SteveG75

FYI, I run Morel hyd roller lifters on my 496 and had a stock '68 tripower manifold for a couple of years. No problems.

Agree with the others re hyd roller. I have a 496, hyd roller, with EFI and run pump gas with 200-210 psi cranking. No problems.

69L71

Great info. Thanks for all the opinions. That's why I put this out there. I know there's a lot of folks that have dealt with this issue. Here's how I'm currently leaning:

I think I'm gonna build up the motor pretty much factory stock, 11:1 and all. I MIGHT tweak the cam profile slightly from the factory 143 since all the major cam companies have their own versions of the 143 cam (still to be decided). I'll run it that way and see how comfortable it is running 93 plus a) race/av gas or b) Lucas/Klotz/Torco Octane Booster. If I'm dissatisfied I'll yank the whole motor and put it on a stand as factory original to eventually be sold with the car. I have a std bore 4-bolt 454 block sitting in my storage garage. I'll build that up with a Hydraulic Roller and aluminum heads but keep the tripower. Go EITHER factory old-school original OR totally modern. Not try to tapdance in the middle. Who knows, maybe I'll even drop in a 496 stroker kit while I'm at it. But as 3x2 said, as a weekend toy it might be fine keeping it just the way GM built it.

stingr69

That's all you can do. Find that place where you can build a baseline and mod from there as needed.

Dealing with all this decision mess in my build too,

cv67

At least get a modern version of that cam, sorry but those old grinds lasted forever but you are cheating yourself of power.
Find an old Crane, Isky, Crower grind at least. If it were me get a modern cyl head on there, mill off the logo and paint it. Port the intake if you can, should make some oats.
Rebuilds dont really make it any more powerful than it was when worn. Do it once!

69L71

I know this comment will raise some eyebrows but... I'm not sure how much extra power I really need. My wife's '66 Corvette has a ZZ4 with an LT4 HOT cam, M-21, and 3.73 gears. It's a ball to drive! It's MAYBE pushing 375HP and 390lbft TQ. Even a bone stock L71 is gonna put out about 100HP over that ( ). I can't imagine I'll be disappointed. I'm not gonna bracket race it. And like I said, if I find I'm unhappy I will do up the 454 with all the modern stuff and go hunting for 550HP (and probably blow up my Muncie).

Lunati's updated version of the old 242/242 #143 cam is 402AL1LUN. It's 238/238 with .550/.550 lift and 110LSA. It was designed by UD Harold (Look him up). The Chevelle guys rave about it.

domenic tallarita

One reason they didn't want it used in cars was there was NO road tax on it and it was cheaper 47 years ago when I first started using it. Works great in cars when mixed with pump. The plus is that it will not varnish. Not good for cars with cat converter. To bad it is hard to get, but those against it have never tried it!

Dom

gavino

Every time I read where someone is paying some ridiculous price for higher octane gas to run in a L71 it bothers me. The L71 which was first built in 1966 was supposed to run on 98 octane gas. At that time gas was tested for octane by using only one of the methods used today. This resulted in a higher octane number. Sunoco 260 was 103 octane, perfect for a L88. Todays 93 octane says it is At LEAST 93 octane. So it may in fact be higher. The confusion comes from the fact that if you convert this back to 1968 gas it will come out around 97-98 octane. With some good tuning you could probably get those three deuces to run great. A second tip is to disconnect the vacuum for the wiper door and headlights to make sure you have no vacuum leaks. Those will create many problems. If you want to boost the octane you can google how to boost the octane rating of gas and buy a gallon of a certain solvent at a paint store to do it.

leigh1322

10 to 10.5 seems a safe bet to me. But 200 psi seems high. What seems to be more important is the DCR. 9s seems like race gas territory, where as low to mid 8s should work fine on 93 octane pump gas without having to retard timing. Getting that number is a juggling act between static CR and intake valve closing pt. A little more cam can handle a little more compression. On my LS6 build I am going for true 10.5 CR with Icon pistons and Aluminum heads, and a short IVC of 67 for a DCR of 8.3 to make it pump gas friendly. My 238/246 duration is very L71 and LS6 like but with faster ramps. And I'm going solids 'cause I want to hear the solid lifter rattle.

domenic tallarita

What would bother you more is to live in CA! 91 is best and hardware stores cant sell anything than you can wipe your eyes with or drink!

Dom

suprspooky

No problem, Morel Liters. I had to pull the Intake after the Engine Dyno Pull (long story, needed a spot for the Temp Sender and cracked the boss for the Heater Hose Fitting while removing the Fitting) and everything was fine. I had to do welding, milling etc to repair so I would have seen any contact areas.