Should I mill my P90

[Go240Zags]

Okay, there are lots of discussions on which is the best head. I've decided to go with a P90 (not P90A) on top of my L28 F54 Block that has been bored .40 over. It also has flat top pistons and the standard crank and will be running the four screw SUs, with SM needles and rebuild kits from Ztherapy.

The way I read it I should get a compression ration of about 8.89:1 according to the handy engine calculator with the Felpro or HKS 1mm head gasket. What are your opinions on shaving the head for a little higher compression? I'd like to run regular pump gas, but paying a little extra for premium wouldn't kill me. With regular prices so high right now who'd notice?

I guess what I am shooting for is a nice streetable engine. I'm not looking for a race car, but something I can take for a fast paced cruise with power to spare when it is needed to get out and pass, etc. Would taking .40 off do the trick? The head doesn't need a lot of work and I am pretty sure I have some cam tower shims from another one of the heads I have laying around the garage somewhere. Is milling that pricey? Should I have the P90's cam worked on while I am at it.

The engine will go in my 1971 Series 1 (12/70 build date) project, that is if it ever gets beyond the basketcase stage. The shell, such as it is, is waiting spring for some major rust repair (as well as everything else).

I know that's a lot to think about and I'm sure opinions will vary widely depending on people's taste. When I think of my future driving needs I think highway cruiser with some twisty mountain roads, not stoplight dragster. Any ideas?

I've found your advice helpful in the past. Even though my project has gone in different directions before, the engine portion is starting to gel into something I can use. The boring has been completed, new pistons ordered and installed. Now I need to get the head work done.

[beandip]

I went with my P79 head . Milled .030 gave me 9.5 compression . Stock flat top F-54 block. I run Plus gas . Havent tried regular , with the timing set at 10 BTDC there has not been a problem. If you do go more than .030 then you do need to shim the towers . There is a guy I know that is in the business . His name is Kim Blough I will send you a PM with his email address. You spent the big bucks on the pistons are you going with a cam as well ? Kim is a good one to ask questions about that as well . Gary

[Go240Zags]

I went with my P79 head . Milled .030 gave me 9.5 compression . Stock flat top F-54 block. I run Plus gas . Havent tried regular , with the timing set at 10 BTDC there has not been a problem. If you do go more than .030 then you do need to shim the towers . There is a guy I know that is in the business . His name is Kim Blough I will send you a PM with his email address. You spent the big bucks on the pistons are you going with a cam as well ? Kim is a good one to ask questions about that as well . Gary

Thanks Gary, I'll give Kim a shout. I've thought about a hotter cam, but my wallet is starting to get light pretty fast. I guess if I got off my arse and sold some of the spare parts I have I could finance some more new parts. I have a 1983 280ZX Turbo 2+2 under cover in the back yard I wouldn't mind seeing trailered off for a couple of bucks. Maybe this spring. Gary

[ZSaint]

It looks like you will have about 9.6 cr with a .040 cut. I have 9.2 and experience no problem using premium fuel. I have HP340 Dodge Dart with 9.5 cr and have had all kinds of detonation problems with it. With the aluminum head on the Z, I do not see any problems with this compression ratio.

I think you can get the shims for the head from Motorsports, etc. Are you flattops notched for the valves? With .025 notch you have 8.7 and a .050 valve relief will give you 8.51. I don't know if you have this factored in or not. Maybe the .050 shim will work if you have valve reliefs in your pistons.