Tiger Joe

I’m building an L89 427 for my newest Vette project. It’s my understanding the L89 is identical to the L71 except for Aluminum heads.


my question is- is there a hydraulic roller cam that is close to the stock L71 cam? Or is there a good aftermarket cam guys are using?

when I searched I found some mention of guys using comp cams 288AR. But that’s a solid roller. I’d prefer hydraulic.

gkull

Could you please post the specs of a stock L71 cam using the .050 duration along with the lift and LSA? The general rule using the .050 duration numbers going from a H-flat cam to a modern roller design is that you can run an additional 6-10 degrees duration and still have similar idle quality and vacuum. You also gain additional power because of the superior cylinder filling

Because of the additional lift and valve dynamics you need to install higher seat pressure springs, a quality timing gear set, different pushrods, and of course the lifters

Jebbysan

Apples and oranges......a modern roller hydraulic will make more power but it will not sound the same......the two cams by design could not be further apart.....GM made power with the L-71 using long lazy lobes and lots of overlap.......roller cams are the exact opposite.....so finding a cam like the L-71 in a roller is never going to happen. But it will sound good and make more power......and I urge you if the engine is bone stock, to keep the duration up as they were an 11.5 to 1 engine and a small cam will increase cylinder pressure way too high to run pump gas.
You will need spring, locks, retainers, either spring cups or locators......and possibly new valves depending on the lift.....higher lifts will need a + .100 valve stem. I recommend pulling the heads and having them done professionally by someone like Mark (Vortec Pro)......reason is that you are changing everything and putting components on a head that was never designed for it.......also, he know the benefit of a real valve job......and going to all this modern roller stuff is shooting yourself in the foot if you do not do a pro Serdi valve job and blending.
This can get expensive.......but the upside is when you are through.....with the head mods.....you have a bone stock looking engine that will murder an L-88......be more drivable, and last damn near forever. You could potentially make 100 more horsepower than stock through the original Tri_Power.

Jebby

Jebbysan

BTW....the 1969 L-71 cam was 242/242 @ .050 .520/.520 I and E....on a 108 LSA.......the LS-6 454 and the L78 396 used the same camshaft.

Jebby

derekderek

i like the ZZ502 cam. 224-234 527-544 110 lobe sep. 1 hp per inch and doesn't need as much spring as some. nice sound and. GM hates to give away free engines so they design the valvetrain with longevity as a main factor. 250 buck cam. needs the front machined for the gen 6 cam retainer but they all were 15 years before they made the cam retainer.

Tiger Joe

The engine is in pieces right now.




I have a set of 842 heads at the machine shop now. They were ready to go, but setup for stock. I dropped compression on the motor since I needed new pistons anyway. Should be around 10.5:1 maybe a hair higher.

specs listed above are the same I had for the L71.

gkull

Like I said rollers need more duration to run like their flat tapped counter parts. The GM 242/242 HF would have a lumpy idle because of the valve event numbers along with 108 lsa. 20 years ago I built a 427 with this comp cams HR and I thought that it was way too mild. It was okay, but just didn't sound like a race motor.

https://www.compcams.com/xtreme-ener...k-396-454.html

Tiger Joe

So I missed your link the first time I read this

I was looking at the lunati bare bones
https://www.lunatipower.com/barebone...k-278-288.html

and I also looked at the comp one step below what you linked. The 288Hr. You posted the 294Hr

leigh1322

I collected a lot of cam spec data for my LS6 cam search. You are welcome to it. Here is the HR section.
They are all going to run pretty good. But I liked the Straub GTA and the Comp Cam Custom the best in a HR grind.
think they should run/idle really close to stock, but make more TQ down low, same/better idle vac, and similar/more power than stock..
All of these have tighter LC 110 vs 114 vs the L71 that builds power.and hurts idle.
All have shorter adv duration, faster ramps and shorter hydraulic intensity than factory slow ramp design, that builds TQ. and helps idle.
All have very similar intake valve closing and earlier than GM, that builds compression DCR.
All have more lift than L71 that builds power.
I calculated my DCRs on a 10.5 static CR.and IVC. Low 8s are good for pump gas and TQ.
They are all so close that the minimum rpm suggested will give you an idea of how rough they are just off idle. Depends on what rear gear you want to run, convertor, and idle vac you want to tolerate.etc.
Its very hard to compare solids and hydraulics. especially old GM solids. But a 242 dur @ .050 solid and a 230 dur hydraulic will probably idle and run the same all things equal.
I think they are all good, but the bottom two are starting to get a little rough idle, low vac, etc. All the others should have good vac.

My 454 LS6 clone made 490HP and 550TQ.with 15" idle vac at 850.with 074 GM Alum heads.and a 230/240 SR.tight lashed. A 427 should make similar power but be down 30 ish on the TQ, but all the peaks move up the rpm range about 500. Mine were 3400/5400. My SR has even faster ramps so you may have slightly less vac at idle.

gkull

Let me get this straight. You went with a 230/240 Solid roller in you LS6 and got 490/550 hp/tq? I used the XR294HR in a 427 build combination and I felt like it was on the mild side even with aluminum heads and a single plane. It definitely left me wanting more power. I was always so disappoint in the 427 vets probably because so many were just the 390 hp versions and the tripower didn't seem like a hot rod either.

So weren't you really disappointed in choosing such a mild cam?

Jebbysan

If I owned an L-71/L-89....this would be my choice:

https://www.howardscams.com/hydrauli...-cams-cl120665

Jebby

leigh1322

I understand GKull. You like big power and big rpm. You would not like my cam. I wanted a smooth driving street cam that had as much power as I could get without sacrificing the bottom end. I had a 254 dur "hot rod" cam in my LT-1 for 27 years. You would have liked that one. 7200 rpm. It was great fun to race, and that huge power surge at 3500 really made it feel like a hot rod. But it was really not much fun to drive around the street below the power curve. I did, but when you hit the power curve it was like warp speed ahead and twice traffic speed. Great fun but it got old. It was just too big. It didn't idle well, but it sounded great. It was even faster at the track with the cam "shrunk" some with advanced cam timing and loose lash. None of the original L71, LT-1, or LS6s had that surge, only the 302 Z28.

OTOH we picked this SR cam to replicate the L71 / LS6 power curve, while bolstering both the bottom and the top end. We did not want to go any bigger and cause the bottom end to start to go away, even though the top end would improve. It made 10 more HP than a stone stock LS6 and 40 lb more TQ. I am not racing this one, so I wanted to make sure it drove way better than the old one. It should with an extra 150 ft-lbs TQ at 2500-3500! LOL. The LT-1 did not peak TQ til 5000, this one is 1600 lower. An extra 5 dur was all we would have gone for, if available. And that would not make much difference.

If I was going for power, and a "hot rod" power curve then yeah both the cam and especially the 50 year old exhaust port design would have been bigger. There was 80-100 HP left in it that way, mostly in the heads.
Did it make a "brag-worthy: 560 HP? Nope. Will it drive better than a 560HP motor? Yup. AFR heads alone could've taken it to 540, but I wanted the Winters Snowflake 074 heads more than the bragging rights or the HP. A 240/248 cam would probably have flipped the results and made near stock TQ and 40 more HP. But not as crisp below 2500. That is probably what most people would choose, cause they tend to go for big numbers. I focused on the driveability instead. We talked about what it would take to go for 600HP and a 240 cam could do it,or close, with AFRs, but then the tall Victor single plane needed a big hole in the hood. I'm running the stock BB hood, and that is a non-negotiable, and a big intake manifold constriction.

Life (and especially camshafts) is all about compromises.

My compromises may not be what someone else would choose. which is why I bothered to explain why I chose what I did.