MGJ07C6

Hi all, I'm rebuilding my 67 L71 engine while its out for engine bay / frame and suspension restoration.

The car has a 4 speed, side exhaust and power brakes. I have a set of original 67 aluminum heads that I plan to install after having the ported, polished and a valve job. The engine will be 30 over so new pistons will be ordered. My engine builder advised that since the heads are aluminum we can go up a tad on compression, maybe 11.25 or 11.50 max. I have a second 67 L71 intake that I will have ported and polished to match the heads. I have a set of Stahl headers that will feed into Sweet Thunder Give No Mercy 3" side pipes.

My engine builder has an L72 with an L88 cam that he loves and suggested using that cam in my engine. I had seen the Comp Nostalgia LS6 Plus cam and suggested that might be a better cam for the street and tri power set up.

I'm looking for advise and opinions.

Thank you!

Avispa

That L88 can might be a bit too rough for a street driven car. I had a comp cams nostalgia LS6+ a dozen years ago until it wiped out a lobe from the change in oil formulation in 2005. If you don't mind valve noise, the LS6+ is a good running street cam.

MGJ07C6

Thank you!

20round

I installed the l88 in my 396 car sounds great, but I have not had a chance to drive it yet. im hoping it will pull enough vacuum for power brakes..good luck. troy

MikeM

My suggestion is to drive your engine builder's car around the block a time or two and see if you can put up with the bumping and jumping up and down.

If you're twenty years old, you'll probably love it. If you're drawing SS checks, you likely won't.

Your gear ratios would play in to this as well.

427Hotrod

Unless you're going to twist it to the moon the l88 isn't a good choice. I would do some searching for aftermarket stuff. The LS6 cam is pretty mild with very low lift. The L88 has a ton of duration and still not much lift. You can get Hyd roller stuff to be happy in the 6500+ rpm range. Certainly pick up a ton of drive ability and power.

That said. I've used both. The LS6 cam could run 11's in my oval port 427 with 4.10s. The L-88 ran mid 10's with 5.57 gears and four speed along with 14x32 slicks with 7500-7800 rpm shift points in a 396.

I used a Crane flat tappet in the 427 that did everything better than the LS6.


Jim.

MGJ07C6

I have a 3.36 in my car.

MGJ07C6

Thanks Jim. I don't plan to race the car, just spirited street driving with the occasional street race. I prefer to stick with solid flat tappet as that what was originally in the car. Which ever I choose needs to have good vacuum for the power brakes, makes good power with the tripower and is not a bear to drive.

MikeM

Why not just stick with the stock GM solid lifter cam that was OEM to that engine. It's powerful, sounds good and reliable. Did I mention cheap and it'll work with your gears.

GOSFAST

Keep the cam on a somewhat "wider" lobe-separation for the brakes.

The gears will limit (to a point) the final cam numbers! Would also keep the C.R. at or under 10.5, regardless of the heads!

Thanks, Gary in N.Y.

P.S. When you go through the heads make sure your guy puts in the long exhaust studs, I'm assuming you have the "392" heads?? Any of those early aluminum castings really need the long studs installed!

427Hotrod

I think the L71/L72/LS6 cams are essentially the same aren't they? 242/242 .520 lift on a 114 lsa?

My favorite Crane would be a little lumpy with 3.36s and 4 speed. I drove it with 3.31s but it was happier with 4.10s. Its 256/266 .580/.600 lift on a 110. Old school but runs well and doesn't hurt parts. Your heads will like a pretty big split between intake and exhaust duration.

Jim

427Hotrod

Also since you're not worried about originality with the headers and the heads. I can't figure out why you would draw the line on using a solid flat tappet when it's hidden inside and no one would no the difference other than your car ran a lot better than every one else's?

The right cam can really help get it rolling with the big heads and marginal gearing.
Jim

EMD645F3B

I have the LS6+ in my 67. Very happy with it. It made horsepower up to 6100 rpm on the dyno. It idles well and pulls about 13-14" of vacuum. Really don't notice much noise as valve lash is tight, I think .012. I have 3.55's and It's right on the edge of being balky when pulling out with a M-21. Don't think I would want any higher gear ratio than that.

MGJ07C6

Thank you for the feedback.

vettsplit 63

There are some good points in the above comments to consider if you are interested in running the L88 cam. I changed out the L78 cam, which is the same cam as the L72 in my closed chamber, iron headed 68 Chevelle back in the day, for the L88 cam. I can remember having to use a sectioned head and putting bar stock tool steel welded to the face of an exhaust valve to do a 'poor boy' clearance on the pistons. There was not adequate piston to valve clearance by my calculations. I don't remember how much I flycut the pistons, about .060" as I remember. I remember also having to change valve springs, as the stock springs weren't able to handle the higher rev limit to take advantage of the L88. I spun the motor up to about 7400 consistently. One other thing that I remember is the first time I went out to try out the new setup, when the tach reached 7400 and I shifted it, the clutch stayed on the floor! The 375 horse diaphragm clutch wouldn't take that kind of rpm's. As far as having enough vacuum for the brakes, I remember that with power disc brakes, at a long light, you could run out of brake. It was a great cam, for an inexpensive GM grind though. Now, everybody has their own idea of what is 'streetable'. If you can live with a 1200 rpm EXTREMELY lumpy idle, and a really crappy low end response, that's what it was. That is just what I remember anyway.

63Corvette

I have driven a L-88 on the street. I would recommend either a roller cam (1st) or the stock L71 cam (2nd) which is a GREAT cam for the street or street racing.

65tripleblack

With a 3.36 axle you won't like driving with an L88 cam, and neither will your clutch.

The Nostalgia Plus series are great cams, but you give up quite a bit of durability to make the extra power. I'll go out on a limb and say that a properly broken in NP cam run with at least 1400 PPM ZDDP won't last more than 40,000 miles. Less if the engine is idled or lugged.

There is no way I'd build a new engine today using a flat tappet cam. Use a roller...........hydraulic or solid...............you won't be sorry. If you can afford the mods needed, then the roller by design allows more lift and much faster valve action than a flat tappet, with more durability and no need for high levels of ZDDP in motor oil.

Since your heads are getting a port/polish (and, I assume a 3 or 5 angle valve job to be blended up against) then they will respond dramatically to a faster/higher lift cam. For example, my 327 is a street driver and makes about 480-490 flywheel horsepower.

The L88 cam is EXTREMELY inefficient by todays standards. If you want a lopey engine, then your choices are endless using a roller.....................and you will build a much more powerful and efficient engine that will sound even "meaner" (if that's what you want) than the L88.

Your final SCR will be determined by your cam. First decide on a cam, then your engine builder, if he's worth his salt, will calculate a safe SCR. If he's any good, then he will advise you to use between .030 and .040 "quench", with .035 being a safe but effective value. Tight quench builds in resistance to detonation allowing your engine builder to specify more SCR and/or faster spark advance.