BB cam question for Duke Williams

[George Poynter]

I would like to install the first desigh L-88 camshaft in my BB 67, 427. I've followed your logic on vacumn canisters in reguards to proper advance and what the "engine likes"(after reading several other posts). My question is will I pull enough vacumn with this camshaft to effectively use your "process" with this camshaft? What about cam timing? Would advancing help? As to why the first desigh L-88 cam, I like the sound of this set-up idling through a parking lot with side pipes and the first desigh was the mildest of the series of L-88 cams that followed.

Thanks in advance

[Duke W.]

Re: BB cam question for Duke Williams

With a NAPA/Echlin VC1810 vacuum can that provides 16 degrees at 8" you might be able to pull 8-10" at 1200-1500 RPM to keep the vacuum can pulled to the limit, and achieve something approaching a stable idle, but it's iffy.

The L-88 cam is an extremely poor choice for a street engine and selecting a cam based on how it sounds at idling through a parking lot is a very poor way to choose a cam. The L-88 cam has an extrmeme amount of overlap that is designed to work in conjunction with tuned headers to maximize WOT power in the 4500 to 7000 range at the expense of the bottom and mid range.

With the cast iron manifolds the overlap will work against the engine throughout the range and the bottom and mid range torque and throttle response will be particularly poor and fuel consumption will be very high. I don't think advancing the cam will have much benefit. With that amount of overlap, there's not much you can do. It is just too extreme for the street.

The L-72 cam is a much better choice for a street engine. It will have a noticeable "hot cam" idle quality - not as aggressive at the L-88 can, but the L-72 cam is driveable in normal traffic.

Duke

[Duke W.]

PS

I meant to say that the L-88 cam is meant to be used in conjunction with headers AND open exhaust as are ALL Chevrolet racing cams.

Any exhaust backpressure from a street exhaust system will work in conjuction with the overlap to REDUCE power throughout the range. Headers will help somewhat, but even headers with mufflers will create too much back pressure and have a severe impact on top end power.

Duke

[George Poynter]

Re: PS

The reality is, you are right, though I ran this combo as a kid when 67's were new. I appear to have blocked out the negitives. Are you convinced that there is not a better (thru the exhaust) high performance flat tappet cam than the L-72? I'll put up my "ego shield" and await your response.

[Mike McKown]

Some people wanna' race and some just want to idle

bad. Good cam choice for that.

[Duke W.]

Re: PS

For the SB and BB ,respectively, I don't think there is a better choice of cams than the LT-1 and L-72. Both work fine with OE valvetrain components for long and trouble free longevity, yield acceptable torque bandwidth, and have that SHP idle quality we find so desireable while maintaining reasonable driveability.

No matter what our fantisies, the reality is that in our advancing middle age we are really not willing to put up with the cantankerous engines that we thought were so neat in our teens and twenties.

Duke

[Patrick H.]

An alternative

George,

Another alternative (although a fair amount more money) would be a retrofit roller cam.

I'm sure that Joe Lucia could give you some input on this, as he is (or someday when he ever gets around to it will be ) using this type of camshaft in his ZL-1.

See Crane's link below.

Patrick




Crand Roller Cams

[George Poynter]

Re: An alternative

My first choice was a hyd. roller, but the "classic mechanical valve clatter sound" issue came up. Drive ability is the first priority,no one want's to give us usable H.P. for just "the sound". I thought there might be some middle ground somewhere. One would think after 35 years that there would be a cam that gave you everything the L-72 has and then some, without sacrificing low end torque and other creature comforts. I've used several "race only" roller cams over the years in race applications, not in a real street car. I ran my 61 Vette (540 B.B.) in the first "Fastest street car shoot out" events,
8:81 at 150+. That was faster than an idle in a parking lot.

[Patrick H.]

Re: An alternative

George,

With the side pipes, I'm not sure how much of the clatter you'll hear anyway, especially when you're IN the car.

Patrick