1970 w/L88 cam&10.50 comp.. Question

[Jim R.]

Hi guy's Talking with my freind yesterday he has a 1970 454/390 4spd coupe that has been apart for 15 years ,told me that the engine was rebuilt just before the (15 years of storage and never started), that it was rebuilt with the L88 cam and 10.50 compression, I mentioned to him that i think the L88 cam needs 12.50 comp to run correct. but told him i would post it so Duke and some others could chime in with some thoughts.

[Michael F.]

Re: 1970 w/L88 cam&10.50 comp.. Question

I built up a BB using L-88 block, rods and crank. 10.5 to 1 pistons with the L-88 cam. I used the rectangular port aluminum heads. Not the round ports in the 390hp.I had a Factory Tri-Power set up with 3.73 rear end. More compression was desired. But this was a 1980 build. Not a good time for octane. The car screamed. I felt the cam performed well.

"The L-88 cam is worse than useless with round port heads."

I put all of this in a '79 Z-28. They came with an anemic 160hp 350ci. But had a solid driveline,super T-10 with a 3.73 posi. It Just screamed TRANSPLANT!

And it all fit under the stock hood. That car really surprised the Turbo Porsches that dominated the streets back then."my streets anyhow"
Not much else could touch me either. A true sleeper.

[William C.]

Re: 1970 w/L88 cam&10.50 comp.. Question

I had a L-88 cam in my '67 Chevelle 396/325 hp in the early 70's, not for street driving, but ran mid 12's with an otherwise stock engine. not the thing I would put into a car I was going to drive to the local drive in resturant, but great if you want to run to 7000 rpm

[Joe C.]

Re: 1970 w/L88 cam&10.50 comp.. Question

The intake valve closes at 105 degrees ABDC (!!!!) @ J604d with the 3928909 cam.
My DCR calculator doesn't accommodate such a late closing intake valve.
Well, let's see, with 10.5 SCR, a 4.00" stroke..................that would give it a DCR of about............................................. .................................................. .................................................. .................................................. ............................
4.345:1
Such a motor will deliver about 2 ft-lbs of torque at 1500 RPM.

[William C.]

Re: 1970 w/L88 cam&10.50 comp.. Question

Idles at about 1200, makes GREAT power from 4500-7000, drops off pretty quickly below that, but launching at 4500, and shifting at 7000, it makes a fun ride!

[Jim R.]

Re: 1970 w/L88 cam&10.50 comp.. Question

not a good combo, i would like him to go with the 396/427=425hp solid cam instead.

[William C.]

Re: 1970 w/L88 cam&10.50 comp.. Question

The 425 solid cam works much better on the street than the L-88. Especially if you have to use mufflers! The L-88 is a BIG race cam from the 60's not as good for racing as modern designs, and nearly undrivable on the street with mufflers.

[Dick W.]

Re: 1970 w/L88 cam&10.50 comp.. Question

The 425 solid cam works much better on the street than the L-88. Especially if you have to use mufflers! The L-88 is a BIG race cam from the 60's not as good for racing as modern designs, and nearly undrivable on the street with mufflers.

Trust me, Clup is spot on. Everything vacuum worked fine on my L/88 while it had the factory headers and side exhaust. Once the factory exhaust was installed everything barely worked. Not a very satisfactory set up

[Duke W.]

Re: 1970 w/L88 cam&10.50 comp.. Question

The L-88 cam has extremely high overlap designed specifically for headers and open exhaust. It's the overlap that gives it terrible street manners- idling and around town driving, with or without headers. Leave if for the racers and posers.

The best way to get "more power" from the L-36/68 and LS-5 is massage the heads and use the OE cam retarded five degrees.

I am willing to bet that the above will beat a Tonawanda-built L-72 either across the intersection or to the end of the quarter mile.

In addition, it will look unmodified, have a decent 600 RPM idle, stump pulling low end torque, get "reasonable" fuel mileage, and be docile enough for his grandmother to drive.

Now, if all he wants is a cantakerous, but "mean" sounding engine driving through the cruise night parking lot, go with the L-88 cam, but it will be an absolute POS for normal driving and barely get 8 MPG.

You'll also probably have a hell of a time getting the OE Q-jet to work with that cam.

Duke