Compression of an E88 head

[Sailor Bob]

Any block numbers to watch for in the 81 - 83 series to ID them?

[Jeff G 78]

'81-'83 is an F54 block. I believe it is cast in the RH side of the block.

[ChrisZ]

Some claims that the N42 block is the best for a stroker, anyway for a California car i guess that combo isn't anything special, but if it were here where the avalibility of Z parts are very low, that combo would be special.

Still your motor isn't stock, witch must make it special.

Chris

[guy_geo]

Problem is, the compression is causing knocking from time to time.

I'm doing my headgasket right now. I have installed right now a new set of rebuilt SUs, put a 280ZX Turbo head gasket as well as a metal spacer to have 0.040'' of additional clearance to lower the comp. ratio.

I have changed points for a electronic distributor as well as the coil.

I will see in 2 weeks, when the job is done, if the car runs better.

Oh yeah, and a brand new radiator as well.

[bigoak]

I assume you are running high octane fuel. If you are still getting a knock, you can add octane to avoid and keep the high compression.

[ChrisZ]

I'm curious to know what kind of E88 head you have, can you post a photo and also a measurement of the valves size.

Chris

[blue 72]

If we can see a photo of the chambers on the E88 then we could probably tell you which of the four versions of the E88 cylinder head you have. Also, which pistons do you have, flat top or dished in your L28? Seeing as you had the head off it'd be easy to see.

[sblake01]

He answered that earlier:

Also, which pistons do you have, flat top or dished in your L28? Seeing as you had the head off it'd be easy to see.

Looks like I have flat top pistons....

What would correct the pinging would be a P79 or P90 head since it sounds like you have an F54 block.

Edited May 10, 2009 by sblake01

[Carl Beck]

A picture of the combustion chambers would "help" us see what he's got. Big difference between the 72 and 73 Model Year E88's in combustion chamber design. But it really would not supply exact answers.

Also a big difference between an E88 with stock valves and one with 280Z valves - as far as the total size of the combustion chamber goes. Installing larger valves and unshrouding them can add 2 to 4 cc's easily. A picture would help us "guess" what was done...

We really don't have enough information to know if the problem he has with "ping" is related to the compression ratio - or a screwed up timing curve - or simply the gasoline he has available in his area.

He really needs to know very exact and specific information about the engine he has - now that it's apart - is the time to find out.

-Measure the cc's of the combustion chambers - take the head to a machine shop and have them do it.

-Measure the bore

-Pretty safe to believe that it's a stock stroke...

Summer or Winter blends of gasoline, some with or without "E85" ratings in Canada can vary by 3 to 5 octane points.

Bottom line - I run an L28 with +0.5mm, Euro Spec. Nissan Pistons {plus 2cc dome}, and a 72 E88 head with 280Z valves {unshrouded/reworked chamber}, Nissan Cam Kit, triple Webers and Unilite distributor - - no problem at all with "ping". My compression ratio is right at 10:1.

FWIW,

Carl B

[Carl Beck]

Hi Arne:

Jim Wolf gathered the following info - and it has been verified by several of the top engine builders that specialize in the L series engines. I'll add it to this thread so if anyone in the future reads it -the information will be constant

There were at least 4 major versions of heads which carried the E88 casting number.

1. Late '71 were very similar to the E31 combustion chamber, but slightly lower compression, had a CR of 8.7:1 or so.

The heads with casting number E88, found on the late calendar year production Series II {Late 71 Model Year} and Series III {72 Model Year} 240-Z's had the exact same combustion chamber as the E31. 42.4cc's so compression stayed the same.

'72 had a different combustion chamber shape, and a CR a bit lower yet, about 8.3:1. (Sometimes called "small-chamber" E88.)

The 72 Model Year E88 has the same combustion chamber shape/design - only it's 44.7cc rather than the 42.4 of the E31.
Casting improvements to the exhaust valve seat area, and exhaust port improved the flow of this head, and today you see far fewer with cracks around the exhaust valve seats than is common on the E31's.

'73 changed the chamber shape yet again, CR about the same as the '72, maybe a touch lower. (Sometimes called "larger-chamber" E88.)

Yes - the combustion chamber shape/design was changed significantly for the 73 Model Year - this is known as the Emissions Head - as it was designed to meet the strict 73 Emissions standards.. This head has a 47.8cc combustion chamber - You can easily see the difference in combustion chamber design for these and the 74 heads.. Not good for performance...

'74 was much the same chamber as the '73, but had larger exhaust valves.

Correct -

FWIW,

Carl B.

[guy_geo]

Thanks for all the input. Problem is, I'm not a mechanic and my mechanic lives 45 miles from my place...

I'll ask him if they are flat pistons, and if he can take some pictures...

Other problem, he's retired and works on the car during the day, alas, I work also in daytime Mtl downtown, a drag, since I cannot be there to watch him and ask questions!

I have also very worn carbs right now, the one in the front is too rich, (blackened sparks) , and guess what, the carb in the back, too lean, white sparks..

As soon as I can have drive with the car and maybe some pictures, I'll keep on posting.

As for the fuel, I'm using Petro Canada 94 octane gas, available only in the Mtl area, not available outside Mtl, so I keep some octabe booster cans in the car.

[Carl Beck]

Petro Canada 94 octane should be fine for anything in the 9:1 to 9.8:1 range with factory cam and proper timing etc..

I hasten to add - as long as the filling station is actually selling what they claim on the pumps...

Most mechanics have a machine shop they deal with - without knowing the exact size of the combustion chambers - you have no way of knowing what your C/R is. In that case - Overkill - is a last resort. Adding head gasket thickness is perhaps the least expensive way to go..

I just hope that when you are done - the problem has in fact been too high a C/R... and not simply a case of having the wrong timing curve in an unknow distributor... Here a again, any good mechanic can measure and tell you exactly what you have... IF the mechanic doesn't have a distributor machine, he should know a shop that does..

good luck,... shooting in the dark you'll need it.

Carl