L88 / ZL1 Question

[Tim S.]

Story,

I recently purchased an unrestored 25k mile 68 Camaro L78 that has a 68 L88 (CE block). A prior owner informs me when he freshened the engine, he installed an NOS ZL1 cam he had in it.

My question is..............

We all know L88's and the few ZL1's had long duration cams in them.

We all know L88's and the few ZL1's had power brakes.

Did Chevrolet really release a car that made poor vacuum at idle to run the brakes? Or, is there something I am unaware of Chevy did to compensate for it?

Here is a link to a video my wife took when I was unloading the car.

https://www.youtube.com/watch?v=tHkrKu5HNNY&feature=youtu.be

In advance, thanks for your consideration.

Tim

[Carl N.]

Re: L88 / ZL1 Question

Nice ride. Love the color. Enjoy😉

[Duke W.]

Re: L88 / ZL1 Question

High overlap "racing cams" that generate low vacuum at idle won't affect power brake operation in most conditions. The booster has enough reserve for two or three brake applications and merely blipping the throttle at idle will re-evacuate the booster reservoir due to the brief period of high vacuum when you let off the throttle.

Either of those cams are very poor choices for a road engine. Minimum idle speed is about 1500 and very rough. Low end torque is lacking and fuel consumption will likely be well under 10 MPG. If the original pistons are in place compression ratio is way too high for pump gas, so avgas or racegas will be required.

It will be much more pleasant to drive if you "detune" it to L-72 spec - no more than 10.25:1 CR, the SHP mechanical lifter cam and a distributor set up with a B26 VAC connected to a full time manifold vacuum source, 30 degrees centrifugal all in by about 3500, and 6-10 initial timing - as much as it will tolerate without detonation.

Duke

[Anthony P.]

Re: L88 / ZL1 Question

Tim what a great find! congrats. Wish I could help with your vacuum question but I just don't remember if they had a separate system (IE hydro-boost, vacuum pump) for these beasts.
Someone will have the answer, I'm courious as well

[Tim S.]

Re: L88 / ZL1 Question

High overlap "racing cams" that generate low vacuum at idle won't affect power brake operation in most conditions. The booster has enough reserve for two or three brake applications and merely blipping the throttle at idle will re-evacuate the booster reservoir due to the brief period of high vacuum when you let off the throttle.

Either of those cams are very poor choices for a road engine. Minimum idle speed is about 1500 and very rough. Low end torque is lacking and fuel consumption will likely be well under 10 MPG. If the original pistons are in place compression ratio is way too high for pump gas, so avgas or racegas will be required.

It will be much more pleasant to drive if you "detune" it to L-72 spec - no more than 10.25:1 CR, the SHP mechanical lifter cam and a distributor set up with a B26 VAC connected to a full time manifold vacuum source, 30 degrees centrifugal all in by about 3500, and 6-10 initial timing - as much as it will tolerate without detonation.

Duke

Duke,

You are spot on as for the manners. Yes, the pistons are original, thus.....................race gas..............and I'm fine with that for this car. The car has a great story and is in its preserved Day 2 condition. The original owner has the car through 71(he installed the wheels you see on the car). The second owner bought the car to drag race it (he had success with it too at Lions Drag Strip). The second owner first blueprinted the L78 (which I have), and then installed the L88. Shorty thereafter, he was killed in a car accident. The car remained stored in southern California (purchased at Harry Mann Chevrolet) by the second owners Mother until 2001.

It has a Roto Phase distributor thus, no vacuum advance. Perhaps, the Camaro booster does not have the volume the Corvette Booster? I can tell the booster is coming in and out (if that makes sense).

Just curious as to the manners of a production car versus one modified like mine.

Tim

[Joe L.]

Re: L88 / ZL1 Question

Tim what a great find! congrats. Wish I could help with your vacuum question but I just don't remember if they had a separate system (IE hydro-boost, vacuum pump) for these beasts.
Someone will have the answer, I'm courious as well

Tony------


L-88 or ZL-1 had no separate vacuum system. Engine vacuum was used for the power brakes (as well as headlights, wiper door, and heater/ventilation system actuators). The headlights, wiper door, and heater/ventilation system actuators did have the benefit of the vacuum reserve tank, though.

[Anthony P.]

Re: L88 / ZL1 Question

Tony------


L-88 or ZL-1 had no separate vacuum system. Engine vacuum was used for the power brakes (as well as headlights, wiper door, and heater/ventilation system actuators). The headlights, wiper door, and heater/ventilation system actuators did have the benefit of the vacuum reserve tank, though.

Now I remember, they looked like a big juice can with no label lol thanks Bill.

[Joe L.]

Re: L88 / ZL1 Question

Now I remember, they looked like a big juice can with no label lol thanks Bill.

Tony------


The "juice can" vacuum reservoir tank came along much later in the C3 years-----1980-82 to be exact.

[Tim G.]

Re: L88 / ZL1 Question

Tim, I followed that car on another website and thought is was an absolutely amazing find. What a cool day 2 car. Enjoy it..........