Need more octane

[leecheater]

Xnke, thanks for looking at this thread. The head is an E88. No idea if it is from a 71-73 or if it is from a 74-off a 260z. I understand the 240Z e88 heads had smaller valves then the ones off the 260z.. The block is N42.

 

Here is a bit more about these heads. You z guys probable know this one, copied from zhome.com

 

E88 HEAD '72-'74

The compression ratio is around 8.7:1 for all of these years. This is where things get confusing. There are three E88 heads, one for each of the three years. The 72 differs from the '73-'74 mostly in the quench area. This is significant as the '73-74 head has a raised quench area that increases chamber temperatures for improved combustion. Contrary to what you might think this is not good for H/P. These are the least desirable of the Z heads and the only way to tell them apart is to identify the combustion chamber. I think the '73-'74 head only differs in that the 260 has a larger exhaust valve. The '72 combustion chamber is similar to the E31 with the hemisphereical quench area a little deeper than the earlier head. Some IT competitors prefer the early E88, sighting that its valves are a little less shrouded than the E31. I've run both and saw no difference in ET'

 

 

Here is the link to the comp cam web page:

 

http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=1152&sb=2

 

  I also went through e-mails from the seller. He apparently moved just after the machine work was done and can't find the box with receipts. The machine shop closed right afterwards and so no way to know for sure. I looked at his emails and no mention of what type of Venolia pistons.  He did mention the 240 rods were used. Supposed to be better at high rpms? He also mentioned the valves are bigger than stock.

 

  When I get time I will try your method to see if they are flat or domed

[Xnke]

Not nearly enough cam for 13:1 compression. That's a good cam to run in a STOCK engine; for a nice little wakeup and a not-terribly frumpy idle.

 

Lift is too low for the duration, will rev very freely and make a wide power band but power will be lower than other cams.

 

If you have the domed venolia pistons, look for something in the 305* duration, 0.510" lift range; but MAKE SURE you have valve springs, retainers, lash pads, rocker arms, and valve stem seals that can handle that much lift.

 

If you are going to run big compression, you need to run a big cam.

 

I think all the venolia pistons were setup with the short pin height; do you know if it's been overbored or if it's a stock bore?

 

Need to know what bore diameter you're working on and we can see how well the head matches up. From the cam spec, it sounds like the shop that built it probably was building a "hot street" engine, without knowing much about the L-series behaviours. Just seems to me that there is a serious mismatch in the compression-to-cam department, and hopefully you have a big enough bore to let the also-unknown headwork shine.

Edited October 13, 2013 by Xnke

[djwarner]

Leecheater,

 

any update?

[leecheater]

dj, the latest:

 

I drove her over to Midwest Motor Sports and talked to them about my issues. I have not been hearing pinging but the car is loud and so I wanted to check if I was doing it correct. I listen carefully when I have her in high gear going up a decent sized hill. Lug her just a bit. I can honestly say I don't hear it pinging. Perhaps my ears arn't trained well for this, but I am fairly confident with running a combo 110 octane combined with 93 octane she isn't pinging.

 

  We did talk a bit about timing and I will be adjusting it towards a more stock setting.

 

The biggest news that really sucks is that yesterday we got our first snow here! Many years we can drive cars with sticky tires into November. I have the Z parked in my attached garage as I have been driving her to work each day. The forecast is not looking good so until we get a warmer non freezing day, she will sit. I have been compiling my list of winter upgrades.

 

1. Figure out this compression issues. I am also seriously thinking of biting the bullet, remove the head and look to see what's going on in there. Might be easiest solution, plus the valves need adjusting anyway, so if I have to take the valve cover off, might just do it. I have talked to the guy who converts carbs to e-85 and may go that route. E-85 is so cheap here it's hard to argue with 100+ octance at $2.30 a gallon

 

2. Install the RT differential mount

 

3. New wheels, looking for a set of light 15"

 

4. Install limited slip differential

 

5. Minor touch up paint work

 

6. Continue to work on my exhaust smell in cabin with windows open issue. I have reduced it by 85% or so by installing a new inner shift boot, and plugging several small holes I found.

 

7. Pull off wiper assembly and clean her up a bit.

 

8. Fabricate the front grill so I actually have working turn signals.

 

   Going to be a long winter. I should be able to concentrate a lot on the Z, because the Supra is doing pretty well other than some tweaking of the interior and getting paint touched up.

Edited October 22, 2013 by leecheater