Has anyone upgraded from a hydraulic flat-tappet to a hydraulic roller while keeping the rest of the combo the same? If so, what was the power difference. I am currently ready to buy a cam for the 383 that I built for my '81 street car and just don't know about the cam as yet.

FWIW... It has ported 487 heads with 9.6 verified compression. 3.55 rear gears, a 200r4 trans and 2500 lock-up converter.

I was leaning toward the Xtreme Energy XR282HR which is 230/236 @ .050" with .510"/.520" lift but was just wondering if the added cost of the roller is justified for a weekend cruiser.

Thanks.

 

I cannot give you real world numbers, but you have to buy a retrofit roller setup if your block does not already have the factory roller bosses, which it wouldn't if it is an 81. They are pretty $$$$.

The roller cam gives you more lift with the same amount of duration.

 

A non-roller block can be converted to use factory roller lifters.

 

It's not really all that hard. You have to buy V6 lifters, and things like longer push rods, and machine the block for the lifter guides and spider bar...but it's not too hard at all. I did it to my 400 and wouldn't mind walking you through the process if you want to PM me your email address.

 

I've read the post about the details of fitting new style lifters in my older block and I can handle that part just fine. I already have a set of new lifters and short pushrods for the application but the question I originally asked was about the performance difference between the 2 cams.

If you have a hydraulic flat tappet cam and replace it with a hydraulic roller with similar specs, what would the difference be? I'd bet not much. Lets say I have an (for example) the Xtreme Energy hydraulic 230/236 @ .050" with .487"/.490" lift and replace with the Xtreme hydraulic roller with 230/236 @ .050" with .510"/.520" lift. What would the performance difference be? Has anyone done a swap similar to this?

Thanks

 

Money being tight,when I did my 406 I asked my machinist his opinion,and with 45 years experience,his Grandfatherly advice was that on a street engine,they just are not worth it.You will not be able to use a cam with huge lift and duration and still keep it streetable.

That said,I took the grand I would have spent on a roller conversion,and put it into my heads.I run a circle track solid flat tappet cam with 1.60 rockers,to in effect trick my engine into thinking it's a roller cam.Quick rates,lots of lift.

Back to the original question. I suspect the difference to be only a few horse if all specs are closely similar,due the frictional loss the roller lifters advantage would have.

 

I have to disagree with your mechanic. There are more and more profiles coming onto the market all the time specifically designed for the street, and even the factories are getting on board with the idea, so a blanket statement that rollers aren't streetable just doesn't fly.

The thing with rollers is that you can have higher lift w/o being required to have the kind of excessive duration associated with high lift and traditional tappets. And, lift is your friend. Also, there's less friction, and that's always a good thing. Depending on the purposes of the engine, it may not be worth the cost to everyone, but the roller hydraulics are inherently superior to hydraulic flat tappets, and your mechanic needs to catch up with the times.

 

The only recent "apples-too-apples" test we performed was on a 396 BB 100% stock-appearing restoration. It was a 1967 BB oval-port, 9.2:1 C.R., a "Holley" cast-iron intake, and all factory components.

While still bolted on the dyno we "pulled" the hydraulic flat-tappet and valve springs and installed a retro-hyd roller.

Left the dyno room with 380 HP and 415 Torque with the "retro"!!

On this particular build, as I stated, without leaving the dyno room, we "found" 20+ HP by this change only. In the past from our records with some "similar" combo's, we've been able to surmise some gains somewhere between 20 HP and 30 HP due to eliminating those "internal-frictional" losses.

Thanks, Gary in N.Y.

P.S. You all need to remember something else here also, there is absolutely NO risk with "losing" a flat-tappet cam lobe/lifter when you "cross-over" to the other side!! That'd be the hyd-roller side!

 

20 to 30 HP. Check www.ryanscarpage.50megs.com/combos1.html for back to back dyno results with the only change going to hydraulic roller. combo's 12 through 17 are similar 383 builds with different cams. The advantage of a hydraulic roller is not just reduced friction but the ability to use faster ramp rates and higher lift to get better flow through the heads without increasing duration which leads to a loss of streetability or flat cam lobes.

 

This is what I was refering to with my reply.I am fully aware that roller cams have the ability to be ground with faster ramps and more lift. That was the reason they were invented. BUT,if the specs are kept close to the same as an apples to apples comparison,the difference wouldn't be as dramatic as you'd think.

Alot of money for little return.

Oh,my machinist builds and races smallblocks turning in the 8500 rpm range with flat tappet solids that cost about $150.

 

A flat tappet motor that is raced 1/4 mile @ 8500 RPM will last how many miles before needing a complete overhaul? A new hydraulic cam kit with new springs, retainers, pushrods, rockers, lifters, timing set and cam cost maybe $600. The hydraulic roller kit is around $1200. $600 difference which is a lot of money. HP costs money. If it is worth it to you do it. If it's not go with the hydraulic. For apples to apples comparison check the site I posted in my first post.

EDIT: You won't get a true apples to apples comparison because the Flat tappet cam at a given duration won't be able to have the same fast ramp and lift that the roller will have. Some cam companies have tried to do this (comp cams Extreme Energy hydraulic cams) and have higher failure rates.

 

The only flat tappets that can approach the ramp rates of a roller are mushrooms (BTDT), which have an enlarged foot. They are capable of delivering more lift with less duration than any other flat tappet design, and can make some tremendous power, but they are extremely hard on parts. The only reason to consider them is if rollers are against the rules or if rollers aren't available for the engine in question.

I still have a few, along with the special tool for altering the lifter bores to accept them, but I don't plan on ever going there again.

 

Let me clear up an item or two you seem to have missed!

First, on the 396 we tested, the cam spec's were "identical" on both the flat-tappet AND the retro.

The flat-tappet specs were 222/235 x .501" x 114 LS (109 ICL)
The retro specs were 224/230 x .510" x 112 LS (110 ICL)

This was as close as we could make it with the available grinds!

Second, IF you lose a flat-tappet cam one time, the additional "cost factor" goes "right-out-the-window". As it is now my customer doesn't have to worry one bit about the amount of "zinc/phosphates" that are in or NOT in his oil!

It's really nice to know you can "start it up and let it idle" and not be "sweating bullets" for the first 20 minutes or so wondering whether your 16 lobes are going to make it or not. If the retro's don't start it doesn't hurt a thing while your "crankin' it", as long as you have oil pressure!!

Thanks, Gary in N.Y.

P.S. As to your remark about "a lot of money for little return", it's actually all relative. I'll just add this: a few months back we had the opportunity to do 3 cam changes in the dyno room "chasing" HP. The 3 cams (solid-rollers) ran the customer $1050.00. Along with the parts (cams) and the labor for the 3 changes while on the dyno, remember, this is a BBC with a jesel/dry-sump setup, the entire deal ended up costing them 3000.00+ with the dyno time. They got all of 5 add'l HP!! Now that's "a lot of money for a little return" even in my book!

 

I agree roller cams are a better technology than the old fashioned flat tappets,and I wish I had to cash to do one myself.But if I had to chose between 15-25 hp if you're lucky by keeping you stock heads,but still spending a grand on a retro roller setup,or running a flat tappet,and better heads,and gain 60-70 hp,my money's on the heads.Which is exactly what I did.

Keep this in mind. The horsepower can be made either way. The roller cammed engine will be more civilized,and still make the power,but if you add a few degrees of duration,the flat tappet will make the power too.(Plus I kind of like the rumpy idle.)Take a peek at Comp Cams own dyno tests,particularly the bigger cams where they used Sportsman heads and Vic Jr intakes.

http://www.compcams.com/Technical/DynoSheets/


I've read build ups that tested what the original post was asking,as closely as they could match cams,and the difference on the same otherwise unchanged engine wasn't more than 20 hp,which to me isn't worth getting my hands dirty for.Look at the average stock roller cammed engines today. There're nothing to write home to mom about,but they are rollers.

I lost one flat tappet cam in thirty years of engine building,and to be honest,the cam was a Comp XE-274,and running fairly stiff AFR springs. I replaced it with a Comp XE-284,same springs,but used 1.50 rockers to break it in. NO PROBLEM.With the Isky solid I now run I wimped out,and broke the cam in with stock 85 lb springs,then swapped in the AFR set.

I got to admit I was sweating a bit on the cam break in,and the roller setup would elimate that.

 

i have a roller cam in my engine and my mate has a similar hydraulic flat tappet in his . we have the same heads and carb but i have a air gap and he has a gm ( cant remember the nam but something like exterminator or enforcer) something like that.. but anyway once mine gets up in the revs it feels like a supercharger kicking in compared to his.. they are worth the extra money !!!

 

You can do the retrofit with the stock GM parts and V6 lifters for far, far less than $1k.

If roller lifters weren't superior in every way, GM wouldn't be using them in everything. They are more expensive than flat-tappet setups.

 

I wanted to do the same for my 383 for the slight performance gains but more for the oil problems that are causeing so many flat tappet cam failures (additives being removed for smog control), my problem with this is that I set my cam to piston rod clearance at .060" and balance the assembly and my springs are rated at .490" max, for me I would have to pull and tear down the a new engine, add new springs, grind more off the piston rod bolts and sides, rebalance the assembly, change the distributor gear and timing cover plate.
Pease

 

Try and get a torque "curve" like this with a flat tappet cam
When I saw this I new I would never run anything but a roller cam in the future

 

Motorhead,

Nice curve. I see what you're trying to say about the rollers,and believe me I'd have one myself if I could afford the coin.In my case,I was in need of basicly every nut, bolt, and gasket to build my 406 from the ground up. While the "both would be good",sounds great, I had to choose between good heads,not so good cam,or good cam,not so good heads.I started with a bare block.

Heads win.

On a side note,was this dyno pull run with annular boosters,or downleg.I remember you did a swap a while back,and am interested in doing the same for my 406.But again,big buck carb,or rethink cam and intake.

Hate to loose the 7000 rpm top end though.

 

I post that graph everytime someone asks about the benefits of roller cams

One thing that is really impressive is how low he could start going full throttle, he started at less that 2000 RPM.

Pull was done with downleg boosters, I would assume the torque would be even higher now that I have the annular boosters, I could feel a torque increase when I did the swap so I would think it would show up on a graph if I do another dyno pull. I don't think the top end will sacrifice either, the 825 Race Demon flows 975cfm according to Barry Grant