Topic: Roller Cam Conundrum

[transam101]

Hi All,
My apologies if this is long winded, so I'll attempt to keep this as short as possible.  I currently have a few bad lifters in my 78 Pontiac 400.  So, rather than do the easy thing by simply replacing the lifters, I'm contemplating on swapping out my Edelbrock RPM performer cam for that of a hydraulic roller.  First off, I'm very happy with my cam's current performance, but perhaps I'm missing out since I have nothing to compare against in terms of cam evaluations within my specific motor.  I'll list my current specs below, but I can provide other stats if needed.  Probably the most important piece of this puzzle is that I'm running the Edelbrock 72cc RPM heads, edelbrock rpm intake, a 2200 stall, and 3.73 rear in a streetable weekend warrior.  I really don't want to make a $500-$1K+ mistake by falling into the common trap of over duration and thinking that 'bigger is always better', so I'd like to hear from anyone that may have experience with a similar setup.

1.) My current cam stats can be found here
http://www.edelbrock.com/automotive/mc/camshafts/locator.php?part_number=7157&submit=go 

2.) I don't want to sacrifice low end torque, but I'm also tinkering with increasing my duration by 5 degrees...  Bad idea?  My intake is designed for 1500rpm, so would the roller cams with the 2200rpm-6500rpm be too much?  Would I end up with the dreaded 'bog' on heavy acceleration if I take it one step up?  Is the power band mismatch from 1500 vs. 2200 too much?

3.) I've been looking a few rollers and will list them below, but most of them recommend a 2800rpm stall.  I understand that's a subjective value to some point depending on compression and other factors.  Would my 2200 be ok?  Do I really need a 2800 with my other motor elements?

4.) I've got zero understanding on valve separation angles and what the recommended 'max' values should be for a power break application?

5.) Perhaps I've not looked hard enough, but I couldn't find a roller cam with the same duration as the rpm performer cam that also start at the 1500rpm power band range.  I've found some rollers that started at 1500, but it's always a step down in duration vs the edelbrock rpm cam.  Anyone see a good roller duration cam starting at 1500?


Cams I've been kicking around in my head:
https://www.summitracing.com/parts/cca-cl51-433-9/overview/make/pontiac - One step 'up' in duration vs. my current cam
https://m.summitracing.com/parts/lun-20510712 - Better matched to my current cam, but higher rpm start range

Car's current setup:
Edelbrock RPM performer heads, rpm cam, and rpm intake for pontiac 400
Stock but rebuilt bottom end (.30 over) 400 pontiac block - I don't trust pushing it over 5500rpm
2200 stall, I don't want to go higher if possible since it is still used on the street on the weekends.  (Seems silly to me to run a stall at almost 3K when the motor pops at 6.5K)
3.73 rear gears and 350t tranny with shift kit
1.5 ratio generic roller rocker arms
Weekend warrior use (some drag track runs from time to time)
Power brakes
650CFM Edelbrock Carb
Doug's headers with dual exhaust / no cat
MSD 6-AL Programmable

So all this said, should I just replace the current flat tappet lifters?  Better roller cam suggestions?  Have I 'overkilled' things for the street with these choices?     Many thanks for your considerations.
TA101

[77TRANS-AM400]

is this a daily driver or just a weekend toy??
how do you know your lifters are bad and that your cam is ok? have you checked to see if you have any filings/shavings from cam wear ??
and if you are not taking it over 5500 rpm then why bother with an expensive roller cam set up?  you might as well save your money and stick with the flat tappet
plus depending on your set up I've heard of some guys having issues with the valley pan clearance when going to a full roller set up, so just something to think about....

just asking questions

[76Tranz]

I'm a little confused, my thinking is kind of on the same line as 77T/A400, and my question is...why are you running a 650cfm carb on your motor? Just my 2 cents, but you're starving those E-Heads to death. You said it's a weekend warrior, put an 850 cfm carb on there and see the performance difference. Stock 400's came from the factory with 800 cfm quadrajets, why would you go smaller? I'm just asking questions, not trying to rile anyone up. It just blows my mind when people put small carbs on a Pontiac motor, my question has always been why??

[transam101]

Thanks for the replies gets,

Believe me, i've taken grief over the carb from many different avenues.  Fuel injection is the better game plan here, so I'm biding my time with my current config.  The carb was free, so that's how it ended up on top in this case.  Don't worry, the heads will be fed in the end.  Sadly the card I have been dealt currently deals with two bum lifters.  i'd like to steer the conversation away from the fuel delivery though and focus on the cam if we could.

I've been doing more reading and I no longer feel that "duration" is an apples to apples comparison between a flat t. and roller setup.  So I now believe that the two cams I was evaluating in my prior post are too big in terms of duration.  Since there is a difference in lobe shape, my understanding is that the valve fully opens more quickly and hence does not require the same amount of lobe duration @.50 to achieve the same amount of air/fuel volume into the chamber.  Again, this is just my current perception and could be incorrect.  Hence I have accepted that I am bound to roughly a 2000-6000 rpm power band (using ~.520 lift) in the neighborhood of 226I/235E.  I'm now considering Crane Cams part 289661.  http://www.cranecams.com/278-279.pdf

Again, just looking for anyone with the 72cc heads and some roller experience that may be able to weigh in.  The 2200 rpm stall seems to be subjective since there can be a small rpm difference between it and the true powerband.  Thoughts?

-TA101

[transam101]

Also, I forgot to note that I have two current hydraulic lifters that have gone 'flat'.  By that, I have two rocker arms that refuse to hold adjustment even with fully adjustable / polylocked rocker arms.  I have not checked the oil for shavings, but it's any easy check.  I doubt the current cam has been effected by the two lifters, but it's possible that the corresponding lobes have died.

This is indeed a weekend warrior and is not a daily driver.  It will see both street and strip action during the summer for sure.

I don't necessary feel that a roller cam would only be beneficial at high RPM though...  I think that's mostly controlled by the duration if I understand things correctly.  It should free up rotating resistance at any RPM I would think.

I'm just a hobbyist, but this was confirmed by a friend who is a full time tech with his own projects.
-TA101

[78w72]

i have the 72cc e-heads on my 400 based stroker engine making over 500hp with a roller cam.  there are benefits to a roller at any rpm but they are usually reserved for higher power engines to get the max hp out of any given engine combo.  if you aren't looking for max hp from your engine & just want to fix your lifter issues i would suggest sticking with the flat tappet cam.  a roller cam will be an almost $1000 expense... personally i would save that money for something else like a new carb.  your car came with a q-jet & when built properly to match your engine that would be the best way to spend your money. fuel injection would be even better way to spend $1000 IMO. 

but to stay on your cam subject, a roller will be ~$350 for the cam, $500 for roller lifters & $100 for a composite dist gear.  plus your stock valley pan probably wont clear the roller lifters if its post 1971 or 72.  you can get by with taking a hammer to clearance the low spots but a $125 new tomahawk valley pan would be best.  so youre over $1000 there & the benefits of a roller cam as small as you want to match your stall & compression may not be worth the cost. i would look into a "better" FT cam & new lifters, many cams out there are better than the RPM cam, like a crower thats a little bigger, or summits 2801 or even a comp XE series, although some dont like the XE, they do work pretty good if you have the rest of the tune up to par. 

i strongly suggest verifying the cam lobe on those 2 lifters, flat tappet lifters rarely go bad internally to tyhe point they lose adjustment, sounds to me like you have a lobe wearing down along with the lifter, losing adjustment is a tell tale sign of a cam going bad.  if you have to pull the lifters anyways to fix them, i would do that 1st & inspect the cam, flat lobes are usually easy to see or can verify with a micrometer.  concaved lifter faces go hand in hand with a bad cam lobe.  then, after you verify the issue you can decide what to do, but my bet is the cam/lifters are shot. 

for your purposes you described on the car i would say replace with a better FT cam & good USA made lifters & spend the $1000 elsewhere.  also if you arent aware there are lots of problems with the roller lifters available for our pontiacs, the $500 range roller lifters are usually noisy & can also collapse internally or lose pressure just as easy as a FT lifter if not easier.  to get the most out of $1000 i would get new FT cam/lifters & a better stall converter.  advertised stall speeds are usually quite inaccurate & the quality or brand of the stall makes a huge difference.  i have a continental brand converter rates at 3000-3200 rpm FLASH speed, but its made to be so tigh that it acts like a stock converter for normal driving, cant hardly tell its not a stock stall.  there are other good tight converter companies out there but they are cheap like the standard 2200 b&m converters... expect to pay 350-600 for a goood converter.  TCI makes a nice street fighter one for about $375 i think.   

as long as you break in the FT cam correctly & use a good quality oil you shouldnt haveissues with most street cams.

hope that info helps. 

[transam101]

Interesting, I did not know that the $500 variants were plagued with issues.  One of my searches regarding it turned up a post that blamed spring weights on the premature lifter failures.  That and overseas cheap manufacturing.

I guess I'm looking toward the future as well.  Once the initial investment is made, only a cam swap should be needed if I end up with a higher RPM limit.  The same could be said about the new pro-flo 3 efi system.

Out of curiosity, if you have the 72cc heads and a 400 base block, what stroker assembly did you end up selecting?  Are you still able to run on 93 octane without doctoring your fuel?

-TA101

[78w72]

sorry for the late reply....

the roller lifter issues are mainly noise related, many of the 1st gen comp rollers were noisy, the didnt break or malfunction, just ticked a lot.  the later current versions of comps lifters are much better.  there are other brands out there like lunati but i havent read many reviews on them.

i use a butler forged crank/rods stroker kit.  crank is 4.25" stroke & .060 bored 400 makes it a 467ci.  because of the 72cc heads i did have the ross pistons dished a little to get teh compression down to 10.75 & it runs fine on 91 octane pump gas thats in my area.  there is a 93 octane but its 10% ethanol & the engine runs better on 91 straight gas.  its mostly a street car with a very stiff PTFB suspension, but so far does a best time of 11.2 at 121+mph. 

[transam101]

Hey guys, I wanted to follow up with this post now that the project is at another major milestone.  I ended up going with the crane cam 226/234@.050 with .518 lift and couldn't be happier.  In all due fairness, I did end up taking 78w72's advice in that I had also upgraded to the Pro-flo 3 system as also previously mentioned in this chain.  So I did end up changing two variables at once, but it was worth it in the end.  The torque and upper end are noticeably different with a huge difference in off the line response.

https://plus.google.com/photos/112779033304453669987/album/6471775660940695921/6471775665226244482?authkey=CKPa3IXX5u-Wbw

Now onto the bodywork