right the first time.

 

Good advice on the adj push rod. You can't possibly know for sure what push rod length you'll need, until after it's all built; so don't order push rods until AFTER you get everything else installed and measured.

Here's the timing cover I'd suggest.

http://store.summitracing.com/partde...=CLO%2D9%2D221

 

Yeah, thanks for the advice. Like I said above, I'll need to check pushrod length which I assume will require an adjustable pushrod.

I'll need to do some research on how measure for length. I assume I want the contact pattern centered on the valve stem where the roller contacts - correct?

Sofa - I already ordered the timing cover - it happens to be the same one you recommended!

 

Great!!

The goal of push rod selection isn't so much to get the pattern centered on the valve stem; it's more to get the pattern as small as possible.

The rocker tip moves in an arc. At all points in the arc except when it's "level", there will be some degree of side loading on the valve stem; i.e. the rocker is partly trying to push it sideways toward the exhaust side of the head, as well as pushing it down. You want to minimize that. Ideally, the rocker should be "level" (at which point the tip contacts the valve stem at the farthest point toward the exhaust side, as it makes its travel) at about half-lift, or just a little more than half-lift; since the spring tension, and therefore the overall forces on everything, increase as lift increases.

I usually shoot for the narrowest possible pattern on the stem, using a light spring of some sort and white lithium grease or gear marking compound to make it visible; and then use the next shorter push rod that's available. They usually come in .050" increments. So if it turns out that by experiment the optimum length is let's say 7.330", I'll use 7.300", rather than 7.350".

You want to set the cam button for around .012 - .015" or so of cam end play. Just enough for some oil to be able to get behind the cam sprocket, and for the whole thing not to be in a bind all the time. If you're using a Torrington timing set like a Rollmaster or something, you can set it a little closer.

 

Hey, thnx Sofa,That's good advice!!

I think I understand what you're saying about getting the right pushrod length. I can see that it doesn't necessarily need to be "centered". I looked up this article, and I wonder if doing it this way would be as accurate as what you've written above, (the smallest pattern) - and I'm not saying you're wrong by any stretch - I believe you've done this a few times...

Anyways, this makes it sound easy:
So what do you think? Would this be another way to do it, or is there room for error doing it this way?

-Thx again.

 

It's impossible to guess exactly where on the valve stem tip the mark will land. Too many variables. Not all rocker arms are the same length, for example; in fact, to get 1.6 ratio on a small block, you can either lengthen the long arm (between the stud and the valve), shorten the short arm (push rod to stud), or some of each. Do you know how yours are made, in this respect? The stud holes could be drilled a few thousandths one way or another, or they could be drilled at a slight angle with respect to an average stock head. Valve lengths, even the amount that the seats have moved up into the casting from grinding or down from seat replacement, will affect all of this. Replacing the guides can move the valves; either toward or away from the stud, or tilt them at an angle, either of which will change where the rocker tip lands on the stem. Your heads are aftermarket, which means that in the mfr's efforts to improve flow and other properties, all sorts of things are different (after all, if they were the same as stock in every way, they would be sort of pointless, no?). In fact I'm fairly sure that the intake valve is moved over .030" from the stock location in your heads, which all by itself, will alter where on the valve stem the rocker tip lands when the geometry is set up perfect. And on and on and on. What all this means, is that the exact spot on the valve stem that the rocker tip lands at zero lift, IS NOT a reliable indicator for the push rod length. That's not the thing to look for.

Basically you could follow those instructions, and if some other one out of that long list of variables has varied, they would put your push rod length out in left field somewhere.

In short, the only thing I see in that write-up that's useful, is the suggestion of a felt-tip marker for your telltale. Those instructions don't even take into account what happens when the valve goes through its cycle, as you'll notice, they tell you to do what they tell you to do, with the valve on the seat. That all by itself is a clue that they're inadequate.

Bottom line is, you want the narrowest possible mark, after the valve makes its complete motion cycle from seat to full lift and back. The narrower the mark, the less the rocker tip is sliding (or rolling) across the valve stem, and consequently the lower the side loading. Which is of course the object (or one of them at least) of the exercise.

If I could draw worth a crap on a computer in a reasonable length of time, I could show you what you're looking for; but alas, I'm too much of a moron and an imbecile for that.... you'll just have to use your imagination to draw the picture.

 

Ahhh....I see. I guess there ARE alot of variables that would effect everything. I was a little suspicious when the article didn't cycle the valve too. But you explained it perfectly - but I'll admit I had to read it a few times!

Ok - got it!

Last question...
I imagine the light spring "of some sort" you mention, has to be heavy enough to opperate the valve, but light enough not to compress the lifter correct? Where do I get one? (ok 2 last Q's) lol

 

You could use almost anything; a suitably sized one from the hardware store, on up to the "checking springs" that Comp sells. Basically, you called it right; heavy enough to return the valve reliably and hold everything together, but light enough to avoid compressing the lifter.

I usually melt some Vaseline or TransGel, immerse a lifter pair from the set I'm going to use in it, let it get full, then cool it. That will keep it at its full height. I'm not sure if any of the solid rollers I ever have laying around, are the same height internally as hyd roller lifters, so I always try to use the actual ones that I'm measuring for.

 

Thanks again Sofa.

I ordered a comp pushrod checker - and I guess I'll find a hardware store spring that will work since I can't seem to find a "checking spring" anywhere on the net. Still waiting on the cam and other parts to arrive anyway, which is OK since I'm not quite done installing SFC's yet (been a 2 week project).

Soon as I'm done with those, I can get the engine pulled and fix my rear main seal and install the retro-roller!

EDIT: I do plan on calling Comp again to see if they sell any kind of checking spring - I know I couldn't find it through Jeg's or Summit....

 

http://www.compcams.com/Technical/Cu...ML/368-389.asp p 378

Type the part # into the search function at Summit or Jeg's, use prefix CCA for summit and I forget what 3 digits at Jeg's for Comp Cams; followed by the whole part #, no dashes.

You'd be positively AMAZED at what you can find at both places, that doesn't "appear" to be in their catalog, if you have a part # and know how to use it.

Hey that should be a movie line. One cop to another: "Look out! He's got a part number and he knows how to use it!!!"

 

Post some pictures as you do this new cam. I have heard about the roller in a non roller block but have never seen what is actually involved. Ball park, how much will it cost to do this.

 

Sorry it took so long to get back to this post, but I was waiting till I made some progress!

Just got the old style Spohn SFC's in the car, and since I had done nothing yet when it comes to installing the retro-roller, I let the car off the stands and took it for a spin....feels much stiffer....no longer do the T-tops creak going up the driveway!

Didn't get rid of -ALL- the interior rattles though - still some left...

Sofa - again thx!! - I'll order the spring from Jeg's then!
I'm willing to do that if the Mods are willing. There's a limit of only 3 pics per post normally....and of course, I would exceed that in order to do this right...but I have a cheap digital cam that takes decent pics!

-But I need to know from the mods before I go wasting time taking pics that'll be deleted...

 

Browsing the web i cam acrsoo these new Comp Cams....all factory roller

#1 pn: 08-465-8 260XFI h13
Specs: 1200-5200 rpm
260/270 210/218@.050 .560/.555 @1.6:1 113 LSA

#2 pm: 08-466-8 268xfi h13
Specs: 1800-5800 rpm
268/276 218/224@.050 .570/.565@1.6:1 113LSA

Look pretty good what dou you all think

Thanks
J

 

Them are for fuel injection and pretty small for his 400.

 

They're WAY WAY small for the application at hand. They would work well with unmodified factory computer-controlled fuel injection on little motors, a 305 or a 350 respectively. They are inappropriate for a significantly modified high-compression 400 with a carb.

 

Well. I don't know what happened, but I got a delivery today from Comp. I now have the retainers, springs, hardened fuel pump pushrod and cam. It was packaged suprisingly skimpy, but it looks like there's no damage.

Only problem is - it's not exactly the cam I thought I ordered!! When I called them back to order everything, I referred to the date I orignally spoke with them (they asked me to do that) - which I did - because supposedly, they had the specs written down. Here's what they sent me straight off the cam card:

GRIND#: CS 3316S / 3317S HR110.0
-GRIND ON 1.050 BASE

GROSS VALVE LIFT: .520/.540
DURATION AT .006 TAPPET LIFT 287/293
VALVE TIMING @ .050 - INT. OPEN 12 BTDC, CLOSE 44 ABDC
EXH. OPEN 55 BBDC, CLOSE 7 ATDC
THESE SPECS ARE FOR CAM INSTALLED @ 106.0 INTAKE CENTER LINE:
DURATION @ .050 INTAKE-236 EXHAUST-242
LOBE LIFT INTAKE- .3470 EXHAUST- .3600
LOBE SEPARATION 110.0

-As you can see, it's not what I posted above after I spoke with the guy at Comp the first time. For some reason, this cam has slightly more lift, and the LSA was ground at 110...not 112 like I asked for. I got a feeling that if I call them, it's gonna be one of those "he said she said" kind of deals I suspect.

Is the difference in lift and LSA worth arguing about - I mean will the 110 LSA instead of 112 make a huge difference in idle quality?? If so, I guess I'll be calling them for another cam...

 

Hmmm....no answer to this one. Doesn't matter anyway I guess. I decided to keep this one instead of trying to convince Comp that I wanted the cam ground on a 112 LSA from the start.

After doing a little research, I tend to think it'll make a little bit of a difference in idle quality, but not enough to warrant the hassle of trying to get a replacement cam custom ground again from Comp, so I'm staying with this cam.

Thanks for all the help sofakingdom, rjmcgee and others...pulling the engine starting this weekend - wish me luck!!

 

Good luck!

Comp should have no problem making that right if you have the time. Your probably right though, not enough differance to warrent the hassle.

When I assembled the valvetrain on my Camaro I ordered my pushrods from Comp after finding the right length. They show up Saturday morning and I am stoked about finally getting the car up and running and the right pushrods were the last thing needed to finish the engine. Open the package and find a set of Big Block pushrods, I was pissed. Call and they next day aired the correct ones out to me. Screwed up the weekend but they made it right.