L/88 vs. ZL/1 pistons

[Steve Antonucci]

Hello,

Can anyone tell me if there were technical differences between the 1969
L/88 pistons and the Zl/1 pistons? Or, were they the same piston?
Thanks,
Steve

[Dick W.]

Re: L/88 vs. ZL/1 pistons

2nd design i.e. open chamber L/88 and ZL1 shared the same pistons. 2nd design went into production June? July? 1969. I believe that 1st design engines all had the "I" prefix codes, and the 2nd design had the "L" and "M" prefix. Do not have JG to be sure though.

[Steve Antonucci]

Re: L/88 vs. ZL/1 pistons

OK, so 67 & 68 L/88's qualify as 1st design and they must have been closed
chambered design. Were the actual piston designs ( domes ) any different
than the 69 pistons, or just the combustion chambers in the cylinder heads?

[Mark D.]

Re: L/88 vs. ZL/1 pistons

Steve,

That is mostly correct, the 1967 through mid 1969 L88 pistons were the same. Along about the end of the strike (69) the 'open chamber' cylinder head was introduced. This incorporated a redesign of the piston. The goal was to achieve better emissions by more thoroughly burning hydrocarbons (better breathing). Another result of this redesign was a lowering of compresiion from 12.5/1 to 12.0/1 . A resultant increase in horsepower was also achieved.

So, to answer your initial question, there is no difference in piston configuration in the late (second design) L88 and the ZL1. The difference (configuration) is between the 67 through mid 69 L88 and the second design L88/ZL1.

Regards,

Mark

[Steve Antonucci]

Re: L/88 vs. ZL/1 pistons

Thanks Mark. I got it now.
Steve

[Mark #28455]

Re: L/88 vs. ZL/1 pistons

actually there is a difference in the piston design. The 1st design piston dome is designed to clear the closed chamber head at the spark plug side of the head, the 2nd design piston has a larger dome (even though the installed compression is actually lower) and will absolutely not work with a closed chamber head. The earliest second design heads I have seen were dated Jan 1969 but were not released into production vehicles until June 1969. L88's are very unpredictable when it comes to casting dates, etc. Most engine assembly dates for L88's are about three months before the car, but Al Grenning has seen one '69 (VIN approx 20000)with a 321 casting '68 block - go figure!

[Patrick H.]

Re: L/88 vs. ZL/1 pistons

Mark,

Just because one was seen with a 321 doesn't mean that one was built that way.

I assume Al thought the car was real?

Patrick

[Joe L.]

Re: L/88 vs. ZL/1 pistons

Mark-----

The closed chamber and open chamber cylinder heads have significantly different combustion chamber volumes. The closed chamber run about 107 cc; the open chamber are about 118 cc. That's why the open chamber have a bit lower compression even though the piston dome volume is greater.

[Mark #28455]

Re: L/88 vs. ZL/1 pistons

he believed the car to be original and not a restamp.

[Dick W.]

Re: L/88 vs. ZL/1 pistons

I are gittin' dumb in my ole age. Kain't tell difference between prefix and suffix. I meant suffix
'