'72 240Z Rebuild

[Mark Maras]

 When you're done lapping the valves and have installed the springs, tip the head port side up and pour any solvent you have into the ports. Take a look in the combustion chamber. If the valves are sealed, no solvent will seep past the seats.

[siteunseen]

11 hours ago, Mark Maras said:

 When you're done lapping the valves and have installed the springs, tip the head port side up and pour any solvent you have into the ports. Take a look in the combustion chamber. If the valves are sealed, no solvent will seep past the seats.

Thanks for reminding me about that Mark, I'll write that in "what to do next" timeline/steps. The first head I tried to reassemble I put the springs on and forgot the valve seals.  

It seems like someone said rubbing alcohol would be good? What would you recommend? 

Thanks again

Cliff

[Mark Maras]

 Rubbing alcohol may have too much water in it. I did a test using water, vs  mineral spirits a while back. Started with water and it showed no leaks. Then tried m.s. and it leaked. I think the reason that m.s. worked better is because the valve and seat had trace amounts of oil on them. The water wouldn't seep past the two oily surfaces. IMO any solvent from acetone to xylene will do the job as long as it will mix with oil. 

[siteunseen]

I've got acetone and lacquer thinner and could get some mineral spirits, I use a good bit of oil based paint.  I'll try acetone first.  It would evaporate before damaging the seals.  No, no.  If I do what you say and dribble it through the ports directly onto the valve, it'll never get to the seals!  I'm looking forward to doing this, got the desire back after a short lull.  Damn leaky oil pan made me mad, I thought I'd done a good job. 

Thank you Mark!

[Mark Maras]

 Be sure to pour enough solvent into the port to submerge the entire valve head.

 I've always wondered why designers didn't use more bolts to seal sheet metal covers properly. Seems there is never enough. Hmm, It doesn't seem like it would be too difficult to fab. a full length reinforcing plate for both sides. Has anyone tried it?

[rossiz]

re: using the stock head then swapping in the new one -

i've always liked incremental upgrades vs. the "all at once" approach. for example in the bike world, you know that with a new bike you're going to swap pipes, re-map the ecu, do head work, fiddle w/timing to get the most ponies, and a lot of guys will have that all done at the dealer before they pick it up. but then you only get one shot, and no matter how hot the motor is you always wind up wanting more in 6 months, and the next stages of performance get much more expensive. i prefer to ride it stock, then in 6 months swap the pipes, enjoy the nice boost, then in a few months do some head work, enjoy the nice boost, then in a few months do the timing/tuning... you get the idea - kinda like opening xmas presents one-a-week vs. all on xmas morning.

so if you run the stock head, enjoy your lovely new motor, tune it really well, then in a month or two do an afternoon head swap it's a free kick in the pants that you get to enjoy. also, you will have a nice butt-dyno comparison to measure the new head improvement.

i did my f54-p79 build w/stock cam for this reason - been driving it and loving it for the past six months knowing that i'm gonna put in a hot cam later and i'm looking forward to the extra kick. after all, the LAST thing i want is to be "done" working on it, right? where's the fun in that??

[siteunseen]

I've got those two flat steel bars for the rear of the pan I'll be using, for sure. I guess the reason they only did the rear is because thats where the load is? 5 quarts is pretty heavy with such a fragile pan, i.e dimpling and low torque specs. That's my guess.

Rossi your are great idea, ah ha! inspiration person! You always have a good common sense reply that make me think "why didn't I think of that"

Thank you both. Now back downstairs for more sanding, I'm painting the pan and rails black like they should be.

 

[madkaw]

Lapping in the valves seems to have strong opinions amongst builders from what I've read. Some machinist argue that a properly done valve job there is no lapping necessary. almost like it's like old school voodoo and todays modern cutters make lapping obsolete. I guess if anything it's a way to check to see if the valve job was done properly. You could just throw some dykem on there and give it a quick whirl.

Sounds like a good plan to start with the milder cam, it might make initial tune easier, although I've never had much issue making the stage 3 run well, and I don't say that in a bragging way. I think even a stage 3 is very drivable with a good idle and very tunable.

[gundee]

8 hours ago, siteunseen said:

I've got those two flat steel bars for the rear of the pan I'll be using, for sure. I guess the reason they only did the rear is because thats where the load is? 5 quarts is pretty heavy with such a fragile pan, i.e dimpling and low torque specs. That's my guess.

Rossi your are great idea, ah ha! inspiration person! You always have a good common sense reply that make me think "why didn't I think of that"

Thank you both. Now back downstairs for more sanding, I'm painting the pan and rails black like they should be.

 

I understood those oil pain rails only came on the Automatic Transmission versions.

Not sure why.

[siteunseen]

Having a hard time replying with my Samsung phone?

Anyway, my '77 5 speed has the rails and the ones I'm using on my 240 are off a '79 ZX 5 speed. Maybe they were on the auto 240s? Both my '72s 4 speeds do not have them though. I think that extra flange looking thing on the straight side is for the autos though? Maybe the line to the radiator protection somehow? Do not know for sure but they are on my five speeds. FWIW.

Steve I'm kinda on the edge with my carbs. I just had rebuilt them thinking the car would run better but of course that wasn't the fix so I pulled the motor in a all out effort. I hope it pulls after this.  

At least past six thousand! 

It was flat at about fifty five hundred before. I know theres more. My 110 red and white stock hits six grand in a heartbeat.  This orange one was off a tooth or two somewhere. I never could figure it out and I like to tinker more than drive, (read DRINK)!

Cliff

[siteunseen]

Finally!  After much prep work and some other outside my control deals I got the oil pan back on, RIGHT! this time.

Golf tees helped hold the gasket in place while I brushed a thin layer of aviation gasket sealer on. Used the flat rails off a ZX motor I had to secure the rear of the pan. So happy I re-did this, it gave a chance to paint the pan blacl like I should've done to begin with. I'll re-tighten the bolts over the next few days.

Thanks eveybody for your suggestions!

Cliff

[siteunseen]

Finally, no leaks!  Now I can stress on the carbs. 

If someone could answer a couple of questions, I'll sleep like a baby tonight.

1st is my timing chain.  Super tight but the whole motor seems tight as well so I guess I'm just overthinking?

2nd is the motor is really tight!  It turns smoothly by hand using an 8" socket wrench with the 27mm socket, overthinking again?  Spark plugs are out.

All new parts, timing kit, bearings and chrome faced moly rings.  Honestly I just don't remember the 2.8 I built being this tight.  But I keep telling myself, before I bought a remote starter, the motors were pretty tough to move when I adjusted the valves.  I remember using a 36" piece of pipe on the crank bolt as a cheater bar and so I could turn it from the top side.

Thanks for any confidence building advice or just put it in and crank it, it'll loosen up.

Cliff